Q. My sister-in-law has been diagnosed with multiple sclerosis that her doctor says related to demyelination. What does that mean in regular words?
A. Myelination is a term that describes the process the nervous system goes through to put insulation around nerve fibers. It is analogous to using insulated wire in a building (e.g., to enhance safety, prevent shorting out, avoid fires, prevent electrical leakage).
Myelin is a cholesterol sheath that coats neuronal axons acting as a form of insulation. Specific skills can be perfected only when appropriate myelinization of the nerve pathways or enervation of the muscle tissue is incomplete (e.g., expecting conscious control of the anal sphincter and bowel movements in a child who is only 14 months old is unrealistic).
Myelination of the reticular formation (brain tissue that helps you to maintain attention) is probably completed around puberty or sometime soon thereafter. Myelination of the corpus callosum occurs at a highly predictable rate from back to front, spanning birth to approximately 21 years of age, or longer. Myelination of the frontal lobes begins about the time verbal language develops but the process can take years to complete, until the early twenties.
Demyelination is a term used to describe the reverse process.
Multiple sclerosis is thought to be an autoimmune condition where the body turns against part of itself. In this case, it involves destruction of the myelin sheath. Something triggers the stripping away of the insulation. Depending on the location of the affected nervous tissue, a variety of symptoms can ensue, involving enervation of muscle tissue and the conscious control of bodily functions.