Diagnosis of Multiple Sclerosis
Diagnosing multiple sclerosis (MS) is not simple. Its symptoms often come and go, and they are different for every person. No single test, scan, or symptom proves MS. Instead, the diagnosis rests on the right mix of findings over time. For someone with a typical pattern, it may take only a few weeks. For others, it can take months or even years.
How the Diagnosis is Made
To diagnose MS, your doctor reviews your history and does a physical exam. An MRI of the brain is almost always needed too. Some people also need an MRI of the spinal cord, a spinal fluid test, or a vision test called visual evoked potentials. Repeat exams and scans over time may be needed before the picture is clear.
Doctors follow a standard set of rules to diagnose MS, called the McDonald criteria, which were updated in 2024. In general, the doctor must find signs that MS has affected more than one area of the central nervous system (the brain, spinal cord, or vision nerves), find evidence that the damage happened at more than one point in time, and rule out other conditions that could explain the symptoms. The 2024 update can help confirm MS sooner. For example, the optic nerve, which carries vision, now counts as one of the areas MS can affect, and in some cases an MRI or spinal fluid test can confirm the diagnosis after a single attack. Because many other diseases can look like MS, ruling them out is still a key part of the process.
Understanding Your MRI Report
Because MRI is such an important part of diagnosis, it helps to understand your report. An MRI makes detailed pictures of the brain and spinal cord. It is safe and uses no radiation. As more patients can see their own records, you may read your MRI report before talking with your neurologist. The report is written for doctors, so it can be confusing, and it is always best to review it with your provider.
A few terms help. An MRI is taken in different settings that each highlight something different. Some settings show old damage, sometimes called “black holes,” where tissue has shrunk. Others show the total number of MS spots, or lesions, which appear as bright marks. A dye called contrast can be given through an IV to show new, active spots. Together, these views tell your doctor about old injury, the overall number of lesions, and any new activity.
Keep in mind that an MRI alone cannot diagnose MS or show how well you are doing. Many people without MS have spots on their MRI, so your provider has to read it alongside your symptoms, history, and exam. One of the most useful things about MRI is comparing scans over time, which works best when they are done at the same place. If you switch facilities, ask for a copy of both the images and the report to share with your team.
Measuring MS Over Time
Once you have a diagnosis, your care team will track how MS affects you. One common tool is the Expanded Disability Status Scale, or EDSS. It runs from 0 to 10 and looks closely at walking, along with other functions such as vision, balance, and strength. A lower score means little or no disability, while higher scores reflect more trouble with walking and daily activities. The EDSS helps your team see whether you are stable or changing over time.
When to Talk to Your Provider
If you are worried about symptoms that might be MS, or you have questions about your diagnosis or your MRI report, talk with your health care team, in person or by phone or video. The VA offers the specialized testing needed to diagnose MS accurately.
Additional Information
- How is MS Diagnosed? (podcast)
- Importance of MRI in MS Care (podcast)
- National MS Society: Diagnosing MS
