How Multiple Sclerosis Is Diagnosed

Diagnosing multiple sclerosis (MS) is complex and challenging. Everyone's symptoms are unique, and symptoms can be similar to those of many other diseases.

You'll need to see a neurologist, a doctor who specializes in diseases of the brain, spinal cord, and nerves. As there is no single test that can confirm MS, they will use a variety of diagnostic methods including neurological tests, imaging, and blood tests.

They will also reference a set of criteria that, as of a 2017 revision, make early diagnosis more likely. Early diagnosis means early treatment, which may slow down the disease.

This article walks you through the long MS diagnostic process and what other conditions may be considered.

How Multiple Sclerosis Is Diagnosed
Verywell / Emily Roberts

Medical History

Your medical history is made up of your current health and past illness and injuries. A neurologist will ask a lot of questions about symptoms you're having or have had before.

It's a good idea to keep a symptom log before this appointment. Include information on how long a symptom lasted, what time of day it occurred, and what you were doing when it happened. Be thorough and even list symptoms other healthcare providers said not to worry about.

Also:

  • Your healthcare provider will also ask about any medications you're taking.
  • Bring the results of prior medical tests or make sure your healthcare provider has them.
  • Be ready to answer about your drug and alcohol use and other health issues.
  • Expect the healthcare provider to ask about your family health history.

All of this will help a neurologist decide whether MS is likely. The Healthcare Provider Discussion Guide below can help you have a productive conversation.

Multiple Sclerosis Healthcare Provider Discussion Guide

Get our printable guide for your next healthcare provider's appointment to help you ask the right questions.

Doctor Discussion Guide Woman

McDonald Criteria

Multiple sclerosis is an autoimmune disease. That means your immune system is attacking healthy cells. In MS, it attacks an important coating on the nerves called the myelin sheath. The damage this causes is known as demyelination.

Attacks from the immune system cause inflammation, which causes MS lesions. These are damaged or scarred areas of the central nervous system (CNS), which includes your brain and spinal nerves.

The McDonald Criteria take this into account. Healthcare providers use these guidelines to diagnose MS. The criteria have grown more accurate with revision and can now diagnose MS earlier than ever before.

Your healthcare provider may gather evidence through a neurological exam, testing, and taking steps to rule out other possible conditions.

With this information in hand, and according to the McDonald Criteria, they can diagnose MS if you've had:

  • Two or more relapses
    —AND—
  • At least two lesions in different parts of the CNS
    —OR—
  • Evidence of one lesion and reasonable evidence of a previous relapse

If you only meet some of those criteria, your healthcare provider may order more testing. Or they may keep a close eye on you for a year to see if more evidence develops.

Recap

Your medical history and the McDonald Criteria will guide your healthcare provider's diagnostic process. They'll look for multiple areas of central nervous system damage that vary in age, plus other conditions that may explain your symptoms.

Neurological Exam

This is performed in the neurologist's office through a variety of simple tests. The healthcare provider is checking your:

  • Coordination
  • Strength
  • Reflexes
  • Sensation
  • Cranial nerve function

What Are Cranial Nerves?

Cranial nerves are those that originate in the brain rather than from the spinal cord. They control your senses (e.g., vision and hearing) and your ability to talk and swallow.

You'll be asked to do things like touching your nose and then the healthcare provider's finger. They'll also touch you with various instruments to measure your sensation or response.

The exam will probably last between 45 minutes and two hours.

Testing

Your doctor may also perform the following, which can show evidence of MS:

  • Magnetic resonance imaging (MRI)
  • Evoked potentials tests (EPTs)
  • Lumbar puncture

Additional bloodwork, imaging, and other tests may also be done to rule out other conditions.

Magnetic Resonance Imaging

MRIs use magnetic waves to produce images of the brain and spinal cord.

An injected contrast material called gadolinium reacts to inflammation. During a gadolinium MRI, active or recent lesions appear lit up.

MRI is considered the best test for diagnosing MS. It finds lesions in more than 95% of people with the condition.

