What is myelin?

Myelin is a fatty material that coats, protects, and insulates nerves, enabling them to quickly conduct impulses between the brain and different parts of the body. Myelin also contains proteins that can be targeted by the immune system. Myelin coats the nerves of both the central nervous system and the peripheral nervous system; the destruction of the myelin in the central nervous system is what triggers many of the symptoms of multiple sclerosis (MS).

Nerve cells are coated with sections of myelin, and the tiny spaces between the sections are called nodes. As the brain sends messages through the nerves of the spinal cord, the impulses jump from node to node. Myelin prevents these impulses from escaping from the nerve at the wrong point.

In multiple sclerosis, T cells from the body's own immune system attack and destroy the myelin sheath, leaving the nerve cell fibers unprotected.