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