Brain abscesses are caused by an infection with bacteria, parasites, or fungi.

The most common organisms responsible for brain abscess include:

• Streptococcus
• Staphylococcus aureus
• Enterobacter
• Proteus
• Pneumococci
• Toxoplasmosis
• Fungi

There are two main ways in which a brain abscess can form:

• Infection of the brain tissue or surrounding structures
• Metastatic spread:
• Spread of organisms via the bloodstream, from another site of infection