Walsh & Hoyt: Viruses and the Central Nervous System

A variety of both DNA and RNA viruses can infect the CNS. Most of these viruses either affect the meninges, causing aseptic meningitis, or cause a meningoencephalitis. Pure encephalitis may also be caused by viral infection, but it is less common than meningitis or meningoencephalitis. Rare patients develop encephalitis in the aftermath of an acute systemic viral infection (postinfectious encephalitis or encephalomyelitis, acute disseminated encephalomyelitis), and still others develop a chronic degenerative encephalopathy. The spinal cord and peripheral nerves occasionally become inflamed during a viral infection, producing myelitis, radiculitis, or radiculomyelitis. Nevertheless, the number of patients who actually develop symptomatic viral infections of the CNS is extremely small compared with the number of patients who experience a systemic viral illness.