A developmental process whereby a protective fatty material wraps around nerve cells.
Myelinization is a gradual developmental process whereby a protective, fatty material called myelin wraps around nerve cells in the peripheral and central nervous system. The myelin sheath protects the nerve fibers in much the same way as insulation covering electrical wiring. Although the process can take up to 10 years to reach completion, the bulk of myelinization occurs during the fetal and infancy stages.
Several degenerative diseases can result when the myelin sheath is destroyed. The most common is multiple sclerosis (MS), which affects 250,000 people in the United States. MS occurs when deviant white blood cells destroy the myelin layers. Sclerotic plaque forms on the fibers, short-circuiting electrical signals in the nervous system. Victims of the disease may suffer recurring episodes of numbness and muscle weakness, uncontrollable tremors, slurred speech, loss of bowel and bladder control, memory lapses, and/or paralysis. A vaccine is cur rently under development and some victims have responded favorably to bee venom therapy.
Adrenoleukodystrophy (ALD) is caused by an enzyme deficiency that fails to break down very long chain fatty acids, or VLCFAs, that are found in foods and produced by the body. When the VLCFAs build up, they attack the myelin sheath. Affecting one or two out of every 100,000 people in the United States, boys between the ages of five and 10 are the most susceptible. Victims quickly lose their sight and speech; death usually follows quickly. A highly purified oil has been developed by the
Transverse myelitis is a sudden inflammation of the myelin sheath that results in the loss of motor control and sensation below the level of attack. The cause is unknown but often occurs after a viral infection. It usually begins with severe back pain, followed by muscle weakness, flaccid paralysis, bladder and bowel dysfunction, and progressive spasticity. Eighty-five to 90% of its victims recover all or most of their functioning.
Canavan disease, a rare and fatal brain disorder brought on by myelin destruction, primarily affects Jewish infants. Although appearing normal at birth, affected babies become severely retarded quickly and usually die by the age of two or three. A blood test is available to test prospective parents for the hereditary gene.
Duncan, I. D., R. P. Skoff, and D. Colman. Myelination and Dysmyelination. New York: York: New York Academy of Sciences, 1990.
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