Subacute Sclerosing Panencephalitis (SSPE). Dowson encephalitis.
Incidence
SSPE affects primarily children and adolescents. It occurs rarely in the United States in fewer than one per one million children, with less than 10 new cases each year. SSPE is not inherited, and boys are affected more often than girls. Most children with SSPE have a measles infection before two years of age, with the first signs of SSPE presenting eight to ten years later. The incidence of SSPE among non-immunized children is 100-200 times higher than among those who have been immunized effectively. Measles vaccine does not cause SSPE.
Clinical Characteristics
Subacute sclerosing panencephalitis (SSPE) is a progressive disease of the brain caused by an unusual response to the measles virus. Following a measles infection, the virus may rarely persist within the brain in an inactive state. The virus may then reactivate several years later to cause SSPE, a swelling of the brain with associated mental and physical deterioration. A child with SSPE will initially experience a change in behavior, irritability, memory loss, and difficulty with learning and schoolwork. Subsequently, an increase in neurological damage results in additional, more obvious symptoms, including involuntary spasms and seizures. Eventually, further mental deterioration occurs, with associated impairment in speech and comprehension. A child will become unable to walk and may experience blindness. It is unclear why some children develop SSPE following a measles infection while most do not. Indeed, the mechanism by which the measles virus persists in the brains of children with SSPE is also poorly understood.
Precipitants
It is unclear why some children develop SSPE following a measles infection while most do not. Indeed, the mechanism by which the measles virus persists in the brains of children with SSPE is also poorly understood.
Provocation Tests
None
Diagnostic Procedures
The diagnosis of SSPE is considered clinically in a child with a previous measles infection who is experiencing mental deterioration and spasms. To confirm the diagnosis, the blood and spinal fluid are tested to determine if antibodies to the measles virus are present at high levels. Sometimes an EEG, or brain wave test, and an MRI are also conducted to detect characteristic abnormalities.