Subacute sclerosing panencephalitis (SSPE) is a progressive neuropsychiatric disorder occurring after natural infection with measles virus. There is typically a history of measles infection at an early age followed by an asymptomatic period, with onset of symptoms starting 7-10 years after primary measles infection. The pathogenesis is unknown but is thought to be related to infection with a variant of measles virus.

The disorder is characterized by development of personality and behavioral changes, progressive cognitive decline, and dementia with seizures, myoclonus, spasticity, ataxia, and vision loss. The final stages of the disease progress to flaccidity, decorticate rigidity, autonomic dysfunction, and eventual coma and death. Disease course is typically progressive but can fluctuate, with some patients having relapsing and remitting symptoms. Patients have elevated antimeasles antibody concentrations in serum and cerebral spinal fluid. Prognosis is poor, and death usually occurs within 3 years of symptom onset.