Slow infections of the central nervous system.

This review describes the recent advances in slow infections of the nervous system emphasizing the pathogenetic aspects of these diseases. A theoretical model for the pathogenesis of subacute sclerosing panencephalitis (SSPE) is proposed, illustrating the factors that may affect host response to the measles virus and allow it to persist and produce the panencephalitis. The isolation of an oncogenic virus from progressive multifocal leukoencephalopathy (PML) has implications in the consideration of a viral etiology for some brain tumors. The agent responsible for the transmissibility of kuru and Creutzfeldt-Jakob disease (CJD) remains uncharacterized despite recent interest in viroids and abnormalities in replication of cell membranes. The epidemiological data on multiple sclerosis suggests an exposure to an infectious agent at an early age of life modified by the host response. No specific agent has been consistently associated with multiple sclerosis. Amyotrophic lateral sclerosis (ALS), Parkinson's disease, Mollaret's meningitis and Behcet's disease are other examples where a virus is suspect but unproven. The ability of viruses to persist in the host for months to years has linked many chronic neurologic diseases to an infectious agent, enlarging the spectrum of disease caused by viruses.