Definition
Subacute sclerosing panencephalitis (SSPE) is a long-lasting (chronic) infection of the central nervous system that causes inflammation of the brain. The infection is caused by an altered form of the measles virus. The symptoms appear years after the initial infection, following re-activation of the latent virus.
Description
SSPE is one of three types of encephalitis that can occur following infection with the measles virus. The other forms are an acute (sudden appearance of symptoms) form that is typically associated with the rash that forms during the measles infection. The other form of SSPE affects the myelin sheath surrounding nerve cells, and is likely part of an autoimmune reaction.
SSPE develops when the measles virus, which is still present but is in an inactive (or latent) form, is reactivated. The appearance of symptoms typically leads to a disease that last from one to three years.
The disease is also known as subacute sclerosing leukencephalitis and Dawson's encephalitis.
Demographics
Children and young adults are primarily affected with SSPE. Males are also more affected than females, with a male-to-female ratio of 4:1. As well, there is a geographical component to the infection, with those in rural areas being much more susceptible (approximately 85% of cases arise in rural environments). Since the measles vaccine has been introduced, the disease has become rare in many areas of the globe, particularly the western world (about one in 1,000,000 people). Fewer than 10 cases per year occur in the United States. However, in the Middle East and India the incidence of the disease remains high (over 20 cases per 1,000,000 people).
Causes and symptoms
The disease is caused by the reactivated form of a mutated measles virus. The inactive form of the virus can be present in the body for up to 10 years following the initial bout of measles before the symptoms of SSPE develop. While normally the measles virus does not infect the brain, the mutated virus is capable of invading the brain.
When symptoms do develop, motor skills and mental faculties become progressively worse. Initial symptoms include a change in behavior, irritability, memory loss, and difficulty in forming thoughts and solving problems. Subsequently, a person can experience involuntary movements and seizures (also known as myoclonic spasms), loss of the ability to walk, difficulty speaking, and swallowing difficulty (dysphagia). Blindness can occur. In the final stages of the disease, a patient with SSPE may become mute and can lapse into a coma.
Monitoring the electrical activity of the brain has shown that SSPE causes disruptions that are consistent with the deterioration of the central nervous system. These changes tend to occur in stages, and so can be diagnostic of the progression of the disease. A different pattern of brain deterioration has been detected using the techniques of computed tomography and magnetic resonance imaging. However, this latter pattern is not yet refined enough for diagnostic use. Examination of brain tissue has shown that the disease is associated with the deterioration of the cortex and loss of white matter.
Diagnosis
SSPE is diagnosed based on the early symptoms, detection of antibodies to the measles virus, detection of protein in the spinal fluid, and the information gained from monitoring of the brain.
Treatment team
Initially, the family physician and local clinicians provide care. With the progression of the disease, specialists such as neurologists can become involved. Nurses are critical for those patients with advanced disease. Family and friends are an important source of care throughout the disease.
Treatment
There is no cure for SSPE. In the past, the primary means of treatment included therapy to curb seizures and the use of supportive measures such as feeding tubes when swallowing becomes difficult. During the 1990s, evidence accumulated in the medical literature to support the contention that SSPE can be stabilized and the progressive deterioration can be slowed by drug therapy. The drugs used lessen the damage inflicted by the immune system (immunomodulators such as the interferons), or attack the virus. The drugs used are an orally administered form of the antiviral drug inosine pranobex (oral isoprinosine), oral isoprinosine combined with interferon alpha or beta, and interferon alpha combined with intravenous ribavirin (another antiviral). In particular, the isoprinosine-interferon alpha combination has been reported to produce up to a 50% rate of remission or improvement in symptoms. As promising as these results are, no controlled studies have yet been performed. Therefore, the treatments are not typically used.
Recovery and rehabilitation
As SSPE is almost always fatal, emphasis is placed upon maintaining comfort, rather than rehabilitation.
Clinical trials
There were no clinical trials in progress or planned in the United States as of January 2004. However, organizations such as the National Institute for Neurological Diseases and Stroke undertake and fund research aimed at furthering the understanding of the causes, prevention, and treatment of subacute sclerosing panencephalitis and related diseases.
Prognosis
Without treatment, death usually occurs within one to three years following the first appearance of symptoms. Treatment with immunomodulators and antiviral drugs has achieved remission of the disease in some cases. As well, remission can occur spontaneously in approximately 5% of cases.
Resources
BOOKS
Icon Health Publications. The Official Parent's Sourcebook on Subacute Sclerosing Panencephalitis: A Revised and Updated Directory for the Internet Age. San Diego: Icon Grp. Int., 2002.
PERIODICALS
Forcic, D., M. Baricevic, R. Zgorelec, et al. "Detection and characterization of measles virus strains in cases of subacute sclerosing panencephalitis in Croatia." Virus Research (January 1999): 51–56.
Hayashi, M., N. Arai, J. Satoh, et al. "Neurodegenerative mechanisms in subacute sclerosing panencephalitis." Journal of Child Neurology (October 2002): 725–730.
OTHER
National Library of Medicine. "Subacute Sclerosing Panencephalitis." MEDLINE plus.http://www.nlm.nih.gov/medlineplus/ency/article/001419.htm (January 25, 2004).
"Subacute Sclerosing Panencephalitis Information Page." National Institute of Neurological Disorders and Stroke.http://www.ninds.nih.gov/health_and_medical/disorders/subacute_panencephalitis_.htm (January 26, 2004).
ORGANIZATIONS
National Institute for Neurological Diseases and Stroke (NINDS). 6001 Executive Boulevard, Bethesda, MD 20892. (301) 496-5751 or (800) 352-9424. http://www.ninds.nih.gov.
National Organization for Rare Disorders. 55 Kenosia Avenue, Danbury, CT 06813-1968. (203) 744-0100 or (800) 999-6673; Fax: (203) 798-2291. orphan@rarediseases.org. http://www.rarediseases.org.
Brian Douglas Hoyle, PhD
