A brain abscess is a collection of immune cells, pus, and other material in the brain, usually from a bacterial or fungal infection.
Brain abscesses commonly occur when bacteria or fungi infect part of the brain. Swelling and irritation (inflammation) develop in response to this infection. Infected brain cells, white blood cells, live and dead bacteria, and fungi collect in an area of the brain. Tissue forms around this area and creates a mass. While this immune response can protect the brain by isolating the infection, it can also do more harm than good. The brain swells. Because the skull cannot expand, the mass may put pressure on delicate brain tissue. Infected material can block the blood vessels of the brain. The germs that cause a brain abscess usually reach the brain through the blood.
- Streptococcus pneumoniae
- Staphylococcus aureus and epidermidis: following neurosurgery
- Gram negative species more common in infants
- Listeria in pregnant women and older patients
- Group B strep (GBS) and E coli in neonates
The immunocompromised patient is susceptible to a host of other organisms including:-
- Toxoplasma gondii
- Nocardia asteroides
- Candida albicans
- Listeria monocytogenes
- Mycobacterium sp
- Aspergillus fumigatus
Symptoms may develop slowly, over a period of 2 weeks, or they may develop suddenly. They may include:
- Changes in mental status
- Decreasing responsiveness
- Eventual coma
- Slow thought processes
- Decreased movement
- Decreased sensation
- Decreased speech (aphasia)
- Fever and chills
- Language difficulties
- Loss of coordination
- Loss of muscle function
- Stiff neck
- Vision changes
If untreated, a brain abscess is almost always deadly. With treatment, the death rate is about 10 – 30%. The earlier treatment is received, the better. Some patients may have long-term neurological problems after surgery.
Cefotaxime or ceftriaxone plus metronidazole for Bacteroides sp or vancomycin for Staphylococcus aureus based on suspicion
All patients receive antibiotics for a minimum of 4 to 8 wk. Initial empiric antibiotics include cefotaxime 2 g IV q 4 h or ceftriaxone 2 g IV q 12 h; both are effective against streptococci, Enterobacteriaceae, and most anaerobes but not against Bacteroides fragilis.
If clinicians at all suspect Bacteroides sp, metronidazole 15 mg/kg (loading dose) followed by 7.5 mg/kg IV q 6 h is also required.
If S. aureus is at all suspected, vancomycin 1 g q 12 h is used (with cefotaxime or ceftriaxone) until sensitivity to nafcillin (2 g q 4 h) is determined.