To be diagnosed with MS, a person must meet certain diagnostic criteria (the evidence that must be present to make a diagnosis) showing damage to the central nervous system (CNS).

How is MS diagnosed?

No single set of symptoms or laboratory test, such as a blood test, imaging test, genetic test, or immune function test, can independently identify MS.

How doctors test for MS

A doctor must use multiple tools to diagnose MS. The most important tools are the medical history, a careful and thorough neurologic exam, and magnetic resonance imaging (MRI). Other tests include visual evoked potentials (VEP) and analysis of spinal fluid taken by lumbar puncture.

The diagnosis of MS is a clinical diagnosis, meaning that the physician relies less on specific test results, but more on symptoms reported by the patient as a part of the medical history and signs detected by the physician during the neurologic exam.

Evidence of disease activity

The diagnosis of MS is based on evidence of disease activity (e.g. demyelinating lesions) which has occurred in at least two separate locations of the central nervous system (CNS) at two different points in time. Before imaging technology (MRI) was used to detect damage in the CNS, the diagnostic criteria for MS required a wait-and-see approach for multiple attacks (relapses, exacerbations, or flare-ups).

1: Evidence of damage in 2 or more separate areas of the CNS
(this includes the brain, spinal cord, and optic nerves)

2: Evidence that the damage (in 2 or more places) happened 1 or more months apart
3: The damage (or symptoms) did not happen because of another disease
Diagnosis of MS


What is the McDonald Criteria for MS diagnosis?

In 2001, an international panel of experts updated the criteria for diagnosing MS to incorporate the latest in imaging technology (MRI). These criteria have become known as the McDonald Criteria, criteria which has been revised in 2005 and 2010 to make the diagnosis of MS more efficient and reliable. The latest revision or improvement, published in 2010, is commonly called the Revised McDonald Criteria and require the following combination of evidence:

Since 2001, the McDonald Criteria have included guidelines for using magnetic resonance imaging (MRI), visual evoked potentials (VEP) and analysis of cerebrospinal fluid to make a diagnosis. These tests can help identify a second area of damage in the CNS in a person who has had only one attack (relapse, exacerbation, or flare-up).

How many different tests do I have to take to confirm an MS diagnosis?

In some cases, a physician may make a diagnosis of MS based on the results of the medical history and neurologic exam. If these evaluations show clear evidence of two or more areas of damage in the CNS that happened at different times (at least one month apart) and can’t be explained by another medical condition, then no other testing may be necessary to diagnose MS.

However, most physicians will use at least one other test besides the medical history and neurologic exam, such as magnetic resonance imaging (MRI), visual evoked potentials (VEP) testing or analysis of cerebrospinal fluid (CSF), to confirm the diagnosis. This is especially true when the history and exam have not clearly indicated two or more areas of damage in the brain or spinal cord.

What if a person has only one attack of MS-like symptoms?

When an individual has experienced only a single episode of an MS-like attack involving symptoms caused by demyelination in the CNS, that individual is said to have clinically-isolated syndrome (CIS). In an individual with CIS, it may take months or years for another episode to happen and a confirmed diagnosis of MS to be made. However, a person with CIS may never develop MS.

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Written by: Jonathan Simmons | Last reviewed: May 2015.