Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS), which includes the brain, spinal cord, and optic nerve.

In people with MS, the immune system mistakenly attacks myelin. This substance covers and protects nerve fibers.

Damaged myelin forms scar tissue, or lesions. That results in a communication gap between your brain and the rest of your body. The nerves themselves can also become damaged, sometimes permanently.

The National Multiple Sclerosis Society estimates that more than 2.3 million people worldwide have MS. That includes an estimated 1 million people in the United States, according to a 2017 study by the Society.

You can develop MS at any age. MS is more common in women than men. It’s also more common in white people compared with people of Hispanic or African descent. It’s rare in people of Asian descent and other ethnic groups.

First symptoms tend to appear between the ages of 20 and 50. For young adults, MS is the most common disabling neurological disease.

For your doctor to make a diagnosis, evidence of MS must be found in at least two separate areas of the central nervous system (CNS). The damage must have occurred at separate points in time.

The McDonald criteria are used to diagnose MS. According to updates made in 2017, MS can be diagnosed based on these findings:

  • two attacks or symptom flare-ups (lasting at least 24 hours with 30 days between attacks), plus two lesions
  • two attacks, one lesion, and evidence of dissemination in space (or a different attack in a different part of the nervous system)
  • one attack, two lesions, and evidence of dissemination in time (or finding a new lesion — in the same location — since the previous scan, or presence of immunoglobulin, called oligoclonal bands in the spinal fluid)
  • one attack, one lesion, and evidence of dissemination in space and time
  • worsening of symptoms or lesions and dissemination in space found in two of the following: MRI of the brain, MRI of the spine, and spinal fluid

MRIs will be performed with and without contrast dye to locate lesions and highlight active inflammation.

Spinal fluid is examined for proteins and inflammatory cells associated with, but not always found in, people who have MS. It can also help rule out other illnesses and infections.

Evoked potentials

Your doctor might also order evoked potentials.

Sensory evoked potentials and brainstem auditory evoked potentials were used in the past.

Current diagnostic criteria include only visual evoked potentials. In this test, your doctor analyzes how your brain reacts to an alternating checkerboard pattern.

There’s no single test doctors use to diagnose MS. First, other conditions must be eliminated.

Other things that can affect myelin include:

Blood tests can’t confirm MS, but they can rule out some other conditions.

Lesions can form anywhere in the CNS.

Symptoms depend on which nerve fibers are affected. Early symptoms are more likely to be mild and fleeting.

These early symptoms may include:

These symptoms could be due to any number of conditions, so your doctor may request an MRI to help them make the correct diagnosis. Even early on, this test may reveal active inflammation or lesions.

It’s important to remember that MS symptoms are often unpredictable. No two people will experience MS symptoms in the same way.

As time goes on, you may experience one or more of the following symptoms:

Although you can never have more than one type of MS at a time, it’s possible for your diagnosis to change over time. These are the four main types of MS:

Clinically isolated syndrome (CIS)

Clinically isolated syndrome (CIS) is a single instance of inflammation and demyelination in the CNS. It must last for 24 hours or more. CIS can be the first attack of MS or it might be a single episode of demyelination and the person never has another episode.

Some people who have CIS eventually develop other types of MS, but many don’t. The chances are higher if an MRI shows a lesion on your brain or spinal cord.

Relapsing-remitting multiple sclerosis (RRMS)

According to the National Multiple Sclerosis Society, about 85 percent of people with MS initially receive an RRMS diagnosis.

RRMS involves clearly defined relapses, during which there’s a worsening of neurologic symptoms. Relapses last anywhere from a few days to several months.

Relapses are followed by partial or complete remission, in which symptoms are milder or absent. There’s no disease progression during remissions.

RRMS is considered active when you have a new relapse or an MRI shows evidence of disease activity. Otherwise, it’s inactive. It’s called worsening if you have increasing disability following a relapse. Otherwise, it’s stable.

Primary progressive multiple sclerosis (PPMS)

In primary progressive multiple sclerosis (PPMS), there’s a worsening of neurologic function from the onset. There are no clear relapses or remissions. The National Multiple Sclerosis Society estimates that about 15 percent of people with MS have this type at diagnosis.

There can also be periods of increased or decreased disease activity when symptoms worsen or improve. This used to be called progressive-relapsing multiple sclerosis (PRMS). Under updated guidelines, this is now considered PPMS.

PPMS is considered active when there’s evidence of new disease activity. PPMS with progression means there’s evidence of worsening disease over time. Otherwise, it’s PPMS without progression.

Secondary progressive multiple sclerosis (SPMS)

When RRMS transitions to progressive MS, it’s called secondary progressive multiple sclerosis (SPMS). During this course, the disease steadily becomes more progressive, with or without relapses. This course may be active with new disease activity or inactive with no disease activity.

Just as the disease itself is different for each person, so are the treatments. People with MS typically work with a neurologist. Others on your healthcare team may include your general physician, physical therapist, or nurses who specialize in MS.

Treatment can be divided into three main categories:

Disease-modifying therapies (DMTs)

Most of these drugs are designed to reduce the frequency and severity of relapses and to slow the progression of relapsing MS.

The Food and Drug Administration (FDA) has only approved one DMT to treat PPMS. No DMTs have been approved to treat SPMS.

Injectables

  • Beta interferons (Avonex, Betaseron, Extavia, Plegridy, Rebif). Liver damage is a possible side effect, so you’ll need regular blood tests to monitor your liver enzymes. Other side effects may include injection-site reactions and flu-like symptoms.
  • Glatiramer acetate (Copaxone, Glatopa). Side effects include injection-site reactions. More serious reactions include chest pain, fast heartbeat, and breathing or skin reactions.

Oral medications

Infusions

  • Alemtuzumab (Lemtrada). This medication can increase risk of infections and autoimmune disorders. It’s typically used only when there’s no response to other medications. This medication can have serious side effects to the kidneys, thyroid and skin.
  • Mitoxantrone hydrochloride (only available in generic form). This medication should only be used for very advanced MS. It can harm the heart and is associated with cancers of the blood.
  • Natalizumab (Tysabri). This medication increases the risk of progressive multifocal leukoencephalopathy (PML), a rare viral brain infection.
  • Ocrelizumab (Ocrevus). This drug is used to treat PPMS as well as RRMS. Side effects include infusion reactions, flu-like symptoms, and infections such as PML.

Treating flare-ups

Flare-ups can be treated with oral or intravenous corticosteroids, such as prednisone (Prednisone Intensol, Rayos) and methylprednisolone (Medrol). These drugs help reduce inflammation. Side effects can include increased blood pressure, fluid retention, and mood swings.

If your symptoms are severe and don’t respond to steroids, plasma exchange (plasmapheresis) is an option. In this procedure, the liquid part of your blood is separated from the blood cells. It’s then mixed with a protein solution (albumin) and returned to your body.

Treating symptoms

A variety of medications can be used to treat individual symptoms. These symptoms include:

  • bladder or bowel dysfunction
  • fatigue
  • muscle stiffness and spasms
  • pain
  • sexual dysfunction

Physical therapy and exercise can improve strength, flexibility, and gait problems. Complementary therapies may include massage, meditation, and yoga.

There’s no cure for MS, nor is there a reliable way to gauge its progression in an individual.

Some people will experience a few mild symptoms that don’t result in disability. Others may experience more progression and increasing disability. Some people with MS eventually become severely disabled, but most people don’t. Life expectancy is near normal, and MS is rarely fatal.

Treatments can help manage symptoms. Many people living with MS find and learn ways to function well. If you think you may have MS, see a doctor. Early diagnosis and treatment can be the key to maintaining your health.