Diagnostic Imaging Principles and Applications in...

Diagnostic Imaging Principlesand Applications in Head and NeckPathology

Andy Whyte, Rudolf Boeddinghaus, andMarie Anne Teresa J. Matias

AbstractHead and neck pathology encompasses multi-ple, diverse conditions and disease processes,many of which are complex and require imag-ing as adjunct to clinical examination. Imagingtechniques can provide anatomical or functionalinformation, some using ionizing radiationwhile others do not. Plain radiographs providea two-dimensional overview of the region ofinterest, and cross-sectional imaging modalitiessuch as computed tomography (CT), cone beamcomputed tomography (CBCT), and magneticresonance imaging (MRI) provide multiplanarevaluation of osseous structures of the oral andmaxillofacial region. CT and MRI have theadditional advantage of providing high-

resolution imaging of soft tissues. Initial evalu-ation of superficially located head and neck softtissue lesions frequently utilize ultrasound.Nuclear medicine techniques provide functionalinformation, evaluating metabolic turnover oftissue and differentiating pathological from nor-mal tissue. The applications of these imagingtechniques are discussed in several clinical sce-narios under the headings of mass lesions, sali-vary gland disease, oral cavity malignancy,osteonecrosis of the jaws, temporomandibularjoint disorders, orofacial pain, obstructive sleepapnea, and headaches. This chapter provides themost current data regarding the advantages anddisadvantages of imaging techniques as theyrelate to head and neck pathology.

KeywordsMaxillofacial imaging • Cross-sectional imag-ing •Cone beam computed tomography •Mag-netic resonance imaging • Ultrasound • Dentalpanoramic tomography • Nuclear medicine •Computed tomography • Osteonecrosis ofjaws • Temporomandibular disorders •Obstructive sleep apnea • Headache

ContentsIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Imaging Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Anatomical Techniques Using Ionizing

Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Anatomical Techniques Without Ionizing

Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

A. Whyte (*)University of Melbourne, Carlton, VIC, Australia

University of Western Australia, Nedlands, WA, Australia

Perth Radiological Clinic, Subiaco, WA, Australia

Ear Science Institute, Subiaco, WA, Australiae-mail: [email protected]

R. BoeddinghausPerth Radiological Clinic, Subiaco, WA, Australia

School of Surgery, University of Western Australia,Nedlands, WA, Australiae-mail: [email protected]

M.A.T.J. MatiasPerth Radiological Clinic, Subiaco, WA, Australia

Qscan Radiology Clinics, Herston, QLD, Australiae-mail: [email protected]

# Springer International Publishing AG 2017C.S. Farah et al. (eds.), Contemporary Oral Medicine,DOI 10.1007/978-3-319-28100-1_6-1

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mailto:Andy.�[email protected]

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Functional Imaging Techniques . . . . . . . . . . . . . . . . . . . . . . . 6

Principal Applications of Advanced Imaging inOral Medicine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Imaging of Mass Lesions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Imaging of Salivary Gland Disease . . . . . . . . . . . . . . . . . . . 19Imaging of Malignancy of the Oral Cavity . . . . . . . . . . . 26Imaging of Osteomyelitis and Osteonecrosis

of the Jaws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41Imaging of Temporomandibular Disorders . . . . . . . . . . . 44Imaging of Orofacial Pain . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56Imaging of Sleep-Disordered Breathing . . . . . . . . . . . . . . 63Imaging of Headache . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Conclusion and Future Directions . . . . . . . . . . . . . . . . . . 76

Cross-References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Introduction

Imaging is an adjunct to, and not a substitute for,an optimal clinical examination. Intraoral radio-graphs, extraoral radiographs, and dental pano-ramic tomography (DPT) (also known asorthopantomograph, OPG) provide an overviewof the mandible and maxillofacial skeleton andallow more detailed analysis of the dentition andalveolar process.

Cross-sectional imaging modalities such ascomputed tomography (CT) and magnetic reso-nance imaging (MRI) provide high-resolution,multiplanar evaluation of the osseous structuresand soft tissue of the oral andmaxillofacial region,respectively. These modalities, in addition to conebeam computed tomography (CBCT), providedetailed analysis of the dentition and of corticaland medullary bone free of the superimpositioninherent in radiographs. CBCT can visualize theoutline of skin and also the mucosal outline of thepharynx and oral cavity but lacks soft tissue con-trast resolution. Ultrasound is frequently used asthe initial diagnostic imaging modality in headand neck imaging, especially for evaluating softtissue lesions and guiding biopsy.

Nuclear medicine techniques involving radio-isotopes evaluate metabolic turnover of tissue,differentiating pathological from normal tissue,and are primarily used in the evaluation of malig-nancy and infection.

The applications of these various imaging tech-niques are discussed in various clinical scenarios,including mass lesions, salivary gland disease, oralcavity malignancy, osteonecrosis of the jaws, tem-poromandibular joint disorders, orofacial pain,obstructive sleep apnea, and headaches.

Imaging Techniques

Imaging techniques can provide anatomical orfunctional information. Techniques can also bedivided into those using ionizing radiation andthose that do not use ionizing radiation.

Anatomical Techniques Using IonizingRadiation

An imaging technique should only be used if thepotential diagnostic benefit exceeds the estimatedrisk from ionizing radiation. There is substantialevidence for a dose-related stochastic response tohigh levels of ionizing radiation in the form ofcancer developing years after initial exposure(Hendee and O’Connor 2012). Although there isdebate as to the level of risk associatedwith the lowradiation doses employed in diagnostic radiology,including dental and maxillofacial radiology(DMFR), a linear non-threshold (LNT) model isassumed for purposes of radiation protection. ThisLNT model implies that even very low doses ofionizing radiation have the potential to result in asmall increased incidence of cancer. This stochasticcarcinogenic effect has been very difficult to dem-onstrate directly because of the high backgroundprevalence of malignancy, the fact that radiation-induced malignancy has no features which candistinguish it from any other malignancy, and thelong lead time between radiation exposure and aclinically apparent cancer. However, there is nowdirect epidemiological evidence of a small increasein cancer incidence after CT scanning in childrenand young adults (Pearce et al. 2012; Mathewset al. 2013). Children are consideredmore sensitiveto radiation-induced carcinogenesis due to imma-turity of developing tissues, their smaller size and

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proximity or inclusion of more radiosensitiveorgans such as the brain, thyroid, salivary glands,and mucosa of the maxillofacial region as well asthe longer life expectancy in which a radiation-induced malignancy may manifest.

Background radiation is an important conceptwhen considering total radiation dose. It is pre-dominantly comprised of terrestrial radiation inrocks and soil, radon gas that seeps from theground, and cosmic sources. This therefore variesfrom place to place: it is estimated at 2.4 milli-sieverts (mSv) per annum worldwide (AustralianRadiation Protection and Nuclear Safety Agency2015), equating to about 6.6 microsieverts (μSv)per day, but ranges from less than 1 mSv perannum to over 10 mSv (and exceptionally over70 mSv) per annum. Radiation doses from differ-ent imaging modalities can be expressed in termsof multiples of the daily background dose (Back-ground Radiation Equivalent Time: BRET, alsoknown as BERT) a more meaningful concept formost patients than comparing absolute dose.

Different tissues in the body have differentcancer risk from the same radiation dose, andthis concept is incorporated when calculating theEffective Dose (E) of an imaging examination andto which region of the body it is applied. In addi-tion to the brain and thyroid, the mucosa of theoral cavity, pharynx, and upper respiratory tractand the salivary glands have relatively high tissueweighting when calculating the potential deleteri-ous effects of imaging of the dental and maxillo-facial region (Ludlow and Ivanovic 2008).

i) Radiographs: Intraoral radiographs are read-ily available and provide a low cost, low radi-ation dose, and high spatial resolutionmodality for evaluating the dentoalveolarstructures and specifically for detecting caries,periapical pathology, and periodontal disease.For each radiograph, the field of view is lim-ited and a full-mouth evaluation may requireup to 18 radiographs resulting in a radiationdose of up to 150 μSv, equivalent to 23 days ofbackground radiation (BERT).

In contrast, the DPT is a curved panoramictomogram that provides an overview of the

dentition, mandible, temporomandibular joints(TMJ), and maxilla and maxillary sinuses. It isalso a readily available, low-cost, and low-radiation-dose imaging modality but is ofmuch lower resolution than intraoral radio-graphs and is prone to artefacts inherent in thetechnique but also dependent on the patient andtechnical errors.

The lateral cephalogram provides a stan-dardized assessment of the dental andskeletal relationship of the jaws as well astwo-dimensional (2D) evaluation of the airway.

Digital rather than traditional film-screentechniques have numerous advantages includ-ing significantly lower radiation dose, imageprocessing, fewer repeat examinations, digitalstorage, and potentially higher resolution. Theaverage effective dose of a digital DPT is15 μSv (2.5 days of BERT) and that of a lateralcephalogram is 3 μSv (less than half a dayof BERT).

ii) Computed tomography (CT): The invention ofCT in 1972 allowed true cross-sectional imag-ing for the first time, initially of the brain. AllCT scanners utilize a thin, fan-shaped X-raybeam which passes through the area beingscanned, with the variable attenuation of thebeam being detected by a detector array. In thelate 1980s, slip-ring technology was devel-oped allowing continuous rotation of thering-shaped gantry containing the X-ray tubeand detector array around the patient, thetable, and the patient travelling at a constantspeed through the gantry. The X-ray beamdescribed a helical path around the patient:helical CT (also known as spiral CT).

Multidetector or multislice CT (MDCT orMSCT) was a critical technological develop-ment in 1998 replacing the single long detec-tor (up to 20 mm in the longitudinal axis) usedin single slice scanners with multiple smalldetectors. This enables large volumes of tissueto be scanned rapidly with the simultaneousgeneration of thick and thin slices. The thinslices contain isotropic voxels (i.e., volumeelements which are of equal length in allthree dimensions of space) allowing for

Diagnostic Imaging Principles and Applications in Head and Neck Pathology 3

multiplanar 2D reconstructions of equivalentresolution to the acquired axial slices. Cur-rently, 64- to 320-slice MDCT representsstate-of-the-art technology.

Additional hardware and software devel-opments have contributed to significant reduc-tion in radiation dose without deleteriousincrease in image noise or loss of diagnosticefficacy. CurrentMDCTscanners will result inan effective dose of 200–300μSV for amedium field of view scan in the oral andmaxillofacial region, equivalent to between30 and 45 days of BERT.

Intravenous iodinated contrast medium isused to increase the difference in attenuation(density) between pathological lesions andadjacent normal tissue, either inflammatoryor neoplastic. Hypervascularity within or atthe margin of the lesion leads to accumulationof radiodense iodine, and it becomes “whiter”on a gray-scale image and more conspicuous.On the other hand, central necrosis or puswithin a tumor or abscess does not enhanceand is more clearly visualized than onnon-contrast scans. In patients with kidneydisease and those with diabetes on metformintreatment, the risks of contrast medium-induced renal failure and lactic acidosis,respectively, are significantly increased.

iii) Cone Beam Computed Tomography (CBCT):This imaging technique was initially developedfor use with clinical applications in angiogra-phy, nuclear medicine, and imaging-guidedradiotherapy. Initial development of CBCTfor maxillofacial use occurred in the late1990s with rapid evolution into scanners withdecreased scanning times, a range of scanningoptions, and less predisposition to artefacts.

CBCTuses a cone-shaped X-ray beam cen-tered on a flat panel 2D detector. The sourcedetector performs a single 360-degree rotationaround the head producing a series of 2Dimages from which a volumetric data set isreconstructed using algorithms similar tothose used in MDCT. Multiplanar 2D recon-structions in the axial, coronal, sagittal, andcurved planes are produced from the volumedata set, and, using dedicated software, three-dimensional (3D) reconstructions of the skinsurface, airway, or maxillofacial bony skele-ton can be obtained. Scan times are greaterthan those of MDCT (9–27 s, compared to2–4 s for MDCT) with patients generallybeing scanned in the erect or sitting position(a single supine CBCT scanner is currentlyavailable).

Themain advantages of CBCT (overMDCT)are higher resolution (0.075–0.15 mm voxellengths as compared with 0.5–0.625 mm forMDCT) and lower radiation dose: 60–250 μSvfor state-of-the-art equipment (Ludlow andIvanovic 2008; De Vos et al. 2009; Casselmanet al. 2013), (equivalent to 9–38 days of BERT).Streak artefacts resulting from beam hardeningby metallic restorations are less pronounced andmore localized with CBCT. In addition, a CBCTscanner is smaller and is generally lower in costthan MDCT.

Significant disadvantages include theabsence of soft tissue contrast which is princi-pally related to the lower radiation dose butalso the detector design and inability to accu-rately measure tissue density (in Hounsfieldunits) as compared with the high accuracy ofconventional CT (Table 1).

Table 1 Comparison of intra-oral radiographs, DPT, CBCT, and CT

Modality Intra-Oral Radiographs DPT CBCT CT

Volumetric data set No No Yes Yes

Spatial resolution +++ + ++ +

Soft tissue contrast No No No Yes

Effective dose ofradiation

150 μSv (full mouth) 15 μSv 60–250 μSv 200–300 μSv

Scan time (seconds) very short (<<1s); multipleexposures

10s:long

9–27 s: long 2–4 s: short(less motion artefact)

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Anatomical Techniques WithoutIonizing Radiation

There are no known significant side effectsresulting from the use of ultrasound or magneticresonance imaging, the principal imaging tech-niques which do not use ionizing radiation.

i) Ultrasound (US): This is widely available,inexpensive, noninvasive, and highly accuratein the evaluation of superficial structures of thehead and neck, including the oral cavity. Ultra-sound, especially in the head and neck, doeshave some limitations. The accuracy relies onthe experience and knowledge of the operatorand also the habitus and cooperation of thepatient. In addition, ultrasound requires a “win-dow” that is unimpeded by bone or air, limitingthe type of examination it can provide whencompared to CT or MRI.

For evaluation of the neck and maxillofacialregion, high-frequency transducers are used,using sound waves between 7.5 and 15 MHz:compared with conventional transducers usedfor abdominal and pelvic imaging; these resultin higher spatial resolution but are unable topenetrate as deeply into the soft tissues.

Sound waves are reflected back from everyanatomical interface in the tissue being exam-ined. Echogenicity is the degree to which theinterface reflects sound and returns a signal tothe transducer, which also acts as receiver.Hyperechoic structures appear whiter on agray-scale image and include bone or calculi.All sound is reflected and an acoustic shadowis created. If sound is poorly reflected or notreflected at all and passes easily through thestructure, it appears darker or black and isdescribed as hypoechoic or anechoic, respec-tively. Acoustic enhancement occurs deep tothese structures as the easily propagated soundwaves are reflected at the next tissue interface,examples being cysts and some tumors such aspleomorphic adenomas. Isoechoic structureshave the same echogenicity as their surround-ings, for example, muscle.

Color Doppler US is an additional ultra-sound technique which supplements the gray-

scale examination and can be used to deter-mine the presence, distribution, and type ofblood vessels in a lesion, often increasing thespecificity of diagnosis.

In the maxillofacial region and neck, US isan excellent initial examination for the salivaryglands, thyroid, lymph nodes, congenitallesions, and miscellaneous mass lesions. Eval-uations of complications of infection or post-surgical sequelae, with or without CT or MRI,are further potential uses. US can also be usedto guide an imaging procedure such as fineneedle aspiration cytology (FNAC), corebiopsy, aspiration or drainage of collections,and also placement of a needle into the TMJfor therapeutic injection of steroids and localanesthetic. The use of a small footplate, veryhigh-frequency probe used intraorally is anestablished, fast, and accurate method of deter-mining the depth of submucosal invasionof squamous cell carcinoma (Yesuratnamet al. 2014).

ii) Magnetic resonance imaging (MRI): Thisimaging modality is based on the principlesthat atoms with an odd number of neutrons orprotons have spin and that a moving electricalcharge produces a magnetic field. Hydrogen isthe atom most commonly imaged in MRIbecause of its abundance in the body. Hydro-gen nuclei in tissue spin randomly until placedin the strong magnetic field of an MRI scanner,which causes the protons to align with theexternal magnetic field, analogous to miniaturecompass needles. If the protons are thenexposed to a short burst of electromagneticenergy in the form of a radiofrequency pulse,they will momentarily flip from their axis. Inthe process of returning to their original orien-tation, they emit a characteristic radio-frequency signal which is detected by areceiver coil adjacent to the region of interest.The intensity of this emission reflects a combi-nation of the density of protons and the chem-ical qualities of the surrounding tissues.

MRI scanners used in current clinical prac-tice generally have magnetic field strengths of1.5 or 3 Tesla (T). Higher field strength (3 T)magnets generate more signal and improved


image quality, especially of small structuressuch as cranial nerves or small joints such asthe TMJ.

The contrast of a routine MRI image isdependent on whether the image is T1- orT2-weighted (determined by the specific timingof radiofrequency excitations and readouts) andreflects the different magnetic spin properties ofhydrogen according to how it is chemicallybound within different tissues. Fat and waterare the standards used to describe a T1- orT2-weighted image: fat is bright and waterdark on a T1-weighted image while water isbright on a T2-weighted image. Fat is classicallydescribed as dark on T2, but this is not the caseon most currently used fast T2 sequences.T1-weighted images are optimal for assessinganatomy and T2 (often usedwith a technique forsuppressing the signal from fat) for differentiat-ing pathology from normal tissue (Fig. 1). Mostinflammatory and neoplastic lesions are water-rich and therefore are of higher signal thansurrounding tissue on a T2-weighted image.Because air and cortical bone have no mobileprotons, they have no signal on any MRIsequence. The presence of signal within corticalbone is always pathological apart from normalneurovascular canals and sutures.

Intravenous contrast agents can also beused to increase the signal intensity differencebetween a pathological lesion and normaltissue. The most commonly used MRI contrastagent is gadolinium (a trivalent rare earthelement) bound to a chelate. Gadoliniumincreases the signal intensity of enhancing tis-sues on T1-weighted imaging: this greater con-spicuity can be further improved by using afat-suppression sequence to remove the normalhigh signal from fat. Patterns of enhancementcan increase the specificity of diagnosis, andthis is of value in differentiating cystic fromsolid lesions and differentiating between com-mon types of tumors. Gadolinium iscontraindicated in patients with impaired kid-ney function in whom it may rarely result innephrogenic systemic fibrosis, a debilitatingand occasionally fatal condition. Althoughgadolinium chelate is almost completely

excreted in urine within 24 h of injection,there is recent evidence that traces of unboundgadolinium accumulate and remain in thebrain, probably indefinitely (Kanda et al.2014; McDonald et al. 2015). Although thishas not been shown to have clinical effects,gadolinium should not be used indiscrimi-nately but reserved for cases where its use islikely to improve diagnostic accuracy.

Compared with other anatomical imagingmodalities, MRI has excellent contrast resolu-tion, allowing optimal delineation of normalfrom abnormal tissue. Like MDCT andCBCT, MRI is now capable of submillimeterimaging which is essential for evaluation of thetrigeminal and the lower cranial nerves in theevaluation of orofacial pain and optimal for theassessment of soft tissue and bone. High-spatial-resolution MRI of the oral and maxillo-facial region requires high field strength (3 T)and optimal receiver coils to maintain adequatesignal.

The technique of magnetic resonance angi-ography (MRA) can be used to study arterialanatomy and flow in the maxillofacial region.It can determine if there is arterial supply to asuspected vascular malformation. MRA can beperformed either using gadolinium contrast orwithout contrast, using special techniques rely-ing on higher signal from flowing protons.

One in three patients experiences anxietyand one in six patients becomes claustrophobicin an MRI scanner (Enders et al. 2011): mostcan complete the examination with encourage-ment and simple measures but some mayrequire sedation. The development of shorterand wider bores in current MRI scanners hasalso improved patient acceptance.

