Understanding Multiple Sclerosis

In MS, the body’s immune system attacks nerves in the brain and spinal cord. Experts don’t know what causes MS, but they have identified trends in who gets it.

Things to know:

  • Most MS patients are diagnosed between ages 20 and 50.
  • Vision problems are often the first symptom.
  • About four in five patients have relapsing-remitting MS, marked by alternating periods of symptoms and recovery.
  • MS symptoms vary widely from patient to patient.
  • Most MS patients see symptoms worsen over time, but most can expect a normal life span.
  • Research at OHSU is opening promising new paths for treating MS.

What is multiple sclerosis?

Diagram of cells with multiple sclerosis
In multiple sclerosis, the immune system attacks brain and spinal cord nerve coverings (myelin). This disrupts their ability to send signals to the rest of the body.

An autoimmune disease: Multiple sclerosis is an autoimmune disease. This means the immune system attacks the body’s own tissues. In MS, immune system cells attacks myelin, the sheath that covers nerve fibers in the brain and spinal cord (the central nervous system).

Myelin and sclerosis: Myelin is the sleeve of fatty tissue that protects and insulates nerve fibers, like insulation around a wire. Myelin helps electrical signals travel along nerve fibers. Damage to myelin and nerve fibers is called demyelination. The scar tissue that results is called sclerosis.

Disrupted signals: The damage can slow or block the electrical signals that carry information between the central nervous system and the rest of the body. That can cause problems with vision, movement, muscle strength, coordination and thinking.

Outcomes vary: Symptoms and how fast the disease worsens vary from patient to patient. Some people have few or mild symptoms. Some have months or years with few or no symptoms. For others, MS becomes disabling. MS cannot be cured yet, but treatments can slow the disease and manage symptoms. Most patients can expect a normal life span.

Who gets multiple sclerosis?

It’s not clear why some people develop multiple sclerosis, but experts have identified trends and risk factors.

How common is MS? A 2017 study tallied more than 900,000 U.S. adults with MS, more than twice previous estimates. The Centers for Disease Control and Prevention has launched a system to gather data on neurologic conditions, starting with MS and Parkinson’s disease.

Age: MS is most often diagnosed in people between ages 20 and 50, though it can occur in younger and older people.

Gender: MS is two to three times more common in women. Research suggests hormones may play a role.

Race/ethnicity: MS occurs in almost all ethnic groups, but it is more common among white people with Northern European ancestry.

Genetics: Scientists don’t fully understand the genetic pattern in MS. It is not directly inherited, but risk is higher in people who have a close relative (parent, sibling) with MS.

Geography: MS is more common in areas that are farthest from the equator. But not everyone in the same area is equally at risk. Some groups living very far north — the Inuit of the North American Arctic, for instance — almost never develop MS.

What causes multiple sclerosis?

Experts don't yet know what causes MS. They suspect it is a complex combination of factors. For example, an infection may trigger a genetic predisposition to MS. Or MS could be linked to an immune system problem or an environmental cause.

Some studies indicate that the risk of MS increases with:

  • Low vitamin D levels
  • Obesity in childhood and adolescence
  • Smoking

Symptoms of multiple sclerosis

Diagram of MS, Multiple Sclerosis
Because MS affects nerves that send signals throughout the body, symptoms can be wide-ranging. (Click image to see larger.)

Multiple sclerosis can cause many symptoms that can come and go. You might have some symptoms but not all.

Many symptoms can be managed with medication or rehabilitation.

Common signs of MS include:

  • Visions problems (often the first sign of MS) such as blurry or double vision
  • Fatigue
  • Trouble walking
  • Problems with balance and coordination
  • Muscle weakness in arms and legs
  • Numbness or tingling on your face, body, arms and legs
  • Feelings of stiffness and involuntary muscle spasms
  • Pain, sometimes ongoing
  • Dizziness or vertigo
  • Bladder and bowel problems
  • Sexual dysfunction
  • Emotional reactions, including irritability or uncontrollable laughing or crying
  • Depression

Less common symptoms:

  • Tremor
  • Slurred speech or loss of volume
  • Trouble swallowing
  • Trouble breathing
  • Seizures
  • Itching
  • Hearing loss

Secondary symptoms:

Some conditions aren’t from nerve fiber problems but are complications of other symptoms. These might include:

  • Urinary tract infections from bladder problems
  • Loss of muscle tone from inactivity

Types of multiple sclerosis

MS experts now consider there to be four types (or courses) of MS, including one precursor. Each is distinct, but each has periods when the disease:

  • Is progressive (getting worse)
  • Has symptoms suddenly return (relapse)
  • Has symptoms that improve (remission)

Clinically isolated syndrome (CIS)

This is a first episode of symptoms caused by inflammation and damage to myelin. The episode lasts at least 24 hours. It may be a sign that someone will develop MS.

If an MRI scan finds brain lesions like those found in MS, the patient is likely to get an MS diagnosis. If no lesions are found, an MS diagnosis is unlikely.

Relapsing-remitting MS (RRMS)

About 85 percent of people with MS are first diagnosed with relapsing-remitting MS. In this type, patients have clear attacks of new or worsening symptoms that last days, weeks or months.

The attacks are followed by periods of partial or full recovery that can last months or years. Sometimes symptoms vanish. Other times, some symptoms remain and become permanent. The disease does not appear to get worse during remissions.

Primary progressive MS (PPMS)

About 15 percent of people with MS have this type, with symptoms growing worse over time from the start. Later on, patients with PPMS can have relapses with quickly worsening symptoms, followed by some recovery.

Secondary progressive MS (SPMS)

Most people who have relapsing-remitting MS eventually develop SPMS. In this type, symptoms worsen over time. People with secondary progressive MS may also have relapses followed by some recovery.

Related disorders

Many conditions are similar to multiple sclerosis. Some, like MS, are demyelinating disorders, meaning the body attacks and damages the myelin sheath around nerves. They include:

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