Brain Abscess

What is brain abscess?

Focal collection within brain parenchyma

Pathogenesis?

Direct 20-60% of the cases Focal abscess

Hematogenous Multiple abscesses No identifiable souces in 20-40% of the cases

Primary sources in direct spread and distribution of abscess Otitis media – inferior temporal lobe and

cerebellum Frontal or ethmoid sinuses – frontal lobe Dental caries – frontal lobe Foreign bodies - bullet

Primary sources hematogenous spread Chronic pulmonary infections – lung abscess

and empyema Skin infection Intrabdominal and pelvic infection Bacterial endocarditis Cyanotic congenital heart disease – most

common in children

Microbiology

Clues to the primary source

Anaerobics

Usually mouth flora May be from pelvic or intraabdominal

infections – multiple abscesses Examples – anaerobic streptococci,

bacteroides species, fusobacterium

Aerobics

Gram positive Staphylococcus aureus – neurosurgery and trauma Streptococcus milleri – proteolytic enzymes that cause

necrosis Others – viriddans streptococci, microaerophilic streptocci

Gram negative Usually from trauma or neurosurgery Klebsiella pneumoniae, Pseudodomonas species, E. coli,

and Proteus species

Immunocompromised hosts?

Opportunistic infections Toxoplasma gondii Listeria Fungi – Aspergillus, cryptococcus

neoformans, coccidiodidides immitis, Candida albicans

Immigrants

Parasites Cysticercosis – 85% of brain infection in

Mexico city

Symptoms?

Headache – most common Neck stiffness

Associated with occipital abscess Abscess leaks into lateral ventricle

Altered mental status – cerebral edema Vomiting – increased intracranial pressure

Physical finding?

Fever – not very reliable, since only 45-50% present Focal neurological deficit – days or weeks after

onset of headache Seizure

25% of the cases May be first manifestation of brain abscess Grand mal in frontal infection

Third or sixth cranial palsy – increased intracranial pressure

Papilledema – cerebral edema

Tests?

CT scan with contrast MRI with gadolinium diethylenetriamine Lumbar puncture

Contraindicated Analysis

WBC < 500/mm3 with predominately lymphocytes WBC > 1,000/mm3 consistent with meningitis but not

improved with antibiotics, consider MRI for ruptured abscess

Treatment options?

Antibiotics – 6 to 8 weeks Surgical drainage

Antibiotics?

Penicillin G – aerobic and anaerobic streptococci from mouth flora

Metronidazole – against anaerobes but not aerobes, good intralesional penetration

Ceftriaxone or cefotaxime – Enterobacteraciae, particular chronic ear infection

Ceftazidime – neurosurgery and p. aeruginosa Oxacillin or nafcillin – head trauma or neurosurgery,

mainly staphylococcus aureus coverage Vancomycin – MRSA Aminoglycosides – poor blood brain barrier, not use

Indications for surgical drainage? No clinical improvement within a week Depressed sensorium Increased intracranial pressure Progressive increase in the ring diameter of

the abscess

Surgical approach

Needle aspiration Prefer approach because of less neurological

deficit Under ultrasound or CT guided

Surgical excision More neurological deficit Prefer in traumatic abscess, particularly with

foreign body,and encapsulated fungal abscess Advantages: shorten antibiotics to 2 to 4 weeks

and less relapse

Steroid use?

Mainly for mass effect Disadvantages

Reduce contrast enhancement on CT scan Slow capsule formation Increase risk of rupture Decrease penetration of antibiotics

Complications

Neurological deficits – commonly seizure with frontal lesion

Poor prognosis – mortality rate up to 30% Rapid progression of the infection Severe mental changes Rupture into ventricle