Most cardiac pacemakers and a variety ofmetallic implants and coils may contraindicateMRI; safety is paramount and all implanteddevices require rigorous evaluation.

Functional Imaging Techniques

Functional methods of imaging usually involveradioisotopes and therefore ionizing radiation.

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They assess metabolic turnover and can be com-bined with anatomical imaging (MDCT or MRI).MRI can also be used to assess function, primarilyof the brain but also in the oral and maxillofacialregion.

i) Conventional Nuclear Medicine: A minuteamount of a radioactive isotope is bound to acarrier molecule, and this combination (calleda tracer) is injected intravenously to study aparticular body function by evaluating thespatial and temporal distribution of the tracerwithin the body. The isotope decays by emit-ting gamma rays (photon of a specific energy)which are measured by a gamma camerawhich maps the detected gamma rays.

The most frequently used radioisotope istechnetium-99 m (99mTc) which is commonly

bound to a diphosphonate carrier molecule.It emits a gamma ray of an energy which isoptimal for detection by the scintillationdetector of the gamma camera and loses50% of its radioactivity in 6 h making itideal for medical imaging. Radiolabeleddiphosphonates bind to hydroxyapatite atsites of active osteogenesis which is a non-specific response of bone to a range of stimuli,including injury, infection, or tumor.

Bone scans are of low sensitivity fortumors confined to the marrow (such as mye-loma) and those that are osteolytic with littleor no osteogenic reaction (such as myelomaand renal cell carcinoma). The effective radi-ation dose (about 6 mSv, BERT of about2.5 years) is relatively high when comparedto maxillofacial CBCT or MDCT.

Fig. 1 Basic MRI sequences: (a) T1 – fat is hyperintense;simple fluid (globe – g) is hypointense. (b) T2 – fat isslightly less hyperintense; simple fluid is hyperintense.(c) Fat saturation T2 – fat is hypointense (the signal issuppressed); simple fluid remains hyperintense. Air and

cortical bone have no signal on any sequence. The dashedwhite arrow indicates hyperintense proteinaceous fluid inthe left posterior ethmoid air cells on the T1 sequencewhich then loses signal on the T2 sequences mimickingclear air cells


Bone scans can be either conventional (pla-nar 2D) or tomographic (single photon emis-sion computed tomography, SPECT). SPECTcan also be combined with low-dose CT toprovide a fused SPECT/CT image providingoptimal anatomical localization of abnormalbone scan activity. Images can bereconstructed in axial, coronal, and sagittalplanes.

When sepsis is thought to be the likelycause of increased osteogenesis on a bonescan, a specific diagnosis of infection can beprovided by an additional nuclear medicinescan using white cells labeled with the isotope(indium-111 or technetium-99 m) or a galliumscan, the latter having increased sensitivity forthe detection of chronic infections such asosteomyelitis.

ii) Positron emission tomography (PET): Themain tracer used is F18 -fluorodeoxyglucose(18F–FDG); fluorine-18 is the isotope and isproduced in a cyclotron with a half-life of justless than 2 h. As the carrier molecule is aglucose analogue, 18F–FDG is taken up bytissues within 1–2 h according to metabolicactivity, producing a “glucose map” withphysiological activity in the brain and heartas well as (in the head and neck region) thesalivary glands, tonsils, and larynx. Diseasedmetabolically active tissues, in particularmalignant tumors, exhibit a high rate of glu-cose metabolism.

The decay of F-18 produces a positronwhich travels a short distance before annihi-lating with an electron, producing two pho-tons propagating in opposite directionswhich are detected simultaneously by a ringdetector. PET is usually combined withlow-dose CT on the same scanning platform(PET-CT) producing co-registered images toimprove anatomical localization as well ascorrection of the PET emission data for atten-uation by the tissues of the body (Fig. 2). APET scan covering the brain to the thighstakes 20 min with 30 s for the CT of thesame region and a combined radiation doseof 14 mSv (equivalent to a BERT of nearly6 years).

The principal use of PET-CT in oral andmaxillofacial region is in the assessment ofhead and neck cancer. A large field of viewmeans that metastatic disease and second pri-mary tumors can be detected, and PET maydetect malignancy in structures which appearnormal or are difficult to assess on CT andMRI, such as small volume lymph nodemetastases. A large multicenter study ofpatients with head and neck cancer hasshown that PET was able to detect additionalsites of disease in 39.4% of patients andresulted in management change in 33.8% ofpatients. PET therefore has a vital role in opti-mal staging, treatment planning, and follow-up post-therapy for head and neck cancer(Castaldi et al. 2013; Purohit et al. 2014).

iii) Functional MRI techniques:Diffusion weighted imaging (DWI) is a

form of MRI which quantifies diffusion ofwater occurring naturally at a molecular level(Brownian movement). The dense cellular tis-sue of tumors, cellular edema of recent cere-bral infarcts, and the proteinaceous contents ofan abscess or a keratocystic odontogenictumor of the jaw restrict the random motionof water molecules and lower diffusion, mea-sured as a diffusion coefficient (Sumi et al.2008). DWI is a rapid means of tumorcharacterization and assessing response ofmalignant tumors to treatment in the oral andmaxillofacial region (Thoeny et al. 2012;Payne et al. 2015).

Diffusion tensor imaging (DTI) visualizesthe location, orientation, and microstructure ofwhite matter tracts as well as the root-entryzone of the cisternal segment of the trigeminalnerve to the pons. It has been applied to thestudy of the pathophysiology of neuropathicpain and the response to treatment.

Magnetic resonance spectroscopy (MRS)supplements anatomical MRI and allows thepresence and concentration of key metabolitesto be measured within lesions, aiding the dis-tinction between inflammatory and neoplasticprocesses in the brain.

Functional magnetic resonance imaging(fMRI) is a technique that measures brain

8 A. Whyte et al.

activity. Cerebral blood flow and blood oxy-genation are coupled to neuronal activity. Theprimary technique used in fMRI is blood-oxy-gen-level-dependent (BOLD) contrast, whichis based on the different magnetic propertiesof oxygenated and deoxygenated hemoglobin.fMRI provides a noninvasive means of map-ping brain function. It can be used in assessingorofacial pain processing areas. It can be com-bined with spectroscopy (fMRS). At present,this is primarily a research tool which has beenused in migraine and pain research to evaluatechanges in metabolites in areas involvedin pain.

Voxel-based morphometry (VBM) is awidely used and validated technique usinghigh-resolution 3D MRI data to evaluatebrain structure. This technique has shownreduction in gray matter volume in the pain

processing areas of the brain in patients withsevere chronic facial pain and migraine. Thesechanges are reversible with successful treat-ment in a matter of weeks, a direct measure ofneuroplasticity (May 2009).

Principal Applications of AdvancedImaging in Oral Medicine

The applications of advanced imaging techniquesare discussed in various clinical scenarios belowunder the headings of imaging of (1) mass lesions,(2) salivary gland disease, (3) malignancy of theoral cavity, (4) osteomyelitis and osteonecrosis ofthe jaws, (5) temporomandibular joint disorders,(6) orofacial pain, (7) obstructive sleep apnea, and(8) headaches. A comprehensive description ofthe radiologic features of all types of pathology

Fig. 2 PET-CT of a left retromolar trigone squamous cellcarcinoma with metastatic left level 2 nodes. The superioraxial scans (a, b, and c) correspond to the primary tumor.Inferior scans: d, e, and f demonstrate the metastases.Scans a and d are the non-contrast CT component of thePET-CT scan used for localization and attenuation correc-tion.Scans b and e are the fused CT and metabolic images;

the intense metabolic activity in the small primary (whitearrow) and nodes (dashed white arrow) are shown inorange. Scans c and f are post-contrast CT scans; the siteof the primary is difficult to appreciate and is indicated by awhite arrow and the metastatic nodes by a dashed whitearrow


is beyond the scope of this chapter. The reader isreferred to other chapters for descriptions of theimaging features of the main conditions describedin those chapters.

Imaging of Mass Lesions

Mass lesions may arise from orofacial soft tissues,the maxillofacial skeleton, or odontogenic tissues:

a. Orofacial soft tissues. Palpable lesions in theorofacial region may arise from skin, subcuta-neous tissue, pilosebaceous glands, muscle,fat, fascia, nerves, blood vessels, lymphnodes, or embryonic remnants. The differentialdiagnosis may be wide, and the majority ofthese lesions will be benign. The location ofthe lesion, the patient’s age, and medical his-tory including a history of previous malig-nancy are important factors in approaching adiagnosis.

If imaging is required because the diagnosisis not clear after clinical examination, US withcolor Doppler should be the initial imagingmodality, if necessary proceeding toultrasound-guided fine needle aspiration cytol-ogy (FNAC) which provides a definitive diag-nosis in most cases. US can usually distinguishbetween a simple cyst, a more complex lesioncontaining debris or small solid components,and solid lesions of various types. CT or MRImay be required if US suggests that the lesioncontains fat or is hypervascular, if it cannotdemonstrate the full extent of the lesion orthere is sonographic or cytological evidenceof malignancy.

Cystic lesions in younger patients are usu-ally congenital in nature, arising from embry-onic remnants (Woo and Connor 2007; Mittalet al. 2012). Thyroglossal duct cysts (TGDC)occur along the embryologic path of descent ofthe thyroid gland from the foramen cecum atthe tongue base to the lower neck. They are thecommonest congenital neck masses. Many pre-sent in childhood but they may not present untillater in life, often when the cyst becomesinfected (Fig. 3). Most are located at or inferior

to the level of the hyoid bone in the midline, butinfrahyoid lesions may deviate away from themidline. Rarely, thyroid neoplasms (usuallypapillary thyroid carcinoma) may arise withina TGDC.

Branchial cleft anomalies arise from incom-plete obliteration of the embryonic branchial(pharyngeal) clefts or pouches, resulting ineither a cyst or, less frequently, a sinus orfistula. First branchial cleft anomalies areintra-parotid or peri-auricular in location. Sec-ond branchial cleft cysts comprise 95% of allbranchial cleft lesions and most commonlypresent in the 20–40 year age group, oftenbecoming evident after an upper respiratoryinfection. They are most commonly positioneddeep to sternomastoid, lateral to the carotidspace, and posterior to the submandibular sal-ivary gland (Fig. 4).

The widely accepted International Societyfor the Study of Vascular Anomalies (ISSVA)classification divides vascular lesions into twocategories: vascular tumors and vascularmalformations (Guneyli et al. 2014; Gamsset al. 2015). Vascular tumors are true neo-plasms which proliferate secondary to mitosisand include infantile hemangioma and congen-ital hemangioma. In contrast, vascularmalformations are structural abnormalities ofthe capillary, venous, lymphatic, or arterialsystem that grow in proportion to the child.Vascular tumors and vascular malformationsmust be distinguished from hypervascular neo-plasms derived from non-vascular tissues aris-ing in the maxillofacial region, such as juvenileangiofibromas and paragangliomas (glomustumors) (Fig. 5). Imaging, especially MRI andUS, plays a key role in the diagnosis and clas-sification of vascular lesions.

Hemangiomas are benign and divided intoinfantile and congenital subtypes. Infantilehemangiomas arise 2–8 weeks after birth andundergo a proliferative growth phase until theyreach their full size. In contrast, congenitalhemangiomas are fully formed at birth andmay be further subdivided into involuting hem-angiomas, which regress completely within2 years, and non-involuting hemangiomas,

10 A. Whyte et al.

which show proportional growth withoutregression. MRI optimally demonstrates thetypical imaging features.

Low-flow vascular malformations includecapillary, venous, lymphatic, and combinedvenolymphatic malformations and are thecommonest vascular lesions. They demon-strate proportional growth and do not involute.Venous malformations (still widely and incor-rectly termed cavernous hemangiomas) havecharacteristic imaging features includingstrong contrast enhancement and oftenphleboliths (Fig. 6). Lymphatic malformations(still widely termed lymphangiomas) occurmost commonly in the head and neck in thefirst 2 years of life. They are subdivided intomacrocystic (cysts > 20 mm, also known ascystic hygromas),microcystic (cysts<20mm),

and mixed types. They are commonly situatedin the floor of the mouth or the posterior trian-gle of the neck. They have an infiltrative pat-tern of growth, extending freely betweenadjacent fascial spaces. Unlike venousmalformations, they do not enhance with con-trast (Fig. 7).

High-flow vascular malformations are rare;they usually present after a period of rapidgrowth and include arterial malformations, arte-riovenous malformations, and arteriovenous fis-tulae. They are best demonstrated by MRI withmagnetic resonance angiography (MRA). Feed-ing arteries, the malformation or fistula, largedraining veins, and possible osseous involve-ment are the principal imaging features.

Epidermoid cysts are thin-walled cysticlesions that commonly occur in the floor of

Fig. 3 Thyroglossal duct cyst, indicated by a white arrow.This small lesion is hypodense on CT consistent with fluidand is situated inferior to the hyoid bone (H). It extendsinferiorly into the superior thyroid notch (b) and then

invaginates the left strap muscles (c). (a) Sagittal, midlineCT reconstruction. (b and c) Axial CT reconstructions. (d)Axial US scan showing a sonolucent lesion. Posterioracoustic enhancement is indicated by the white dotted oval


the mouth superior to mylohyoid and oftenmimic a simple ranula. Dermoid cysts aremost common in the submandibular space(i.e., inferior to mylohyoid); they mimic plung-ing ranulas or lymphatic malformations andoften appear as a complex cyst due to thepresence of debris, fat, or calcium producedby skin appendages in the lining of keratinizedsquamous epithelium (Fig. 8).

Most apparently cystic lesions in patientsover the age of 40 years will be due to meta-static carcinoma to cervical lymph nodes, mostcommonly human papillomavirus (HPV)-related squamous cell carcinoma (SCC) of theoropharynx or papillary thyroid carcinoma(Fig. 9). Nodal necrosis or abscess formationcan be due to various inflammatory and infec-tive conditions (Mittal et al. 2012).

The nature of solid lesions can usually bedetermined by imaging. The location, mor-phology, margin, vascularity, and multiplicityare the principal diagnostic features. Palpablelymph nodes are the commonest mass lesiondetected by clinical examination; normal-sizedor enlarged, reactive-appearing nodes areovoid with a vascular supply via the hiluswhich commonly contains a small nidus of fat

(Fig. 10). Reactive cervical lymph nodes tendto be larger in children, the largest usuallybeing the jugulodigastric node. Absolutenodal size is less important than change innodal morphology when assessing for meta-static disease or lymphadenitis. Pathologicalnodes tend to be round rather than oval, withloss of normal hilar fat and blood flow. US withcolor Doppler demonstrates abnormal vascularpatterns in larger nodes. With CT and MRI,abnormal nodes are of heterogeneous attenua-tion or signal, respectively, especially afterthe administration of intravenous contrast(Fig. 11). Diffusion-weighted imaging (DWI)is a rapid MRI technique that can be usedto characterize enlarged lymph nodes by mea-suring the apparent diffusion coefficient(ADC) which help to distinguish between reac-tive, lymphomatous, and metastatic causes(Ali 2012).

Lipomas are common in the neck, includingthe peri-parotid region. The appearance of fatwithin lipomas varies on US; US-guidedFNAC is rarely diagnostic, and confirmationof the nature of these lesions commonlyrequires CT or MRI (Fig. 12). Atypicallipomas which contain enhancing tissue or

Fig. 4 Second branchial cleft cyst: (a) axial post-contrastCT scan and (b) color Doppler US. The lesion is of lowdensity on CT (white arrow) and contains internal echoes

on US, usually indicative of inflammation. The deeplysituated common carotid artery (CCA) is indicated by adashed white arrow

12 A. Whyte et al.

septa in addition to fat require excision toexclude malignancy. Spindle cell lipomas,characteristically occuring in the subcutaneousfat of the posterior neck of middle-aged men,although benign can contain enhancing softtissue mimicking a liposarcoma (Choiet al. 2013).

b. Maxillofacial skeleton. Lesions arising withinthe mandible or bones of the midface usuallypresent as a mass or facial asymmetry. Theselesions may be tori, hamartomas, or

neoplasms, either benign or malignant. Malig-nant tumors of bone may be primary orsecondary.

An exostosis is a hyperplastic protuberanceof normal cortical and cancellous bone, theprevalence of which is higher in certain ethnicgroups and increases with age. Those arisingfrom the midline of the palate or the lingualcortex of the mandible are designated as tori(torus palatinus and torus mandibularis,respectively). Size varies, but all lesions

Fig. 5 Carotid body tumor (a type of paraganglioma orglomus tumor). These uncommon tumors arise fromneuroectodermal cells acting as chemoreceptors for majorarteries. (a) Post-contrast CT: enhancing mass in the rightcarotid sheath (dotted white arrow). The separated internaljugular vein (IJV) and internal carotid artery (ICA) areindicated. (b) Post-contrast MRI showing the same

features. (c) Fat saturation T2 coronal MRI (dotted whitearrows): the tumor is hyperintense and contains multiplepunctate and curvilinear low-signal vessels. (d) ColorDoppler US: blood flow is color coded according to thedirection of flow (white arrows) – either blue or red.Multiple small vessels are shown either within or aroundthe tumor (dotted white arrow)


contain normal-appearing bone and have asmooth surface (Fig. 13). The major differen-tial is an osteoma which presents as an exo-phytic, pedunculated sclerotic lesioncommonly arising from the ramus and inferiorborder of the mandible or within the frontal orethmoid sinuses.

Fibrous dysplasia (FD) is a dysplastic con-dition of bone leading to its replacement withfibrous tissue. In its distribution, it can bemonostotic or polyostotic, but in the craniofa-cial region, it can involve contiguous bonesacross sutures; hence craniofacial FD com-prises a third subtype, with a mean age of

diagnosis of 25 years, no sex predilection,and with the maxilla being involved twice asoften as the mandible (Menon et al. 2013). Inthe mandible, posterior involvement predomi-nates: superior displacement of the inferioralveolar canal is virtually pathognomonic.Midface involvement may be confined to asingle bone (i.e., monostotic) or be part of theentity of craniofacial FD in which multiplecontiguous facial bones and the skull basemay be involved. The classic expansile,ill-defined lesion exhibiting ground-glass scle-rosis is the commonest appearance on radio-graphs, MDCT, or CBCT. However, the

Fig. 6 Venous malformation with a lymphatic componentin the left submandibular space (dotted oval). This lesioninferiorly displaces and compresses the submandibularsalivary gland (SMG). Post-contrast CT in the axial (a)and coronal (d) planes. There is central enhancement(white arrow) within the venous component surrounded

by the lower-density lymphatic component. The dense,calcified foci represent phleboliths. Post-contrast, fat satu-ration T1-weighted MRI (b); the enhancement is moreconspicuous than on CT, and the phleboliths are not seen.The fat saturation T2-weighted MRI (c) demonstrates uni-form hyperintensity in both components of the lesion

14 A. Whyte et al.

Fig. 7 Lymphatic malformation (L) deep to the rightsternomastoid muscle (sm) extending toward the posteriortriangle and supra-clavicular fossa (white arrows). Post-contrast CT in the coronal (a) and axial (b) planes. Open

white arrows indicate mediolateral airway narrowing (thepatient also has obstructive sleep apnea). Longitudinal US(c) showing the macrocystic structure and color Doppler(d) confirms absence of internal blood flow

Fig. 8 Epidermoid/dermoid in the right submandibularspace. Axial (a) and coronal (b) CT reconstructions show-ing a bilobulate cystic lesion containing debris with a thin

enhancing wall, compressing the right submandibulargland


patterns of radiolucency and radiopacity aswell as the signal of FD on MRI are variable(Fig. 14).

