Epidemiology
Etiology
Primary source of infection
Contiguous spread of an infection (most common cause)
Can be otogenic (e.g., otitis media , mastoiditis) Sinus (e.g., sinusitis ): most commonly seen in men and caused by Streptococcus milleri Oral (e.g., dental infection)
Meningeal (e.g., meningitis )
Direct injection, e.g., head trauma, neurosurgery
Hematogenous spread, e.g., patients with cyanotic heart disease (least common cause): multiple abscesses located in the middle cerebral artery distribution at the gray-white junction
Pathogens: brain abscesses are most commonly polymicrobial
Most common pathogens
Obligate anaerobes, e.g., Bacteroides species, (mainly due to dental infections)
In immunocompromised states: Toxoplasma , Aspergillus , Candida, Mucormycosis (also known as Zygomycosis), Cryptococcus
Pathophysiology
Clinical features
Diagnostics
Imaging :
Initial Imaging : CT head w/ IV contrast (demonstrates hypodense core with a uniform, thin ring-enhancing rim and surrounding vasogenic edema).Confirmatory / Gold Standard Imaging : Brain MRI w/ gadolinium (higher sensitivity; diffusion-weighted imaging [DWI] shows hyperintense/restricted diffusion within the necrotic core).
Definitive Microbiologic Diagnosis :
CT-guided stereotactic aspiration or surgical drainage (Gram stain, aerobic/anaerobic/fungal/AFB cultures, and histopathology).
Key Labs :
Blood cultures x 2 (positive in ~30% of hematogenous cases; obtain before Abx if not delaying urgent care).Elevated ESR, CRP, and peripheral leukocytosis (variable).
CRITICAL CONTRAINDICATION :
Lumbar Puncture (LP) is strictly CONTRAINDICATED due to high risk of uncal or tonsillar herniation from intracranial mass effect.
Treatment