Subacute sclerosing panencephalitis (SSPE) is an important cause of acquired intellectual impairment and cognitive deterioration in children, especially in measles-endemic countries. It is important to understand the clinical spectrum and pathophysiology of SSPE as the initial presentation may closely mimic many other childhood neurological disorders. SSPE is persistent and chronic encephalitis due to an aberrant, wild measles virus infection. It manifests as a progressive neurodegenerative disorder of the central nervous system (CNS). [Page 1602]SSPE was first recognized by James R. Dawson Jr. in 1933. J. G. Greenfield coined the term subacute sclerosing panencephalitis in 1950. The disease is so named because it typically develops over a period of fewer than 9 months (subacute), causes a “sclerosing” type of pathological lesions in the brain, and affects ...