Ossifying fibromas (OF) can appear identicalto active FD on histological examination but arewell defined and occur predominantly in theposterior mandible. The mean age of presenta-tion is 31 years, and they predominate infemales (Cure et al. 2012; MacDonald 2015).Maxillary lesions tend to be larger, because theycan expand into the sinus without producing anobvious mass. The risk of recurrence of OFfollowing excision is of the order of 20%. Thelesions are expansile and well defined with

variable radiopacity of the contents dependenton the maturity of the lesion (Fig. 15).

Primary and metastatic malignant tumors ofthe mandible and maxillofacial skeleton areuncommon. In addition to the rare central car-cinomas which may arise in a preexistingodontogenic lesion or glandular remnants, thejaws may be the site of origin of sarcomas,non-Hodgkin’s lymphoma (NHL), and mye-loma. Often the imaging appearance is non-specific, but internal calcification, aggressivebone destruction, and periosteal new bone for-mation suggest a sarcoma of bone or cartilageorigin (Fig. 16).

Fig. 9 (a) Enlarged left level 2 node (white arrow).The mass has a peripheral enhancing margin with centralfluid attenuation representing nodal necrosis. (b) No oro-pharyngeal abnormality was seen on post-contrast

CT. (c) Occult primary SCC in the left palatine tonsilwhich was only identified on PET-CT (dashed whitearrow). HPV-positive disease in a 42-year-old male

16 A. Whyte et al.

Metastases to the jaws are rare, comprisingonly 1–1.5% of all malignant oral neoplasms(Dunfee et al. 2006). Breast carcinoma pre-dominates in females and lung and prostatecarcinoma in males. The posterior mandible isthe most common location for metastases.Imaging appearances are variable with singleor multiple ill-defined lucencies being the mostcommon appearance on radiographs, CT, orCBCT. However, virtually all metastases fromprostate carcinoma and treated breast carci-noma are sclerotic. MRI and isotope medicinebone scans are more sensitive in detectingmetastases to bone (Fig. 17).

c. Odontogenic tissues. Palpable mass lesionsarising from the dentition, supporting struc-tures and alveolar bone, can be inflammatory,

developmental, or neoplastic. Several excellentreview articles, in addition to the chapter onodontogenic pathology in this textbook, dis-cuss the wide spectrum of odontogenic cystsand tumors and their specific clinical, demo-graphic, imaging, and pathological features(Dunfee et al. 2006; Devenney-Cakir et al.2011; Avril et al. 2014). The peak age of occur-rence of odontogenic tumors and the favoredlocation varies widely according to the histo-logical subtype.

Lesions which present as a painlessmass are most commonly due to an apicalradicular cyst, dentigerous cyst, keratocysticodontogenic tumor (KCOT), or occasional-ly other odontogenic tumors such as anameloblastoma. Apical radicular cysts are

Fig. 10 Normal jugulodigastric lymph node. (a) ColorDoppler US: echogenic fat within the hilus surrounds avascular core (orange) with a “branching tree” appearanceof peripheral vessels. The remainder of the node is uni-formly hypoechoic. (b) Post-contrast CT: the node (dashedwhite oval) is situated anterior to the enhancing vessels of

the carotid sheath. It is of soft tissue density with a smallnidus of low-density fat representing the hilus. (c)T1-weighted MRI: fat in the hilus is hyperintense on thisMRI sequence as is subcutaneous fat. (d) Post-contrast, fatsaturation T1 MRI: the node enhances uniformly apartfrom the low signal fat in the hilus


commonest in middle-aged men and associ-ated with a non-vital tooth. Dentigerous cystsand KCOTs predominate in the second orthird decade, and both lesions occur mostfrequently in the posterior mandible, with50% of KCOTs being associated with anunerupted tooth and mimicking a dentigerouscyst. The keratin-rich debris in a KCOT givescharacteristic imaging findings on MRI andCT (Fig. 18).

The sequelae of acute or subacute dentalsepsis are normally evident clinically, butchronic presentations such as an inflammatorymass in the submandibular triangle, a cutane-ous sinus, or facial pain may be of uncertain

etiology, especially to physicians or surgeonswithout dental training (Fig. 19).

d. Maxillary sinus. The differential diagnosis ofopacification of a maxillary sinus on imaging iswide and depends on specific radiological find-ings, age of the patient, precipitating factors,and clinical features such as pain, swelling,discharge, or sensory changes (Whyte andChapeikin 2005).

It has been estimated that 10–12% of max-illary sinusitis is dental in origin, and this islikely to be an underestimation as otolaryngol-ogists performed these studies so subtle peri-apical pathology may have been missed(Mehra and Jeong 2008).

Fig. 11 Abnormal lymph nodes. Color Doppler US ofmetastatic papillary carcinoma of the thyroid gland tocervical nodes (a and b) in two different patients. Nodalblood flow is abnormal, being peripheral rather than central(hilar) as in normal nodes. Nodes may be more echogenicthan usual, lucent, or mixed as in these examples. The nodein (a) is predominantly echogenic with small cystic foci(short white arrows), and the node in (b) is predominantlycystic with micro-calcifications (white dotted arrows).

Multiple metastatic cervical nodes (dotted white oval) areshown on post-contrast CT, axial reconstructions (c and d).There is also an enlarged node in the tail of the left parotidgland (white arrow) due to undifferentiated carcinoma,probably from a skin primary. The nodes demonstrateheterogeneous enhancement and several have ill-definedmargins with edema of surrounding fat consistent withextra-capsular invasion

18 A. Whyte et al.

Mucous retention cysts are common inci-dental findings on imaging and are estimated tooccur in 30% of the population. Most areasymptomatic, and current clinical opinion isthat they are rarely of relevance (Fig. 20).Opportunistic colonization of the maxillarysinus may lead to development of afungal ball (aspergilloma) with characteristicincreased density and calcification on CT andoccasionally CBCT (Fig. 21). Maxillary sinusmucoceles are uncommon and invariably seenfollowing surgery involving the sinus wallsand mucosa.

The commonest malignant tumor of themaxillary sinus is squamous cell carcinoma(90% of cases). Cross-sectional imaging willdemonstrate an irregular mass destroying the

sinus walls and invading adjacent structuressuch as the cheek, deep fascial spaces,nasal cavity, ethmoid labyrinth, and orbit(Fig. 22). Sinonasal malignancy tends to beadvanced at presentation. MRI, in addition toCT, is essential in treatment planning as it moreoptimally demonstrates soft tissue invasionand large nerve perineural tumor spread(Baulch et al. 2015).

Imaging of Salivary Gland Disease

a) Imaging indications and recommendationsDisease entities may arise within the major

or, less commonly, minor salivary glands. Thehigh resolution of US provides excellent

Fig. 12 Lipoma in the left submandibular space (whitearrows) compressing the submandibular gland (SMG).The density of the lesion is identical to that of subcutane-ous fat. Post-contrast CT in the coronal (a) and axial

planes (b). Lipoma within the left parotid gland on T1 (c)and fat saturation T2-weighted MRI (d) (white arrows).The signal intensity of the lesion is identical to that ofsubcutaneous and deep fat on both sequences


definition of the salivary glands to evaluatesuspected duct obstruction, inflammation, or amass. Duct dilatation and calculi 3 mm orlarger in size can be reliably detected (Burkeet al. 2011). US-guided FNAC is reliable in thepreoperative diagnosis of mass as a primarysalivary gland neoplasm; however, the cyto-logical distinction between different histologi-cal subtypes can be challenging.

CT (or CBCT) can demonstrate calculi thatmay not be seen on US due to very small size orinaccessibility, and CT with contrast will alsodemonstrate duct dilatation, acute or chronicsialadenitis, cellulitis, or a collection (Fig. 23).

MRI is preferable to CT for further assess-ment of solid or cystic lesions that are incom-pletely visualized on US and lesions that aresuspected to be malignant on clinical, sono-graphic, or cytological grounds. Tumors inthe major salivary glands are usually moreclearly visualized using US or MRI thanCT. Following iodinated contrast, tumorsmay enhance such that there is minimaldifference in density (attenuation) between

the lesion and surrounding normal tissue.Detection can be improved by performing aninitial non-contrast CT scan. Pre-contrast CT isalso performed for better detection of subtlesmall calculi (Burke et al. 2011; Abdullahet al. 2013).

MRI provides optimal evaluation of tumorsarising in the major and minor salivary glands,especially malignant lesions exhibiting extra-capsular spread or large nerve perineural tumorinvolvement (Fig. 24). The advanced MRItechniques of DWI and dynamic contrastenhancement (DCE) can improve distinctionbetween benign and malignant parotid tumorsas well as between the commoner benignparotid tumors (Yabuuchi et al. 2003).

Sialography is occasionally indicated forrecurrent swelling and pain of the parotid orsubmandibular glands where US and CT havenot demonstrated a cause. Magnetic resonancesialography is a noninvasive alternative thatdoes not require cannulation and relies on visu-alizing fluid in a dilated duct (Burke et al.2011). Sialography is also performed to guide

Fig. 13 Tori and exostoses. Reconstructions from CBCTand CT demonstrate midline palatal exostoses (a), lingual

tori in the mandible (b), buccal exostoses in the maxilla (c),and mandible (d)

20 A. Whyte et al.

interventional imaging techniques used forextraction of calculi or dilatation of ductstrictures.

b) Unilateral swelling and/or painThese signs and symptoms usually indicate

obstruction of the duct of a major salivarygland by a calculus or a stricture with second-ary infection, glandular inflammation, andenlargement.

Sialolithiasis predominates in the 30–50year age group and is more common inmales. The saliva of the submandibular glandis viscous with a high mucous content pre-disposing to sialolithiasis. Approximately85% of calculi occur in the submandibulargland or duct (Fig. 25). About 50% of calculioccur distally in the duct and 31% at the hilusor in the gland. Calculi are multiple in 25% of

cases (Lustmann et al. 1990; Abdullah et al.2013). Strictures account for 22% of salivaryduct obstruction; they involve the parotid in75% of cases and are more common infemales. The causes of strictures are calculi,recurrent infection, autoimmune disease, andoccasionally trauma (Ngu et al. 2007).

The typical features of bacterial sialadenitisinclude duct dilatation, calculi in about half ofcases, and an enlarged gland which is hyper-vascular and of heterogeneous texture.Enlarged intra-glandular lymph nodes occurin the parotid gland, and enlarged reactive-appearing lymph nodes occur in the subman-dibular space adjacent to the inflamed salivarygland. Occasionally an intra-glandular abscessor pyocele of an obstructed duct may develop,necessitating surgical drainage.

Fig. 14 Fibrous dysplasia (open white arrow) involvingthe frontal process of the right maxilla (a) and more exten-sive involvement of the right maxilla and maxillary sinus(b). Both lesions demonstrate diffuse ground-glass

sclerosis. Longitudinal expansion of basal bone of the leftmandibular body (dotted white oval) shown on a croppedpanoramic radiograph (c) and axial CT (d). There is centrallucency surrounded by ground-glass sclerosis


Obstruction of a sublingual or minor sali-vary gland may result in formation ofa mucocele (Woo and Connor 2007;La’porte et al. 2011). If this is confined to thesublingual space of the floor of the mouth, it isknown as a simple ranula and will be evidentclinically (Fig. 26). A plunging ranula resultsfrom extension to the submandibular spacearound the posterior margin of mylohyoid orthrough a common developmental defect inmylohyoid (Kiesler et al. 2007). MRI is pre-ferred to CT to delineate the full extent of thesetrans-spatial lesions (Fig. 26).

c) Bilateral swellingSialosis refers to diffuse, non-inflammatory,

non-neoplastic recurrent enlargement of themajor salivary glands. It is uncommon andhas a variety of systemic associations includ-ing obesity, diabetes mellitus, and alcoholism(Fig. 27). Most commonly, the major salivaryglands are enlarged and infiltrated with fat.

Mikulicz’s disease is a distinct pathologicentity that is characterized by painless swellingof the parotid, submandibular, sublingual, andlacrimal glands. It is now considered to be oneof the manifestations of IgG4-related disease, asystemic disease that is characterized by abun-dant infiltration of IgG4-positive plasma cellsand lymphocytes with associated fibrosis, lead-ing to organ dysfunction. Involved glands areenlarged and hypervascular on post-contrastCT (Fig. 28). Multi-organ involvement is com-mon, and in the head and neck region, thisincludes inflammatory conditions involvingthe orbits, thyroid, sinonasal cavity and pitui-tary gland in addition to the salivary and lacri-mal glands (Fujita et al. 2012). PET-CToptimally demonstrates IgG4-related diseaseoutside of the head and neck, most frequentlyin the abdomen, where autoimmune pancreati-tis and sclerosing cholangitis are the most fre-quent manifestations.

Fig. 15 Ossifying fibroma in the right maxilla (a) and inthe third molar region of the left mandible (b and c). Thesetumors have similar internal appearances to fibrous

dysplasia but they expand perpendicular to the long axisof the involved bone and have a more clearly definedmargin

22 A. Whyte et al.

Juvenile recurrent parotitis (JRP) is an idi-opathic recurrent inflammatory condition ofthe parotid, occurring in children (Gadodiaet al. 2010). Boys are more commonlyaffected. Symptoms are more commonly uni-lateral than bilateral. In most cases, the symp-toms resolve spontaneously after puberty.Characteristic US features include a hyper-vascular gland containing multiple smallround hypoechoic foci representing sialectaticcavities. Sialectasis can also be demonstratedby MRI sialography and in the past by conven-tional sialography.

Sjögren’s syndrome (SS) is a chronic auto-immune disorder involving mainly the salivaryand lacrimal glands (but also other exocrineglands) with a characteristic clinical presenta-tion of dry mouth, dry eyes, and parotid swell-ing. It is the second most common autoimmune

disorder after rheumatoid arthritis and predom-inates in middle-aged females. In 40% ofcases, SS occurs in isolation, and in theremaining 60%, it is associated with severalother entities, the most common of whichare other connective tissue disorders and pul-monary diseases. In the early phase of thedisease, the salivary and lacrimal glands areenlarged and hypervascular. With disease pro-gression, the glands decrease in size andbecome heterogeneous in texture: atrophy ofthe submandibular glands is pronounced(Fig. 29). They contain small round hypo-echoic foci on US which are hypodense onCT and hyperintense on T2-weighted MRIimages. These reflect focal lymphocyticsialadenitis and/or sialectatic cavities. Accu-mulation of fat in chronic SS also contributesto the heterogeneity of glandular tissue and is

Fig. 16 Uncommon jaw tumors. (a and b) Non-Hodgkinlymphoma of the right maxilla: there is ill-defined bonedestruction from 12 to 16 inclusive as seen on this bonewindowCTscan. Open biopsy demonstrated a rubbery soft

tissue mass, confirmed as NHL. (c and d) Chondrogenicosteosarcoma of the left mandibular body. Bizarre newbone formation overlying the buccal aspect of the alveolarcrest in the 36 region with medullary sclerosis


best demonstrated on CT or T1-weighted MRIsequences (Burke et al. 2011; Abdullah et al.2013). Sialography and MR sialography dem-onstrate typical findings of multiple small cav-ities communicating with the terminal duct-acinar unit (sialectasis), as well as dilatationof the main duct and its proximal branches(Fig. 30). The diagnosis of SS requires histo-logical demonstration of focal lymphocyticsialadenitis in minor salivary glands (typicallyfrom a lip biopsy) plus a positive finding ofeither reduced salivary flow or positive imag-ing features, US being the preferred modality(Vitali et al. 2013). In SS, there is a 5–10% riskof development of mucosal-associated-lym-phoid tissue (MALT) lymphoma, a subset ofB-cell NHL. The involved glands are enlarged,and US demonstrates multiple hypoechoic fociwhich are usually hypervascular (Fig. 31).

d) Focal massFocal chronic sclerosing sialadenitis, also

known as Kuttner’s pseudotumor, usually pre-sents as a painless, palpable mass in the sub-mandibular gland and is a manifestation ofIgG4-related disease. It has characteristic USfeatures (Fig. 32), and FNAC may confirm thediagnosis, although cytological assessmentcan be challenging.

Salivary gland neoplasms are uncommon,accounting for 6% of head and neck tumors.Approximately 80% of tumors occur in theparotid gland, 10% in the submandibulargland, and the remainder in the sublingualand minor salivary glands. The palate is thecommonest site of minor salivary gland tumors(Burke et al. 2011; Abdullah et al. 2013).

The chance of a salivary gland neoplasmbeing malignant increases as the size of the

Fig. 17 Multiple osseous metastases. Initial presentationwith left TMJ pain. CT (a and b) showed permeativelucency and periosteal new bone formation of the posterioraspect of the junction of the condylar neck and ramus(black arrows). SPECT CT (e) combining low-dose CT

(c) with an isotope bone scan (d) demonstrates additionalmetastases in the articular eminence and central skull basenot visible on CT. The primary was a clinically occultcarcinoma of the kidney

24 A. Whyte et al.

affected salivary gland decreases. Thus,about 80% of parotid tumors are benign, butalmost half of all submandibular gland neo-plasms and most of those arising in the sub-lingual and minor salivary glands aremalignant. Malignant tumors are more com-mon in children.

Pleomorphic adenoma is the most commonbenign tumor and is seen in all age groups butpredominates in the superficial lobe of theparotid gland in middle-aged females. It tendsto be round with well-defined, smooth, or lob-ulated margins. Pleomorphic adenoma ishypoechoic on US with moderate vascularityand posterior acoustic enhancement. OnT2-weighted MRI, it is characteristicallyhyperintense (Fig. 33). Rapid increase in sizeof a previously stable lesion could indicatemalignant transformation which occurs in5–10% of pleomorphic adenomas.

Warthin’s tumor (adenolymphoma) is thesecond most common benign salivary glandneoplasm. It predominates in elderly malesmokers and is usually situated in the inferioraspect of the parotid gland (parotid tail), withtumors being multiple in 30% of cases.Warthin’s tumor tends to be ovoid in shapeand well defined. Cystic components are seenin 30% of cases (Fig. 34). A mural nodulewithin the cystic components is a describedfeature (Miao et al. 2015).

The malignant tumors most commonlyaffecting the major salivary glands aremucoepidermoid carcinoma, acinic cell carci-noma, and adenoid cystic carcinoma.Mucoepidermoid carcinoma predominates inthe parotid gland, and adenoid cystic carci-noma is the most common subtype in the sub-mandibular, sublingual, and minor salivaryglands. Small- or low-grade malignant tumors

Fig. 18 Keratocystic odontogenic tumor (KCOT). CT(oblique sagittal reconstruction) shows a large, uniloculatelucent lesion in the right posterior mandible (a). MRI

shows characteristic features: intermediate to low T2 signal(b, white arrows), high central T1 signal (c, dotted whiteoval), and restricted diffusion (d, dashed white oval)


may appear similar to benign lesions on imag-ing. Larger and more aggressive lesions tend tohave an irregular-shaped, ill-defined margins,heterogeneous texture, and hypervascularwith a “chaotic” vascular pattern on DopplerUS. Extracapsular spread and large nerve peri-neural involvement of the facial and/orauriculotemporal nerves require dedicatedpost-gadoliniumMRI for optimal preoperativeevaluation and predicting the necessity forpostoperative radiotherapy (Fig. 35).

Enlarged lymph nodes in the submandibulartriangle due tometastatic malignancy, infection,or other inflammation may not be distinguish-able from a submandibular salivary gland masson clinical grounds. US clarifies the diagnosisand can be used to guide FNAC (Fig. 36).

Accessory parotid tissue is present in21–56% of the population. When unilateral,this may be palpable. Salivary gland tumorsmay also arise in this tissue. Symmetricbenign masseteric hypertrophy may mimicparotid gland enlargement, and asymmetricenlargement may occasionally be mistakenfor a parotid mass on clinical examination(Fig. 37).

