Background
Microbiology
- Direct spread
- Nose/sinuses: Streptococcus species (especially S. milleri), Haemophilus species, Bacteroides species, Fusobacterium species
- Teeth: Streptococcus species, Bacteroides species, Prevotella species, Fusobacterium species, Haemophilus species
- Ears: Enterobacteriaceae, Streptococcus species, Pseudomonas aeruginosa, Bacteroides species
- Penetrating head trauma: Staphylococcus aureus, Enterobacter species, Clostridium species
- Neurosurgery: Staphylococcus species, Streptococcus species, Pseudomonas aeruginosa, Enterobacter species
- Hematogenous spread
- Immunocompromised patient
- HIV: Toxoplasma gondii, Nocardia species, non-tuberculous mycobacteria, Listeria monocytogenes, Cryptococcus neoformans
- Neutropenia: Gram-negative bacilli, Aspergillus species, mucormycosis, Candida species, Scedosporium species
- Transplantation: Aspergillus species, Candida species, mucormycosis, Scedosporium species, Enterobacteriaceae, Nocardia species, Toxoplasma gondii, and Mycobacterium tuberculosis
- Plus anaerobes, which are common
Investigations
- MRI
- Temporal lobe or cerebellum suggests contiguous spread from chronic otitis or mastoiditis
- Frontal lobe suggests contiguous spread from frontal or ethmoid sinusitis
- Multiple abscesses in a middle cerebral artery distribution suggests bacteremia
Management
- Empiric therapy is directed at the likely organisms based on etiology (direct vs. hematogenous spread)
- For likely oral, ear, or sinus source, treated with ceftriaxone and metronidazole at CNS doses
- For likely hematogenous spread, treated with vancomycin
- For uncertain etiology, combination of ceftriaxone, metronidazole, and vancomycin
- For neurosurgical patients, vancomycin plus a broad-spectrum antipseudomonal antibiotic such as ceftazidime, cefepime, or meropenem
Further Reading