False Results

MRI leads to false negatives—i.e., results that say MS is not present when it really is—in about 5% of MS cases. Other times, age-related damage or other conditions (migraine, brain trauma) look like MS lesions. This produces false positives, or results that indicate MS when it's not there. It's for these reasons that healthcare providers use more than one test.

Evoked Potential Tests

Evoked potential tests measure:

  • How quickly nerve signals reach your brain
  • How big the response is

Since impulses move more slowly along damaged nerves, including those with myelin damage from MS, the results can be telling.

Three evoked potential tests can be used to diagnose MS. They each involve placing electrodes on your scalp so that responses to different stimuli can be tracked.

  • Visual evoked potentials (VEPs): Find optic (eye) nerve damage by measuring the response to flashing lights
  • Somatosensory evoked potentials (SSEP): Measures the response to physical sensation
  • Brainstem auditory evoked potentials (BAEP): Uses sounds through headphones to measure auditory (hearing) nerve function.

EPTs are becoming less popular, however, since MRIs are often better at identifying demyelination and excluding other possible conditions.

Even so, EPTs are better than MRIs at viewing certain places, including the optic nerve. It's possible that your provider will order both MRI and EPTs.

Lumbar Puncture

Lumbar puncture is also called a spinal tap. It involves withdrawing cerebrospinal fluid (CSF) from your spinal column. The healthcare provider does this with a small needle inserted between vertebrae in your lower back.

In MS, the CSF will have what's called oligoclonal bands. Those are changes due to high levels of certain antibodies. They result from increased immune-system activity.

This test is positive in up to 90% of people with MS. It's not specific to MS, though. So a positive result could point to another condition.

Not everyone needs a lumbar puncture to be diagnosed with MS. However, it can help rule out other diagnoses.

Recap

Central nervous system damage from MS can be identified through evoked potentials testing, MRI, and possibly lumbar puncture.

Other Possible Conditions

MS has myriad hard-to-describe symptoms. They come and go, and they can't be "seen" by tests.

MS also shares symptoms with lots of medical conditions. Diseases that mimic MS include:

MS is less likely if:

  • You're under 15
  • You're over 60
  • Tingling, numbness, and weakness come with serious back pain
  • Peripheral nerves (those outside the spinal column) are involved

If any of these apply to you, your healthcare provider may explore some of these other potential diagnoses first.

On the other hand, they may bypass considering some of these diagnoses if you have:

  • Symptoms in at least two parts of the central nervous system that come and go
  • Worse neurological symptoms due to heat (Uhthoff's phenomenon)
  • Flares of neurological symptoms that resolve completely or partially

These are all indications that MS is more likely.

Most Common Form of MS

Relapsing-remitting (RM) is the most common form of MS. With this, you alternate between periods of flaring and periods of recovery. RMMS affects 85% of people with the disease. Most people start off with this type, but their disease course worsens over the years.

Summary

MS is difficult to diagnose. There's no single, reliable test, though there is a set of criteria that doctors can use to guide them.

Symptoms, medical history, and results of a neurological exam and several tests to identify MS lesions all factor into reaching a diagnosis. These tests include evoked potentials, MRI, and lumbar puncture.

You'll also undergo other tests that can help neurologists explore other possible diagnoses, of which there are many. These tests will differ depending on what diagnoses the doctor thinks are most likely.

A Word From Verywell

MS can be a tricky disease to definitively diagnose. The process requires patience.

It's important to find a neurologist you're comfortable with and have confidence in. If you do have MS, they'll likely be your partner in health for a long time.

Frequently Asked Questions

  • What do people usually experience as their first symptom of MS?

    The most common first symptoms of MS are:

    • Vision problems
    • Numbness or tingling in the face, body, or limbs
    • Dysesthesia (a tightening sensation around your torso), also known as the "MS hug"
  • How long can someone live with MS?

    On average, people with MS live about seven fewer years than people without it. But the gap is closing thanks to earlier diagnoses and better treatments.

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