Imaging of Malignancy of the OralCavity

Oral cancer is common, accounting for 270,000new cases annually. It has a relatively low survivalrate, fewer than 50% of patients surviving more

Fig. 19 Chronic manifestations of periapical (PA) sepsis.An oblique sagittal CT reconstruction (a) demonstrates achronic PA abscess (dotted white arrow) associated with36. On a coronal soft tissue window CT reconstruction (b),there is a chronic inflammatory phlegmon in the left sub-mandibular space (white arrows) manifesting as a firm,painless swelling. An axial bone window CT scan (c)shows a chronic PA abscess associated with 34 (open

white arrow), a buccal cortical plate fistula, and sinustrack extending to skin (dashed white arrows) on the softtissue window image (d). US (e) was the preliminaryimaging requested for investigation of a dischargingsinus; the track is sonolucent (white dashed arrows), andthe cortical defect is clearly shown (dotted, double-headwhite arrow)

26 A. Whyte et al.

than 5 years (Arya et al. 2014). Etiological factorsinclude smoking, alcohol, areca (betel) nutchewing in India and elsewhere in Asia, a diet

lacking in antioxidants, poor oral hygiene, and toa lesser extent human papillomavirus (HPV)(Mirghani et al. 2015). HPV infection is far more

Fig. 20 Mucous retention cyst. Coronal bone-window CT(a) shows a well-defined dome-shaped lesion in the rightmaxillary sinus (white arrows) that is low density,

equivalent to fluid, on soft tissue windows (b). AxialT2-weighted MRI (c) confirms the hyperintense fluidwithin the cyst (black arrow)

Fig. 21 Aspergilloma (fungal ball) of the right maxillarysinus. The fungal ball is hyperdense on this soft tissuewindow CT (a) due to desiccated contents containingcalcification and heavy metals (dotted black oval). The

fungal ball has no mobile protons and appears as a signalvoid (dotted white oval) on T2-weighted MRI (b). It issurrounded by peripheral mucosal thickening which ishyperintense


important in the etiology of oropharyngeal carci-noma which tends to affect younger males withouta history of excessive intake of alcohol or use oftobacco when compared to older patients withHPV-negative carcinoma (Cantrell et al. 2013).Cystic nodal metastases are very suggestive ofHPV-positive disease which typically shows anexcellent response to chemoradiotherapy andgood prognosis.

More than 90% of malignant lesions of the oralcavity are squamous cell carcinomas (OC-SCC).Low-grade verrucous carcinomas and minor sali-vary gland tumors constitute the remainder. Themean age of occurrence of OC-SCC is 62 years. Itis twice as common in men. There is a 20-fold

increased risk of having a second oral cancer, aswell as an increased risk of carcinoma elsewherein the upper aerodigestive tract. The oral tongue isthe most common subsite of OC-SCC, accountingfor 29%, followed by the lower lip (19%), thefloor of mouth, and then other subsites (gingivae,buccal mucosa, hard palate, and retromolar tri-gone). There has been a substantial decrease inthe incidence of SCC of the lip, which has arelatively high 5-year survival of 90% and unlikeother oral cancers is strongly related to sunlightexposure.

Based on the combination of staging of theprimary tumor (T), nodal (N), and distant metas-tases (M), OC-SCC is divided into stages I, II, III,

Fig. 22 Squamous cell carcinoma of the left maxillarysinus. Coronal CT (a) demonstrates pan sinus opacificationand destruction of the inferolateral wall of the left maxil-lary sinus (open white arrow). Ill-defined soft tissueextends anteriorly into the cheek and posterolaterally intothe infratemporal fossa (white arrows) on this soft tissue

window axial CT reconstruction (b). Fat saturation T2MRIin the coronal (c) and axial (d) planes depict ill-definedtumor of intermediate signal (open white arrows). Thesuperior contrast resolution of MRI (as compared withCT) allows distinction between tumor and the high-signalinflammatory mucosal thickening

28 A. Whyte et al.

IVA, IVB, and IVC. Early stages (I and II) aretreated with a single treatment modality, eithersurgery or radiotherapy. Local disease controland overall survival are similar, but surgery isthe preferred modality because of the significantside effects of radiotherapy.

OC-SCC is almost always preceded by visiblechanges in oral mucosa, and simple screening byperiodic oral examination has been shown to be aneffective screening method for detecting the 36%of oral cancers that present at an early stage: I andII. However, most OC-SCC present at anadvanced stage (III and IV) and have a poor prog-nosis. In an effort to achieve optimal locoregionalcontrol, advanced disease is treated with multi-modality therapy: radical surgery followed byconcurrent chemoradiation.

Imaging is essential to stage accurately notonly the primary tumor (T) but also for N- andM staging. Nodal metastases are seen in 45% ofOC-SCC at presentation and are the single mostimportant prognostic factor, halving survival. Ifnodal metastases (N+) are present, the neck istreated with a neck dissection. If imaging showsno evidence of nodal metastases (N0), the optionsare either regular observation (including repeatimaging) or an elective neck dissection/

irradiation, the latter approach beingrecommended for advanced primary tumors(stages III and IV).

a. Imaging in the primary assessment ofOC-SCC. Imaging can be used to stage theprimary tumor (T), assess cervical lymphnodes (N), and exclude distant metastases (M).

Primary tumor (T-staging): OC-SCC isdiagnosed by clinical examination and biopsy.Imaging is required to evaluate submucosal ordeep soft tissue spread which may not be evi-dent clinically, to exclude involvement of crit-ical neurovascular structures (which areadverse prognostic findings) and to confirm orexclude osseous involvement of the mandibleor maxilla.

Post-contrast MDCT is the most commonlyused imaging technique and is the optimalmethod for evaluating mandibular invasion,which is a priority with gingival, buccal,retromolar trigone, and lip SCC (Arya et al.2013). The volume data set of the scan includesthe skull base to the mediastinum (trachealcarina) with the images being reconstructedonto soft tissue and bone algorithms and sub-sequently evaluated on a workstation allowing

Fig. 23 Submandibular calculi. CBCT (a) and CT (b)demonstrate multiple calculi in the submandibular duct(white arrows). Several calculi within the expected

position of the right intraglandular duct (c) on a croppedpanoramic tomogram are situated within a minimallydilated duct on US (d)


multiplanar reconstructions, cross-referencingin the different planes and comparison withadditional imaging studies. CBCT also accu-rately depicts osseous invasion, but the absenceof soft tissue contrast precludes the routine useof this technique. The “puffed-cheek” tech-nique is routinely used when scanningOC-SCC: the patient distends the cheeks withair (while breathing quietly through the nose),moving apposing mucosal surfaces away fromthe primary tumor, which is hence more clearlyvisualized (Fig. 38).

MRI is optimal for evaluation of tongueand floor of mouth SCC where softtissue contrast resolution is paramount. MRIis also useful in cases where CT is degraded

by beam-hardening (streak) artefact fromdental restorations. High-resolution contrast-enhanced MRI is mandatory in cases whereperineural tumor spread is suspected (seebelow).

Intraoral US using a small high-frequencyprobe is a fast and reliable means of measuringthe dimensions and depth of tongue SCC withthe same accuracy as MRI (Yesuratnam et al.2014). A tumor thickness of greater than 4 mmis associated with a significant risk of nodalmicro-metastases that are not detected by imag-ing, and the evidence-based consensus is thatprimary prophylactic neck dissection should beperformed in these cases (Fig. 39). Biopsy-related changes can lead to overestimation of

Fig. 24 Adenoid cystic carcinoma of the right sublingualsalivary gland. There is a large ovoid mass (white arrows)expanding the right sublingual space, arising from thesublingual salivary gland. The mass deviates the rightgenial muscles and midline fatty septum of the tongue tothe left (white dotted arrow) as seen on the coronalT1-weighted images (a and d). Following contrast, thetumor demonstrates heterogeneous enhancement (b). It isof variable, intermediate-to-high signal on the fat

saturation T2 sequence (c). The magnified T1 image (d)demonstrates the normal neurovascular bundle (lingualnerve, hypoglossal nerve, and lingual vein) in the leftsublingual space (dotted white oval) but not on the right.US-guided FNAC (e) of the tumor (white arrows): thebiopsy needle is clearly visualized (dashed white arrows).Histological evaluation of the tumor following surgicalexcision demonstrated perineural involvement of the lin-gual nerve

30 A. Whyte et al.

tumor depth, and it is therefore important thatimaging be performed prior to biopsy.

For most OC-SCC, there is little benefit insupplementing CT or MRI with PET-CT forstaging of the primary tumor. This differsfrom oropharyngeal SCC, where small oroccult primary lesions are relatively commonin subsites such as the tonsil and tongue base,and a common clinical presentation is withcervical lymphadenopathy, especially inpatients with HPV-positive disease. In thesecases, PET-CT can be used to detect the occultprimary lesion as well as the extent of nodalmetastases (Fig. 9).

The patterns of soft tissue spread ofOC-SCC depend on the location of the primary

lesion. Tongue and floor of mouth carcinomascan involve extrinsic tongue musculature,cross the midline, and infiltrate the contents ofthe sublingual space: lingual and hypoglossalnerves, lingual vein and artery, submandibularduct, and sublingual salivary gland (Fig. 40).OC-SCC of all types, especially retromolartrigone tumors, can spread posteriorly to thetongue base (oropharynx) and when veryadvanced, to the carotid sheath, masticatorspace, parapharyngeal space, and superiorlyto the skull base giving the highest grade ofT-staging: T4b. In OC-SCC, perineural tumorspread occurs in 5–10% of cases and is definedas macroscopic tumor spread away from theprimary site along a large nerve which

Fig. 25 Salivary gland calculi and sequelae. Post-contrastCT in the axial (a and c) and oblique sagittal (b and d)planes. Several small calculi in the mildly dilated rightsubmandibular duct (a and b) associated with a hyper-vascular right submandibular salivary gland (SMG)

indicating sialadenitis. Images (c) and (d) demonstrate alarge calculus (black arrow) in the posterior margin of alarge pyocele (black dotted arrows) in the enlarged andhypervascular right submandibular salivary gland (whitedotted arrows). Multiple additional calculi are present


represents the path of least resistance. This is aseparate entity to “perineural invasion” ofsmall nerves, which is reported on histopatho-logical evaluation of excision specimens and isconfined to the main tumor bulk. MRI withcontrast is mandatory to accurately stagethese advanced tumors and determine if exten-sive surgical resection is a realistic treatmentoption (Baulch et al. 2015).

Floor of mouth, gingival, retromolar tri-gone, buccal, and palatal SCC have a predilec-tion for bone invasion (Fig. 41). Multiplestudies have evaluated the sensitivity and spec-ificity of various imaging modalities in pre-dicting mandibular or maxillary infiltration by

tumor. The OPG has low specificity for man-dibular erosion but is useful for providing anoverview of the dental status prior to treatmentfor OC-SCC. SPECT bone radioisotope scan-ning has 100% sensitivity for bone invasion butvery low specificity as it is unreliable indistinguishing between involvement by tumorand concurrent dental disease. High-resolution,multiplanar reconstructions from a stagingMDCT are highly accurate in assessing boneinvasion by OC-SCC: 94% sensitivity and 90%specificity are reported for the evaluation ofmandibular invasion by retromolar trigone car-cinoma (Arya et al. 2013). MRI also has veryhigh sensitivity but much lower specificity;

Fig. 26 Ranula: this represents a mucocele of the sublin-gual salivary gland. Post-contrast CT in the axial (a) andcoronal (b) planes demonstrating a simple ranula (blackdashed arrows) in the right sublingual space of the floor ofthe mouth as a fluid-density, thin-walled lesion whichcrosses the midline anteriorly. The sublingual salivaryglands (SLG) are demonstrated bilaterally. Fat saturation

T2 axial (c) and coronal (d) MRI scans showing a fluidsignal intensity plunging ranula which extends around theposterolateral border of mylohyoid (myh) from the sublin-gual gland into the submandibular space (white dashedarrow). The ranula displaces the submandibular gland(SMG) inferiorly

32 A. Whyte et al.

it overestimates bone invasion presumablybecause of tumor-related edema which wouldnot be detected on CT scanning because of itslower contrast resolution (Arya et al. 2014).

Neck nodal metastases (N-staging): EitherCT or MRI can be used to stage both the pri-mary site and the neck nodes. The choicedepends mainly on the subsite of the primarylesion in the oral cavity (the superior contrastresolution of MRI being advantageous at sev-eral sites, as discussed above). The benefits ofCT over MRI include wider availability, lowercost, and much faster scan times (and thereforeless chance of patient movement).

Imaging techniques for evaluation of nodalmetastases have been discussed previously. Inmost studies, CT performs as well as or betterthan MRI in staging the neck (Arya et al.2014). US with FNAC is the most sensitive

and specific technique in the detection of cer-vical nodal metastases in head and neck cancer.However, it is not widely available in somecountries, it is time-consuming and requiresconsiderable expertise in the sonographicassessment and selection of nodes to biopsy,the imaging-guided procedure itself, and alsothe cytological evaluation. US-guided FNACcan be used selectively after CTor MRI stagingfor evaluation of suspicious or equivocal cer-vical nodes where the result is likely to altermanagement (Fig. 36). Sentinel node biopsy inearly stage OC-SCC shows great promise inpredicting the likelihood of nodal metastaseswith an overall sensitivity of 93% (Alkureishiet al. 2010).

Several studies have shown no additionalvalue in the use of PET-CT over CT and MRIin evaluating the clinically negative neck or the

Fig. 27 Sialosis. Post-contrast axial CT at the level ofthe parotid (a) and submandibular (b) salivaryglands. The glands are enlarged and of low attenuation

secondary to infiltration with fat as shown on this coronalreconstruction (c)


primary tumor. The current role of PET-CT inhead and neck SCC for pretreatment nodalevaluation lies in delineation of the extent ofregional nodal metastases in the N-positiveneck which could alter radiation therapy fieldsor the extent of neck dissection (Enders et al.2011; Castaldi et al. 2013).

Distant metastases (M-staging): The inci-dence of distant metastases at presentation ofOC-SCC is relatively low; it is more commonwith locally advanced tumors and those withextensive nodal spread (Arya et al. 2014). Thefrequently involved organs are the lungs, bone,and liver. PET-CT is the optimal technique fordemonstrating metastases and second primarytumors. If PET-CT is unavailable, CT of thechest and upper abdomen can be performed.

b. Assessment of treated OC-SCC. Early-stageOC-SCC is treated with a single modality,either surgery or radiotherapy. For locallyadvanced cancer without distant metastases,multimodality treatment is performed: surgeryfollowed by adjuvant radiation therapy, with orwithout chemotherapy, depending on the his-topathological findings. The aim of multi-modality treatment is to optimize cure rateswhile preserving speech and swallowing func-tion with an acceptable cosmetic result.

Curative resection requires wide local exci-sion to obtain negative surgical margins. Smalltumors of the lateral tongue can be treated withthis technique. More extensive lesions requirea partial or total glossectomy resulting in asym-metry on post-surgical CT or MRI. If 30% or

Fig. 28 Mikulicz disease (IgG4-related disease). Post-contrast CT demonstrates homogeneous attenuation andenhancement of the major salivary glands. (a) Axial of

the parotid glands, (b) axial of the submandibular glands,and (c) coronal of the major salivary glands

34 A. Whyte et al.

Fig. 29 Sjögren’s syndrome (SS). In the subacute andacute phase of SS the inflamed salivary glands areenlarged. Color Doppler US (a) demonstrates profusehypervascularity of an enlarged, hypoechoic gland. In thechronic phase (b), the glands contain hypoechoic foci(white arrows) representing lymphoepithelial aggregates

or dilated peripheral ducts and acini (sialectasis). Theechogenic dots (white dotted arrows) are microcalculi.Axial CT (c) and coronal T1-weighted MRI (d) of chronicSS demonstrate atrophic, fat-replaced glands with a nodu-lar texture. PG = parotid gland, SMG = submandibulargland

Fig. 30 Sjögren’s syndrome (SS). Modified MRIsialogram (thin heavily T2-weighted sequence) of chronicSS (a and b) demonstrate marked dilatation of the mainduct with “beading” due to strictures (white arrows). The

gland texture is heterogeneous due to fat and hyperintensefoci of varying size. The small, punctate hyperintense fociprobably represent sialectatic cavities (white dottedarrows)


more volume loss following excision isexpected, reconstruction is planned. Foradvanced OC-SCC requiring extensive resec-tion of soft tissue and bone, complex recon-structive techniques are often required to closethe defect and maintain function. Cliniciansand radiologists should have a basic under-standing of both resection and reconstructiontechniques.

Three main types of flap are used in recon-struction: local, pedicle, and free flaps. Softtissue flaps initially appear as a pseudomassof similar attenuation and signal intensity tomuscle on CT and MRI, respectively(Fig. 42). These flaps will gradually showdenervation atrophy, which causes volumeloss and fatty replacement of the muscle(Saito et al. 2012).

Tumor recurrence usually occurs within thefirst 2 years after treatment, most commonly inthe surgical bed or at its margins, including inthe flap used for reconstruction. Clinical eval-uation will detect superficial recurrence, butrecurrent tumor deep to a reconstruction flapis not visible and is usually impalpable. Recur-rent tumor usually has an infiltrative pattern ofgrowth and demonstrates heterogeneousenhancement on CT or MRI. The major differ-ential is of vascularized scar (early fibrosis).Follow-up imaging will show contraction ofvascularized scar whereas tumor will progress.In addition, the apparent diffusion coefficient(ADC) measured on DWI as part of an MRIallows distinction between tumor and scar(Thoeny et al. 2012; Payne et al. 2015). PET-CT usually shows more intense metabolic

Fig. 31 Sjögren’s syndrome (SS) and MALT lymphoma.MALT lymphoma may develop in patients with chronicSS. The parotid glands (black dotted ovals) are enlarged bymultiple round lesions of varying size representing lym-phoma on T1-weighted MRI axial (a) and coronal (b)

scans. The lymphoma deposits (white arrows) are mildlyhyperintense on this fat saturation T2-weighted sequence(c) and hypoechoic and hypervascular (white dashedarrows) on color Doppler US (d) of the same patient

36 A. Whyte et al.

activity in recurrent tumor than vascularizedscar, but distinction may still be difficult.

The three major types of neck dissection areradical, modified radical, and selective neck dis-sections. Both radical and the more conserva-tive, modified radical neck dissections removeall of the ipsilateral neck nodes. A selective neckdissection is limited to removal of a group orgroups of nodes within the neck and results inlower morbidity. The main indication for radicalneck dissection is extensive metastatic cervicallymphadenopathy, extracapsular spread of nodaltumor, and invasion into adjacent tissues. Imag-ing demonstrates asymmetry of the neck second-ary to unilateral resection of additional structuresin addition to cervical nodes. Fat planes areobliterated, and CT and MRI demonstrate a cir-cumferential “cuff” of scar around the carotidsheath (Fig. 42).

Radiation for head and neck cancer primar-ily consists of external beam radiotherapy. Thisuses photon beam (or less commonly electronbeam, or proton beam) radiation deliveredfrom a source external to the patient, typicallywith a dose of 66–70 Gy delivered daily over aperiod of 7 weeks. In the past 15 years, inten-sity-modulated radiotherapy (IMRT) hasbecome the favored technique for administer-ing external beam photon therapy to patientswith head and neck cancer because it providesbetter conformation of radiation dose to thetumor while sparing adjacent organs.

