Brain abscess

Dr. Joe M DasSenior ResidentDept. of NeurosurgeryBrain abscess

HistoryDefinitionEpidemiologyPathogenesisClinical featuresInvestigationsTreatmentSpecial abscesses

HistoryHippocrates Purulent otorrhea and deleriumThe first successful operation for brain abscess - S.F. Morand (France) in 1752 on a temperoethmoidal abscess.Pyogenic Disease of the Brain and Spinal Cord, Meningitis, Abscess of the Brain, Infective Sinus Thrombosis (1893) - William Macewen Father of modern day abscess managementKing (1924) marsupializationDandy (1926) aspirationSargent (1928) enucleationVincent (1936) complete excisionHeineman et al (1971) successful medical management

Henry II, King of FranceDeath was predicted by NostradamusDied from an orbital wound The skull was not penetrated but infection spread intracraniallyInfection had spread to the brain along the orbital veins, forming an abscess under the cortex.

Oscar WildeIrish writer and poetDied of otogenic brain abscess

DefinitionMathisen GE, Johnson JP: Brain abscess. Clin Infect Dis 1997; 25:763-781.

A focal intracranial infection that is initiated as an area of cerebritis and evolves into a collection of pus surrounded by a vascularized capsule.

Epidemiology1500-2500 cases per year in the US8% of ICSOL in developing countries: = 2-3 : 1Median age 30 40 yrs2 to otitic focus - 40 yrs2 to PNS infection 30-40 yrs25% in children otitic focus / CHD0.2% of cranial operationsImmunosuppression

PathogenesisSources:Contiguous source 25-50 %Hematogenous dissemination / trauma 20-35 %Cryptogenic 10-35 %

Contiguous spreadRoutes of contiguous spread:Direct extension through osteitis / osteomyelitisRetrograde thrombophlebitis via diploic or emissary veinVia local lymphaticsLocalisation:Otitis media Temporal lobe / cerebellumPNS Frontal lobeSphenoid sinusitis Temporal lobe / sellaDental infection (molars) Frontal lobe (M.C) / temporal

India M.C source Middle ear suppurationWestern countries M.C source Spread from PNSSites of bone dehiscence:Post wall of frontal sinusTegmen tympaniTrautmanns triangle

HematogenousMultiple, multiloculated abscesses - mortalityM.C sources in adults chronic pyogenic lung diseases (especially lung abscess), bronchiectasis, empyema, and CF. Distant sources wound & skin infections, osteomyelitis, pelvic intra-abdominal infections; after esophageal dilation or sclerosing therapy for esophageal varices.CCHD (TOF/ TGV) 5-15% of brain abscess cases. Temporal > Parietal > Cerebellum > Occipital

Classic triad of headache, fever, and focal neurologic deficit is rarely seen (< 5-20% of cases in case series)1/3rd polymicrobialIncidence of negative cultures - 25-30%Sudden worsening of a preexisting headache accompanied with meningismus may be indicative of a catastrophic eventrupture of the abscess into the ventricular space.

When there is no obvious source (up to 25% of cases), upper respiratory tract flora and anaerobes are often isolated.Several sources have identified a patent foramen ovale by echocardiogram in these cases and propose this as a possible mechanism for seeding oral flora to the brain.Khouzam RN, El-Dokla AM, Menkes DL. Undiagnosed patent foramen ovale presenting as a cryptogenic brain abscess: case report and review of the literature.Heart Lung. Mar-Apr 2006;35(2):108-11.

