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Other Primary Demyelinating Diseases
(See also Overview of Demyelinating Disorders.)
Disorders that cause demyelination and have no known cause are called primary demyelinating disorders. Demyelination is the destruction of the tissues that wrap around nerves, called the myelin sheath.
Sometimes primary demyelinating disorders develop after a viral infection or vaccination against a viral infection. A likely explanation is that the virus or another substance somehow triggers the immune system to attack the body’s own tissues (autoimmune reaction). The autoimmune reaction results in inflammation, which damages the myelin sheath and the nerve fiber under it.
Multiple sclerosis is the most common primary demyelinating disorder.
This rare type of inflammation leads to demyelination of nerves in the brain and spinal cord. Acute disseminated encephalomyelitis is more common among children than among adults.
This disorder usually develops after a viral infection. Acute disseminated encephalomyelitis is thought to be a misguided immune reaction triggered by the virus. In the United States, this disorder usually results from some types of influenza, hepatitis A or B, or infection with enteroviruses, Epstein-Barr virus, or human immunodeficiency virus (HIV). Measles, chickenpox, and rubella used to be common causes before childhood vaccination became widespread.
Typically, the inflammation develops 1 to 3 weeks after the viral illness begins.
Symptoms of acute disseminated encephalomyelitis appear rapidly. At first, people may have a fever, a headache, nausea, and vomiting and feel tired. When the disorder is severe, it can cause seizures and coma.
Vision in one or both eyes may be lost. Muscles may become weak, and coordination may be impaired, making walking difficult. People may become paralyzed. Sensation may be lost in parts of the body, making them feel numb. Mental function (including thinking, judgment, and learning) may be affected.
Most people recover within days, and within 6 months, most have totally or almost totally recovered. Other people may remain impaired the rest of their life. Muscles may remain weak, and areas of the body may remain numb. They may not recover their vision or mental function.
Doctors may be able to diagnose acute disseminated encephalomyelitis based on symptoms and results of a physical examination. Magnetic resonance imaging (MRI) may be done.
Acute disseminated encephalomyelitis can be treated with corticosteroids given intravenously.
Adrenoleukodystrophy and adrenomyeloneuropathy are rare hereditary metabolic disorders.
Adrenoleukodystrophy affects young boys, usually between the ages of 4 and 8. A milder, more slowly developing form of the disorder can begin during adolescence or young adulthood.
Adrenomyeloneuropathy is a milder form. It begins when men are in the 20s or 30s,
In these disorders, widespread demyelination is often accompanied by adrenal gland dysfunction. Boys have behavioral problems and problems with hearing and vision. Eventually, mental deterioration, involuntary and uncoordinated muscle contractions (spasticity), and blindness occur. Some boys with adrenoleukodystrophy are totally disabled or die 2 to 3 years after diagnosis. Often, adults with adrenomyeloneuropathy first notice a problem when their legs become weak and stiff, they lose control of their bladder or bowels (incontinence), and/or erectile dysfunction develops.
The diagnosis is confirmed by genetic testing.
No cure for either disorder is known. Dietary supplements with glycerol trioleate and glycerol trierucate (known as Lorenzo’s oil) may help, but further study is needed. When the adrenal gland (but not the brain) is affected, treatment with adrenal hormones may be lifesaving. Many experts now recommend stem cell transplantation if the brain is affected.
Leber hereditary optic neuropathy is more common among men. Usually, symptoms begin between the ages of 15 and 35. This disorder is inherited through the mother, and the defective genes seem to be located in mitochondria (structures in cells that provide energy for the cell).
Vision may become blurred in one eye or in both eyes at the same time. But if vision in one eye is affected, vision in the other eye begins to be lost within weeks or months. The sharpness of vision (acuity) and color vision deteriorate over time.
Some people also have heart problems or muscle symptoms (such as involuntary muscle contractions, muscle weakness, or muscle spasms), which may resemble symptoms of multiple sclerosis.
Doctors can often diagnose Leber hereditary optic neuropathy based on symptoms and results of a physical examination. Testing can identify some of the abnormal genes responsible for the disorders. Electrocardiography may be done to check the heart.
No treatments are available. But limiting consumption of alcohol, which may affect the mitochondria, and not using tobacco products may help.
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