Early changes after radiation therapyare those occurring up to 90 days after com-pletion of treatment and include edemaand inflammation which usually resolvewithin several weeks. Imaging demonstratesmucositis, diffuse soft tissue edema, and

Fig. 32 Kuttner’s pseudotumor (IgG4-related disease).Post-contrast CT coronal reconstruction (a) showing ahypervascular protuberance from the inferolateral marginof the left submandibular gland (SMG). US (b) shows ageographical-shaped lesion of reduced echogenicity (white

dotted arrows) which is also hypervascular on color Dopp-ler analysis (c). US-guided FNAC (open white arrows in d)confirmed chronic sclerosing focal sialadenitis (Kuttner’spseudotumor)


enlargement and hypervascularity of the majorsalivary glands.

Late complications are defined as sequelaeof treatment that manifest more than 90 daysafter the completion of radiation therapy. Theymay take months to years to emerge and areoften irreversible. They include salivary glandatrophy, osteoradionecrosis, soft tissue necro-sis, and radiation-induced vascular complica-tions (Saito et al. 2012).

Osteoradionecrosis (ORN) is a condition inwhich irradiated bone becomes devitalized andexposed through the overlying skin or mucosa,persisting without healing for at least 3 months.A meta-analysis of the literature reported a 7%incidence of ORN after conventional radio-therapy (Deshpande et al. 2015). It usually

presents 1–3 years after radiation therapy andmost commonly occurs in patients who receivehigh radiation doses (greater than 70Gy) orradiotherapy after surgery. Later presentationof ORN can occur and is thought to be due tolow-grade trauma in a chronic hypoxic envi-ronment. The mandible is the most commonsite of ORN because of its superficial locationand relatively poor blood supply. Additionalrisk factors include neo-adjuvant chemother-apy, poor oral hygiene, periodontitis, alcohol,and tobacco use as well as the proximity of theprimary tumor to the mandible. The currenttrend to the use of IMRT reduces the dose tothe mandible and therefore the risk of ORN.

CT is the preferred imaging modality, andtypical imaging findings include cortical

Fig. 33 Pleomorphic adenoma of the left parotid gland.T1 (a), fat saturation T2 (b), and post-contrast T1 fatsaturation (c) axial MRI scans demonstrating a well-

defined mass in the left parotid gland (white dottedarrows). The tumor has a lobulated margin and is markedlyhyperintense on the T2-weighted sequence

38 A. Whyte et al.

erosions, medullary lysis, surrounding sclero-sis, mixed lysis and sclerosis, bone fragmenta-tion, sclerotic sequestra, and gas within a bonecavity (Fig. 43). Pathological fractures mayoccur. Soft tissue abnormalities can occur inORN, including enlargement and enhancementof the adjacent muscles of mastication to forma pseudomass.

Distinction from recurrent tumor and infec-tion may be difficult; cortical erosions distantfrom a soft tissue mass or the site of the originaltumor are more suggestive of ORN as is a lateonset (over 2 years after the completion ofradiotherapy). Routine MRI and PET-CT donot improve specificity, but diffusion-weightedimaging (DWI) can improve distinction

between recurrent tumor and ORN (Thoenyet al. 2012).

c. Imaging guidelines. Recommendations forimaging can be divided into the initial assess-ment and subsequent follow-up of treatedOC-SCC. A delay of 12 weeks after surgeryor the completion of radiotherapy decreases thepost-treatment sequelae to a stable and accept-able level for evaluation.

Initial assessment:

• MDCT of the oral cavity and neck (skull baseto carina).

Post-contrast, puffed-cheek, and bone and softtissue reconstructions

Fig. 34 Multiple Warthin’s tumors. Three tumors arepresent, two in the left parotid gland and single lesion inthe right parotid gland (white arrows). Post-contrast CT (a,b, and d) demonstrates that all lesions are ovoid in shapeand situated in the inferior half of each gland. The tumorsdemonstrate moderate contrast enhancement. The largest

tumor in the inferior half of the left parotid gland (a) is alsodepicted on color Doppler US (c) which demonstrates alobulated contour, internal vascularity (color flow), andsonolucent foci corresponding to fluid on the CT (whitedashed arrows)


• MRI added for tongue and floor of mouthtumors, or when CT degraded by severe streakartefact, or when advanced tumor and peri-neural tumor suspected.

• US-guided FNA of suspicious neck nodes,where this will alter management.

• PET-CT added for advanced tumors.• DPT for general dental assessment.

Post-treatment assessment (surveillanceimaging):

• Baseline MDCTof the oral cavity and neck forearly stage tumors treated with a single modal-ity, 12 weeks post-treatment.

• PET-CT added for advanced tumors, 12 weekspost-treatment.

• For the first 2 years, repeat imaging accordingto local guidelines; most institutions wouldrepeat imaging at least twice.

Restaging for clinically suspected primary(T) or nodal (N) recurrence:

Fig. 35 Mucoepidermoid carcinoma of the left parotidgland. A slightly ill-defined mass (white arrows) withfoci of calcification (black arrow) in the medial margin ofthe tumor is seen on post-contrast CT (a), T1-weighted (b),and post-contrast T1-weighted fat-saturated (c) MRI. Athickened and enhancing facial nerve branch is present at

the anterior margin of the tumor consistent with large nerveperineural tumor spread (white dotted arrows). Metastaticnodes (white dashed ovals in c and d) are present bothwithin the inferior aspect of the gland and in the upper neckdeep to the left sternomastoid muscle

40 A. Whyte et al.

• PET-CT for T, N, and M assessment• MRI for optimal staging of the recurrent pri-

mary tumor (T)• Surgical biopsy for recurrent T and US-guided

FNAC for N

Imaging of Osteomyelitisand Osteonecrosis of the Jaws

Osteomyelitis represents inflammation of thebone, commencing in the medullary cavity andextending to the cortex and periosteum. It pre-dominates in adult males and in the posteriormandible. Acute osteomyelitis of the jaws is

usually due to pyogenic infection resulting fromperiapical sepsis. Periodontitis, pericoronitis,and compound fractures are other potentialcauses. The prompt and widespread use of anti-biotics for dental sepsis has led to a markeddecline in the incidence of acute osteomyelitis.Inflammatory edema leads to radiolucency of theinvolved bone, but this takes 2–3 weeks to bevisible on a radiograph. CT is more sensitive butthe most accurate means of establishing the diag-nosis of osseous edema are MRI and isotopebone scans (ideally using SPECT-CT). Labeledwhite cell scans can confirm that the inflamma-tion is due to infection (Boeddinghaus andWhyte 2008).

Fig. 36 SCC of the floor of the mouth with metastaticnodes. Post-contrast axial CT (a) shows a small primarylesion of the anterior floor of the mouth (white openarrow). There is extensive metastatic lymphadenopathy(b and c) in the left submandibular space (white arrows)

compressing the salivary gland (SMG) and in the leftjugulodigastric region (dotted white arrows). US-guidedFNAC of the left jugulodigastric node (d) confirmed thediagnosis


If osseous inflammation persists for more than4 weeks due to inadequate treatment, bacterialload, or impaired host resistance, the condition isknown as secondary chronic osteomyelitis(chronic suppurative osteomyelitis). CToptimallydemonstrates mixed sclerosis and lysis withinmarrow, periosteal new bone formation, scleroticsequestra of dead bone, and inflammatory swell-ing of the muscles of mastication (Fig. 44).

Primary chronic osteomyelitis (chronicnon-suppurative osteomyelitis) is not precededby acute infection. Sclerosis is the dominant fea-ture, and it is of unknown cause. Pus and sequestra

are absent. It includes several conditions, whichcan be divided into juvenile and adult forms andsecondarily by variants which only involve themandible and those which affect bones outsidethe jaws.

Osteonecrosis of the jaws (ONJ) was initiallydescribed in patients who had undergone treat-ment with intravenous bisphosphonates (hencebisphosphonate-related ONJ or BRONJ), usuallyto manage complications of metastatic malig-nancy to the bone. Bisphosphonates are oneclass of antiresorptive agents that cause ONJ, theother being denosumab, which is an inhibitor of

Fig. 37 Masseteric hypertrophy. T1 coronal (a) and T2axial (b) MRI demonstrating symmetric masseteric(M) hypertrophy. There is inferolateral displacement of

accessory parotid tissue. The medial pterygoid (mp) andtemporalis (t) muscles are of normal size in this individual

Fig. 38 “Puffed-cheek” technique for mucosal malig-nancy. Post-contrast CT with oral distension in the axialand coronal plane with soft tissue (a) and bone (b)

reconstructions. There is a small protuberant SCC at thejunction of gingiva and mucosa in the 37/38 region (openwhite arrows). No bone erosion is evident

42 A. Whyte et al.

the receptor activator of nuclear factor kappa-Bligand (RANKL). Antiangiogenic drugs (e.g.,bevacizumab) block the formation of new bloodvessels and are a relatively new means of treatingcertain cancers; they can also cause ONJ. Theremodeling rate of alveolar bone exceeds mostother skeletal sites. The jaws are vulnerable tomedication which inhibit bone turnover. In addi-tion, antiangiogenic drugs predispose to avascularnecrosis. Inflammation, infection, and mucosaltrauma are strongly associated with ONJ, andtooth extraction is a common precipitating event.

The current position paper on ONJ from theAmerican Academy of Oral and MaxillofacialSurgeons in 2014 recommends the term “medica-tion-related osteonecrosis of the jaws” (MRONJ).Patients have MRONJ if the following criteria arefulfilled (Ruggiero et al. 2014):

1. Treatment with antiresorptive or anti-angiogenic agents

2. Exposed bone or bone that can be probedthrough a fistula in the maxillofacial regionthat has persisted for more than 8 weeks

3. No history of radiation and no evidence ofmetastases to the jaws

The radiological appearances of ONJare similar to osteoradionecrosis; bothconditions are significantly more commonin the mandible. The appearance of ONJon radiographs and CT is variable andincludes ill-defined areas of lucency, corticalpermeation and destruction, sequestra, aperiosteal reaction, sclerosis, and anon-healed extraction socket (Fig. 45). Path-ological fractures can occur in all types ofosteonecrosis.

Fig. 39 Tongue cancer. Post-contrast CT (a) and post-contrast T1-weighted MRI (b) in the coronal plane dem-onstrate a small tumor of the right lateral tongue (whitearrows). Comparison of magnified MRI (c) and intraoral

US (d) in demonstrating tumor depth and diameter forprognosis and staging. Both methods indicate a depth of7 mm (white dotted lines)


Imaging of TemporomandibularDisorders

The TMJ can be involved by a spectrum of disor-ders similar or identical to those in other synovialjoints. Temporomandibular disorder (TMD) is acollective term involving several disorders ofmuscles, the TMJ, or both. Patients with TMJdisorders most frequently present with pain, lim-ited or asymmetric mandibular motion, and jointnoises.

The prevalence of TMJ symptoms is high, butonly 5–10% of those with symptoms require

treatment, and it has been estimated that in up to40% of patients, the symptoms resolve spontane-ously. TMDs primarily involve young- to middle-aged patients and are significantly more commonin females. The etiology of these disorders iscomplex and multifactorial (Scrivani et al. 2008)and is detailed in the chapters on TMD.

The most common TMDs in adults are masti-catory myalgia, disc displacement, intra-articularinflammation, osteoarthritis, and rheumatoidarthritis. Other disorders specifically affectingchildren and teenagers are juvenile idiopathicarthritis (JIA) and the entity of idiopathic condylar

Fig. 40 Spread of SSC of the floor of the mouth. Normalanatomy of the floor of the mouth on a T1-weighted MRIimage (a) where slg = sublingual salivary gland,SMG = submandibular salivary gland, gm = genial mus-cles, and mh = mylohyoid. The mandibular cortex ishypointense (black) and the marrow is hyperintense(white) due to its fat content. Post-contrast CT (b) and

post-contrast T1-weighted MRI (c) demonstrate a largeSCC of the anterior floor of the mouth with midline cross-over (white arrows) with subtle erosion of the lingualcortex (white open arrow in c). The tumor is more clearlydemarcated by MRI. A larger tumor with extensive infil-tration of the anterior mandible and spread into the labialsulcus is demonstrated on axial post-contrast CT (d)

44 A. Whyte et al.

resorption (ICR). Both can cause TMJ pain andlimited opening.

a. Indications for imaging of TMDs. Imaging israrely indicated for masticatory myalgia unlessthere is a history of a precipitating event, suchas dental treatment or trauma, or if there areother symptoms and signs such as significanttrismus (Fig. 46).

Internal derangement is defined as interfer-ence with a joint’s smooth action and in theTMJ is most commonly due to disc displace-ment. MRI studies have shown mild degrees ofdisc displacement in one third of asymptomaticvolunteers, but disc displacement is more com-mon in symptomatic patients, and the degree of

disc displacement is more severe (Petscavage-Thomas and Walker 2014). Although mostpatients improve on long-term follow-up, MRIevidence of advanced internal derangement andarthritis is associated with a poor prognosis. Theprincipal indications for imaging includesuspected advanced internal derangement, arthri-tis, failure of nonsurgical treatments, and whenthe diagnosis of TMD is in doubt, for example,when there is pain of an atypical character, apalpable mass, and sensory or motordysfunction.

b. Comparison of imaging modalities. The OPGprovides an overview of the dentition and max-illofacial region. If of high quality, it is auseful screen for moderate to marked TMJ

Fig. 41 Osseous invasion by oral carcinoma. Post-contrast CT scan shows SCC of the right maxillary buccalmucosa/gingiva (white arrows) eroding the alveolar pro-cess shown on axial soft tissue CT (a) and extending intothe inferior aspect of the right maxillary sinus shown on acoronal bone-algorithm reconstruction (b). A right

retromolar trigone SCC smoothly erodes the lingual aspectof the right retromolar fossa shown on axial (c) and coronal(d) CT. Tumor spreads posteromedially along thepterygomandibular raphe toward the oropharynx (whitedotted arrows). There is a small metastatic node in theright submandibular triangle (N)


arthritis and asymmetric condylar morphologyand size.

CBCT has replaced conventional tomographyas an imaging technique that provides very goodbone detail and multiplanar 2D and 3D recon-structions of the TMJ and adjacent skull base butno information concerning the soft tissue compo-nents of the joint. Its advantages and disadvan-tages have been discussed previously.Widespreadavailability of CBCT to the dental profession hasbeen associated with a proliferation in dental and

maxillofacial imaging, with numerous publica-tions pertaining to its value in assessing TMJdisorders. Overall, CBCT has a similar, high accu-racy to conventional CT in detecting corticalabnormalities of the TMJ (Larheim et al. 2015).A major review article analyzing the publishedliterature concluded that there was a lack ofknowledge about the impact of CBCT changingthe outcome of patents with TMJ disorders(Palconet et al. 2012).

Current CT technology (Multidetector CT:MDCT) also provides multiplanar 2D and 3D

Fig. 42 Postsurgical appearances of the neck. Post-contrast CT (a) demonstrates a left radical neck dissection(RND). An RND requires removal of sternomastoid (SM),the internal jugular vein (IJV), and the cervical nodes(black dashed oval). The left common carotid arteryremains in situ surrounded by low-density scar. Post-contrast CT (b) shows a right modified neck dissection(MND). Either the IJV, SM, or both are preserved with anMND, and in this case the right SM has been removed inaddition to the nodal chain (black dotted oval). In both

cases (a and b), there has been compensatory hypertrophyof the levator scapulae muscle on the side of surgery whichcan simulate a “mass” on clinical examination. A series ofaxial post-contrast CT images (c) from superior inferiorshows a right pectoralis major flap (white dotted arrows)situated anterior to the vessels of the carotid sheath, trans-posed to replace a right parotidectomy defect (not shown).The superior portion of the graft in the parotid bed consistsof fat and the right sternomastoid has been removed as partof a MND

46 A. Whyte et al.

bone detail of the TMJ similar to or better thanCBCT mainly due to the fact that, although CT isof lower spatial resolution than CBCT, CT imagesare less affected by image noise from the densebone of the skull base. The radiation dose ofMDCT is usually higher than that of CBCT, butas previously discussed, this difference is not asgreat as in the past (Boeddinghaus and Whyte2013). The major advantage of CT over CBCT isits far superior soft tissue contrast, which allowsdetection of significant internal derangement andextra-articular pathology (including neoplasticcauses of TMJ pain and otalgia) that would notbe detected on CBCT (Fig. 47).

Magnetic resonance imaging (MRI) is the opti-mal imaging technique for evaluating patientswith TMJ disorders (Whyte et al. 2006; Hasanand Abdelrahman 2014; Petscavage-Thomas andWalker 2014). The excellent soft tissue contrast

combined with the high signal-to-noise ratio ofmodern scanners using dedicated surface coilsand a high magnetic field strength of 3 Tesla pro-vides exquisite soft tissue, cortical, and bone mar-row evaluation. The size, morphology, position,and integrity of the disc can be assessed as canthe bilaminar zone and lateral ligament. MRIis the only technique reliably showing all thesoft tissue sequelae of either acute or chronicinflammation including joint fluid, intra-articularsynovitis, capsular or peri-capsular edema, andstructural changes in the lateral pterygoid muscle.CT and especially CBCT have been extensivelyreported to be superior to MRI in evaluating thebone including remodeling, cortical changes,sclerosis, erosions, and osteophytes (Larheimet al. 2015). However, most of this evidencecomes from studies performed prior to 2010,including a frequently referenced study from

Fig. 43 Osteoradionecrosis (ORN). Initial post-contrastCT (a) showing a large tongue base SCC (black oval) withbilateral metastatic lymphadenopathy (black arrows). Nodental or bony abnormality was evident (b). 3 years fol-lowing radiotherapy, there is extensive bilateral ORN

(white dashed ovals) of the mandible with a non-healed36 socket (c). ORNwas significantly more extensive on theright. As shown on this oblique sagittal reconstruction (d),there is early ORN of the right posterior maxilla (whitedashed ovals)


1987 comparing CT and MRI (Westesson et al.1987). With state-of-the-art MRI, there is accu-rate depiction of cortical integrity, adaptivechanges to internal derangement, erosions, andestablished osteoarthritis. Erosions (especiallywithin the condyle) are commonly associatedwith marrow edema (which is not visible on CTor CBCT), and both correlate with the severity ofsymptoms. CT (or CBCT) may still be preferredfor evaluation of TMJ disorders in middle-agedto elderly patients where the symptoms are morelikely to be due to arthritis rather than internalderangement.

Ultrasound (US) has been proposed as a usefuland cheap technique in evaluating internalderangement, but only the lateral aspect of thedisc, lateral capsule, and lateral joint can be visu-alized (Petscavage-Thomas and Walker 2014). Inaddition, it is highly operator dependent, and find-ings are not always reproducible. It has been use-ful in assessing joint fluid, synovitis, and erosionsin the lateral aspect of the joint in young patientswith JIA (Ringold and Cron 2009; Mohammedet al.2012). US is reliable for guiding needleplacement into the TMJ for injection of intra-articular corticosteroids for symptom relief. It

Fig. 44 Osteomyelitis. 6 months post-open reduction andinternal fixation of right parasymphyseal and left mandib-ular body fractures of the mandible. Presented with painand swelling associated with the left mandible. The rightparasymphyseal fracture has healed (a, solid whitearrows). There is extensive buccal and to a lesser extentlingual periosteal new bone formation (a and b, white

dotted arrows) in the left mandibular body with focallucency around the most mesial screw of the mini-plate(b and c, black arrow) which traverses the distal apex of36. There is a small sequestrum buccal to the screw head(b, white open arrow). A gallium scan (d) confirms abnor-mal uptake in the left body consistent with osteomyelitisbut not in the right parasymphyseal region

48 A. Whyte et al.

Fig. 45 Osteonecrosis of the jaws (ONJ). Sagittal CTreconstruction (a) showing sclerotic metastases from car-cinoma of the prostate involving the basiocciput, sternum(white arrows), and the cervical and partially visualizedthoracic spine. The patient was treated with high-dosebisphosphonates, and bilateral non-healing molar

extraction sockets were present on intraoral examination.An axial reconstruction (c) shows bilateral MRONJ (openwhite arrows) which is severe and extensive on the left.38 is unerupted and there is carious destruction of thecrowns of 34 and 35 (b)

Fig. 46 Hematoma in the medial pterygoid muscle. Pre-sented with severe trismus 6 days following a left inferioralveolar block. The left medial pterygoid muscle (blackdashed ovals, a and b) is swollen and slightly hyperdense

consistent with a needle-induced hematoma. The left man-dibular foramen is indicated (black arrows). The normalright medial (MP) and lateral (LP) pterygoid muscles areshown for comparison


can replace other methods of needle placementincluding palpation and fluoroscopic or CTguidance.

