How Multiple Sclerosis Is Diagnosed

Diagnosing multiple sclerosis (MS) is complex and challenging. Symptoms are unique to each individual and can mimic those of a number of other diseases. In addition, there is no one test that can confirm MS. Instead, doctors use your medical history and a variety of diagnostic methods—from neurological tests to imaging and more—to come to this conclusion.

The McDonald Criteria is of special importance in this process. It was revised in 2017 to incorporate specific guidelines that use magnetic resonance imaging (MRI) and the spinal fluid to allow for an earlier diagnosis, which means people who have it can start treatment earlier and the disease can often be slowed down.

Medical History

The doctor will ask a number of questions about the symptoms that you are currently experiencing and any that you have experienced in the past. It's a good idea to keep a symptom log before you see the doctor, listing anything you've experienced, how long it lasted, and other information about it. Be sure to list all symptoms, even if previous doctors told you they were nothing to be concerned about.

In addition, your doctor will ask about any medications you are taking and the results of any medical tests you may have had in the past. You will also be asked several questions about the medical history of relatives, drug and alcohol use, as well as other prior health issues.

All of this information will help a neurologist piece together a picture to help determine if MS is a likely diagnosis.

McDonald Criteria

The revised 2017 McDonald Criteria allows the use of MRI to look for a second area of damage in a patient who has had only one MS flare. MRI can also be used to confirm MS damage that has occurred on two different occasions. In addition, the presence of oligoclonal bands in the spinal fluid can be used in some circumstances to confirm the MS diagnosis.

Neurological Exam

In a neurological exam, the doctor tests for:

  • Function of the cranial nerves (these control the senses, as well as how you talk and swallow)
  • Coordination
  • Strength
  • Reflexes
  • Sensation

He will do this by having you perform tasks (like switching between touching your nose and his finger), touching you with various instruments (and having you report a sensation or looking for a response himself), and doing an examination of your eyes. Be assured that these tests do not hurt.

The entire examination will probably last about 45 minutes, but it may last as long as two hours.

Evoked Potential Tests

Evoked potential tests measure how long it takes for stimulation of different nerves to reach the brain and how big the response is. Impulses move more slowly along nerves that have been damaged, such as those impacted by the demyelination that occurs in MS.

Three evoked potential tests can be used in evaluating MS. For all them, electrodes are applied to the scalp with conducting gel, and placement depends on the test being performed.

  • Visual evoked potentials (VEPs): Visual evoked potential testing looks at your brain's response to light. It can be particularly helpful in confirming a diagnosis of MS because it can reveal nerve damage along your optic nerve pathways even if you've never had any associated symptoms. The test uses flashing lights, which don't bother most people. Some, however, say it gives them symptoms similar to mild motion sickness.
  • Somatosensory evoked potentials (SSEP): SSEP measures the brain's response to sensation through electrical pulses via electrodes stuck to your skin. Most people say it's painless.
  • Brainstem auditory evoked potentials (BAEP): BAEP measures the brain's response to sound by playing clicks, tones, or beeps into your ear through headphones.

Evoked potential tests are becoming less popular, as MRI scans are favored. However, these tests are still useful for identifying damage in places that are hard to capture with an MRI, such as the optic nerve.

Magnetic Resonance Imaging

Some diagnoses of MS are made through a combination of clinical findings and evidence of an MS lesion on an MRI.

MRIs use magnetic waves to produce images of the brain and spinal cord. If MS is suspected, a special contrast material (gadolinium) injection is usually administered at the time of the scan, as it reacts to areas of inflammation and will "light up" when a lesion is active. This indicates that demyelination is occurring now or has occurred within the last several weeks.

The MRI does not hurt, but it can be a strange experience. It helps if you know what to expect during this test. There are also some things you can do to make your experience better.

MRI is considered the best test for diagnosing MS, as abnormal lesions appear on MRIs in more than 95 percent of people with the condition.

In the other 5 percent, MRI can lead to a false-negative. Some age-related damage or other conditions, like a migraine or brain trauma, look like MS lesions and can produce a false-positive. This is why doctors use more than one method to confirm a diagnosis.

Lumbar Puncture

Also called a spinal tap, this test requires that a small amount of cerebrospinal fluid (CSF) be taken from your spinal column via a needle that is inserted between your vertebrae. The doctor will send the fluid for evaluation, looking for the presence of oligoclonal bands (an increased number of certain antibodies)—an indicator of increased immune activity in the spinal fluid.

This test is positive in up to 90 percent of people with MS but is not specific to MS, so a positive result could indicate another disease or disorder.

Depending on results from the MRI, neurological exam, and symptom history, it's possible that you may not have to get a lumbar puncture to receive a definitive diagnosis of MS. However, lumbar puncture results can be useful for ruling out other things if there is still a question about diagnosis.

Differential Diagnoses

MS has numerous symptoms, many of which are vague, difficult to describe, cannot be measured by tests, and come and go. In addition, many MS symptoms are shared by other medical conditions.

Examples of diseases that can mimic MS include:

Your doctor may suspect other conditions as well, depending on your symptoms.

There's no blood test for MS, but your doctor may order bloodwork to look for or rule out other possible diagnoses.

Clues You May Not Have MS

Most of the diseases that mimic MS have other clues that suggest an alternative diagnosis. For instance, while it's not unheard of, it's rare for someone over age 60 or younger than 15 to be diagnosed with MS.

MS is less likely when neurological symptoms (numbness, tingling, weakness) are associated with significant back pain. That symptom combination isn't common in MS and is more likely to be caused by a structural problem in the spine.

Some clues pointing to a diagnosis other than MS are specific to a single condition. For example, if the peripheral nervous system (nerves that travel from the spinal cord to the rest of your body) is involved, in addition to the central nervous system, Lyme disease is more likely.

Clues That Suggest MS

Clues that your symptoms are likely from MS include:

  • Symptoms in at least two parts of the central nervous system that reoccur at different intervals (at least one month apart)
  • Worsening of neurological symptoms with heat (called Uthoff's phenomenon)
  • Flares of neurological symptoms that either resolve completely or partially, which is indicative of relapsing-remitting MS

The relapsing-remitting pattern is the most common MS pattern, affecting 85 percent of people with the disease.

A Word From Verywell

MS can be a tricky disease to definitively diagnose, and the process often requires patience. With that, it's important to find a neurologist that you feel comfortable with and have confidence in to work on your diagnosis. After all, if you do have MS, this person will likely be your partner in health for a long time.

Was this page helpful?
Article Sources