Adult-onset subacute sclerosing panencephalitis: immunocytochemical and electron microscopic demonstration of the viral antigen.

We report a case of subacute sclerosing panencephalitis (SSPE) in a 52 year-old man, who developed rapidly progressive mental deterioration, myoclonic seizures, quadriplegia, and remained incapacitated until his death 4 years after the onset of symptoms. Immunocytochemical and electron microscopic studies are reported. Titers of measles virus antibodies were consistently high in both serum and cerebrospinal fluid, and periodic synchronous discharges were recorded on EEG. Suppressed cellular immunity was noted in skin test with phytohemagglutinin. The brain was extensively destroyed by inflammatory processes. There were either laminar or widespread areas of cortical necrosis associated with neuronophagia, neuronal loss, glial proliferation, and perivascular lymphocytic cuffing. Numerous intranuclear inclusions, in the neurons and glial cells, stained with immunoperoxidase using antiserum to SSPE virus; ultrastructurally, these inclusions were made of tubular nucleocapsids of paramyxovirus. Neurofibrillary changes were occasionally encountered in the pigmented neurons. The white matter showed extensive loss of myelinated fibers and increased numbers of astrocytes with bizarre nuclei. This well-documented case of SSPE in an adult might be related to a condition of impaired cellular immunity.