Multiple sclerosis (MS) is an autoimmune disease, a condition in which the body’s immune system attacks its own tissues. In MS, the immune system attacks the central nervous system (CNS), which includes the brain and spinal cord. The immune system targets myelin, a substance that serves as a protective covering for nerve fibers. This is why MS is also known as a demyelinating disease. When the myelin sheath is damaged, it can cause symptoms of MS in different parts of the body, leading to muscle weakness, numbness, and vision problems.

What role does myelin damage play in the MS disease course? To learn more, MyMSTeam talked to Dr. Barry Singer, director and founder of The MS Center for Innovations in Care at Missouri Baptist Medical Center in St. Louis. Dr. Singer has run the award-winning MS website MS Living Well since 2007. The website has become a valuable resource for people living with MS in more than 190 countries. He’s also the host of the MS Living Well podcast, which includes an episode titled “Remyelination: Repairing Multiple Sclerosis.”

What Is Myelin?

Myelin protects axons in the CNS. Axons are extensions of individual neurons (nerve cells), which allow them to communicate with other cells. Axons are like electrical wire, and myelin is like the plastic coating that protects those wires.

The transmission of nerve signals allows your body to perform normal functions without you having to think about it. This includes seeing, hearing, and controlling bodily functions.

Myelin damage can slow or even stop signals from the CNS from reaching the rest of the body, causing MS symptoms.

Researchers believe that in MS, the immune system responds abnormally, producing inflammation in the CNS. This inflammation then damages both myelin and oligodendrocytes, the cells that create myelin.

Does Myelin Damage Lead to MS Symptoms?

Myelin damage in MS can result in lesions and scar tissue in the brain and spinal cord. These lesions can slow or even stop signals from the CNS from reaching the rest of the body. This disruption in the normal transmission of signals can cause MS symptoms.

Most people with MS experience a relapsing-remitting disease course, meaning they have periods of new or worsening symptoms (called flares), followed by periods of remission, when symptoms fade or disappear. There are also other forms of MS, such as primary progressive MS and secondary progressive MS. These types of MS worsen gradually over time without periods of remission.

Does Myelin Damage Cause Disease Progression?

Although there’s evidence that suggests demyelination plays a role in how MS progresses, some scientists argue that more research is needed to know for certain. Myelin plays an important role in keeping axons healthy. Loss of myelin may make neurons more vulnerable to injury over time, leading to a worsening of the disease. When a person loses axons more quickly than their CNS can compensate for the damage, they may transition from relapsing-remitting MS to progressive MS.

It’s vital that people with MS understand that DMTs are meant to prevent future damage, not reverse existing symptoms by creating new myelin.

Do MS Treatments Address Myelin Damage?

Some disease-modifying therapies (DMTs) have been shown to slow down the rate of brain shrinkage and damage, Dr. Singer said. Although some brain shrinkage is an inevitable part of aging, MS can speed up the process. While the main function of DMTs is to prevent relapse, they may also help guard against brain shrinkage, he noted.

“They prevent disability progression over time, so a group of people on a placebo would progress more rapidly than people on a drug,” Dr. Singer said. “They prevent future disease activity.”

Although DMTs have proved effective, they can’t reverse the damage caused by MS. People who’ve lost function due to MS won’t get it back by using DMTs, Dr. Singer added. “Unfortunately, these disease-modifying therapies aren’t going to bring back old function,” he said. “They are not repair drugs.”

Dr. Singer also noted that some people who take these drugs have difficulty sticking to their treatment. Sometimes people stop taking these drugs if they don’t see their symptoms getting better, mistakenly thinking the medications aren’t working. However, it’s vital that people with MS understand that these medicines are meant to prevent future damage, not reverse existing symptoms by creating new myelin, he said. A 2022 study of 279 veterans with MS found that those who stuck with their treatments were 12 times more likely to be alive after a long follow-up than those who didn’t stick to their treatments.

“Unfortunately, we do have patients who have had a lot of disease in their spinal cord or brain, and as they age they start to have cognitive problems and more balance problems,” Dr. Singer said.“ They feel like they’re getting worse despite treatment — but I think if they were off of disease-modifying therapies, things might be getting worse a lot faster.”

Many people in the relapse-remitting phase of MS also switch treatments if they feel their current DMT isn’t working well for them.

Dr. Singer also explained that, in addition to taking DMTs, people with MS can help keep their physical and cognitive states as sharp as possible by practicing healthy habits. He recommends:

• Getting enough vitamin D
• Exercising regularly
• Getting enough sleep
• Keeping the mind active

These activities have proven benefits. “Brain health is really important,” Dr. Singer said. “Exercise has been shown to help keep your brain reserves healthy.”

He also suggested that anyone with MS who smokes should quit. Smoking can harm both physical and cognitive abilities. Researchers have found that smoking can have a negative impact on the course of MS progression.

Research Into Remyelination Treatments

Research laboratories and leading MS centers are actively studying ways to repair damaged myelin, a process called remyelination. Currently, no remyelination treatments are ready for approval by the U.S. Food and Drug Administration (FDA), according to Dr. Singer, but researchers are hopeful.

“We’re looking at antibody therapies [and] oral therapies, so we’re hopeful that one day we’ll be able to have remyelination treatment,” he said. “In the animal models, you can see that these experimental treatments turn on myelin production and can actually recoat the nerves.

“Oligodendrocytes wrap around nerve cells and create myelin,” Dr. Singer continued. He noted that in people with MS, 5 percent to 8 percent of the brain and spinal cord cells are immature oligodendrocytes, lying dormant (not active). The goal of remyelination research is to activate these dormant cells, allowing them to mature and take part in rebuilding myelin. These cells could be recruited into the damaged areas, called MS plaques, to help repair the damaged myelin.

“We’re looking at antibody therapies [and] oral therapies, so we’re hopeful that one day we’ll be able to have remyelination treatment.”

— Dr. Barry Singer

Future remyelination treatments aim to activate these oligodendrocytes, thereby preventing further bodily degeneration and progression of MS, and — perhaps someday — restoring or improving function in those living with MS.

“I’ve been involved in a number of clinical trials,” Dr. Singer said, referring to research studies that test the effectiveness and safety of potential treatments. “My center has been a site for five early phase 1 and 2 clinical trials using antibodies for myelin repair that, unfortunately, didn’t work.”

Dr. Singer remains optimistic and determined. He is planning future trials with new compounds. The next step will be to do large phase 3 trials to show that the treatment is safe and works well.

Talk With Others Who Understand

MyMSTeam is the social network and online community for those living with multiple sclerosis and their loved ones. On MyMSTeam, more than 217,000 people come together to ask questions, give advice, and share their stories with others who understand life with multiple sclerosis.

What questions do you have about myelin and MS? Share your thoughts in the comments below, or start a conversation by posting on your Activities page.