Structural osseous changes within the TMJ arethe result of abnormal metabolic activity which isdetected as increased activity on an isotope bonescan. Although a highly sensitive technique to thepresence of osseous disease, it is nonspecific andinvolves a high radiation dose (Petscavage-Thomas and Walker 2014).

Functional brain imaging studies support theconcept that TMJ disorders are very similar toother chronic pain disorders and may be relatedto abnormal pain processing in the trigeminalsystem. Masticatory muscle disorders appear tohave little, if any, abnormality of the muscles orperipheral tissues and may represent a pain-producing process caused by central sensitization(Scrivani et al. 2008).

c. Imaging of the major causes of TMD. Exclud-ing masticatory myalgia, the major types of

TMD which require imaging in adults includedisc displacement, osteoarthritis, and inflam-matory arthritis (especially rheumatoid arthri-tis). JIA, by definition, commences in childrenyounger than 16 years, and idiopathic condylarresorption occurs almost exclusively in teenageor young adult females.

Disc displacement. The fibrocartilaginousarticular disc (meniscus) is biconcave in sagittalsection with an anterior band, a slightly thickerposterior band, and a thin intermediate zone.There is a bilaminar zone posterior to the posteriorband, attaching it to the temporal bone and thecondyle. The disc separates the joint into superiorand inferior compartments. The normal positionof the disc is usually defined such that the junctionof the posterior band and bilaminar zone is at the12 o’clock position on a sagittal view (Fig. 48).Using this criterion, 34% of asymptomatic indi-viduals will have disc displacement. Therefore, ithas been suggested that minor degrees of disc

Fig. 47 CT of the TMJs. Sagittal closed- (a) and open-mouth (b) soft tissue window images showing an anteri-orly displaced disc (D) which is not recaptured on mouthopening; there is normal condylar translation. Minimalsuperior condylar cortical flattening, sclerosis, and focalirregularity are shown on the bone window sagittal (c) and

coronal (d) reconstructions (white open arrow). Axial softtissue reconstruction (e) through the right parotid gland in apatient with right TMJ pain. The irregular mass (whitearrows) was proven to represent undifferentiated carci-noma with proximal perineural tumor spread along theright facial nerve (white dotted arrows)

50 A. Whyte et al.

displacement are probably a normal variant andthat the normal position should be defined as12 o’clock +/�10 degrees.

Anterior and anterolateral disc displacementaccount for 63% of all cases, with anteromedial,medial, and lateral displacement being uncom-mon, each accounting for about 10% of cases(Whyte et al. 2006). Assessment of disc position,especially the degree of mediolateral displace-ment, requires correlation of sagittal and coronalimages. Assessment of mobility of the disc andcondyle as well as recapture of a displaced disc(i.e., a return to its appropriate position relative tothe condyle with mouth opening) is performedwith a fast open-mouth scan or with a sequenceof low-resolution, fast scans performed as a grad-ual sequence of progressive mouth opening(Fig. 49). There may be normal condylar move-ment (the most superior point of its articular sur-face is situated inferior to the most inferior pointof the articular eminence), hypermobility, orhypomobility (restricted anterior translation).

Being composed of fibrocartilage, the disc isnormally of uniform low signal. However,depending on the type of MRI sequence,mild increased signal may be present in the pos-terior band. Initially, with significant internal

derangement, there is edema or myxoid degener-ation of the swollen posterior band. Chronic discalchanges include atrophy, change in shape, tears,and fragmentation (Hasan and Abdelrahman2014). Hypertrophy of the tendon of the superiorbelly of the lateral pterygoid muscle is also seen inmarked and longstanding disc displacement andthought to be related to chronic muscle hyperac-tivity (Fig. 50).

In patients with more significant degrees ofdisc displacement, often without recapture,whose symptoms do not resolve or progress onnonsurgical management, an intra-articularinflammatory response is common. MRI will usu-ally demonstrate joint effusion, predominantly inthe superior compartment. Synovitis may beseen in the inferior compartment and aroundthe bilaminar zone. Erosions usually involve thecondyle and when acute or subacute areassociated with marrow edema. Synovitis andactive erosions enhance with gadolinium butalso have typical signal characteristics onfat-saturated T2-weighted sequences (Fig. 51),and therefore gadolinium is not routinelyrequired. The signs of joint inflammation onMRI have generally correlated with the severityof pain (Farina et al. 2009).

Fig. 48 MRI of the TMJ: normal sagittal appearances inthe closed- (a) and open-mouth (b) positions. The bicon-cave fibrous disc is of uniform low signal and consists of ananterior band (AB), intermediate zone (IZ), and a slightlylarger posterior band (PB). The thin bilaminar zone isindicated (blz). The normal disc position is described as

between the junction of posterior band and bilaminar zonebeing at or close to the 12 o’clock position (12). Impor-tantly, the narrowest part of the disc (IZ) corresponds to thenarrowest inter-bony distance (white dotted arrows) withthe mouth closed and also during opening. Condylar trans-lation is normal


Osteoarthritis. From a rheumatologic stand-point, osteoarthritis (OA) is now thought to bean inflammatory condition involving all compo-nents of a joint rather than a purely degenerativeprocess (Berenbaum 2013; Larheim et al. 2015).In the TMJ, it is usually considered to arise sec-ondary to internal disc derangement. Given thecomplexity of the TMJ, excessive and prolongedmechanical loading exceeding the adaptive capac-ity of articular cartilage and subchondral bone forremodeling is likely to be a significant factor inpathogenesis. OA is usually seen in an older agegroup than internal derangement, and both disor-ders predominate in women. Most patients withOA of the TMJ have a history of preceding inter-nal derangement, and available evidence suggests

that patients with severe internal derangement canprogress to OA after a variable interval, oftenseveral years.

The imaging features of OA in the TMJ areidentical to those seen in other affected joints:asymmetric joint space narrowing, articular sur-face remodeling and flattening, cortical sclerosisand thickening, subcortical cysts, osteophytes,and calcified intra-articular bodies (Fig. 52). Osse-ous changes are much more common in the con-dyle than in the articular eminence or glenoidfossa (Boeddinghaus and Whyte 2013). A simpleimaging classification of OA in the TMJ which isuseful for longitudinal studies is that proposed byAhmed et al. in 2009: A, Normal, B, Indetermi-nate, and C, Osteoarthritis (Ahmad et al. 2009).

Fig. 49 MRI of internal derangement. Anterior disc dis-placement with reduction (a and b): the disc is indicated(white arrows) and recaptured on mouth opening, the con-dyle being hypermobile (white open arrow). Anterior disc

displacement without reduction (c and d): the anteriorlydisplaced disc (white arrows) is not recaptured on mouthopening, although there is normal condylar translation(white open arrow)

52 A. Whyte et al.

The described features in category B of condylararticular surface flattening and sclerosis are typi-cal of adaptive remodeling.

As is typical of this condition in any joint, thechanges seen on imaging correlate poorly, or notat all, with symptoms (Palconet et al. 2012). Manypatients may be pain-free despite advanced OA,and the only complaint may be of joint noises orgrating.

Rheumatoid arthritis and related joint dis-eases. Rheumatoid arthritis (RA) is a systemic,autoimmune, inflammatory disorder which mani-fests as peripheral polyarthritis. Women areaffected more commonly than men (3:1) and thedisease predominates in the 35–45 year age group.Clinical evidence of TMJ involvement is found inmore than half of patients (Petscavage-Thomasand Walker 2014).

Typical imaging findings in active RA are oferosions on both sides of the TMJ and symmetricjoint space narrowing without osseous prolifera-tion (Fig. 53). MRI demonstrates diffuse synovi-tis, and the disc may be of abnormal morphologyand displaced due to inflammation and weakeningof the attachments. In chronic disease, especiallyfollowing treatment, the erosions will heal, andsecondary osteoarthritis may develop withchanges of osseous remodeling and proliferationincluding flattening, sclerosis, and osteophytes.

Seronegative spondyloarthropathies such aspsoriatic arthritis and ankylosing spondylitis alsoproduce articular surface erosion, but usuallythere is also evidence of bone proliferation includ-ing periosteal new bone formation.

TMJ disorders in childhood. Disc derangementdisorders have a predilection for teenage and

Fig. 50 MRI of chronic internal derangement of the TMJ.The margins of the disc are indicated with white arrows.(a) Crumpled meniscus: there is a superior compartmenteffusion distending the anterior recess (white dashedarrow). (b) Degenerate or edematous meniscus: diffuseincrease in discal signal. (c) Small meniscal remnant: asmall disc fragment is seen anterior to the condyle andthe bilaminar zone (blz) is retracted (white open arrow).

(d) Hypertrophy of the lateral pterygoid (LP) tendons: thecrumpled disc is displaced anteriorly and medially; inferiorto the disc are the hypertrophied tendons of LP giving a“triple disc” appearance. (e) Coronal oblique image of theleft TMJ: separated disc fragments (white arrows) in themedial (med) and lateral (lat) aspect of the joint. Thedegree of separation is shown by the dotted line


young adult females. MRI is the optimal imagingmodality because of the excellent soft tissue detailand absence of radiation. The imaging features ofadvanced derangement disorders with develop-ment of intra-articular inflammation, condylarerosions, remodeling, and osteoarthritis are aspreviously described.

Idiopathic condylar resorption (ICR), alsoknown as progressive condylar resorption, isthought to represent a severe and acceleratedform of condylar erosion that affects adolescentfemales with disc derangement. Three phases ofICR are described: soft tissue, destructive(active), and reparative (Hatcher 2013). Thesoft tissue phase corresponds to disc derange-ment, joint laxity, and intra-articular

inflammation. Combined with altered or exces-sive biomechanical loading of the TMJ, perhapsin a specific hormonal environment, the destruc-tive phase ensues with extensive condylar ero-sion and resorption (Fig. 54). Resorption anddisturbance of condylar growth result in mandib-ular retrognathism, an anterior open bite, andincreases in the maxillary-mandibular planeangle and anterior lower facial height. ICR isusually bilateral but can be asymmetric, resultingin facial asymmetry. The final reparative phaseresults in a flat articular surface with reformationof the cortex. The different stages should beassessed by imaging, either CBCT or preferablyMRI, as timing of orthodontic or orthognathictreatment is crucial.

Fig. 51 Intra-articular inflammation of the TMJ. Compar-ison of CBCT (a), proton density (b), and fat saturationT2 (c) MRI. All images show subtle articular surfaceirregularity of the condyle (open black arrow in a). Theanteriorly displaced disc (white arrows) is shown on MRI(b and c) as is the irregular and edematous bilaminar zone(blz). Hyperintense marrow edema is shown on the fatsaturation T2 image (open white arrow in c), the mostsensitive sequence for inflammation. Images d and e

show two cases of marked anterior disc displacement(white arrows), hyperintense fluid in the distended anteriorrecess of the upper joint space (dotted black arrow), andmoderately hyperintense synovitis (white dotted arrows) inthe inferior joint space and around the bilaminar zone.There is subtle erosion of the posterosuperior condylarcortex and diffuse marrow edema (white open arrows).Perforation of the malformed disc and edematousbilaminar zone (white arrowhead) is shown in (e)

54 A. Whyte et al.

Juvenile idiopathic arthritis (JIA) includes allforms of arthritis that develop before the age of16 years, persist for at least 6 weeks, and have noidentifiable cause. The TMJ is one of the mostfrequently involved joints, involved in as many as75% of children with JIA, and involvement ishigher in those with the polyarticular form of thedisease with systemic symptoms (Mohammedet al. 2012). MRI is the most sensitive techniquein the diagnosis of TMJ involvement, demonstrat-ing joint fluid, synovitis, and erosions of both sidesof the joint. Most children with JIA are asymptom-atic at the time their TMJ arthritis is diagnosed butare still at risk of long-term joint damage if nottreated. Imaging-guided injection of intra-articularsteroids shows promise in reducing the severity ofintra-articular inflammation, resulting in improvedjoint opening and decreased pain in symptomaticpatients (Ringold and Cron 2009).

d. Referred pain to the TMJ region. In addition tobeing the principal sensory nerve to the TMJ,the auriculotemporal branch of the mandibulardivision of the trigeminal nerve (V3) alsoinnervates the anterior wall of the externalauditory canal, the pre-auricular area and tra-gus, and the temporal scalp. It can be difficultto distinguish between pain originating in theTMJ and pain from the ear (otalgia).

Sensory innervation of the ear is complex andincludes the glossopharyngeal (IX), vagus (X),and upper cervical (C2 and C3) nerves in additionto the trigeminal (V) nerve (Fig. 55). Any pathol-ogy residing within the sensory distributionof these cranial and upper cervical nerves canpotentially cause pain referred to the ear:referred otalgia (Chen et al. 2009) (Fig. 56). Thisincludes the nasopharynx, oropharynx, oral

Fig. 52 Osteoarthritis. CT of early (a and b), moderate(c), and severe (d) osteoarthritis. Proton density MRI (e)for comparison. Case (a) shows early erosion, flattening,and sclerosis of the superior condylar articular surface(open white arrow). Mild anterosuperior joint spacenarrowing, condylar articular surface flattening, and asmall osteophyte (white arrow) are shown in case (b).With disease of moderate severity (c), there is more

advanced joint space loss, articular surface remodeling,and subcortical sclerosis (white arrow). CT (d) and PDMRI (e) images demonstrate marked joint spacenarrowing, articular surface flattening, cortical irregularity,a condylar osteophyte, subcortical sclerosis, and cysts(white dotted arrows). An ossified intra-articular body isshown by both modalities (black arrows)


cavity, larynx, paranasal sinuses, major salivaryglands, maxilla, and mandible. Approximately,75% of referred otalgia is thought to be dental orTMJ in origin (Jaber et al. 2008). Upper cervicalfacet degeneration (C2/C3 supply) is an importantcause in the elderly (Kim et al. 2007).

Imaging of Orofacial Pain

Advanced imaging of orofacial pain is guided bythe findings of a thorough and comprehensivehistory and examination by an experienced clini-cian, in conjunction with an OPG. Ideally, thelikely etiology of pain can be confined to a limiteddifferential diagnosis, and imaging can betargeted to confirmation of the exact cause.

However, in some patients this is not the caseand imaging must be more comprehensive toexclude potential end-organ, peripheral, skullbase, and central causes of pain. This is bestperformed using state-of-the-art technology byradiologists who have an in-depth understandingof trigeminal anatomy and the multiple potentialcauses of orofacial pain.

a. Application of imaging to the major causes oforofacial pain

End-organ and peripheral causes: In additionto supplying the hard- and soft-tissue componentsof the oral cavity, the trigeminal (V) nerve alsoprovides sensation to the anterior scalp, facialskin, nasal cavity and paranasal sinuses, orbits,

Fig. 53 Rheumatoid arthritis. CT (a) and fat saturation T2MRI (b) of active and severe rheumatoid arthritis withgross erosion and deformity of the articular surfaces.MRI demonstrates that the joint is distended by hyper-intense synovial proliferation and fluid (white dottedoval) with the deformed disc (D) being markedly anteriorly

displaced. The disc attachments are destroyed by inflam-matory tissue. Less severe erosion of the articular surfaceson both sides of the joint with remodeling and sclerosis in acase of inactive disease (c). Ankylosis has developed fol-lowing multiple episodes of inflammatory arthritis (d)

56 A. Whyte et al.

temporomandibular joints, external auditorycanal, and salivary glands.

Post-contrast CT with soft tissue and bonewindow multiplanar reconstructions providesoptimal imaging evaluation when a peripheral orend-organ cause is suspected. Scanning shouldextend from the vertex of the skull (post-erosuperior extent of scalp supplied by the oph-thalmic division: V1) to the C3/C4 intervertebraldisc level (to cover the submandibular glands andspinal trigeminal nucleus). A wide range of boneand soft tissue pathology which may not havebeen appreciated on clinical examination or OPGcan be shown by this technique. This includescommon causes of orofacial pain such as subtleperiapical pathology, internal derangement, andarthritis of the TMJ, as well as uncommon causesincluding occult malignancy (Fig. 57). If CT con-trast is contraindicated, either non-contrast CT or

CBCT can be performed, with the addition ofMRI.

If there are other sensory symptoms (e.g.,dysesthesia, paresthesia, or hypoesthesia) in addi-tion to pain, dedicated MRI of the trigeminalnerves with contrast enhancement is mandatoryto exclude large nerve perineural tumor spread,particularly in patients who report prior excisionor cryotherapy of skin lesions, even if these werenot known to be malignant (Fig. 58).

Skull base causes. The skull base represents theinterface between the maxillofacial region, phar-ynx, and neck below and the intracranial contentsabove. Gross or subtle pathology within or adja-cent to the skull base involving the trigeminalnerve can cause V2 or V3 pain and be clinicallyoccult (Fig. 59). Tumors within the nasal cavity ornasopharynx can erode the skull base from below,as can pituitary tumors or meningiomas from

Fig. 54 Idiopathic condylar resorption (ICR). ICR usu-ally involves teenage females, and mandibularretrognathism is a common associated factor (a, lateralcephalogram). Erosive, symptomatic phase of ICR shownon cone beam CT (b) and MRI (c): there is extensive

condylar erosion/resorption (dotted white arrows), a wid-ened joint space, diffuse edema of condylar marrow (openwhite arrow), marked anterior disc displacement (D), andintra-articular synovitis (white arrows)


above. Intrinsic skull base tumors are rare, and, inolder patients and those with a history of malig-nancy, a metastasis should always be considered.

The bony skull base contains numerous foram-ina and canals occupied by traversing cranialnerves and vessels. Both anatomy and intrinsicor extrinsic skull base pathology are optimallydemonstrated by a combination of MRI andCT. High-resolution 3-Tesla MRI can clearlyshow the trigeminal ganglion and nerve rootletsin Meckel’s cave, the trigeminal nerve divisions(V1, V2, and V3) within and adjacent to the skullbase foramina, as well as the cranial nerves (III,IV, V1, V2, and VI) within the cavernous sinuses(Fig. 59).

Central causes: These either involve the trigem-inal sensory nuclei (within the brain stem and uppercervical cord) or result from compression of thecisternal segment of the V nerve (between its rootentry to the pons and its passage through the porustrigeminus) (Fig. 60). MRI is the optimal imagingtechnique and the study must extend from thevertex to the cervical spinal cord (C3/C4) to coverthe entire sensory distribution of the V nerve aswell as the spinal trigeminal nucleus.

Intrinsic brain stem pathology is a rare cause oforofacial pain (Leclercq et al. 2013). Multiple

sclerosis and tumors account for 3% and 0.8%,respectively, of all causes of trigeminal neuralgiaand are clearly demonstrated by MRI (Fig. 61).Multiple sclerosis usually presents in patientsunder age 40. There are updated imaging criteriafor diagnosis by MRI, dependent on the numberand distribution of demyelination plaques (Filippiet al. 2016). Even if there are no visible lesions inthe brain stem or cervical cord on imaging, thepresence of plaques elsewhere in the brain sug-gests that demyelination is the likely cause oftrigeminal neuralgia in a patient with multiplesclerosis.

