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Subacute Sclerosing Panencephalitis (SSPE)

By Mary T. Caserta, MD, Professor of Pediatrics, Division of Infectious Diseases; Attending Physician, University of Rochester School of Medicine and Dentistry; Golisano Children’s Hospital at Strong, University of Rochester Medical Center

Subacute sclerosing panencephalitis, a progressive and usually fatal brain disorder, is a rare complication of measles that appears months or years later and causes mental deterioration, muscle jerks, and seizures.

  • Subacute sclerosing panencephalitis is caused by the measles virus.

  • The first symptoms are usually poor school performance, forgetfulness, temper outbursts, distractibility, sleeplessness, and hallucinations.

  • The diagnosis is based on symptoms.

  • This disorder is usually fatal.

  • There is no treatment for subacute sclerosing panencephalitis.

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 7 to 300 people per million people who had wild measles infection and in about 1 person per million people who received the measles vaccine. However, doctors think the people who developed encephalitis after vaccination likely had a mild, undiagnosed case of measles before they were vaccinated and that the vaccine did not cause the subacute sclerosing panencephalitis.

Subacute sclerosing panencephalitis is rare 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.


Subacute sclerosing panencephalitis 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.


  • Tests on cerebrospinal fluid or blood or imaging tests

A doctor suspects subacute sclerosing panencephalitis in young people who have mental deterioration and muscle jerks and a previous history of measles. The diagnosis may be confirmed by examination of cerebrospinal fluid, 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. A biopsy of the brain may need to be done if the tests cannot reveal a cause.


Subacute sclerosing panencephalitis 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.


  • Anticonvulsant drugs for seizures

Nothing can be done to stop the progression of subacute sclerosing panencephalitis. Anticonvulsant drugs may be taken to control or reduce seizures.