InvestigationsX-ray skull:Often normalPost-traumatic air inside cranial cavitySinusitis/mastoiditisCT brain:Diagnosis, localisation and treatmentSinisitis/mastoiditisStaging, HCP, ICP, edema, associated subdural empyema, meningitis, ventriculitis, multiplicityNCCT - Isodense / hyperdenseCECT - Smooth, thin, regular wall with decreased density both in the centre and surrounding

MRI BrainT1Central low intensity (hyperintense to CSF)Peripheral low intensity (vasogenic oedema)Ring enhancementVentriculitis may be present, in which case hydrocephalus will commonly also be seenT2 / FLAIRCentral high intensity (hypointense to CSF, does not attenuate on FLAIR)Peripheral high intensity (vasogenic oedema)The abscess capsule may be visible as a intermediate to slightly low signal thin rimDWI/ ADCHigh DWI signal is usually present centrallyLow signal on ADC

SWILow intensity rimComplete in 75%Smooth in 90%Mostly overlaps with contrast enhancing rimDual rim sign- a hyperintense line located inside the low intensity rimMR perfusion- RCBV is reduced in the surrounding oedema c.f. to both normal white matter and tumour oedema seen in high grade gliomasMR spectroscopy- elevation of a succinate peak is relatively specific but not present in all abscesses ;high lactate, acetate,alanine, valine, leucine, and isoleucine levels peak may be present ; cho / crn and NAA peaks are reduced

What are the imaging differential diagnoses?

How to differentiate between peripherally enhancing neoplasm and abscess radiologically?

Laboratory investigationsTC Normal / mild ( if meningitis / acute systemic infection)ESR - in >90%CRP - . Useful marker to differentiate between brain abscess and slowly progressive ICSOLsBlood culture - +ve in IE / mycotic aneurysmsCSF analysis Non-specific. Mild pleocytosis. CSF potein mild Glu NormalLP dangerousPCR analysis of 16S rDNA to identify to species level111In-labelled leukocytes

Treatment

Surgical therapyThe optimal approach to patients with bacterial brain abscessAspiration after bur-hole placement or complete excision after craniotomy (no prospective trial comparing these two)May be performed under stereotactic neuroimaging guidanceStereotactic aspiration is a useful approach even for abscesses located in eloquent or inaccessible regions; repeat aspiration should be considered if the initial aspiration proves ineffective or partially effective. Intraoperative ultrasound - for the aspiration of small abscesses and can delineate abscess pockets,Recurrence rates after stereotactic aspiration range from 0-24 %.

Pus has been aspirated. What all investigations are to be sent?StainsGram stainAcid-fast stain (AFB stain) for MycobacteriumModified acid-fast stain (for Nocardia) looking for branching acid fast bacillusSpecial fungal stains (e.g., methenamine silver, mucicarmine)CulturesRoutine cultures: aerobic and anaerobicFungal culture: this is not only helpful for identifying fungal infections, but since these cultures are kept for longer period and any growth that occurs will be further characterized, fastidious or indolent bacterial organisms may sometimes be identifiedTB culture

What are the indications for initial surgical treatment?Significant mass effect exerted by lesion (on CT or MRI)Difficulty in diagnosis (especially in adults)Proximity to ventricle: indicates likelihood of intraventricular rupture which is associated with poor outcomeEvidence of significantly increased intracranial pressurePoor neurologic condition (patients responds only to pain, or does not even response to pain)Traumatic abscess associated with foreign materialFungal abscessMultiloculated abscessFollow-up CT/MRI scans cannot be obtained every 1-2 weeks

What are the indications for complete excision by craniotomy ?Multiloculated abscesses in whom aspiration techniques have failedAbscesses containing gasAbscesses that fail to resolvePosttraumatic abscesses that contain foreign bodies or retained bone fragments to prevent recurrenceAbscesses that result from fistulous communications (e.g., secondary to trauma or congenital dermal sinuses)Abscess localized to one lobe of the brain and contiguous with a primary focus.Cerebellar abscess in childrenDifficulty in diagnosisSuspected fungal abscess

What are the contraindications for craniotomy and evacuation?

Abscess in the cerebritis stageDeep-seated abscess in eloquent areaMultiple abscesses

Aspiration vs. CraniotomyCraniotomy is now rarely practiced as the first line of treatment. Aspiration repeated as necessary or with drainage, has widely replaced attempts at complete excision.Several reports have advocated excision as the procedure of choice because it is often followed by a lower incidence of recurrence and shorter hospitalization.Xiao et al reported that favorable outcome was not significantly different between the patients treated by excision or aspiration. However, the mortality rate was significantly lower in the patients treated with excision than the patients treated with aspiration. This is probably due to the better general condition and/or more favorable location of abscess that could be excised surgically in such patients.Stereotactic aspiration should be considered the treatment of choice in all but the most superficial and the largest cerebral abscesses.

