Herpesvirus infections of the nervous system.

There are eight human herpesviruses (HHVs). Primary infection by any of the eight viruses, usually occurring in childhood, is either asymptomatic or produces fever and rash of skin or mucous membranes; other organs might be involved on rare occasions. After primary infection, the virus becomes latent in ganglia or lymphoid tissue. With the exception of HHV-8, which causes Kaposi's sarcoma in patients with AIDS, reactivation of HHVs can produce one or more of the following complications: meningitis, encephalitis, myelitis, vasculopathy, ganglioneuritis, retinal necrosis and optic neuritis. Disease can be monophasic, recurrent or chronic. Infection with each herpesvirus produces distinctive clinical features and imaging abnormalities. This Review highlights the patterns of neurological symptoms and signs, along with the typical imaging abnormalities, produced by each of the HHVs. Optimal virological studies of blood, cerebrospinal fluid and affected tissue for confirmation of diagnosis are discussed; this is particularly important because some HHV infections of the nervous system can be treated successfully with antiviral agents.