Synonyms of Subacute Sclerosing Panencephalitis

1. Dawson’s Disease
2. Dawson’s Encephalitis
3. Panencephalitis, Subacute Sclerosing
4. SSPE

General Discussion

Subacute sclerosing panencephalitis (SSPE) is a progressive neurological disorder characterized by inflammation of the brain (encephalitis). The disease may develop due to reactivation of the measles virus or an inappropriate immune response to the measles virus. SSPE usually develops 2 to 10 years after the original viral attack. Initial symptoms may include memory loss, irritability, seizures, involuntary muscle movements, and/or behavioral changes, leading to neurological deterioration.

Signs & Symptoms

Subacute sclerosing panencephalitis is a rare neurological disease of childhood or young adulthood. The first signs are usually behavioral changes such as failing schoolwork, memory loss, and/or irritability. Involuntary muscle movements (myoclonic jerks) and generalized seizures follow. Subacute sclerosing panencephalitis is a progressive disease which results in personality changes, outbursts of temper, sleeplessness, disorientation, stupor, spasticity, loss of previously acquired intellectual skills, poor memory and judgment (dementia), and general neurological deterioration. Blindness may develop because of a lesion in the vision center of the brain (cortical blindness) and the nerves of the eyes may waste away (optic atrophy). The late symptoms of subacute sclerosing panencephalitis may include muscle rigidity, elevated body temperature (hyperthermia) and/or abnormalities of respiration, heartbeat, and blood pressure. These disturbances of normal bodily functions (homeostasis) indicate that the hypothalamus gland, which is located deep inside the brain, may be affected.

The complications of subacute sclerosing panencephalitis, such as severe pneumonia or coma, usually become life-threatening within 1 to 3 years. However, there may be an improvement in some affected individuals for extended periods of time.

Causes

Subacute sclerosing panencephalitis is thought to be caused by a slow measles virus (paramyxovirus). Slow viruses may stay dormant in humans for extended periods of time, then for reasons yet unknown may become reactivated. The role of heredity which may make a person susceptible to slow viruses is not well understood.

The symptoms of SSPE, including inflammation of the brain (encephalitis) and the loss of the fatty covering on nerve fibers (demyelination), may develop due to reactivation of the virus many years after the initial illness. It may also be associated with an inappropriate immune response to the rubella virus (measles). Typically, affected individuals have a history of measles infection 2 to 10 years before the onset of subacute sclerosing panencephalitis.

A few cases of subacute sclerosing panencephalitis in the medical literature have been associated with animal contact. These affected individuals had contact with pets such as monkeys, dogs, or kittens that later died of the same illness.

Affected Populations

With the widespread use of the measles vaccine in the United States, the incidence of subacute sclerosing panencephalitis has been reduced dramatically, although about 10 cases per year are reported. However, in less developed parts of the world, this disorder is much more common. In India, for example, the incidence is estimated at about 20 cases per year per million of the population. Subacute sclerosing panencephalitis seems to affect males more often than females and occurs far more often in children and adolescents than in adults.

Related Disorders

Symptoms of the following disorders can be similar to those of subacute sclerosing panencephalitis. Comparisons may be useful for a differential diagnosis:

Progressive rubella panencephalitis is a rare slowly progressive neurological disorder that closely resembles subacute sclerosing panencephalitis. It is caused by the rubella virus and develops because of congenital rubella syndrome or childhood rubella infection (German measles). Symptoms usually include behavioral changes, the loss of previously acquired intellectual skills, inability to coordinate movement (ataxia), involuntary muscle movements (spasticity), and/or seizures. There is no known treatment for this disorder. Fewer than 20 cases have been reported in the medical literature.

Progressive multifocal leukoencephalopathy is a rare progressive neurological disorder that occurs in people with certain forms of cancer, an Acquired immunodeficiency syndrome (AIDS), or those who are receiving immunosuppressant drugs. The disease develops during adulthood and symptoms may include paralysis of one side of the body (hemiplegia), loss of vision in one eye (hemianopsia), loss of verbal communication skills (aphasia), inability to coordinate movement (ataxia), stupor, and/or coma. Progressive multifocal leukoencephalopathy may be the result of the reactivation of a slow virus (polyoma).

Inclusion body encephalitis (subacute sclerosing leukoencephalitis) is a rare progressive neurological disorder that occurs mostly in children under the age of 12 years. The symptoms begin gradually and may include behavioral changes, loss of previously acquired intellectual skills, involuntary muscle contractions or spasms (myoclonus) of the trunk, arms, and/or legs, and the inability to communicate verbally. Later symptoms usually include loss of vision and hearing, muscle rigidity, and/or dementia.

Standard Therapies

The diagnosis of subacute sclerosing panencephalitis may be confirmed by clinical evaluation and blood testing that reveals abnormally high levels of the measles antibody. The examination of the electrical activity of the brain (EEG) usually shows a characteristic pattern. The fluid surrounding the brain and spinal cord (cerebrospinal fluid) typically have elevated levels of gammaglobulin and measles antibody.

There is no specific treatment for subacute sclerosing panencephalitis. Anticonvulsants may help to control seizure activity. Another treatment is symptomatic and supportive.

Investigational Therapies

Several antiviral agents, which have been investigated for the treatment of subacute sclerosing panencephalitis, have not been successful. Isolated reports about the effectiveness of the drug isoprenaline have not been confirmed by controlled clinical trials. More studies are needed to determine if the drug might be effective for some people under certain circumstances.

Other studies are ongoing for the treatment of subacute sclerosing panencephalitis. The drug interferon-alpha (IFN), delivered directly into the spinal column (intrathecal) with and without the addition of oral in simplex, is being tested for the treatment of this disease. Approximately 50 percent of affected individuals who had a slowly progressive form of the disease experienced an improvement in their symptoms with this treatment. More research is needed to determine the long-term safety and effectiveness of interferon-alpha for the treatment of this disorder.