New McDonald criteria revisions: 6 key updates

The McDonald criteria have long served as the global standard for diagnosing multiple sclerosis (MS).

In 2025, an expert task force convened by the National MS Society and the European Committee for Treatment and Research in MS (ECTRIMS), released updated recommendations to provide a unified approach for diagnosing multiple sclerosis in individuals with relapsing or progressive courses throughout the lifespan to both attain earlier diagnoses and reduce misdiagnoses.

In collaboration with the MS Society, touchNEUROLOGY provides key updates on the updated McDonald criteria.

Recently published McDonald criteria revisions¹ reaffirm the use of magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) oligoclonal bands (OCBs) to support diagnosis but provide important clarifications and guidance to help reduce misdiagnosis, particularly in complex cases.

This update was informed by a rigorous review of new data, expert consensus, and the need for improved application in real-world clinical practice. Implementing the revised criteria will help patients to begin treatment sooner and achieve better long-term outcomes.

Key updates include:

1. Refined application of MRI criteria for dissemination in space and time, including additional imaging biomarkers (central vein sign and paramagnetic rim lesions).
2. Additional CSF biomarker to assist with MS diagnosis, with kappa-free light chain (kFLC) as an alternative to OCBs.
3. Emphasis on early MS diagnosis, including ability to diagnose RIS as MS before symptoms start when other conditions are met.
4. Specific considerations for paediatric, older age, and patients with comorbidities.
5. Clinical judgment remains central to diagnostic accuracy, but paraclinical evidence is required with or without typical clinical presentations.
6. Optic nerve added as a 5th anatomical location to meet dissemination in space criteria, with vision biomarkers that can be demonstrated using OCT or VEPs.

These changes reflect evolving scientific understanding and are intended to enhance diagnostic confidence for clinicians, while ensuring timely intervention for patients.

What this means for patient care

Delays in MS diagnosis can lead to worse long-term outcomes and unnecessary progression. Early diagnosis allows for earlier treatment initiation, improved symptom management, and better quality of life. However, misdiagnosis can lead to unnecessary treatments and psychological distress. These revised criteria aim to strike the right balance, supported by clearer application of radiologic and laboratory evidence.

National MS Society: Tools and resources for clinicians

To help implement these updates, the MS Society has launched a series of educational resources and tools for healthcare professionals, including:

• Diagnostic workup – online guide, including tests and findings required to diagnose MS³
  
• MS diagnostic algorithm – printable flyer that can be used as a quick reference guide⁴
  
• Requirements for diagnosing MS – printable flyer with quick reference to diagnostic requirements based on number of DIS anatomical locations⁵
  
• Imaging and fluid biomarkers glossary – descriptions of the new biomarkers that can aid in earlier and accurate diagnosis⁶

Resources for your patients

National MS Society resources can assist HCPs to address patients’ questions, whether they have MS or possible MS.

Permission obtained from the MS Society for reuse and wider reuse of the following information and infographics:

• 2024 McDonald Diagnostic Criteria webpage⁷
• Momentum article⁸
• The Revised MS Criteria: What You Need To Know video⁹

Access more on MS and the McDonald criteria

Editor: Katey Gabrysch, Editorial Director.

Disclosures: No funding was received in the publication of this article.

This content has been developed independently by Touch Medical Media for touchNEUROLOGY, in collaboration with National MS Society. Information has been provided to touchNEUROLOGY by the National MS Society. No fees or funding were associated with this short publication.

Cite: McDonald criteria revisions: Earlier, more accurate diagnosis in multiple sclerosis. touchNEUROLOGY. 22 September 2025.

References:

1. The Lancet Neurology. Revised 2024 McDonald criteria for the diagnosis of multiple sclerosis. Lancet Neurol. 2025. Available at: https://www.thelancet.com/journals/laneur/article/PIIS1474-4422(25)00270-4/abstract (accessed September 2025).

2. National MS Society. Revised 2024 McDonald Criteria for MS Diagnosis – Expert Video Discussion. YouTube. 2025. Available at: https://www.youtube.com/watch?v=HWC_JlaI14Q (accessed September 2025).

3. National Multiple Sclerosis Society. Diagnostic Criteria & Workup. Available at: https://www.nationalmssociety.org/for-professionals/for-healthcare-professionals/diagnosing-ms/diagnostic-criteria-workup (accessed September 2025).

4. National Multiple Sclerosis Society. Diagnostic Algorithm for Multiple Sclerosis. 2025. Available at: https://cdn.sanity.io/files/y936aps5/production/24e63a2a352bfba7aeb9224a167874ef6284dc33.pdf (accessed September 2025).

5. National Multiple Sclerosis Society. Requirements for Diagnosing MS. 2025. Available at: https://cdn.sanity.io/files/y936aps5/production/24e63a2a352bfba7aeb9224a167874ef6284dc33.pdf (accessed September 2025).

6. National Multiple Sclerosis Society. Imaging and Fluid Biomarker Glossary. nationalmssociety.org. 2025. Available at: https://www.nationalmssociety.org/for-professionals/for-healthcare-professionals/diagnosing-ms/imaging-and-fluid-biomarker-glossary (accessed September 2025).

7. National Multiple Sclerosis Society. 2024 McDonald Diagnostic Criteria. 2025. Available at: https://www.nationalmssociety.org/understanding-ms/what-is-ms/how-ms-is-diagnosed/2024-mcdonald-diagnostic-criteria (accessed September 2025).

8. National Multiple Sclerosis Society. Updated Diagnostic Criteria. Momentum Magazine. 2025. Available at: https://www.nationalmssociety.org/news-and-magazine/momentum-magazine/research-and-science/updated-diagnostic-criteria (accessed September 2025).

9. YouTube. National MS Society. Q&A: 2024 McDonald Criteria – Clinical Insights. 2025. Available at: https://www.youtube.com/watch?v=SK12kEKtmOo (accessed September 2025).

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