Myelin is a fatty, white substance that wraps around the axons of nerve cells, forming a sheath that speeds up and protects electrical nerve signals. In multiple sclerosis, the immune system attacks and destroys myelin, disrupting communication between the brain and the rest of the body. Myelin can regenerate to some extent, but repeated damage can lead to permanent nerve fiber loss.
What is myelin?
Myelin functions like the plastic insulation around an electrical wire. Without it, the nerve signal — a precise electrical impulse — leaks out and travels slowly or not at all. With a healthy myelin sheath, nerve signals can travel at speeds up to 70 meters per second, allowing for rapid, coordinated movement, sensation, and thought. The myelin sheath is not a continuous tube but a series of segments produced by specialized cells called oligodendrocytes in the brain and spinal cord, and Schwann cells in the peripheral nervous system.
In multiple sclerosis, the immune system identifies myelin proteins as foreign and mounts an inflammatory attack against them. This process — called demyelination — slows or blocks nerve conduction, producing the symptoms characteristic of MS. The areas of damaged myelin appear as lesions on MRI scans, appearing as bright spots in the white matter of the brain and spinal cord.
After an inflammatory attack subsides, oligodendrocytes can produce new myelin in a process called remyelination. In early MS, remyelination is often sufficient to restore function, which is why symptoms may improve after a relapse. Over time, however, repeated demyelination can outpace the brain's repair capacity, and the underlying nerve axon can be permanently damaged — explaining why some people accumulate disability over the course of the disease.
Why it matters
Understanding myelin explains why MS symptoms can come and go, and why early treatment matters. When myelin is inflamed but not yet fully destroyed, there is a window for recovery. Disease-modifying therapies for MS work in part by reducing the frequency and severity of myelin attacks, which can slow long-term damage to nerve fibers.
Research into myelin repair — finding ways to stimulate remyelination — is one of the most active areas in MS science. For people living with MS, this means that the scientific community is actively working not just on suppressing attacks but on restoring function that has been lost. Staying connected with an MS specialist keeps you aware of emerging therapies as the field advances.
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