What is multiple sclerosis?

Multiple sclerosis (MS) is a condition where the body’s immune system attacks healthy tissue in the central nervous system (CNS). Areas affected include the:

  • brain
  • spinal cord
  • optic nerves

Several types of multiple sclerosis exist, but doctors don’t currently have a definitive test to determine if someone has the condition.

Because there isn’t a single diagnostic test for MS, your doctor may run several tests to rule out other possible conditions. If the tests are negative, they may suggest other tests to find out if your symptoms are due to MS.

However, innovations in imaging and continued research on MS in general have meant improvements in diagnosing and treating MS.

The CNS acts as the communication center in your body. It sends signals to your muscles to make them move, and the body transmits signals back for the CNS to interpret. These signals could include messages about what you’re seeing or feeling, such as touching a hot surface.

On the outside of the nerve fibers that carry signals is a protective casing called myelin (MY-uh-lin). Myelin makes it easier for nerve fibers to transmit messages. It’s similar to how a fiber-optic cable can conduct messages faster than traditional cable.

When you have MS, your body attacks myelin and the cells that make myelin. In some cases, your body even attacks the nerve cells.

MS symptoms vary from person to person. Sometimes, symptoms will come and go.

Doctors associate some symptoms as being more common in people living with MS. These include:

  • bladder and bowel dysfunction
  • depression
  • difficulty thinking, such as affected memory and problems focusing
  • difficulty walking, such as losing balance
  • dizziness
  • fatigue
  • numbness or tingling of the face or body
  • pain
  • muscle spasticity
  • vision problems, including blurred vision and pain with eye movement
  • weakness, especially muscle weakness

Less common MS symptoms include:

  • breathing problems
  • headache
  • hearing loss
  • itching
  • problems swallowing
  • seizures
  • speaking difficulties, such as slurred speech
  • tremors

If you have any of these symptoms, talk to your doctor.

MS isn’t the only condition that results from damaged myelin. There are other medical conditions your doctor may consider when diagnosing MS that could include:

Your doctor will start by requesting your medical history and reviewing your symptoms. They will also perform tests that can help them assess your neurological function. Your neurological evaluation will include:

  • testing your balance
  • watching you walk
  • assessing your reflexes
  • testing your vision

Blood testing

Your doctor may also order blood tests. This is to rule out other medical conditions and vitamin deficiencies that could be causing your symptoms.

Evoked potential tests

Evoked potential (EP) tests are those that measure the brain’s electrical activity. If the test shows signs of slowed brain activity, this could indicate MS.

Testing EP involves placing wires on the scalp over specific areas of your brain. You’ll then be exposed to light, sounds, or other sensations while an examiner measures your brain waves. This test is painless.

While there are several different EP measurements, the most accepted version is the visual EP. This involves asking you to view a screen that displays an alternating checkerboard pattern, while the doctor measures your brain’s response.

Magnetic resonance imaging (MRI)

Magnetic resonance imaging (MRI) can show abnormal lesions in the brain or spinal cord that are characteristic of an MS diagnosis. In MRI scans, these lesions will appear bright white or very dark.

Because you can have lesions on the brain for other reasons, like after having a stroke, your doctor must rule out these causes before making an MS diagnosis.

An MRI doesn’t involve radiation exposure and isn’t painful. The scan uses a magnetic field to measure the amount of water in the tissue. Usually myelin repels water. If a person with MS has damaged myelin, more water will show up in the scan.

Lumbar puncture (spinal tap)

This procedure isn’t always used to diagnose MS. But it’s one of the potential diagnostic procedures. A lumbar puncture involves inserting a needle into the spinal canal to remove fluid.

A laboratory professional tests the spinal fluid for the presence of certain antibodies that people with MS tend to have. The fluid can also be tested for infection, which could help your doctor rule out MS.

Doctors may have to repeat diagnostic tests for MS several times before they can confirm the diagnosis. This is because MS symptoms can change. They may diagnose someone with MS if testing points to the following criteria:

  • Signs and symptoms indicate there’s damage to the myelin in the CNS.
  • The doctor has identified at least two or more lesions in two or more parts of the CNS via an MRI.
  • There’s evidence based on a physical exam that the CNS has been affected.
  • A person has had two or more episodes of affected neurological function for at least one day, and they occurred a month apart. Or, a person’s symptoms have progressed over the course of one year.
  • The doctor can’t find any other explanation for the person’s symptoms.

Diagnostic criteria have changed over the years and will likely continue to change as new technology and research comes along.

The most recent accepted criteria were published in 2017 as the revised McDonald Criteria. The International Panel on the Diagnosis of Multiple Sclerosis released these criteria.

One of the more recent innovations in diagnosing MS is a tool called optical coherence tomography (OCT). This tool allows a doctor to obtain images of a person’s optical nerve. The test is painless and is much like taking a picture of your eye.

Doctors know that people with MS tend to have optic nerves that look different from people who don’t have the disease. OCT also allows a doctor to track a person’s eye health by looking at the optic nerve.

Doctors have identified a number of MS types. In 2013, the International Advisory Committee on Clinical Trials of MS revised the descriptions of these types based on new research and updated imaging technology.

Although the diagnosis of MS has initial criteria, determining the MS type a person has is a matter of tracking a person’s MS symptoms over time. To determine the type of MS a person has, doctors look for

  • MS activity
  • remission
  • progression of the condition

The types of MS include:

Relapsing-remitting MS

It’s estimated that 85 percent of people with MS are initially diagnosed with relapsing-remitting MS, which is characterized by relapses. This means new MS symptoms appear and are followed by a remission of the symptoms.

About half of the symptoms that occur during relapses leave some lingering problems, but these may be very minor. During a remission, a person’s condition doesn’t get worse.

Primary progressive MS

The National MS society estimates that 15 percent of people with MS have primary progressive MS. Those with this type experience a steady worsening of symptoms, usually with fewer relapses and remissions early in their diagnosis.

Secondary progressive MS

People with this type of MS have early incidences of relapse and remission, and symptoms worsen over time.

Clinically isolated syndrome (CIS)

A doctor may diagnose a person with clinically isolated syndrome (CIS) if they have an episode of neurologic symptoms associated with MS that lasts at least 24 hours. These symptoms include inflammation and damage to myelin.

Having just one episode of experiencing a symptom associated with MS doesn’t mean a person will go on to develop MS.

However, if the MRI results of a person with CIS show that they might be at higher risk for developing MS, the new guidelines recommend starting disease-modifying therapy.

According to the National MS Society, these guidelines have the potential to reduce the onset of MS in people whose symptoms are detected in the very early stages.