What to Know About the Multiple Sclerosis Diagnostic Criteria

Diagnosing multiple sclerosis (MS) can be challenging because there is no one way to reach a proper diagnosis. A combination of symptoms, lab tests, and exams need to be measured against a specific set of criteria known as the McDonald criteria for doctors to reach a diagnosis.

Since many symptoms of MS can develop from other health conditions, diagnostic tools are also used to rule out other disorders while diagnosing MS. Diagnosing MS as early as possible is crucial to ensuring that a person with the disease has the best quality of life for as long as possible.

Doctor helping patient with MRI scan

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Types of MS and Symptoms

The central nervous system, which includes the brain and spinal cord, is made up of cells and nerves that deliver messages to and from the brain. MS develops when the immune system begins attacking the myelin sheath, the covering of nerve fibers. Multiple sclerosis is an autoimmune disease.

When myelin becomes damaged, it can form lesions, or scar tissue, that prevent the brain and body from communicating properly. In some cases, nerves can become permanently damaged.

There are four main types of MS, all of which have different symptoms and progression timelines. In some cases, a person can develop one type of MS and it will progress to another over time.

Clinically Isolated Syndrome (CIS)

Clinically isolated syndrome is defined by an isolated incident of inflammation and damage to the myelin sheath. It may be the first sign of MS.

CIS refers to a first episode of neurological symptoms that lasts at least 24 hours. Symptoms may include:

  • Numbness or tingling
  • Vision problems
  • Stiff or weak muscles
  • Uncontrolled bladder or bowel movements
  • Issues with coordination or walking
  • Dizziness
  • Sexual dysfunction
  • Mild cognitive impairment

Relapsing-Remitting Multiple Sclerosis (RRMS)

RRMS occurs in flare-ups (when symptoms worsen) and relapses, meaning that the symptoms of the condition come and go sporadically. Between flare-ups, you have periods of recovery, or remissions. This type of MS is marked by relapses that last at least 24 hours. During a relapse, symptoms get worse. During a remission, symptoms partly or completely go away.

As many as 85% of people with MS are diagnosed at this stage. The symptoms of RRMS are the same as those in CIS, but they come on more frequently. Other symptoms that can happen with RRMS include fatigue, sensitivity to heat, and depression.

Primary Progressive Multiple Sclerosis (PPMS)

PPMS continues to worsen over time. There are no symptom flare-ups and no remissions. How fast the disease progresses may vary. There can be times when the condition is stable, and there can be periods of short-term minor improvements. About 10%–15% of people with MS have this type.

People with PPMS have the same symptoms as those with CIS and RRMS. However, they can also have additional symptoms, such as:

  • Chronic pain in the head, legs and feet, back, and muscles
  • Electric-shock sensations that run down the back and limbs when the neck is bent (Lhermitte's sign)
  • Paralysis

Secondary Progressive Multiple Sclerosis (SPMS)

If the relapsing-remitting MS progresses to a point at which there are no discernible relapses and remissions, it has transitioned to secondary progressive MS. In this type, symptoms accumulate and worsen without any remission.

There may be periods in which symptoms are stable. Often an individual will describe a change in their abilities when comparing current to past function but cannot identify an episode that led to the worsening.

Recap

There are four main types of MS: clinically isolated syndrome (CIS), relapsing-remitting MS (RRMS), primary progressive multiple sclerosis (PPMS), and secondary progressive multiple sclerosis (SPMS). Relapsing-remitting MS is the most common type, affecting 85% of people with multiple sclerosis.

Importance of Timely Diagnosis

Getting diagnosed with MS early can help you get treatment faster. This is important because your doctor will prescribe medications that can help reduce inflammation and slow disease progression once it's confirmed that you have MS.

The symptoms that occur with MS are similar to other diseases and disorders, so getting tested can help rule out any other health conditions or infections. Conditions that can mimic MS include:

Tests

Your neurologist, a specialist in diseases and disorders of the nerves and nervous system, or other doctor will conduct a physical exam and ask about your symptoms. They will also order blood tests and imaging to rule out other conditions and diagnose MS.

Blood Tests

A blood test is used to help rule out conditions such as Lyme disease or other disorders that can be diagnosed with blood tests alone. The same goes for vitamin or mineral deficiencies.

MRI

Magnetic resonance imaging (MRI) uses radio waves and magnetic fields to get a clear picture of the inside of your body. Your doctor will order an MRI of the brain and spinal cord to look for demyelination, which is damage to the myelin sheath. If no other conditions are present and there is evidence of damage to the myelin, it’s likely that you have MS.

Spinal Tap

A spinal tap, also known as a lumbar puncture, is done by inserting a needle into the low back and the spinal canal to collect a sample of cerebrospinal fluid (CSF). It can help determine the level of IgG antibodies, which are specialized proteins that bind to pathogens. In people with MS, IgG levels are often excessively high compared to those in people without the disease.

The spinal tap also looks for a large number of white blood cells, which are immune cells, and proteins known as oligoclonal bands. Oligoclonal bands are also antibodies that can indicate the body is experiencing a long-lasting overreaction from the immune system. A higher count of oligoclonal bands can help diagnose MS.

