Merck Manual

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Subacute Sclerosing Panencephalitis (SSPE)


Brenda L. Tesini

, MD, University of Rochester School of Medicine and Dentistry

Reviewed/Revised Jun 2023

Subacute sclerosing panencephalitis, a progressive and usually fatal brain disorder, is a rare complication of measles Measles Measles is a highly contagious viral infection that causes various cold-like symptoms and a characteristic rash. Measles is caused by a virus. Symptoms include fever, runny nose, hacking cough... read more 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.

  • There is no treatment for subacute sclerosing panencephalitis.

  • This disorder is usually fatal.

SSPE occurs because the measles virus reactivates. In the past in the United States, for reasons that are not known, the disorder occurred in about 7 to 300 people per million people who had measles infection and in about 1 person per million people who received the measles vaccine. However, doctors think the people who developed SSPE after vaccination likely had a mild, undiagnosed case of measles before they were vaccinated and that measles infection, and not the vaccine, caused the SSPE.

SSPE is very rare in the United States and Western Europe because of widespread measles vaccination Measles, Mumps, and Rubella Vaccine The measles, mumps, and rubella (MMR) vaccine is a combination vaccine that helps protect against these three serious viral infections. The vaccine contains live but weakened measles, mumps... read more . However, analyses of more recent measles outbreaks suggest that the incidence of SSPE may be higher than previously thought.

Males are affected more often than females. The risk of developing SSPE is highest in people who contract measles before they are 2 years of age. SSPE usually begins in children or young adults, usually before age 20.

Symptoms of SSPE

The first symptoms of SSPE 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 Seizure Disorders In seizure disorders, the brain's electrical activity is periodically disturbed, resulting in some degree of temporary brain dysfunction. Many people have unusual sensations just before a seizure... read more 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.

Diagnosis of SSPE

  • Tests on cerebrospinal fluid or blood

  • Imaging tests

A doctor suspects SSPE in young people who have mental deterioration and muscle jerks.

A biopsy of the brain may need to be done if the tests cannot reveal a cause.

Treatment of SSPE

Prognosis for SSPE

SSPE 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.

Some people have periods where they have relatively good health and periods of flare-ups of the disorder.

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