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Diagnosing Tools

Read about the tools the doctor uses to diagnose MS, including your medical history, a neurologic exam, MRI and other laboratory tests.

Tests for Diagnosing MS
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Tests for Diagnosing MS

Mary Hughes, MD, discusses tests used for the diagnosis of multiple sclerosis.

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In this article

Timely and accurate diagnosis

There are many possible causes of neurological symptoms. When MS is considered as a potential diagnosis, other causes must be excluded — through the tools and tests outlined below — before an MS diagnosis is considered definitive. While this process of exclusion may be very rapid for some individuals, it can take a much longer time — with repeat testing — for others. Making the diagnosis of MS as quickly and accurately as possible is important for several reasons:

  • People who are living with frightening and uncomfortable symptoms want and need to know the reason for their discomfort. Getting the diagnosis allows them to begin the adjustment process and relieves them of worries about other diseases such as cancer.
  • Since we now know that permanent neurologic damage can occur even in the earliest stages of MS, it is important to confirm the diagnosis so that the appropriate treatment(s) can be initiated as early in the disease process as possible.

Criteria for a diagnosis of MS

At this time, there are no symptoms, physical findings or laboratory tests that can — by themselves — determine if a person has MS. The doctor uses several strategies to determine if a person meets the MS diagnostic criteria. In order to make a diagnosis of MS, the physician must:

  • Find evidence of damage in at least two separate areas of the central nervous system (CNS), which includes the brain, spinal cord and optic nerves AND
  • Find evidence that the damage occurred at two different points in time AND
  • Rule out all other possible diagnoses.

Beginning in 2001, the International Panel on the Diagnosis of Multiple Sclerosis began updating these longstanding criteria to include specific guidelines for using magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) analysis, and visual evoked potentials (EP) to speed the diagnostic process. These tests have been used to look for a second area of damage in a person who has experienced only one relapse (also called an attack or exacerbation) of MS-like symptoms — referred to as a clinically-isolated syndrome (CIS). A person with CIS may or may not go on to develop MS. With advances in MRI technology and other developments, the criteria (now referred to as The Revised McDonald Criteria) were revised again in 2005,  2010 and 2017 to make the process easier and more efficient. The 2017 revision specifies how findings on MRI and in the cerebrospinal fluid can determine whether a person has MS. 

Tools for making a diagnosis

Medical history and neurologic exam

The physician:

  • Takes a careful history to identify any past or present symptoms that might be caused by MS.
  • Gathers information about birthplace, family history, environmental exposures, history of other illnesses and places traveled that might provide further clues.
  • Performs a variety of tests to evaluate mental, emotional and language functions, strength, coordination, balance, reflexes, gait, vision, and the other four senses.

In many instances, medical history and neurologic exam provide enough evidence to meet the diagnostic criteria. Other tests are used to confirm the diagnosis or to identify other possible causes of the symptoms or neurological exam findings.

Blood tests

While there is no definitive blood test for MS, blood tests can rule out other conditions that cause symptoms similar to those of MS, including lupus erythematosis, Sjogrens, vitamin and mineral deficiencies, some infections, and  rare hereditary diseases.

Optical coherence tomography

Optical coherence tomography (OCT) is a relatively new, non-invasive and painless imaging tool for viewing retinal structures at the back of the eye. Although the optic nerve is often a target of MS disease activity — leading to episodes of optic neuritis — it cannot be easily seen. Doctors can use OCT to see the condition of the retinal nerve (which carries visual information before it leaves the back of the eye) after an episode of optic neuritis. Because the retinal nerve has no myelin covering, OCT images provide important information about the health of the nerve itself.

OCT studies have shown that the retinal nerve fiber layer is different in people with MS than in people without MS, even when there is no history of optic neuritis — making OCT a useful tool for learning more about the pathology of optic neuritis and of MS, and for gathering additional evidence of disease activity when the diagnosis of MS is suspected.