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Nose and paranasal sinuses
Normal anatomy, IFA classification& variations relevant for surgery
Bernhard Schuknecht
Medical Radiological Institut Zurich
European Course in Head and Neck Neuroradiology Nov 4-6, 2020
Normal anatomy ? → anatomic variations !frontal sinus –ethmoid - sphenoid
lack of consensus with respect to the clinical significance of anatomic variations !→ uniform acceptance regarding the relevance for endoscopic surgery !!
frontal beakdepth of frontal sinusposition of ethm. roofOnodi cell
If you go to the mountain often enough, you will meet the tiger
ZH paranasal sinus CT protocoll
how scan axial alveolar process ‐ top of frontal sinus (DLP ↓)
→ low dose acquistion, eff. mAs 90‐120 (dose ~ 0.1 mSV)→ reconstruction of data 0.6mm → 3 planes @ 0.75 mm, → bone window H70h, W 3200/ C 700→ soft tissue window H30s 0.75 →3mm ax/corW 300/ C 100→ navigation data: axial including. nose, front, ears→ correct pat. positioning and plane orientation
•al
coronal axial sagittal
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Zürich paranasal sinus CT protocol
how : iv contrast*:
• not required for preop. assessment of anatomy
• acute inflammation with complications
• suspicion of tumor (inverted papilloma, neoplasm)
• vascular lesions (angiofibroma, vascular malformations )
• (unilateral lesions!)
Paranasal sinus – CT ± navigation !!
When: chron. rhinosinusitisc s symptoms >12 weeks
ff maximal + optimal conservative tx
→ visualize drainage pathways + anatomy
→ assess persistent/recurrent unilateral disease
acute rhinosinusitis symptoms < 12 weeks
→ identify complications (MR?)
→ verify location and extension
→ reassure diagnosis (insuff tx response)
neoplasm w. osseus erosion or tu of bone /cartilage origin
suspected inverted papilloma
persistent mucosal swelling, chronicity of disease?
treatment: culture or empirically driven antibiotics for 2 w topical steroid for 3w or systemic steroids for 5 days
anterior ostiomeatal complex disease
posterior ostiomeatal complex diseaseLense dose CT 0.1 - 0.5 mSv
CBCT 0.05- 0.3 mSv
Lens protection device Ø navigation
well considered indication + good technique + communication= best radioprotection
Radiologist
Rhinologist
How?
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the nose and septum are part of the exam ! Nasal cavity→ middle meatus
Concha bullosa Haller cells Maxillary sinus pneumatisation
Anatomy coronal + osteomeatal complexEthmoid roof = fovea ethmoidalisOlfactory fossaCribriform plate – lateral lamellaMiddle turbinate vertical lamellaInferior turbinatePerpendicular laminaOlfactory rimAgger nasiEthmoid bullaFrontal recessHaller – infraorbital ‐ cell
Ostiomeatal complex → middle meatus• frontal recess + frontal sinus ostium• ethmoid infundibulum• hiatus semilunaris
obstruction of ostia→ stasis of secretions→ propagation of infection/inflammation Frontal sinus beak‐ depth
Frontal recessOlfactory fossaCribriform plateMiddle turbinate vertical/basal lamella
Inferior turbinateOlfactory rimAgger nasiEthmoid bullaUncinate process
posterior ostiomeatal complex• spheno‐ethmoid recess‐ sphenoid sinus• superior meatus ‐ posterior ethmoid –Onodi‐ cells
Anatomy sagittal plane : osteomeatal complex
obstruction of ostia → stasis of secretions→ propagation of infection/inflammation
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Middle turbinate
Transition of vertical to ground lamella separates ant. and post. ethmoid
vertical lamella
ground lamella
8 –point preoperative CT checklist :
• uncinate process
• ethmoid roof
• ant. ethmoid artery
• lamina papyracea
• optic nerve
• internal carotid artery
• bony defects/dehiscences
• ethmoid cells → frontal sinus + sphenoid.
= universal description of anatomic variations irrespective ot the surgery planned
1. attachment of uncinate processtype A (lateral) type B1 type B2 medial
different configuration of fs outflow tract
LT
How to identify uncinate process attachment ? RT
LT
→
direct drainagevia frontal recess
Rt side type Alateral
Lt side type Bmedial
indirect drainagevia ethmoid +hiatus semilunaris→ cor plane
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Ouflow of frontal sinusDistancefrontal beak‐ post wall
Positionof ethmoid roof
Ouflow of maxillary sinusuncinate process⇔ ostium
position of orbital floor+ Haller cells
narrowostium
wideostium
Anatomic features related to maxillary sinus
lacrimal recessus= surgical route free infraorbital nerve ~ zygomatic recess
accessory ostium
silent sinus (lt), atelectatic ostium
Underwood septum (sinus lift ) ???
2. position of ethmoid roof ⇔3. course of ant. ethmoid artery
right
left
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Identification ant. ethmoidalis artery : „v“ configuration 2. ethmoid roof⇔ cribriform plateStankiewicz JA, Chow JM. The Low Skull Base: An Invitation to DisasterAmerican Journal of Rhinology 2004; 18 35–40
Keros type 1: 1-3mm 2: 4-7mm 3: 8-16mm
susceptible to injury of ethmoid artery susceptible to injury of ethmoid roof‐ dura
ethmoid roof⇔ cribriform platemarked asymmetry ~ 7% !
Variation? meningocele, arachnoid herniation? MR exam!
meningo‐encephalocele
34. lamina papyracea ethmoid
Posttraumatic bone intact bony dehiscence (= point 7 checklist)
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5. optic nerve ⇔ ethmoid/sphenoid sinus
„intrasphenoid optic nerve position
sagittal
?
? = internal carotid artery = point 6 checklist
6. internal carotid artery⇔ sphenoid sinus
bony dehiscence = point 7 checklist
7. osseous defectscommonly w ~ polyposis
agger nasi cell supra agger cell supra agger frontal cell
International Frontal Sinus Anatomy Classification (IFAC) Wormald PJ, Hosemann W, Callejas C, Siow JK, et al. The Internationals Frontal Sinus Anatomy Classification (IFAC) and Classification of the Extent of Endoscopic Frontal Sinus Surgery (FSS). Int Forum Allergy Rhinol. 2016
classifying all cells as either anterior or posterior or medial8. ethmoid cells:
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International Frontal Sinus Anatomy Classification (IFAC)
classifying all cells as either anterior or posterior or medial or lateral
Suprabulla cell
Supra bulla frontal cell Frontal septal cell
Supraorbital ethmoid cell (lat.)
Wormald PJ, Hosemann W, Callejas C, Siow JK, et al. The Internationals Frontal Sinus Anatomy Classification (IFAC) and Classification of the Extent of Endoscopic Frontal Sinus Surgery (FSS). Int Forum Allergy Rhinol. 2016
Supra bulla cell 95%
49%
25%
89%
27%
28%
9%
Sommer F. et al. European Arch Oto‐Rhino‐Larngol 2019;271:39‐46
Preoperative CT checklist :
• uncinate process √
• ethmoid roof √
• ant. ethmoid artery √
• lamina papyracea √
• optic nerve √
• internal carotid artery √
• osseous defects √
• ethmoid cells → frontal s. √
الحفر من يهاب صعود الجبال يعيش دائما وسطWho is afraid to climb mountains will stay in a hole forever (arab proverb
If you go to the mountain often enough, you will meet the tiger chinese proverb
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