IV rupture with ventriculitis and HCP What to do?Rapid evacuation and dbridement of the abscess cavity via urgent craniotomy+Ventricular drainage+Intravenous or intrathecal administration of appropriate antimicrobial agents

When to opt for medical therapy alone?Patients with medical conditions that increase the risk associated with surgeryMultiple abscessesAbscesses in a deep or dominant locationCoexisting meningitis or ependymitisEarly reduction of the abscess with clinical improvement after antimicrobial therapyAbscess size < 3 cm

What is the optimal duration of medical treatment?Bacterial brain abscess 6-8 weeks IV 2-3 months oral antimicrobial therapyPost-surgical excision - Courses of 3 to 4 weeks of antimicrobial therapy Medical therapy alone - up to 12 weeks with parenteral agentsA combination of surgical aspiration or removal of all abscesses larger than 2.5 cm in diameter 6 weeks or more of antimicrobial therapy, and weekly neuroimaging to document abscess resolution Repeat neuroimaging studies - biweekly for up to 3 months after completion of therapy

How will you follow up an abscess case radiographically?CT scans weekly during the course of therapy One week after discontinuation of antibiotics Scan one month later Monthly or bimonthly till radiographic resolutionTime course for abscess resolution: in abscess size 2-3 weeks after initiating therapyComplete resolution of abscess cavity, mass effect 3-4 monthsResidual contrast enhancement 6-9 months

Brain abscess Management algorithm

Any role for steroids? host defense mechanisms and penetration of some antimicrobial agents into the brain abscess cavityMay result in improvement of neurological symptoms and signs.Therapy started in abscess patients with:Associated edema and mass effectProgressive neurological deteriorationImpending cerebral herniation.Dose:Dexamethasone, 10 mg every 6 hours is generally administered initially and then tapered once the patient has stabilized. The use of prolonged courses of corticosteroids is discouraged. May also decrease contrast enhancement of the abscess capsule in the early stages of infection, thereby being a false indicator of radiologic improvement.

What is the role of anticonvulsants?Initiated immediately and continued at least 1 year due to high risk in the brain abscesses.The treatment can be discontinued if no significant epileptogenic activity can be shown in electroencephalogram (EEG).

How to treat otogenic brain abscess?Initial neurosurgical removal of abscess, which after improvement of general condition of the patient should be followed by radical otosurgical removal of the process from the ear.Otogenic brain abscess: diagnostic and treatment experience. D DjericN ArsovicV Djukic. International Congress Series, 2003; 1240 (61-65)Brain abscesses of otogenic origin. [Article in Serbian] Nesi V1, Janosevi L, Stojici G, Janosevi L, Babac S, Sladoje R. Srp Arh Celok Lek. 2002 Nov-Dec;130(11-12):389-93.

How to manage multiple brain abscesses?Incidence 10-50%Emergent stereotactic aspiration for all lesions > 2.5 cm diameter and those causing mass effect, located deep in brain stem or close to ventricular wallIf all the lesions are < 2.5 cm and not producing mass effect, the largest one should be aspirated for diagnostic cultures.Antibiotics withheld till culture resultsAntibiotics for 3 months (Immunosuppressed 1 yr)Repeat surgical aspiration if radiographic enlargement after 2 weeks of therapyFailure to diminish in size after 4 weeks of antibioticsClinical deterioration

How to treat Nocardial brain abscess?A sulfonamide trimethoprim, is recommended.Alternative agents include minocycline, imipenem, amikacin, third-generation cephalosporins, and linezolidIn immunocompromised patients or those in whom therapy failsa third-generation cephalosporin or imipenem + a sulfonamide or amikacinNocardia farcinica, a species that may be highly resistant to various antimicrobial agents, successful treatment has included moxifloxacin.Craniotomy with total excision is difficult in patients with Nocardia brain abscess because these abscesses are often multiloculated.The duration of therapy - 3 to 12 months, but it should probably be continued up to 1 year in those who are immunocompromised.

