Tools Your Doctor May Use to Diagnose MS

Written by: Katie Murphy │. Last reviewed: June 2022. | Last updated: June 2022

Multiple sclerosis (MS) is a disease that doctors diagnose by looking at a person's symptoms and using various tests. There is no one test that can tell if you have it. Instead, your doctor will use a variety of tools to make a diagnosis.1,2

Some of the most common tools are:1,2

  • Medical history
  • Brain and nerve (neurological) exam
  • Advanced imaging of the brain and spinal cord
  • Nerve tests
  • Spinal fluid tests
  • Blood tests

Medical history

When noting your medical history, your doctor will ask you lots of questions. The questions will be about:1-3

  • Your symptoms and when they began
  • Past and current illnesses
  • Other medical conditions
  • Medicines you are taking
  • Your family medical history
  • Whether anyone else in your family has MS or other autoimmune diseases

You will also be asked about past brain or nerve (neurological) signs. For example, if you have muscle weakness but had vision problems months ago, your doctor will want to know.1-3

Neurological exam

A neurological exam is a thorough assessment of your brain and nervous system. The exam may include tests of your:4

  • Reflexes
  • Muscle strength
  • Coordination
  • Walking
  • Vision
  • Hearing
  • Feelings in your body (sensations)

Your doctor will use the results of this exam to look for any signs of damage or disease in your brain and nervous system. This exam can help rule out other conditions and confirm a diagnosis of MS.4

Magnetic resonance imaging (MRI) test

An MRI is a test that uses powerful magnets and radio waves to produce detailed images of your brain and spine. MRI tests can show areas of damage (lesions) associated with MS. It is the most common test used to help diagnose MS. Lesions related to MS often have a specific pattern and location in the brain. However, not everyone with MS has these more common patterns.5

Evoked potentials test

Your doctor may also order an evoked potentials test. This test measures the electrical activity in your brain in response to visual, auditory, or sensory stimuli. A delay in response time may mean you have damage to the nerves in your brain and spine (central nervous system).6

Some people with MS have nerve damage, but it might not cause any noticeable symptoms. This damage might not even be picked up on a neurological exam or MRI. Evoked potentials tests can be used to detect nerve problems in these cases.6

Cerebrospinal fluid (CSF) analysis

CSF surrounds your brain and spinal cord. It is collected through a procedure called a lumbar puncture, or spinal tap. Doctors can test your CSF for several things, including the presence of oligoclonal bands (O-bands). These are proteins made in response to an infection or other inflammatory process.7

Most patients with MS have O-bands, though O-bands can also occur in other neurologic conditions. CSF studies can also help rule out other brain and nerve issues like meningitis.7

Optical coherence tomography (OCT)

OCT is a noninvasive imaging test that uses light waves to take a detailed picture of the back of the eye (the retina). Thinning of certain layers of the retina can occur in people with MS. This thinning is due to damage to the nerves of the retina and optic nerve.8

The optic nerve is a large nerve that carries visual information from the eye to the brain. This nerve is often a site of inflammation and damage (optic neuritis) in people with MS.8

Similar to the evoked potentials test, OCT often can see damage that may not have caused any noticeable symptoms.8

McDonald criteria

The McDonald criteria is a set of guidelines used to help diagnose MS and exclude other conditions that may have similar symptoms. Along with several clinical criteria, it recommends specific tests in certain situations. The results of these tests show whether a person meets the criteria to be diagnosed with MS. The tests include:8,9

  • MRI of the brain and spine
  • Evoked potentials test
  • O-bands in the CSF

While meeting the criteria greatly increases the possibility of MS, there is no one test or clinical history that can diagnose MS. Sometimes people with neurologic conditions other than MS may meet the McDonald criteria. These cases can be difficult to diagnose. Additional tests often are necessary to find the true cause of a person's symptoms.8,9

Similarly, sometimes people who have MS do not meet the McDonald criteria when they first see their doctor. This is common if they are evaluated after their first flare-up, or if a scan shows lesions that might be caused by something else (such as a headache). Usually, people with MS meet the McDonald criteria further into their disease progression.8

Blood tests

There is no blood test that can diagnose MS. However, a blood test may be used to rule out other conditions that may cause similar symptoms. Your doctor will talk to you about the tests and tools used to help diagnose and rule out MS.1,2

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