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Subacute sclerosing panencephalitis, a progressive and usually fatal disorder, is a rare complication of measles that appears months or years later and causes mental deterioration, muscle jerks, and seizures.
Subacute sclerosing panencephalitis results from a long-term brain infection with the measles virus. The virus sometimes enters the brain during a measles infection. It may cause immediate symptoms of brain infection (encephalitis), or it may remain in the brain for a long time without causing problems.
Subacute sclerosing panencephalitis occurs because the measles virus reactivates. In the United States, for reasons that are not known, the disorder occurs in about 65 to 110 people out of 1 million who had wild measles infection.
The number of people with subacute sclerosing panencephalitis is declining in the United States and Western Europe just as the number of people with wild measles infection has declined. Males are affected more often than females.
Symptoms and Diagnosis
The disorder usually begins in children or young adults, generally before age 20. The first symptoms may be poor performance in schoolwork, forgetfulness, temper outbursts, distractibility, sleeplessness, and hallucinations. Sudden muscular jerks of the arms, head, or body may occur. Eventually, seizures may occur, together with abnormal uncontrollable muscle movements. Intellect and speech continue to deteriorate. Later, the muscles become increasingly rigid, and swallowing may become difficult. The swallowing difficulty sometimes causes people to choke on their saliva, resulting in pneumonia. People may become blind. In the final phases, the body temperature may rise, and the blood pressure and pulse become abnormal.
A doctor bases the diagnosis on the symptoms. The diagnosis may be confirmed by a blood test that reveals high levels of antibody to the measles virus, by an abnormal electroencephalogram (EEG), or by magnetic resonance imaging (MRI) or computed tomography (CT) that shows brain abnormalities.
Prognosis and Treatment
The disease is nearly always fatal within 1 to 3 years. Although the cause of death is usually pneumonia, the pneumonia results from the extreme weakness and abnormal muscle control caused by the disease.
Nothing can be done to halt progression of the disease. Anticonvulsant drugs may be taken to control or reduce seizures.
Last full review/revision May 2007 by Mary T. Caserta, MD
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