Compression of the V nerve in the pre-pontinecistern is a much more common cause of trigem-inal neuralgia. 90% of cases are caused by vascu-lar impingement, usually by the superiorcerebellar artery (Fig. 62). Contact between avessel and the cisternal segment of the V nerveoccurs in 40% of asymptomatic subjects. In apatient with trigeminal neuralgia, the importantimaging findings which are likely to be clinicallyrelevant are arterial impingement on the proximal50% of the nerve, known as the root entry zone.This portion of the nerve has thinner central mye-lin which is more vulnerable to vascular compres-sion and focal demyelination than the distal,

Fig. 55 Sensory innervation of the TMJ, external earcanal, pinna, and skin. Cranial nerves V, VII, and X inner-vate the external auditory canal (EAC) and lateral surfaceof the tympanic membrane. Cranial nerve V(V3) innervates the TMJ, anterior wall of the EAC, tragus,pre-auricular skin, and temporal scalp. Cranial nerve IXinnervates the medial surface of the tympanic membrane,

middle ear, mastoid air cells, and the upper pharynx,including the tongue base. Branches of the cervical plexusderived from C2 and C3 innervate the pinna and skinextending anteriorly and inferiorly to the mandibularangle (greater auricular nerve) as well as skin/scalp poste-rior and superior to the scalp (lesser occipital nerve)

58 A. Whyte et al.

peripherally myelinated nerve which has a thickermyelin sheath (Hughes et al. 2016). Distalimpingement and veins are uncommon causes oftrigeminal neuralgia.

Extra-axial tumors and other mass lesions areresponsible for 6.2% of cases of trigeminal neu-ralgia. Nerve sheath tumors, especially vestibularschwannomas (acoustic neuromas) and meningi-omas, are the most common tumors to compressthe trigeminal nerve (Fig. 63). An epidermoid cystarising in the cerebellopontine angle cistern may

extend superiorly to the trigeminal nerve, andpetrous apex lesions can also compress the nerveat the porus trigeminus.

b. Optimizing imaging when the cause oforofacial pain is uncertain

MRI is the investigation of choice when thecause of orofacial pain is uncertain after clinicalevaluation and OPG. The scan protocol mustcover the central, skull base, and peripheral course

Fig. 56 Otalgia and referred otalgia. Otalgia is defined aspain originating from the ear: it is due to inflammatory or(less commonly) neoplastic conditions of the ear and pre-dominates in young patients. Otitis externa andotomastoiditis is a common cause (a). There is skin thick-ening in the external auditory canal: EAC (black dottedoval) and multiple fluid levels in the mastoid air cells(black arrows). Cholesteatoma is a misnomer: this inflam-matory lesion is an epidermoid (b) and is characterized by afocal soft tissue mass causing erosion of the posterior wallof the EAC (white arrows). Referred otalgia originatesfrom outside the ear and originates from any structure

innervated by the multiple cranial nerves and branches ofthe cervical plexus which innervate the ear. It is seen inolder patients and may be myofascial, inflammatory,degenerative, or neoplastic in origin. Overall, 75% ofreferred otalgia is dental or TMJ in origin; a further com-mon cause in elderly patients is upper cervical facet jointdegeneration (c, white dotted rectangle). Occult malig-nancy should always be considered. A large left-sidedtongue base carcinoma (d) extends anteriorly into the oraltongue and floor of the mouth (black arrows). The tumorcrosses the midline and also involves tissue innervated bycranial nerves V and IX (boundary: white dashed line)


of the trigeminal nerve with T1 and T2 sequences,including high-resolution 3D analysis of the cis-ternal segment and post-gadolinium evaluation toexclude enhancing tumors (Leclercq et al. 2013).

Involvement of marrow of the skull base, max-illa, or mandible by tumor or infection can beappreciated on MRI before CT, CBCT, and (espe-cially) radiographs are abnormal. Nevertheless,artefact from dental restorations is unpredict-able on MRI: it may be focally severe, obscuringipsilateral upper and lower quadrants. Periapicalpathology can be obscured and either CBCTor CT should be performed for optimaldentoalveolar, TMJ, and sinonasal evaluation.

If MRI is unavailable, post-contrast CT withsoft tissue and bone window reconstructions

(covering the same anatomical extent as describedfor MRI) is also an excellent and comprehensiveexamination. However, CT will miss demyelin-ation and cannot show vascular impingement onthe cisternal segment of the trigeminal nerve.

c. Functional imaging and research for orofacialpain

Neural impulses resulting from painful stimuliin the orofacial region supplied by the divisions ofthe trigeminal nerve relay in the trigeminal gan-glion and pass via the cisternal segment of thenerve to the pons. The nociceptive impulses thendescend in the spinal trigeminal tract of themedulla to synapse in the nucleus caudalis

Fig. 57 Miscellaneous unsuspected causes of chronic leftfacial pain detected on CT. (a) Chronic periapical abscessassociated with 27, perforation of the sinus floor (whitedotted arrow) and reactive mucosal thickening (whitearrows) in the floor of the left maxillary sinus. (b) Leftparotitis (white dotted gland outline) with a tiny, faintly

opaque, linear calculus (arrow) in the left parotid duct. (c)Elongated styloid process with hypertrophic degenerationat two pseudo-arthroses (white dotted arrows). (d) Chronicperiapical abscess (white dotted arrows) associated with37 in a patient already commenced on medical treatmentfor “left V3 trigeminal neuralgia”

60 A. Whyte et al.

in the upper cervical cord, cross over into thecontralateral spinothalamic tract, and ascend tosynapse in posterior nuclei of the thalamus. Mod-ulation of nociceptive impulses occurs in the brainstem. Neural projection is principally to the pos-terior insular cortex as well the sensory and ante-rior cingulate cortices.

Pain is a complex and subjective perceptionwith sensory, cognitive, and emotional compo-nents. Functional imaging of the response ofhealthy volunteers to painful stimuli has led tothe characterization of a network of brain areasforming a “pain matrix” (Fig. 64). This centralnetwork mainly involves the thalamus, the amyg-dala, the insular cortex, the supplementary motor

area, the posterior parietal cortex, the prefrontalcortex, the cingulate cortex, the periaqueductalgray matter of the midbrain, the basal gangliaand cerebellar cortex, and the primary and sec-ondary sensory cortices. As a generalization, thelaterally situated areas are involved with sensationand the medial areas with cognitive and affectivecomponents of pain. The components of the painmatrix interact with each other to generate theindividual perception of pain (May 2009; Moissetet al. 2011).

There has been extensive research with func-tional imaging to elucidate the pathologicalbasis of neuropathic pain. Neuropathic painresults from a lesion or disease of the

Fig. 58 Melanoma involving the maxillary division of theleft V nerve. The post-contrast T1 axial scan (b) shows asmall, enhancing subcutaneous mass in the medial aspectof the cheek (dotted white oval) which is difficult to appre-ciate on the non-contrast T1 axial scan (a). Coronal post-

contrast T1 scans (c and d) demonstrate large nerve peri-neural tumor spread along the left infra-orbital nerve (ION)in the orbital floor which extends proximally to the maintrunk of V2 nerve within the foramen rotundum (FR)


somatosensory system and may be continuous orepisodic in nature, trigeminal neuralgia(TN) being the classic example of the latter.Recent studies using functional MRI (fMRI)have demonstrated significant differences in theneuronal activity in asymptomatic subjects ver-sus pain patients. In addition, differences wereseen in different neuropathic pain states, andspecific neural signatures were evident for cer-tain neuropathic pain disorders (Scrivani et al.2007).

Recent investigations using fMRI to evaluatecentral pain processing in patients with classicalTN have highlighted not only the value of thetechnique in understanding the pathophysiologybut also demonstrating significant alteration fol-lowing successful neurosurgical treatment(DeSouza et al. 2014). Neurovascular conflict ofthe root entry zone of the cisternal segment of thetrigeminal nerve causes focal demyelinationand edema as measured by the MRI techniqueof diffusion tensor imaging. Gray- and white

Fig. 59 Cavernous sinus, Meckel’s cave, and the centralskull base. (a) Coronal post-contrast high-resolutionT1-weighted image through the cavernous sinus (CS).The three divisions of the trigeminal (V) nerve are labeled(white arrows). V3 exits through foramen ovale (FO).Cranial nerves III and VI are also identified (white dottedarrows). (b) Coronal post-contrast high-resolution imageat a level posterior to (a), through Meckel’s cave (MC).

The U-shaped trigeminal ganglion (TG) is clearly visual-ized (white arrow). (c and d) Post-contrast T1 coronal (c)and axial (d) images of a homogeneously enhancingmeningioma which fills the right cavernous sinus andMeckel’s cave (black arrows). The tumor encases theright internal carotid artery (ICA, dashed white arrow)and extends inferiorly along the V3 nerve and anteriorlyalong V2

62 A. Whyte et al.

matter abnormalities occur in patients with TNin structures involved in pain perception, painmodulation, and motor function including the spi-nal trigeminal nucleus, pain matrix structures, and

interconnecting white matter bundles such as thecorpus callosum. Successful treatment usingmicrovascular decompression results in correc-tion of the abnormal indices measured on fMRIas well as resolution or significant improvementof pain. This includes restoration of gray matterthickness in the anterior insula, indicating thecapacity for neuroplasticity (May 2009; DeSouzaet al. 2015).

Imaging of Sleep-Disordered Breathing

Sleep-disordered breathing represents a spec-trum ranging in severity from snoring to obstruc-tive sleep apnea (OSA). Snoring is common,affecting about 40% of adults in developed coun-tries. The OSA syndrome is defined as a clinicalcondition in which there is intermittent andrepeated upper airway collapse during sleep,resulting in interrupted and irregular breathingat night and excessive sleepiness during theday. It predominantly affects obese, middle-aged males. Diagnosis of OSA requires over-night polysomnography (PSG) which measuresan apnea-hypopnea index (AHI). OSA is gradedas mild, moderate, and severe. Most cases ofOSA are symptomatic. It is common in

Fig. 60 Anatomy of the trigeminal nerve and nucleiwithin the pre-pontine cistern and the brain stem. Anultra-high-resolution 3D T2 volumetric sequence demon-strates the position of the main sensory (S) and motor(M) nuclei at the level of the pons as well as the cisternalsegment of V between the root-entry zone (REZ – blackarrow) and the porus trigeminus (PT – white arrow). Thelow signal trigeminal nerve rootlets are seen withinMeckel’s cave contrasted by the hyperintense cerebrospi-nal fluid

Fig. 61 Multiple sclerosis presenting as trigeminal neu-ralgia. (a) An axial proton density (PD) sequence showsthree hyperintense demyelination plaques in the pons(black arrows), and these are typically situated adjacentto an interface with cerebrospinal fluid. (b) A sagittal fluid

attenuation inversion recovery (FLAIR) sequence showsaddition triangular or cigar-shaped demyelination plaquesadjacent to the corpus callosum (black arrows) overlyingthe lateral ventricle (LV)


developed countries: for example, it is estimatedthat 25% of males and 9% of females will haveOSA in Australia and 15% of these cases will becategorized as moderate to severe (Mansfieldet al. 2013).

Blood gas disturbances (hypoxia and hyper-capnia) during cessation of breathing result inchronic and repeated sympathetic overactivityand hypercoagulability. There is a significantassociation with increased risk of cardiovascularevents, hypertension, and diabetes. A 2.5–7 timesincrease in mortality is associated, proportional tothe severity of OSA.

a. Value of imaging in understanding the patho-genesis of OSA

The sleeper who suffers from OSA periodi-cally struggles to breathe but is unable to inhaleeffectively because the airway has collapsed. It isa mechanical problem due to decreased tone in thepharyngeal dilator muscles during sleep, com-bined with the negative intraluminal pressure dur-ing inspiration, resulting in airway collapse. Inalmost all cases, the etiological factors forincreased airway collapsibility are a combinationof increased soft tissue narrowing the upper

Fig. 62 Compression of the V nerve by the superiorcerebellar artery (SCA) in a patient with right trigeminalneuralgia. (a) A high-resolution T2 sequence shows a loopof the SCA impinging on the root-entry zone of the right Vnerve to the pons. The cisternal segment of the right Vnerve is atrophic when compared to the normal left side.(b) A flow-sensitive sequence: magnetic resonance angi-ography (MRA) demonstrates arterial flow in the

impinging vessel (SCA: red arrow). The basilar (B) andinternal carotid arteries (ICA) are also shown. (c) Magni-fied image (a) showing the plane of sagittal reconstructionthrough the right V nerve and SCA. The root entry zone(REZ) and Meckel’s cave (MC) are shown on the left side.(d) Sagittal reconstruction showing the impingement onthe cisternal segment of V from the SCA (red arrows)

64 A. Whyte et al.

airway lumen and reduced size of the bonyand cartilaginous framework supporting the air-way musculature (Barkdull et al. 2008; Encisoet al. 2010). This results in a narrow and elongatedupper airway (Fig. 65).

Imaging has played a major role in understand-ing the pathogenesis of OSA. The ideal modalitywould image the airway in multiple dimensionsand evaluate the soft tissue and bone when thepatient is both supine and asleep; this ideal isdifficult to achieve.

Lateral cephalogram. This has been the main-stay of evaluation over the last 40 years and

continues to be relevant, especially in children. Itis cheap, widely available, and reproducible. It islimited by giving information only in the sagittaldimension and in the erect position and awake.Measurement of adenoidal size in the nasophar-ynx and an indication of size of the palatine andlingual tonsils are possible: these are of para-mount significance in children with sleep-disordered breathing. Research using this tech-nique, in conjunction with orthodontic assess-ment, has shown an association between OSAand mandibular retrognathism, a high maxillary-mandibular plane angle (high anterior lower facial

Fig. 63 Extra-axial tumors compressing the V nerve inthe posterior cranial fossa. Post-contrast T1 coronal (a) andhigh-resolution T2 axial (b) of a right acoustic neuroma(vestibular schwannoma) extending laterally into the rightinternal auditory canal and superiorly to compress the rightV nerve (open arrows). There is an associated arachnoidcyst (white dashed arrows) of fluid signal situated postero-lateral to the tumor. Post-contrast T1 (c) and T2 (d) axialscans showing a large, enhancing hemispherical-shaped

meningioma (open white arrows) in the leftcerebellopontine angle cistern which obscures the left tri-geminal nerve and extends via the porus trigeminus(PT) into the left Meckel’s cave. The tumor causes com-pression of the brain stem and extends laterally into theinternal auditory canal (white arrow). The tumor formsobtuse angles with the petrous ridge (white dotted arrows),characteristic of meningiomas


height), narrow maxilla, and inferiorly situatedhyoid bone (Gungor et al. 2013).

Cone Beam CT (CBCT). There is a large bodyof literature advocating the use of CBCT for initialand posttreatment assessment of patients withsleep-disordered breathing, including OSA.Many of these publications have significant meth-odological flaws (Alsufyani et al. 2013; Choi et al.2013). CBCT provides multiplanar, area, and vol-umetric analysis of the airway in addition to accu-rate assessment of the maxillofacial skeleton,dentofacial relationship, hyoid bone, andsinonasal cavity. In addition, CBCT is more acces-sible to the dental profession than CTor MRI, andthe relatively low dose is advantageous to youngpatients (Buchanan et al. 2016). The major disad-vantages of CBCT are the absence of soft tissuecontrast, the standing or seated position requiredfor nearly all scanners, and the variation in headposition in the same patient. There is an averageone-third (but unpredictable, and up to two-thirds)reduction in airway area and volume in the supine(versus erect) position (Fig. 66) (Camacho et al.2014). Nonetheless, CBCT has contributed toresearch showing increased airway dimensionsand volume as a result of oral sleep appliances ororthognathic surgery.

Multidetector CT (MDCT). Several well-performed studies using MDCT in the supineposition (as well as a single study using asupine CBCT scanner) have measured airwaydimensions, airway area, and hyoid position inpatients with sleep-disordered breathing andhave shown strong correlation with the AHIderived from polysomnography and other riskfactors such as measures of obesity. A recentstudy demonstrated a strong correlation betweenthe AHI, obesity, and objective measurement ofairway collapsibility during sleep with measure-ment of length of the tongue, length of the oro-pharyngeal airway, and position of the hyoid bone(Genta et al. 2014). MDCT is rapid (about 5-s scantime), is widely available, and uses a relativelylow radiation dose. A preliminary lateral digitalplanning scout view allows cephalometric analy-sis in the supine position. From the volumetricscan data, multiplanar bone and soft tissue recon-structions allow complete evaluation of the airwaydimensions and morphology as well as the softtissue and bony factors contributing to narrowing.

The contribution of nasal factors to OSA isappreciated by physicians and surgeons specializ-ing in sleep medicine but has received littleemphasis in the dental literature. Rhinitis,

Fig. 64 The “pain matrix.” (a) Midline sagittal T1 of thebrain: T = thalamus, AMYG = amygdala, PFC = pre-frontal cortex, CC= cingulate cortex, SMA= supplemen-tary motor area, S1 = sensory cortex (primary), S2 = sen-sory cortex (secondary), PPC = posterior parietal cortex.

Dashed line rectangle= Peri-aqueductal gray matter. Dot-ted black line = trigeminal nuclei and tracts. (b) Para-sagittal through the Sylvian fissure showing the insularcortex (white dashed oval). Frontal (F) and temporal(T) lobes

66 A. Whyte et al.

deviation of the nasal septum, and nasal polypsare highly significant because about half of nor-mal upper airway resistance occurs at the level ofthe nasal cavity.

The airway can be narrowed by enlargement ofseveral soft tissue structures: adenoidal lymphoidtissue in the nasopharynx, the palatine and lingualtonsils and tongue base in the oropharynx, the softpalate, and the fat-filled parapharyngeal spaces.

These structures cannot be adequately evaluatedby CBCT because of its very poor soft tissuecontrast resolution but are well shown withMDCT. Maximum reduction in airway area inpatients with OSA is usually in the retropalatalregion, corresponding to the upper oropharynx.Transverse narrowing of the airway is moreclosely correlated with OSA than reduction inthe anterior-posterior dimension (Ogawa et al.

Fig. 65 Airway morphology and obstructive sleep apnea(OSA). The T1 sagittal and axial images on the left (NOR-MAL) are of an adult patient without OSA who has man-dibular retrognathism (open white arrow). On the right(OSA), the T2 sagittal and axial images demonstrate thetypical changes in airway morphology in an adult patientwith OSA: elongation of the oropharynx (dotted white line)and reduction in area of the airway with the degree of

narrowing in the mediolateral dimension being greaterthan the anteroposterior narrowing (horizontal and verticalwhite lines). Other important findings in OSA are elonga-tion and increased bulk of the soft palate (SP), enlargementof the lingual tonsil (LT), elongation and posteroinferiorprolapse of the tongue (white arrow), expansion of the fatcontaining parapharyngeal spaces (PPS), and thickening ofthe lateral oropharyngeal walls


2007). Elongation of the oropharynx can beassessed and is associated with a low-lyinghyoid bone and posterior prolapse of the tonguebase (Fig. 67).

