Brain Abscess
What is brain abscess? Focal collection within brain parenchyma
Pathogenesis? n Direct q q n 20 -60% of the cases Focal abscess Hematogenous q q Multiple abscesses No identifiable souces in 20 -40% of the cases
Primary sources in direct spread and distribution of abscess n n Otitis media – inferior temporal lobe and cerebellum Frontal or ethmoid sinuses – frontal lobe Dental caries – frontal lobe Foreign bodies - bullet
Primary sources hematogenous spread n n n 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 n n n Usually mouth flora May be from pelvic or intraabdominal infections – multiple abscesses Examples – anaerobic streptococci, bacteroides species, fusobacterium
Aerobics n Gram positive q q q n Staphylococcus aureus – neurosurgery and trauma Streptococcus milleri – proteolytic enzymes that cause necrosis Others – viriddans streptococci, microaerophilic streptocci Gram negative q q Usually from trauma or neurosurgery Klebsiella pneumoniae, Pseudodomonas species, E. coli, and Proteus species
Immunocompromised hosts? n n Opportunistic infections Toxoplasma gondii Listeria Fungi – Aspergillus, cryptococcus neoformans, coccidiodidides immitis, Candida albicans
Immigrants n n Parasites Cysticercosis – 85% of brain infection in Mexico city
Symptoms? n n Headache – most common Neck stiffness q q n n Associated with occipital abscess Abscess leaks into lateral ventricle Altered mental status – cerebral edema Vomiting – increased intracranial pressure
Physical finding? n n n Fever – not very reliable, since only 45 -50% present Focal neurological deficit – days or weeks after onset of headache Seizure q q q n n 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? n n n CT scan with contrast MRI with gadolinium diethylenetriamine Lumbar puncture q q Contraindicated Analysis n n WBC < 500/mm 3 with predominately lymphocytes WBC > 1, 000/mm 3 consistent with meningitis but not improved with antibiotics, consider MRI for ruptured abscess
Treatment options? n n Antibiotics – 6 to 8 weeks Surgical drainage
Antibiotics? n n n n 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? n n No clinical improvement within a week Depressed sensorium Increased intracranial pressure Progressive increase in the ring diameter of the abscess
Surgical approach n Needle aspiration q q n Prefer approach because of less neurological deficit Under ultrasound or CT guided Surgical excision q q q 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? n n Mainly for mass effect Disadvantages q q Reduce contrast enhancement on CT scan Slow capsule formation Increase risk of rupture Decrease penetration of antibiotics
Complications n n Neurological deficits – commonly seizure with frontal lesion Poor prognosis – mortality rate up to 30% q q q Rapid progression of the infection Severe mental changes Rupture into ventricle
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