Brain infections may manifest as a diffuse infection, resulting in encephalitis with focal brain involvement, or as inflammation of the brain secondary to meningeal (see Meningitis) or parameningeal infections. Encephalitis is most commonly due to viruses, such as herpes simplex, herpes zoster, cytomegalovirus, or West Nile virus. Multifocal brain involvement may occur during diffuse disseminated encephalomyelitis (a postinfectious syndrome). HIV infection (see Human Immunodeficiency Virus (HIV)) and prion diseases (see Prion Diseases) can also affect the brain diffusely. Focal brain infections may be due to a brain abscess or to fungal or parasitic brain infections.

Slow virus infections, such as progressive multifocal leukoencephalopathy (see Brain Infections: Progressive Multifocal Leukoencephalopathy (PML)), caused by the JC virus, or subacute sclerosing panencephalitis, caused by the measles virus, also affect the brain; they are characterized by a long incubation and a prolonged course.

Last full review/revision November 2012 by John E. Greenlee, MD