Demyelinated

Part of speech: adjective, verb

Definitions

1. The state in which the protective covering of nerve fibers is lost results in hindered communication between neurons and overall impairment of nerve function
2. An occurrence involving the degradation of the myelin sheath around nerve cells, causing difficulties in signal transmission and neurologic health
3. Describes nerve fibers that have lost their insulating myelin layer, impairing the efficient conduction of electrical signals

Etymology: De- is a Latin prefix meaning "down" or "away from" and is also used to reverse or remove something, as in "decode" or "defrost." Myelin is a much younger coinage: the German pathologist Rudolf Virchow introduced the term "Markscheide" in 1854 for the fatty insulating layer around nerve fibers, and the English "myelin" was adapted from the Greek "myelos," meaning "marrow," because the sheath was first observed in the spinal cord's marrow-like tissue. The myelin sheath wraps nerve fibers and speeds up electrical signals by letting them jump between gaps along the fiber. Attaching "de-" to "myelinate" yields "demyelinate," meaning to strip or break down that sheath. The verb "myelinate" itself was formed in English in the 19th century, and "demyelinated" is simply its past-participle-style adjective form, used to describe nerves or tissue where the sheath has been lost. Medical writing uses the term widely in describing conditions such as multiple sclerosis, where the immune system attacks myelin and disrupts signal transmission.