Dawson´s encephalitis

Definition

Subacute sclerosing panencephalitis (SSPE) is a progressive, debilitating, and fatal brain disorder caused by infection with a mutant measles (rubeola) virus. A mutant virus is one that has undergone genetic changes (mutations).

Alternative Names

Causes

Ordinarily, the measles virus does not cause brain damage, but certain mutant forms may invade the brain, causing severe illness and death. SSPE has been reported in all parts of the world, but in western countries it is considered a rare disease.

Fewer than 10 cases per year are reported in the United States, a dramatic decrease that followed the nationwide measles immunization program. However, in some countries like India, over 20 cases of SSPE per million people are reported each year.

SSPE tends to occur several years after an individual has measles, even though the person seems to have fully recovered from the illness. Males are more often affected than females, and the disease generally occurs in children and adolescents.

Affected individuals frequently die 1 to 2 years after being diagnosed with this condition, but some may survive for longer periods.

SSPE is due to the direct invasion of brain cells by the mutant measles virus, which provokes brain inflammation (swelling and irritation) that may last for years.

Symptoms

• Gradual behavioral changes
• School problems
• Bizarre behavior
• Myoclonic jerking (quick muscle jerking or spasms)
• Seizures
• Dementia (loss of cognitive (thought), emotional, and social abilities)
• Unsteady gait
• Coma
• Rigidity (very tense muscles) or flaccidity (lacking muscle tone), with weakness in both legs

Exams and Tests

There may be a history of measles in an unvaccinated child. A physical examination may show signs of optic nerve (responsible for sight) damage. There may also be damage to the retina (the part of the eye that receives light), poor performance on motor (movement) coordination tests, and muscle twitching.

The following tests may be performed:

• Electroencephalogram (EEG), a test of the electrical activity of the brain, which may show a wave pattern typical of SSPE
• Brain MRI, which provides high-quality pictures of the brain
• Serum antibody titer (concentration of the antibody), showing elevated titer to measles virus
• Spinal tap for analysis of the protein in the collected fluid
• Anti-measles virus antibodies

Treatment

No cure for SSPE exists. However, certain anti-viral drugs can slow the progression of the disease. A combination of oral isoprinosine and interferon-alfa injected directly into the brain appears to be the most effective treatment.

Ribavirin and amantadine are other anti-viral medications that have been used with limited success. Patients responding to treatment need to receive it for the rest of their lives. Effective immunization against measles, to prevent development of this condition, is the only solution presently available.

Outlook (Prognosis)

SSPE is always fatal.

Possible Complications

Prior to death, there may be:

• Behavior changes
• Dementia
• Stupor and coma
• Seizures and subsequent injuries

When to Contact a Medical Professional

Call your health care provider if your child has not completed their scheduled vaccines. The measles vaccine is included in the MMR vaccine.

Prevention

Immunization against measles is the only known prevention for SSPE. This should be accomplished during the recommended American Academy of Pediatric and Centers for Disease Control immunization schedule. See MMR immunization.

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