New McDonald criteria aim for faster MS diagnosis, treatment
Updated guidelines reflect advances in science, technology
Doctors will be able to diagnose multiple sclerosis (MS) faster and with greater accuracy — allowing patients to access treatment and support earlier — following an update to the McDonald criteria, the official guidelines used to diagnose the condition.
The revision reflects advances in understanding the biology of MS and in the development of more advanced imaging and laboratory techniques for detecting MS-related features.
“The 2024 revision of the McDonald Criteria marks an important step forward in how healthcare providers diagnose MS,” Bruce Bebo, PhD, executive vice president of research at the National MS Society, said in a written Q&A with Multiple Sclerosis News Today. “Thanks to progress in areas like biomarkers, brain imaging, and other medical tests, physicians now have better tools to identify MS earlier and with greater accuracy.”
The final updates were published in The Lancet Neurology, in a position paper titled, “Diagnosis of multiple sclerosis: 2024 revisions of the McDonald criteria.”
“Now, instead of waiting months or even years for enough clinical symptoms or MRI changes to confirm a diagnosis of MS, the new tests and updated criteria make it possible to reach a diagnosis more quickly and accurately,” Bebo said.
1st update since 2017 reflects scientific advances
MS is a chronic disorder marked by inflammation that damages healthy cells in the brain and spinal cord. Diagnosing MS can be complex, involving careful evaluation of symptoms, MRI scans, and other assessments. The McDonald criteria were initially published in 2001 to provide clinicians with a framework for interpreting these tests and diagnosing MS.
The criteria have been updated several times since their original publication to reflect advances in scientific understanding of MS. The most recent update was in 2017, but there have been key advances in the years since.
“These advances created a sense of urgency to update the criteria so people can get answers and start care sooner,” Bebo said.
To create the 2024 updates, the U.S.-based National MS Society teamed up with the European Committee on Treatment and Research in MS (ECTRIMS) to bring together dozens of MS experts from 16 countries — neurologists, radiologists, ophthalmologists, laboratory scientists, clinicians, epidemiologists, and people living with MS — to go over the latest evidence and offer recommendations.
“This collaborative and inclusive approach helped ensure that the updated McDonald Criteria reflect not only the latest science, but also the diverse realities of MS care and diagnosis around the world,” Bebo said.
Criteria now ‘globally applicable’
“By integrating novel biomarkers and rigorous consensus methodology, the updated criteria strengthen diagnostic accuracy and become more globally applicable,” Bruno Stankoff, ECTRIMS president, said in a committee press release.
One of the most significant changes is that a criterion called dissemination in time is no longer needed. Previous versions of the McDonald criteria required that a person needs to show signs of MS damage on at least two occasions before the disease could be diagnosed. With the new criteria, MS can be diagnosed without waiting, as long as patients show enough signs pointing to the disease and other diseases have been sufficiently ruled out.
“In the past, people often had to wait months or even years for new MS activity to show up before a diagnosis could be confirmed,” Bebo said. “Removing this requirement means many can now get answers sooner, without long delays.”
The new criteria still include requirements for dissemination in space, meaning that MS can only be diagnosed if multiple regions in the brain and/or spinal cord show signs of damage. But the new criteria are broader, including another potential region to consider: the optic nerve, which connects the eyes to the brain. Although the optic nerve is often damaged in MS, prior versions of the criteria hadn’t considered this region when evaluating dissemination in space.
“By recognizing more patterns of MS activity in the brain and spinal cord, doctors have clearer guidance and fewer gray areas when interpreting scans,” Bebo said.
The new criteria also offer guidance about the use of specific MRI markers such as paramagnetic rim lesions and the central vein sign. While these markers are not necessary to establish a diagnosis, they are highly indicative of MS and can support an MS diagnosis in certain situations.
Other changes include allowing a diagnosis without classic MS symptoms, and updated guidance on biomarkers of MS-related immune activity in the fluid around the brain and spinal cord. In addition to oligoclonal bands, which were part of earlier criteria but can be challenging to measure, the 2024 revision allows kappa free light chains to be used interchangeably, offering a simpler alternative.
“Together, these changes mean doctors can make an MS diagnosis earlier, with more certainty, and with less waiting for ‘proof’ to accumulate,” Bebo said.
He emphasized that diagnosing MS faster and more accurately can help improve clinical outcomes and reduce stress for patients.
“Early diagnosis means that treatment and support can start sooner, which can help manage symptoms, slow disease activity, and improve quality of life,” Bebo said. The updates also “reduce uncertainty,” he said. “Fewer misdiagnoses and a more standardized approach around the world mean less anxiety and more clarity about next steps, giving families peace of mind as they navigate the journey with MS.”
Guidance provides ‘unified framework’ for diagnosing all MS types
When people are told they have MS, they are diagnosed with relapsing-remitting MS (RRMS), which is marked by flares where symptoms worsen and periods of remission where symptoms ease or disappear. About 10%, however, are diagnosed with primary progressive MS (PPMS), marked by symptoms that get gradually worse, even in the absence of relapse activity.
Whereas older criteria had offered distinct guidance for diagnosing RRMS and PPMS, the new criteria call for a unified framework for diagnosing all types of MS. The new criteria also do away with prior distinctions for diagnosing MS in adults versus children.
“Today, research shows that the same core disease mechanisms underlie MS across ages and types, and that new tools—like advanced MRI markers and spinal fluid tests such as kappa free light chains—work just as well in children, adults, and across both relapsing and progressive forms of MS,” Bebo said. “By unifying the diagnostic approach, doctors can now apply one clear, evidence-based framework that makes diagnosis faster, more consistent, and more accurate for everyone.”
Bebo said the National MS Society has a range of resources for patients and clinicians, to help the MS community understand the new updates and incorporate them into clinical practice.
“By offering materials tailored to both professional and lived-experience audiences, the Society is helping ensure that the 2024 criteria are understood and applied consistently—so people can get answers and support sooner,” he said.
Bebo also emphasized that new guidelines do not affect people already diagnosed under earlier versions of the McDonald criteria. “Anyone previously diagnosed continues to have the same diagnosis, and their care and treatment plans remain valid,” he said.
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