Brain abscesses can develop through hematogenous or contiguous spread from infections elsewhere in the body. Common causes include sinusitis, dental infections, and congenital heart defects. Diagnosis involves blood tests, MRI, and sometimes brain biopsy. Treatment consists of 6-8 weeks of IV antibiotics, along with needle aspiration or excision of the abscess depending on its size and location. The choice of antibiotics depends on suspected causative organisms but commonly includes vancomycin, metronidazole, and third generation cephalosporins. Surgical drainage or excision may be needed for large or multi-loculated abscesses.

1. BRAIN ABSCESS
Route
Hematogenous spread: Pneumococcus common
Risk factors: pulmonary abscess or AV fistulas,
congenital cyanotic heart disease,
immunocompromised, chronic sinusitis/otitis, dental
procedures.
Contiguous spread:
Purulent sinusitis (Strep. milleri and Strep.
anginosus)
Mastoiditis:(anaerobic strep., Bacteroides,
Enterobacteriaceae (Proteus)
Odontogenic (Actinomyces)—> Frontal lobe.
Penetrating cranial trauma: (S. aureus or
Enterobacteriaceae) or neurosurgical procedure
(Staph. Epidermis)
Work up
Blood culture: send for culture and initiate
empirical antibiotics
Cultures from cerebral abscesses are sterile in
up to 25% of cases
Organisms recovered varies with the primary
source of infection:
LP is avoided in most cases of cerebral
abscess.
CBC, ESR, CRP
MRI brain: MRS, MRI with contrast with
DWI (Diffusion restriction)
Collagen in thewall of abscess is hypointense
in T1W and hyper in T2W.
MRS: Lactate, alanine peaking.
MR perfusion:Lower rCBV in rim of abscess
Treatment
Medical
Treatment is begun in cerebritis
stage (before complete
encapsulation), even though
many of theselesions
subsequently go on to become
encapsulated.
Small lesions: <3cm lesion
3 cm is suggested as a cutoff,
above this diameter surgery
should be included.
Duration of symptoms ≤ 2wks
(correlates with higher incidence
of cerebritis stage).
Patients show definite clinical
improvement within thefirst
week with medical treatment
ANTIBIOTIC SELECTION
Initial antibiotics of choice when pathogen unknown,
and especially if S. aureus suspected:
Vancomycin: covers MRSA:15 mg/kg IV q8-12
hours to achieve trough 15-20 mg/dl
PLUS
3rd generation cephalosporin (ceftriaxone); utilize
cefepime if post-surgical
PLUS
Metronidazole.Adult:500mg q6-8hours
Alternative to cefepime +metronidazole: meropenem
2gm IVq8h
Make appropriate changes as sensitivities become
available
If culture shows only strep, may use PCNG (high
dose) alone or with ceftriaxone
If cultures show methicillin sensitive staph aureus
and the patient does not have a beta lactam allergy,
can change vancomycin to nafcillin (adult: 2 gm IV q
4 hrs. peds:25 mg/kg IV q 6 hrs)
Fungal: Cryptococcus neoformans, Aspergillus sp.,
Candid as: Liposomal amphotericin B 3-4mg/kgIV
daily +flucytosine25 mg/kg PO QID.
In AIDS patients:Toxoplasma: sulfadiazine
+pyrimethamine+leucovorin.
For suspected or confirmed nocardia: Liposomal
amphotericin B 3-4mg/kg IV daily +flucytosine25
mg/kg PO QID + Imipenem Ampicillin.
IV antibiotics for 6–8 weeks may then D/C even if
the CT abnormalities persist (neovascularity
remains).
Surgical
Needle
Mainstay of surgical treatment.
Especially well-suited for
multiple or deep lesions may
also be used with thin walled or
immature lesions
Most often implemented with
stereotactic localization
especially for deep lesions
May beperformed under local
anesthesia if necessary (e.g. in
patients who are poor surgical
candidates for general
anesthesia).
May becombined with irrigation
with antibiotics or normal saline.
Repeated aspirations are
required in up to 70%of cases.
May bethe only surgical
intervention required (in
addition to antibiotics), but
sometimes must be followed
with excision (especially with
multi-loculated abscess).
Excision
Evidence of significantly
increased ICP.
Significant mass effect
exerted by lesion (on CT or
MRI)
Poor neurologic condition
(patients responds only to
pain, or does not even
responseto pain)
Failure of medical
management:
Resistant to Rx: neurological
deterioration, progression of
abscess towards ventricles, or
after 2 weeks if the abscess is
enlarged. Also considered if
no decrease in sizeby 4
weeks.
Difficulty in diagnosis
(especially in adults).
Proximity to ventricle
Traumatic abscess associated
with foreign material
Fungal abscess
Multilobulated abscess
Follow-up CT/MRI scans
cannot be obtained every 1–2
weeks.
SURGICAL EXCISION:
1. Shortens length of time on antibiotics and reduces risk of recrudescence.
2. Recommended in traumatic abscess to debrided foreign material (especially bone), and in fungal abscess because
of relative antibiotic resistance
3. External drainage: controversial. Not frequently used.
4. Instillation of antibiotics directly into the abscess:has not been extremely efficacious, although it may be used as
for refractory Aspergillus abscesses
FLOW CHART IN BRAIN ABSCESS MANAGEMENT
PERIVENTRICULAR LOCATION IS DANGEROUS
1. Risk of ruptureinto ventricle is high: Life threatening
2. Vascularity is less in medial aspect of brain than lateral
3. Reticular matrix is less toward ventricle,
4. Fiber are converging toward midline so abscess may track down and brust into
ventricl
DR. SURESH BISHOKARMA, MBBS, MS, MCH
NEUROSURGEON, NEPAL