Differential diagnosis of brain abscess
•Epidural and subdural empyema
•Septic dural sinus thrombosis
•Mycotic cerebral aneurysms
•Septic cerebral emboli with associated infarction
•Acute focal necrotizing encephalitis (most commonly due to
herpes simplex virus)
•Metastatic or primary brain tumors
•Pyogenic meningitis
Brain abscess
Direct spread
Post neurosurgery
Dental infection
Frontal or ethmoid sinuses
otitis media and mastoiditis
Bullet wounds
Brain abscess
Hematogenous spread
Intraabdominal infection
Chronic pulmonary infections
Skin infections
Pelvic infection
Esophageal dilation and endoscopic sclerosis of
esophageal varices
Cyanotic congenital
heart diseases
Bacterial endocarditis
Microbiologic pathogens in brain abscesses, according to major primary
source of infection
Source of infection Pathogens
Paranasal sinuses
Streptococcus (especially Streptococcus
milleri), haemophilus, bacteroides,
fusobacterium
Odontogenic sources Streptococcus, bacteroides, prevotella,
fusobacterium, haemophilus
Otogenic sourcesEnterobacteriaceae, streptococcus,
pseudomonas, bacteroides
LungsStreptococcus, fusobacterium,
actinomyces
Urinary tract Pseudomonas, enterobacter
Penetrating head traumaStaphylococcus aureus, enterobacter,
clostridium
Neurosurgical procedureStaphylococcus, streptococcus,
pseudomonas, enterobacter
Endocarditis Viridans streptococcus, S. aureus
Congenital cardiac malformations
(especially right-to-left shunts)Streptococcus
Aerobic
Gram-positive cocci Staphylococcus aureus
Viridans streptococci
Streptococcus milleri
Streptococcus pneumoniae
Gram-negative rods
Escherichia coli,
Pseudomonas spp,
Klebsiella pneumoniae,
Proteus spp
The most frequent anaerobes cultured from a brain
abscess
•anaerobic streptococci.
• Bacteroides spp (including B. fragilis).
•Prevotella melaninogenica.
• Propionibacterium.
•Fusobacterium.
• Eubacterium.
• Veillonella.
•Actinomyces
Immunocompromised hosts
•Toxoplasma gondii
•Listeria
•Nocardia asteroides
•Aspergillums'
•Cryptococcus neoformans.
•Coccidioides immitis.
• Mucormycosis
CT-Scan
Early cerebritis appears as an irregular area of low
density that does not enhance following contrast
injection.
the lesion enlarges with thick and diffuse ring
enhancement following contrast injection
thin ring which may not be uniform in thickness
MRI
•more sensitive for early cerebritis
•more sensitive for detecting satellite lesions
•More accurately
•estimates the extent of central necrosis
•ring enhancement,
•cerebral edema
•Better visualizes the brainstem
LP
a lumbar puncture (LP) is contraindicated
Decompression of the cerebrospinal fluid (CSF)
pressure associated with brain stem herniation
in 1.5 to 30 percent of cases
Culture and biopsy
•Gram's stain
• aerobic
• anaerobic
• mycobacterial
•fungal culture
Antibiotics
•Penicillin G covers most mouth flora including both aerobic and anaerobic
streptococci.
•Metronidazole readily penetrates brain abscesses, Given the excellent
intralesional concentrations and the high probability of anaerobes.
•Ceftriaxone covers most aerobic and microaerophilic streptococci also covers
many Enterobacteriaceae
•Ceftazidime should be used when brain abscess complicates a neurosurgical
procedure or in cases where the abscess culture grows P. aeruginosa.
•Vancomycin should be included when brain abscess follows penetrating head
trauma or craniotomy or when S. aureus bacteremia is documented
Aspiration
•preferred for speech areas and regions of the
sensory or motor cortex and in comatose
patients.
•Not preferred for:•Early cerebritis without evidence of cerebral
necrosis.
•Abscesses located in vital regions of the brain or
those inaccessible to aspiration
Surgery
•indications for excision after initial aspiration
and drainage:
•Traumatic brain abscesses (to remove bone chips
and foreign material)
•Encapsulated fungal brain abscesses
•Multiloculated abscesses