What happens when myelin is destroyed?

When myelin is destroyed, the transmission of nerve impulses is impaired. Messages do not get through quickly and clearly from the brain to the correct body part. The more myelin is destroyed, the slower and less efficient the nerve impulses are. Depending on the severity of the immune system attack, the nerve fibers themselves may be damaged or destroyed. (See Multimedia file 1). Damage to nerve fibers may play an important role in determining how severe disability in multiple sclerosis may become.

When the brain nerves do not communicate well with nerves from other areas of the central nervous system (brainstem or spinal cord) or cannot relay information to nerves that exit these structures (peripheral nervous system), the symptoms of multiple sclerosis can occur.