Summary: The McDonald criteria – a set of guidelines used to help neurologists provide an accurate and timely diagnosis of multiple sclerosis (MS) – was recently updated by a team of global MS experts. The revised criteria will allow for more ways to diagnose MS and may lead to people being diagnosed faster with more certainty and begin an effective disease management plan as quickly as possible for better outcomes. Further consultation with the broader MS community is needed to better understand how these changes will be implemented across different healthcare settings in Canada and globally.
Background: The McDonald criteria is a set of guidelines to help neurologists provide accurate diagnosis of MS, inform treatment decisions, and guide clinical trials in MS. The criteria were first developed and published in 2001 by an international group of experts, convened by the National MS Society in the United States (NMSS), and led by Dr. Ian McDonald. These guidelines have been revised several times to keep up with new information about the disease and advances in technology.
Details: The updates included in the 2024 McDonald criteria are meant to provide healthcare professionals with even more ways to diagnose MS more quickly and accurately.
Key takeaways:
Brain and spinal cord MRI remain the most useful test to aid in the diagnosis of MS.
The recommendations demonstrate the shift toward considering the biologic basis of MS at diagnosis.
The updates include changes to where and how we look for evidence of MS, including new tests and tools for diagnosis while also providing guidance to help prevent misdiagnosis.
The revised criteria will help us advocate for healthcare providers to gain access to these tools and provide more learnings in the future.
This work was led by the International Advisory Committee on Clinical Trials in MS, a group of international MS experts supported by the European Committee for Treatment and Research in MS (ECTRIMS) and the NMSS.
Impact: With more ways to diagnose MS, the updated criteria will help doctors diagnose people faster and accurately, and start the right disease management right away for improved results. Consultation with the wider MS community is needed to better understand the implications of these changes in both the Canadian and global context for healthcare professionals and people affected by MS.
The updated criteria will not affect the diagnosis and care of people who already live with MS. However, in situations where there’s uncertainty around a diagnosis, the new criteria could help confirm or rule out MS. People who suspect they may have MS are encouraged to consult with their healthcare provider.
Reference: Article published in Lancet Neurology on September 17, 2025 – Diagnosis of multiple sclerosis: 2024 revisions of the McDonald criteria. See article.
Additional Resources:
2024 MAGNIMS-CMSC-NAIMS consensus recommendations on the use of MRI for the diagnosis of multiple sclerosis – link
Recommendations on the use of optical coherence tomography and visual evoked potentials for fulfilling dissemination in space as part of the 2024 Revised McDonald Diagnostic Criteria for multiple sclerosis – link
We acknowledge the National MS Society (USA) for authoring the original version of this article. See News Release.