Roughly 5%–10% of people with MS will not have these abnormalities in their spinal fluid, though. That is why it is often used as a supplemental diagnostic tool.

Evoked Potentials

Evoked potentials measure electrical activity in the brain and spinal cord by stimulating connections between the nerves in the body (nerve pathways) with sound, touch, or sight. The most common evoked potential use for MS is sight and can help the doctor determine if there are any problems along the optic nerve pathways, which connect the brain with the eyes.

This test doesn’t determine if a person has MS on its own, but, in combination with other tests, it can help medical professionals reach a definitive diagnosis.  

Cognitive Testing

Cognitive testing may be used to determine the level of damage to the brain. This type of testing is also used throughout a person’s life after they’ve been diagnosed with MS to keep track of disease progression, how well the treatment is working, and cognitive decline.

Recap

There is no one test that can diagnose MS, but when blood and imaging tests are used together, they can help doctors determine if you have MS.

The McDonald Criteria

The McDonald criteria are the baseline for diagnosing MS. Recent updates were made in 2017 that changed the way MS is diagnosed. The McDonald criteria include one MS attack (a worsening of prior symptoms or brand-new symptoms that suddenly begin) and clinical evidence of one MS lesion, plus one criterion demonstrating dissemination in time and one criterion demonstrating dissemination in space.

Disseminated in time means that there is damage on different dates. If evidence of damage is disseminated in space, that means the damage is present in two or more parts of the central nervous system.

Each type of MS will have different results, and that is why the McDonald criteria address several situations that could occur at various stages of the disease. The criteria also contain a set of unique circumstances that go with each criterion to further assist in diagnosing the disease.

Recap

The McDonald criteria require the results of the examinations and tests to determine if the diagnostic criteria set out are met. The criteria take into account the number of lesions and flare-ups you have.

Diagnosis Timelines

Since the diagnosis of MS typically relies on more than one test, as well as the pattern of each person’s disease, it can be hard to determine a timeline from when you first experience symptoms to when you are diagnosed. Often, it can take a few years for a person to be properly diagnosed if they have a progressive form of the disease.

Multiple Sclerosis Doctor Discussion Guide

Doctor Discussion Guide Old Man

After the Diagnosis

Following an MS diagnosis, treatment can begin. You will work with your neurologist to determine the best course of treatment for you.

Monitoring of MS is often done following diagnosis to help keep track of how the disease is progressing over time. This is often done through repeat MRIs. MS can be highly unpredictable, so it’s important to keep the lines of communication open with your physician, live as healthily as possible, and continue with your treatment as prescribed.

Recap

To manage your MS, you will have to continue to monitor how it's progressing and the ways it's affecting your health and life. To do this, your doctors will likely ask you for routine testing and checkups to measure the progression of the disease as well as the efficacy of your specific treatment.

Summary

Diagnosing MS can be difficult because there is no definitive way to tell if a person has it. Examining the results from an MRI, a spinal tap, blood tests, and evoked potentials (measurements of electrical activity in certain areas of the brain and spinal cord) against the McDonald criteria help doctors discern between MS and other diseases that can cause similar symptoms. Getting diagnosed early is vital for planning treatment and your future.

A Word From Verywell

Being diagnosed with MS can be a confusing and difficult time. Because the results of tests aren’t always cut-and-dried, the process between first experiencing symptoms and getting a treatment plan can be a long and arduous one. The good news is that once you finally reach a definitive answer, you can begin to plan for your future.

There will be follow-up appointments to keep track of your disease. In the majority of cases of MS, severe disability or death is rare. Maintaining a healthy lifestyle and adhering to your treatment plan can minimize disease progression and the impact MS have on your life.

Frequently Asked Questions

  • How accurate is an MS diagnosis?

    The criteria used to diagnose MS continue to evolve because it is a tricky disease. A differential diagnosis, which is the process used by medical professionals to discern between two or more possible diseases, is used as a way to accurately diagnose the disease. The symptoms that occur with MS can be found in many other conditions. According to research, as many as 20% of people are misdiagnosed with MS.

  • What does testing for MS involve?

    Testing for MS involves a series of different strategies. There are several tools used such as MRIs, spinal taps, blood tests, and evoked potentials tests. For a proper diagnosis to occur, the results of each of these tests combined must fit a certain set of specific criteria known as the McDonald criteria. Only then can a person be diagnosed with MS.

  • How do you know if you have MS?

    Some of the early signs of MS can include double or blurry vision, numbness or tingling in the limbs or face, muscle stiffness and weakness, dizziness or vertigo, and clumsiness.

    Since these symptoms can occur for a variety of reasons, it’s best to make an appointment with your doctor if you are experiencing any of them. This can help you get to the bottom of why these symptoms are occurring, even if MS isn’t the cause. 

  • What happens after you’re diagnosed with MS?

    After you get diagnosed with MS, you and your medical team will formulate a treatment plan that works best for the type you have. You will also have to undergo sporadic monitoring tests to keep track of the progression of your disease.

    Having to start a new medication and repeat tests can be hard to cope with, but it is the best way to plan for your future and ensure that you live as healthily as possible for as long as you can.

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