What are the treatment options for fungal brain abscess?Patients with fungal brain abscess, especially those who are immunocompromised, have a high mortality rate despite combined medical and surgical therapy. Candidal brain abscess - Amphotericin B preparation + 5-flucytosineThe therapy of choice for Aspergillus brain abscess is voriconazole.Alternative agents include an amphotericin B preparation, posaconazole, and itraconazole.Itraconazole - as an extension of successful treatment rather than as primary therapy. Excisional surgery or drainage is a key factor in the successful management of CNS aspergillosis.

CNS mucormycosis - Amphotericin B deoxycholate or a lipid formulation of amphotericinCorrection of the underlying metabolic derangements and aggressive surgical dbridement The etiologic agents of mucormycosis invade blood vessels, tissue infarction occurs and impairs the delivery of antifungal agents to the site of infection; this often leaves surgery as the only modality that may effectively eliminate the infecting microorganism. In patients not responding to or intolerant of an amphotericin B formulation, posaconazole can be used as salvage therapy.HBO - useful adjunctSurgery is the cornerstone of therapy for brain abscesses caused by Scedosporium speciesVoriconazole is the agent of choice.

What is meant by delayed glue abscess?Delayed multiloculated abscess after embolization of AVM nidusThe duration of the procedure and repeated handling of the catheters along with use of large amount foreign material or Hysto-acryl glue can precipitate infection. Cure of the lesion can only be obtained by surgical excision of the infected and partially embolized AVM. Antibiotic prophylaxis with all endovascular procedures is recommendedMourier L, Bellec C, Lot G, Reizine D, Gelbert F, Dematons C, et al. Pyogenic parenchymatous and nidus infection after embolization of an arteriovenous malformation: an unusual complication. Case report. Acta Neurochir (Wien) 1993;122:130-3.Pendarkar H, Krishnamoorthy T, Purkayastha S, Gupta AK. Pyogenic cerebral abscess with discharging sinus complicating an embolized arteriovenous malformation. J Neuroradiol 2006;33:133-8

What are the factors to be considered in a patient with cyanotic heart disease developing a brain abscess?5-18% population with CHD. 10 times more prone. M.C TOFIntracardiac right to left shunt by-pass allows direct entry of blood containing bacteria to the cerebral circulation without pulmonary filtration. Anaerobic streptococci (Sterile cultures are reported in 16-68%)Cardiopulmonary risk, coagulation defects and variable degree of immunodeficient statesA deeply located parieto-occipital abscess larger than 2 cm diameter which causes mass effect, should be aspirated immediately even in late cerebritits stage using stereotactic or CT guided methods to decrease intra-cranial pressure and avoid intraventricular rupture of brain abscess.Intravenous Beta-lactam antibiotics are started immediately.

Cerebellar abscess6-35% of all brain abscessesOften ominously silent and carry significant mortalityCan cause sudden total occlusion of CSF pathways early in the course of disease.Presence of periventricular lucency is an absolute indication of immediate ventricular drainage regardless of level of consciousness i.e. even if patient is fully conscious.Burr hole aspiration has emerged as a satisfactory method

Sequelae30-50% of survivors are found to have neurological sequelae. The incidence of residual neural deficits - hemiparesis, cognitive and learning deficits in children, is less with aspiration than excision. About 72% of patients can have epileptic seizures upto five years of diagnosis. This incidence is less with aspiration than excision. 5 to 10% abscesses recur due to inadequate or inappropriate antibiotics, failure of removal of foreign body, dural fistula or failure of eradication of primary source. Hydrocephalus may also develop

What is the difference between otogenic and odontogenic brain abscess?Unlike otogenic abscess, odontogenic abscess occurs as a sequel of acute rather than chronic infectionWhat is the most common site of metastatic abscess?In the distribution of MCA Parietal & frontal (left side)Grey-white junction capillary flow slowestDoes a high velocity bullet injury cause an abscess?The fragments do not present a significant risk because of heat sterilisation and do not require removal

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