Acute Disseminated Encephalomyelitis
National Organization for Rare Disorders, Inc.
It is possible that the main title of the report Acute Disseminated Encephalomyelitis is not the name you expected.
Acute disseminated encephalomyelitis (ADEM) is a neurological, immune-mediated disorder in which widespread inflammation of the brain and spinal cord damages tissue known as white matter. White matter is tissue composed of nerve fibers, many of which are covered by a collection of fats and proteins known as myelin. Myelin, which collectively may be referred to as the myelin sheath, protects the nerve fibers, acts as an insulator and increases the speed of transmission of nerve signals. Damage to the myelin sheath (demyelination) affects the nerve's ability to transmit information and potentially can cause a wide range of neurological symptoms. The specific symptoms and severity of ADEM can vary from one individual to another. In some cases, ADEM is preceded by a viral infection or vaccination. The exact cause the disorder is unknown although it is believed that an improper response of the immune system plays a role its development. ADEM must be differentiated from other demyelinating disorders such as multiple sclerosis.
A variety of different terms have been used to describe ADEM in the medical literature creating confusion. The International Pediatric MS Study Group proposed three specific terms to describe the disorder. ADEM, which describes individuals who develop the initial illness that characterizes the disorder; recurrent disseminated encephalomyelitis (RDEM); which describes a new occurrence of ADEM, three or more months after the initial occurrence, that has the same clinical presentation and affects the same areas of the central nervous system; and multiphasic disseminated encephalomyelitis (MDEM), which describes one or more relapses of ADEM, at least three months after the initial occurrence and involving new areas of the central nervous system. Some researchers argue that it is unclear whether cases of RDEM or MDEM represent recurrent or multiphasic cases of ADEM or are actually other conditions such as multiple sclerosis. More research is necessary to accurately and definitively define acute disseminated encephalomyelitis.
NIH/National Institute of Neurological Disorders and Stroke
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Transverse Myelitis Association
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Last Updated: 3/13/2013
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