Multiple sclerosis (MS) is a disease where the body’s immune system attacks healthy tissues in the central nervous system. Areas affected include the brain, spinal cord, and optic nerves. Several types of multiple sclerosis exist, but doctors don’t currently have a definitive test to determine if someone has the disease.

Because there isn’t a single diagnostic test for MS, doctors may run several tests to rule out other possible conditions. If the tests are negative, a doctor may suggest other tests to find out if the 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 central nervous system (CNS) acts as the communication center in a person’s body. It sends signals to the muscles to make them move, and the body transmits signals back for the CNS to interpret. These signals could include messages about what a person is 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 a person has MS, their body attacks myelin and the cells that make myelin. In some cases the body even attacks the nerve cells.

No person with MS has the same symptoms as another person with MS. And sometimes symptoms will come and go. Doctors associate some symptoms as being more common in a person 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:

  • autoimmune disorders, like collagen vascular disease
  • exposure to toxic chemicals
  • Guillian-Barré syndrome
  • hereditary disorders
  • viral infection
  • vitamin B-12 deficiency

Your doctor will start by asking about your health history and reviewing your symptoms. And your doctor will perform tests that can help them assess your neurological function. They will test your balance, watch you walk, assess your reflexes, and test 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 measurements of EP, the most accepted version is the visual evoked potential. This involves asking you to view a screen that displays an alternating checkerboard pattern while a 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 people with MS may have. In MRI scans, these lesions will appear bright white or very dark. Because people can have lesions on the brain for other reasons, like after having a stroke, a doctor must rule these causes out before diagnosing MS.

An MRI doesn’t involve radiation exposure and isn’t painful. It uses a magnetic field to measure the amount of water in the tissues. 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 is one of the potential diagnostic criteria. 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. Doctors can also test the fluid for infection, which could help them to rule out MS.

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

  • A person’s signs and symptoms indicate there is damage to the myelin in the central nervous system.
  • A doctor has identified at least two or more lesions via an MRI.
  • There is evidence based on a physical exam that a person’s central nervous system has been affected.
  • The person is between the ages of 10 and 60.
  • The person has had either two or more episodes of affected neurological function for at least one day, and occurred a month apart. Or their symptoms have progressed over the course of six months.
  • A 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 2010 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. Doctors look for MS activity, remission, and progression of the disease when determining the type of MS a person has.

The following 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 disease doesn’t get worse.

Primary progressive MS

The National MS society estimates that 15 percent of people with MS have primary progress 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 have early incidences of relapse and remission, and symptoms worsen over time.

The updated 2010 criteria for diagnosing MS included a new diagnostic classification for MS called clinically isolated syndrome (CIS). This classification is recognized due to improvements in MRI clarity.

A doctor may diagnose a person with 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 a person 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.

Another promising development for diagnosing MS is on the horizon. It involves pinpointing a gene linked to the development of MS. Researchers found that people with mutations in the gene NR1H3 have a higher likelihood of developing MS.