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.
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 improvement in some affected individuals for extended periods of time.
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 rubeola 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.
With widespread uss 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 population. Subacute sclerosing panencephalitis seems to affect males more often than females and occurs far more often in children and adolescents than in adults.
The diagnosis of subacute sclerosing panencephalitis may be confirmed by clinical evaluation and blood testing that reveals abnormally high levels of the measles antibody. 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 has elevated levels of gammaglobulin and measles antibody.
There is no specific treatment for subacute sclerosing panencephalitis. Anticonvulsants may help to control seizure activity. Other treatment is symptomatic and supportive.
Several anti-viral agents, which have been investigated for the treatment of subacute sclerosing panencephalitis, have not been successful. Isolated reports about the effectiveness of the drug isoprinosine 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 inosiplex, 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.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
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