What Is Multiple Sclerosis? Doctors Explain the Complex Autoimmune Disease

Photo credit: Hiroshi Watanabe
Photo credit: Hiroshi Watanabe

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Multiple sclerosis (MS) is an autoimmune disease of the brain and spinal cord that can cause problems with movement, muscle function, vision, and cognition. When a person has MS, their immune system attacks and damages the fatty outer coating of nerve fibers in the brain and spine, called myelin. “The damage essentially strips the wires of the nerve fibers,” explains R. Glenn Smith, M.D., a neurologist at the Houston Methodist Stanley H. Appel Department of Neurology.

That can slow or stop communication between the brain and other parts of the body and make it harder to perform daily activities. People may have trouble writing or buttoning a shirt, remembering things, or walking steadily, for instance.

For most people, MS is a relapsing-remitting disease. Symptoms typically flare once or twice a year and linger for weeks or months before easing back up, says Michael Sy, M.D., Ph.D., a neurologist with UCI Health in Irvine, CA. But the symptoms don’t always disappear completely, and repeated attacks can cause nerve fibers to develop lifelong damage or scars, called MS plaques. And once those plaques form, a person may experience permanent disabilities.

Nearly 3 million people worldwide live with MS, and women and those in their 20s, 30s, and 40s are most likely to be affected. While the disease is challenging to live with, it doesn’t have to stop you from doing the things you enjoy. “It is possible to live a normal life with MS if it is discovered early and well treated,” says Gary Belt, M.D., a neurologist at the Comprehensive Stroke Center in Summit, NJ.

Multiple sclerosis causes

Experts know that MS is an autoimmune disease, a type of disease where the body’s immune system tries to kill off its own tissues and cells. Experts don’t fully understand why it develops, but genetics seem to be at play. “We know the risk of MS goes up 10- to 20-fold if an immediate family member has it,” Dr. Belt says.

Environmental factors might be involved too. Getting infected with the Epstein-Barr virus, which can cause mononucleosis, can trigger MS. The virus has the capacity to mimic central nervous system proteins, triggering the immune system to mistakenly attack brain and spinal cord cells, recent research has found.

Other factors can also increase MS chances. Low levels of vitamin D seem to raise a person’s risk; the disease is far more common in northern latitudes where people get less sun exposure (which the body needs to produce vitamin D). Your sex matters too. Women are up to three times more likely to get MS than men. Having another autoimmune disease (like a thyroid disorder or type 1 diabetes) or smoking can make you more susceptible to MS as well.

Multiple sclerosis types

Around 85% of people with MS have relapsing-remitting multiple sclerosis. They’ll experience periodic flare-ups—called relapses—where they develop new symptoms or notice that their existing symptoms become more intense. “The symptom severity will worsen over several days to two weeks before beginning to recover or remit,” Dr. Smith explains. There’s no way to predict when a relapse will hit, though, and that unpredictability can be challenging to deal with.

Not everyone’s MS is relapsing-remitting. Primary progressive MS, which occurs in 10 to 15% of total MS cases, causes symptoms that gradually get worse without periods of remission. And about 50% of patients with relapsing-remitting MS go on to develop secondary progressive MS within 10 years of their initial diagnosis, where their flare-ups cause enough nerve damage that they eventually stop experiencing periods of remission. Within 25 years of initially being diagnosed, nearly 90% of patients with relapsing-remitting MS develop secondary progressive MS.

People who experience a first episode of MS-like symptoms are diagnosed as having clinically isolated syndrome or CIS. Sometimes CIS can turn into MS. But some people with CIS never experience another flare. “Those people are not considered to have MS, and most likely, the attack was caused by something other than MS,” says Dr. Sy.

Multiple sclerosis symptoms

MS can cause problems related to movement and muscle function, vision, and cognition. Many people experience:

  • Numbness or weakness in the arms, trunk, or legs

  • Tingling or prickling sensations throughout the body

  • Shakiness or lack of coordination

  • Trouble balancing

  • Dizziness

  • Partial or complete vision loss, usually in one eye at a time

  • Double vision

  • Blurry vision

  • Red-green color distortion

  • Slurred speech

  • Fatigue

  • Problems with sexual, bowel, or bladder function

  • Hearing loss

  • Trouble concentrating or remembering

No two people with MS will experience symptoms in exactly the same way, and it can be hard to predict when a person’s symptoms will hit and how they might progress. That’s because attacks can occur on the myelin in any part of the brain or spinal cord, and different parts of the brain and spinal cord control different functions in the body.

Multiple sclerosis treatments

There’s no cure for MS, but treatment can slow the disease’s progression and manage symptoms so you can feel your best. Medication is usually a cornerstone, though it can take some trial and error to find a drug combo that delivers maximum benefits with the fewest side effects, Dr. Smith notes. Physical therapy and healthy lifestyle habits are important too.

Disease-modifying medications (DMTs)

DMTs work by suppressing the immune system to reduce flare-ups. Fewer flare-ups means less nerve damage, which slows the overall rate at which a person’s MS progresses. Most disease-modifying meds, which can be taken orally or via infusion, are made for people with relapsing-remitting MS. There are a handful of FDA-approved DMTs for primary progressive MS as well. Clinical trials are also looking at how simvastatin, a statin typically used to treat high cholesterol, may be used to prevent relapsing-remitting MS into secondary progressive MS.

Medications for symptom management

You and your provider may opt to try additional drugs aimed at keeping specific MS symptoms in check. Muscle relaxants or tranquilizers can ease stiffness and spasticity, while fatigue-reducing meds or antidepressants can improve overall energy levels. Some people may also take medications for problems like pain, insomnia, bladder or bowel dysfunction, or sexual dysfunction.

Physical therapy and exercise

A physical or occupational therapist can teach you stretching and strengthening exercises to maintain muscle function, making it easier to perform everyday activities like walking and maintaining your balance. Staying active on your own makes a difference too. Aerobic exercise and resistance training are also key for keeping your muscles strong, while flexibility exercises like yoga or pilates can reduce your reliance on anti-spasticity medications, Dr. Smith says.


Healthy lifestyle habits can support the other aspects of your treatment regimen and help you feel your best overall. Eat a healthy, balanced diet, limit your alcohol intake, and take steps to keep your stress levels in check. Make it a priority to get 7 to 8 hours of sleep each night too. Logging enough shuteye may help your nerves repair themselves after a flare-up, says Dr. Smith.

When to see a doctor

Don’t hesitate to tell your doctor if you’re experiencing symptoms that seem like they could be MS, including unexplained numbness or tingling, weakness, vision changes, balance issues, or memory problems. If your primary care doctor suspects MS, they’ll refer you to a neurologist for further testing. “Even if the symptom resolves after several weeks or months, seeking medical attention is important,” Dr. Sy says. “Studies indicate that early treatment with disease-modifying therapy leads to better long-term outcomes.”

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