Magnetic resonance imaging (MRI). Limitedavailability to the dental profession, relativelyslow routine scan times, and the absence of visu-alization of the hyoid bone are the major disad-vantages of this technique. In addition, there is a5–10% failure rate due to claustrophobia, andgrossly obese patients may not be able to beaccommodated in the bore of the magnet. MRIdoes not involve radiation and is performed withthe patient supine. MRI studies of OSA patientsand volunteers without sleep-disordered breathing

have been performed with patients awake,sedated, or during natural sleep, the cardiorespi-ratory status being monitored during this researchto ensure safety. Ultra-fast cine MRI allows “real-time” evaluation of the airway during sleepcycles unlike CTor CBCT. MRI provides optimalevaluation of the soft tissue factors potentiallycontributing to airway collapse (Fig. 68). Conven-tional 3D sequences supplemented by chemicalanalysis of soft tissue using MRI spectroscopyprovides accurate measurement of tongue volumeand the percentage of the tongue volume that isdue to fat. There is a close correlation betweenobesity (BMI), the severity of OSA (AHI), and thetongue volume and percentage of fat. Large,

Fig. 66 Reduction in airway size when changing fromerect to supine. Images performed within 24 h of each otherfor two different patients. A CBCT performed on the firstpatient (a) at the retroglossal level shows a capaciousairway which reduces markedly when MRI was performed

in the supine position (b). Similarly, a mild to moderatelyreduced retropalatal airway area of 127 sq. mm in the erectposition (c) decreases to a critically narrowed airway areaof 34 sq. mm in the supine position (d)

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fat-replaced tongues tend to prolapse inferiorlyand posteriorly resulting in elongation of the oro-pharynx and inferior displacement of the hyoidbone because of the attachments of extrinsictongue musculature (Kim et al. 2014; Kirknesset al. 2014). In addition, replacement of the tongueby fat decreases the number and function of mus-cle fibers and decreases stiffness as recently mea-sured by MRI elastography in patients with OSA(Brown et al. 2015).

b. Indications for imaging

OSA is not a diagnosis made by imaging.Certain skeletal and soft tissue features on imag-ing correlate with sleep-disordered breathing.

Imaging is a static examination performed onpatients who are awake, in quiet breathing withthe added limitation of the erect position if CBCTis the modality used. In contrast, sleep is adynamic process with varying, repetitive phases.Airway collapse during sleep is dependent ondiminished neuromuscular activity as well as pre-disposing anatomical factors.

The clinical suspicion of sleep-disorderedbreathing requires confirmation and evaluationwith polysomnography. Snorers and patientswith OSA treated with continuous positive air-ways pressure (CPAP) do not need imaging unlessthere are other clinical indications. Imaging isadvocated for those patients with nasal obstruc-tion, OSA treated primarily with a mandibular

Fig. 67 CTof OSA. (a) Digital lateral cephalogram in thesupine position. This allows skeletal assessment and dem-onstrates a low-lying hyoid bone. Obesity is evident. (b)Sagittal soft tissue reconstruction: the soft palate (S) iselongated (white arrow), and there is posterior and inferiordisplacement of the tongue (open white arrow) whichcorrelates closely with an inferiorly situated hyoid. The

tongue base is infiltrated with fat (dashed white oval). (c)Marked narrowing of the retropalatal oropharynx espe-cially in the mediolateral dimension and predominantlydue to hypertrophy of the palatine tonsils (PT). (d) Markednarrowing of the retroglossal oropharynx most marked inthe anteroposterior dimension related to enlargement andposterior prolapse of the tongue


advancement device (MAD), failed CPAP, or pre-surgical assessment.

The choice of imaging will depend on localavailability and expertise. Low-dose MDCTwith assessment of the nasal cavity, sinuses,maxillofacial skeleton, hyoid position, airway,soft palate, lymphoid tissue of Waldeyer’s ring,parapharyngeal spaces, and tongue is the opti-mal examination in routine clinical practice.Supine CBCT is an alternative imaging methodbut lacks the important soft tissue informationprovided by CT. Both modalities can assessimprovement in the airway by measuring thenarrowest cross-sectional dimensions and areabefore and after provision of a MAD or

orthognathic surgery. These simple measure-ments provide the closest correlation with theAHI (Ogawa et al. 2007; Barkdull et al. 2008).The site or sites of reduction in dimensions andarea of the upper airway are most commonly inthe nasal cavity, retropalatal region (upper oro-pharynx), and the retroglossal region (junctionof the inferior oropharynx and the hypophar-ynx). In severe OSA, there is often narrowingat multiple levels.

Volume rendering software can also provide a3D representation of the airway and volume mea-surement which can show improvement followingsuccessful treatment. However, several studieshave shown a poor correlation between airway

Fig. 68 MRI of OSA with marked airway narrowing atthe upper (retropalatal) oropharynx but not at theretroglossal level. (a) Coronal T1 of the airway. The oro-pharynx has an “hour-glass” configuration secondary toenlargement of the hyperintense, fat-filled parapharyngealspaces (black dashed arrows) and the palatine tonsils (PT).

(b) Axial T1 of the oropharynx through the narrowestretropalatal level (white dashed lines in a and c). (c) Mid-line sagittal T1. The soft palate (S) is thick and the tongueappears normal. (d) T1 axial through the tongue base(white dotted lines in a and c). There is no airway compro-mise. The epiglottis (E) is shown

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volume in patients who are awake and the severityof OSA as measured by the AHI (Alsufyani et al.2012). Static upper airway imaging during wake-fulness does not fully capture the reduction inupper airway dimensions and increase in pharyn-geal length that is characteristic of airway collapseduring sleep.

Imaging of Headache

Headache is the most common neurologicalsymptom in patients presenting to primary carephysicians. Correct diagnosis and treatment aremandatory. The International Headache Societyproduced an International Classification of Head-ache Disorders (ICHD) of which the third edition(3 beta) was published in 2013. It divides head-aches into three categories: primary, secondary,and a third group consisting of cranial neuralgias,central and primary facial pain, and other head-aches (Headache Classification Committee of theInternational Headache 2013).

Primary headaches account for 90% of head-ache and are subdivided into migraines, tension-type headaches (TTH), trigeminal autonomiccephalgias (a group which includes cluster head-aches), and other primary headache disorders(Headache Classification Committee of the Inter-national Headache Society 2013). There is nounderlying disease or structural abnormality, andprimary headaches tend to be recurrent andchronic. In contrast, secondary headaches aredue to an underlying disease and may be harmlessor dangerous; the latter often have an acute orsubacute presentation.

Primary HeadachesObtaining an accurate headache history is thecornerstone of diagnosis. This should elicit thesite, nature, associated symptoms, frequency,duration, and precipitating and relieving factors.Usually the history allows distinction between thetwo most common types of headache, TTH andmigraine, although it is widely accepted that thetwo conditions may overlap and form a contin-uum. A relevant physical examination is alsomandatory.

Imaging has a limited role to play in makingthe diagnosis of the majority of primary head-aches. Provided that the clinical examination isnormal and that there are no concerning symp-toms to suggest a diagnosis other than TTH ormigraine, the yield from routine imaging of thebrain in patients with chronic headache isextremely low. The incidence of significant abnor-malities on imaging in three large review studieswas 1–3%, a comparable yield to that seen inpatients without headaches. Despite multipleguidelines recommending against routine imagingof patients with chronic headache, the use ofimaging is increasing in the USA. In 2014, 12%of outpatients with headache were scanned at anannual cost of $1 billion (Callaghan et al. 2014).Other concerns are the risk from radiation fromthe use of CT scans and the detection of incidentalfindings which may lead to further investigations,cost, and patient anxiety.

Atypical symptoms, such as exacerbation ofthe headache by exertion or straining and changein the pattern or increased severity of headaches,are indications for imaging of primary head-aches. Trigeminal autonomic headaches areuncommon; neuroimaging should be performedas a proportion will have underlying structuralpathology (Favier et al. 2007), most commonlypituitary tumors, meningiomas, and aneurysms(Fig. 69).

Despite reassurance that chronic headache isnot life-threatening and highly unlikely to be dueto a serious underlying cause, patients may stillinsist on undergoing imaging to exclude a demon-strable cause for their symptoms. CT is widelyused by primary care physicians but MRI is theoptimal study because of its higher contrast reso-lution and the absence of radiation when com-pared to CT. If necessary, noninvasive MRangiography or venography can also be performedduring the same examination.

Secondary HeadachesA headache is secondary when it is caused byanother condition. Warning symptoms and signsthat should alert clinicians to the diagnosis of asecondary headache are commonly called “redflags” (Holle and Obermann 2013):


• First or worst headache• Abrupt onset without warning or progression• Fundamental change in the pattern of recurrent

headaches• Headaches commencing at unusual ages:

�5 years old and �50 years old• Failure to respond to appropriate therapy• The presence of cancer, pregnancy, or HIV• Headaches exacerbated by coughing, sneez-

ing, or straining• Headache onset: with seizure or syncope• Headache onset: with exertion, sex, or a

Valsalva maneuver• Abnormal physical examination: signs of infec-

tion, altered level of consciousness, signs ofmeningeal irritation, evidence of raised intracra-nial pressure, and focal neurological signs

Patients with secondary headache and anabnormal neurological examination are far morelikely to have significant cerebral pathology dem-onstrated by CT or MRI than those who have anormal neurological examination.

The majority of patients with “red flags” willpresent to emergency departments and willundergo CT of the brain as an integral and expe-dited part of their assessment. Key imaging find-ings include:

• Skull vault, skull base, or facial bone fractures(despite no history of trauma)

• Extradural, subdural, or subarachnoidhemorrhage

• A cerebral mass, hematoma, suspected infarct,edema, and imaging signs of raised intracranialpressure

• Dilatation (hydrocephalus), compression, orshift of the cerebral ventricles

• Evidence of intracranial or extracranial infec-tion, including the paranasal sinuses, dentition,upper neck, and orbits

In patients presenting with an abrupt onset ofsevere headache (a so-called thunderclap head-ache), CT has 100% sensitivity and specificityfor the diagnosis of subarachnoid hemorrhage if

Fig. 69 Meningioma of the cavernous sinus associatedwith narrowing of the internal carotid artery (ICA). Coro-nal post-gadolinium T1-weighted MRI with fat saturation(a) showing an enhancing mass (white arrows) filling andexpanding the left cavernous sinus, and surrounding andnarrowing the cavernous segment of the ICA, whichappears as a flow void, smaller than its right counterpart(red arrows). The tumor abuts and mildly displaces the

pituitary gland (asterisk), which shows minimally lessenhancement than it. Reconstruction of the arteries of thecircle of Willis from a time-of-flight MR angiogram(b) again shows narrowing of the left ICA (dotted arrow)(Images courtesy of Dr. Jolandi van Heerden (MBChB, FCRad (Diag) SA, NMED, FRANZCR) Perth RadiologicalClinic)

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performed within 6 h of the onset of the headache(Perry et al. 2011). If subarachnoid hemorrhage isdetected, patients may undergo CT angiography(CTA) to confirm or exclude an aneurysm(Fig. 70) or less commonly other types of vascularabnormalities. Open surgery (craniotomy and sur-gical clipping of an aneurysm) and an endo-vascular procedure (coiling or embolisation) arethe main therapeutic options.

CT also remains the mainstay of imaging forsuspected acute stroke. It is fast, inexpensive,and readily available but has limited sensitivityin the acute setting. In the first 6 h followingarterial occlusion, it will detect 65–70% ofinfarcts (Lev et al. 1999) (Fig. 71a). CTA canalso demonstrate arterial stenosis or occlusion inacute stroke prior to thrombolytic therapy: aproven technique for re-establishing perfusionof the affected tissue thereby reversing or mini-mizing the ischemic sequelae of arterialocclusion.

MRI is less widely available and is a muchslower imaging technique. The high magneticfield and relatively narrow bore of the magnetraise more problems for monitoring of acutely illpatients. MRI is used to clarify the findings on CTon patients presenting with an acute onset of sec-ondary headache. In addition, it will not uncom-monly show relevant pathology whennon-contrast CT is negative. Diffusion-weightedimaging (DWI) is a rapid addition to the conven-tional scan (Fig. 71b) and should always beperformed when cranial MRI is undertaken(Fig. 71c). It has a sensitivity and specificity of88–100% for the detection of stroke up to 7 daysfollowing the ischemic event (Srinivasan et al.2006). MR angiography can evaluate the flowand morphology of intracranial arteries withoutthe need for intravenous injection of contrast(Fig. 71d).

MRI has improved sensitivity and specificityfor the detection of other potential causes ofsecondary headache as compared with CT,with the exception of acute parenchymal or sub-arachnoid hemorrhage. CT remains a very use-ful technique especially when scans before andafter injection of intravenous contrast are used(Fig. 72). Calcification within mass lesions is

also shown more clearly with CT than withMRI.

Painful Cranial Neuropathies, OtherFacial Pains, and Other HeadachesFor those patients thought to have a headachewhichis in the third category of the ICHD classification,imaging has a definite role. Cranial nerve neuralgias(most commonly involving the trigeminal andglossopharyngeal nerves) and central and primaryfacial pain are imaged with high-resolution pre- andpost-contrast MRI including MR angiography. Adedicated and comprehensive study of this typeallows evaluation of the possible central, skullbase, and peripheral causes of neuralgia and pain.

To maximize the yield from this dedicatedinvestigation, the radiologist interpreting andreporting the study should have a comprehensiveunderstanding of anatomy and pathology involv-ing the brain, skull base, maxillofacial region, andneck. CT (either multidetector or cone beam) andpanoramic tomography have a role in evaluatingosseous structures such as the skull base, para-nasal sinuses, midface, mandible, and dentition.

Insights into the Pathogenesisof Headache from Structuraland Functional ImagingThere is strong evidence that migraine is a riskfactor for structural changes in the brain includingwhite matter abnormalities and silent infarct-likelesions. These are more common when themigraine attack is preceded by an aura (Bashiret al. 2013). It has long been hypothesized thatthese changes represent chronic small vessel cere-brovascular disease. There is conflicting evidenceas to whether these white matter changes progresswith time.

Functional imaging has established the exis-tence of a “pain matrix” consisting of specificregions in the cerebral hemispheres, thalami, andbrain stem which form a network which is acti-vated by nociceptive stimuli. This was discussedin the preceding section on the imaging offacial pain.

Research using positron emission tomography(PET) and functional MRI (fMRI) has providednew insights into the pathogenesis of headache,


especially migraine and the trigeminal autonomiccephalgias (May 2009). These headaches are nowthought to neurovascular, rather than purely vas-cular in origin. Trigeminal innervation of cranialvessels, especially the ophthalmic division (V1),leads to significant vasodilation. Pain, per se, trig-gers changes in vessel caliber and not vice versa.

The brain stem has a crucial role in the etiol-ogy of acute and chronic migraine. Activation ofthe dorsal aspect of the pons occurs in migraine;if the headache is unilateral, activation is

unilateral, and bilateral activation is seen withbilateral headache. Increase in cortical bloodflow seen in migraine is a consequence of thissubcortical activation. An aura precedes themigraine attack in 15–30% of cases; decreasein cortical blood flow (“cortical spreadingdepression”) occurs, especially in the occipitallobes, and is associated with visual phenomena.Patients with migraine with aura are at increasedrisk of stroke as compared with patients withoutaura or control subjects; overall, there is a

Fig. 70 Sudden onset of a “thunderclap” headache in a41-year-old female. A CT scan performed within 2 h of theevent (a) shows hyperdense subarachnoid hemorrhage inthe Sylvian fissures (dotted white arrows). Focal hyper-dense hemorrhage (dotted white oval) is present in thesuprasellar cistern (b). 3D reconstructions from a subse-quent CT angiogram in the frontal (c) and lateral

projections (d) show a large saccular aneurysm projectinginferiorly from the anterior communicating artery of thecircle of Willis (open red arrows). ICA = internal carotidartery (Images courtesy of Dr. Jolandi van Heerden(MBChB, FC Rad (Diag) SA, NMED, FRANZCR) PerthRadiological Clinic)

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twofold increase in stroke in patients withmigraine (Lee et al. 2016).

In contrast, activation of the hypothalamus isthe specific and key factor involved in the etiologyof trigeminal autonomic headaches. Functionalimaging of patients with cluster headache led to

successful deep stimulation of this area, and this isnow a recognized treatment option.

Using the MRI technique of voxel-based mor-phometry (VBM), decrease in gray matter volumein pain-processing areas has been demonstrated inpatients with the commonest forms of headache:

Fig. 71 Acute infarct in the distribution of the right pos-terior cerebral artery. Non-contrast CT (a) demonstrates awedge-shaped hypodense lesion in the right parietal andoccipital lobes (dotted arrows). The infarct is hyperintenseon T2-weighted MRI (b). On a diffusion-weighted image:DWI (c), the acute infarct is hyperintense, in keeping withrestricted diffusion. Restricted diffusion, primarily due tocellular swelling, is seen in infarcts almost immediately, up

to about 14 days after arterial occlusion. Time-of-flightangiography of the circle of Willis (d) can be performedwithout injection of contrast. The right posterior cerebralarteries (PCA) are patent and symmetric suggesting throm-bolysis of the clot or embolus which initially caused theinfarct (Images courtesy of Dr. Jolandi van Heerden(MBChB, FC Rad (Diag) SA, NMED, FRANZCR) PerthRadiological Clinic)


migraine and TTH. This is presumably the result ofrepeated and chronic nociceptive input (i.e., pain) asthe severity of cortical loss is proportional to theduration of headaches.

Conclusion and Future Directions

Imaging is an important adjunct to clinical exam-ination. It can confirm or refute a suspected diag-nosis, reveal pathology not evident on clinical

examination, and aid the choice of optimaltreatment.

A basic understanding of the benefits, limita-tions, and risks of different imaging techniques isessential for the specialist in oral medicine toavoid inappropriate investigations. This is espe-cially true for imaging involving ionizing radia-tion; the potential benefit of an imaging testshould always outweigh the potential risk.

Optimal results from imaging are achieved byclose liaison with a radiologist specializing in

Fig. 72 High-grade malignant glioma (glioblastomamultiforme). Non-contrast CT (a) demonstrates a mass inthe right cerebral hemisphere (dotted arrows).Low-density edema is present around the tumor (solidarrows). There is compression and deviation of the ven-tricular midline to the left (open arrow), resulting inobstruction of the left lateral ventricle (LV) which is

dilated. Following contrast (b), the tumor enhances (dottedoval) and contains abnormal vessels. A coronal reconstruc-tion (c) from the post-contrast study also shows the dis-placement of the midline to the left and the dilated leftlateral ventricle (LV) (Images courtesy of Dr. Jolandi vanHeerden (MBChB, FC Rad (Diag) SA, NMED, FRANZCR)Perth Radiological Clinic)

76 A. Whyte et al.

maxillofacial and head and neck imaging. A widerange of pathology that can occur in this complexanatomical region has been illustrated in thischapter.

The benefits of ultrasound as the initial imag-ing investigation for many clinical conditionsare recognized by head and neck surgeons andshould play a more important role in oral med-icine in the future. The absence of soft tissuecontrast is a significant disadvantage of conebeam CT imaging; computed tomography andmagnetic resonance imaging remain the main-stay of comprehensive cross-sectional evalua-tion when ultrasound is not indicated or whenfurther information is required.

Functional magnetic resonance imaging is animportant research tool that has improved under-standing of the pathogenesis of chronic and neuro-pathic facial pain. In the future, this techniqueshould have a major role in classifying patientswith facial pain, developing new pharmacologicalapproaches to treatment and assessing treatmentresponse.

Acknowledgment The author would like to acknowledgesupport from Dr Jolandi van Heerden for providing imagesin figures 69, 70, 71 and 72 and also an acknowledgementto “Dr Andrew Patrikeos,MBBS, MRCP(UK),FRANZCR, ANZAPNM, Perth Radiological Clinic, forhis advice and input on nuclear medicine techniques”

Cross-References

▶Arthritic Conditions Affecting the Temporo-mandibular Joint

▶Clinical Evaluation of Oral Diseases▶Clinical Evaluation of Orofacial Pain▶Head and Neck Malignancies▶Headache▶ Internal Derangements of the Temporomandib-ular Joint

▶Non-odontogenic Bone Pathology▶Odontogenic Pathology▶Oral Mucosal Malignancies▶ Pediatric Oral Medicine▶ Pain and Sleep

▶ Salivary Gland Disorders and Diseases▶ Sleep Bruxism▶ Soft and Hard Tissue Operative Investigationsin the Diagnosis of Oral Disease

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