A focal, suppurative infection within the brain parenchyma, typically surrounded by a vascularized capsule. The term cerebritis is used to describe a nonencapsulated brain abscess. Predisposing conditions include otitis media and mastoiditis, paranasal sinusitis, pyogenic infections in the chest or other body sites, head trauma, neurosurgical procedures, and dental infections. Many brain abscesses occur in immunocompromised hosts and are caused less often by bacteria than by fungi and parasites including Toxoplasma gondii, Aspergillus spp., Nocardia spp., Candida spp., and Cryptococcus neoformans. In Latin America, the most common cause of brain abscess is Taenia solium (neurocysticercosis). In India and the Far East, mycobacterial infection (tuberculoma) remains a major cause of focal CNS mass lesions.