What to Know: New MS Diagnostic Criteria

Research and Science

September 17, 2025

Vicky Uhland

A person gets an MRI — The updated diagnostic criteria include new MRI guidelines.

You’ve heard the stories—or maybe even lived through them yourself.Your doctor attributes the numbness in your leg to a pinched nerve. Your blurred vision is dismissed as eye strain. You’re told your fatigue will improve if you reduce your stress. Or you’re simply viewed as too different from a “typical” multiple sclerosis patient.The result is that it takes months or even years to diagnose your MS diagnosis—and you start disease-modifying therapies (DMTs) later than you could have, which may affect your long-term health outcome.MS is a complicated disease, so it makes sense that recognizing it is complicated as well. Even experienced clinicians can mistake MS symptoms for other health conditions. And doctors who don’t see many people with MS may not know what to look for.“To make the diagnosis of MS is not always straightforward. As clinicians, we have to take into account the history, the physical exam findings, the MRI findings, sometimes spinal tap findings. It's not one thing that makes the diagnosis of MS—we have to put everything together,” says Christina Azevedo, MD, associate professor in neurology and director of the Advanced Imaging in MS Lab at the University of Southern California.“There's always a balance between diagnosing MS as early as possible, but also accurately.”Some studies show that MS is misdiagnosed 5% to 18% of the time. But MS experts around the world are working to change that.

Developing MS Diagnostic Criteria

In 2001, the National Multiple Sclerosis Society convened a group of MS experts, led by renowned neurologist Ian McDonald, MD, to develop a set of guidelines to help clinicians accurately diagnose MS. Since then, these guidelines — dubbed the McDonald Diagnostic Criteria — have been updated every five to seven years based on new research.In late 2023, a committee of 55 experts in MS clinical management, radiology, methodology, epidemiology and patient perspectives (but minus McDonald, who died in 2006), representing 16 different countries, gathered in Barcelona, Spain, to review and update the 2017 McDonald Diagnostic Criteria.One of those participants — Peter Calabresi, MD, professor of neurology at Johns Hopkins School of Medicine — noted that the committee emphasized diversity, paying particular attention to female doctors and scientists, along with people from parts of the world not traditionally represented by these types of efforts.After three days of discussing the latest scientific advances in MS diagnosis, the committee agreed on some key updates to the 2017 criteria. Their paper, “Diagnosis of multiple sclerosis: 2024 revisions of the McDonald criteria,” was published September 17, 2025, in the journal Lancet Neurology.

What This Means for You

Earlier Diagnosis

There are 5 main changes in this category.The first three have to do with a concept called dissemination. Traditionally, an MS diagnosis relies on evidence of damage (lesions) to the central nervous system (CNS) that occurred at different times in someone’s life (known as dissemination in time, or DIT) and in different areas, or spaces, of the CNS (dissemination in space or DIS).The 2024 McDonald Diagnostic Criteria no longer require evidence of DIT for an MS diagnosis. And they make a big change to DIS.The 2017 criteria listed four DIS locations:

The spinal cord
The periventricular part of the brain
The brain cortex
The brain stem and cerebellum

MS diagnoses relied on lesions being found in 2 of these 4 locations.The 2024 criteria add a fifth location — the optic nerve. Now, neurologists or ophthalmologists can demonstrate DIS through MRIs or abnormal results on an imaging test called optical coherence tomography (OCT).This is notable because “optic neuritis is the presenting symptom in 25% of people with MS,” Calabresi says. But traditionally, lesions on the optic nerve have been difficult to see because the nerve is very small. Now, Calebresi says, “we have tools that can detect optic nerve lesions even when they’re asymptomatic.”Another change in the 2024 criteria add a new type of spinal fluid biomarker test. And the fifth and last change creates a single, unified framework of criteria for diagnosing relapsing and progressive forms of MS — including evidence of progression over at least 12 months.

More Specific Diagnoses

There are two key changes in this category — one having to do with MRI testing breakthroughs and the other focusing on specific age groups.The updated criteria note that a patient’s clinical history and a doctor’s exam remain fundamentally important in an MS diagnosis, but they should also be backed up by testing — with brain and spinal cord MRIs being the most useful.Basically, what this means is “you can still diagnose MS the old-fashioned way, and if your center doesn't necessarily have access to some of the advanced imaging tools or OCT, that's okay. You can still use prior criteria,” Calabresi says. “The intent of these new tools is to be more specific and sensitive. We’re trying to use modern technology earlier and more accurately.”The new tools include advanced MRIs that can detect paramagnetic rim lesions and central vein signs. Calabresi says paramagnetic rim lesions are the core of slow progression of the disease without relapses or visible new lesions. Central veins are a way to determine if a lesion is an MS lesion.“The fact that we can image this is just stunning right now,” he says. “Imagine in a year or two an MRI report could come back and say: ‘There are five lesions and three have a central vein or rim, and given the person’s age, MS is highly likely.’ And then a neurologist could do a spinal tap or another confirmatory test.”Another key change in the 2024 criteria has to do with diagnosing people under age 18 and over age 50.“This is the first time age has been incorporated in the criteria,” Azevedo says.She notes that white spots can occur in the brain due to aging, so the new criteria are designed to make sure there are also signs of demyelination in older people as part of an MS diagnosis.The 2024 criteria “strongly recommend” that people age 50-plus who also have headaches or vascular disease, or significant vascular risk factors like smoking, high blood pressure, high cholesterol or diabetes, test positive for a spinal cord lesion, certain proteins in their spinal fluid or a central vein sign before they receive an MS diagnosis.For children under age 12, an additional lab test is recommended to confirm an MS diagnosis. For children and adolescents, imaging biomarkers are recommended.

More Specific Diagnoses

Disseminating the Message

The National Multiple Sclerosis Society is offering a variety of educational tools for both people with MS and providers to acquaint them with the 2024 McDonald Diagnostic Criteria.For people living with MS, “a big part of our messaging is if you already have MS, these criteria are not designed to take your diagnosis away,” says Julie Fiol, the Society’s associate vice president of clinical innovation and strategy.For clinicians, the Society and the European Committee for Treatment and Research in MS (ECTRIMS) are providing education about the 2024 criteria at various professional meetings. There will also be OnDemand, virtual training for clinicians, both MS specialists and generalists.“The goal is not to make patients get all of the tests, but to use the ones that make sense,” Fiol says. The new criteria are “intended to provide more options to do what makes sense for the patient in front of you and to get to an MS diagnosis more quickly.”For people who are being evaluated for MS, Azevedo says the 2024 criteria offer new options to discuss with your healthcare providers as part of a diagnostic workup.“You could ask: ‘Can my MRI include central vein imaging, and will we be able to see paramagnetic rim lesions?’ I also recommend seeing an ophthalmologist for optic nerve testing, and asking about spinal fluid testing,” she says.The bottom line, Azevedo says, is “the updated diagnostic criteria can make life better for people with MS because we’ll be able to diagnose earlier and more accurately, and that’s the foundation of the entire treatment plan.”

Vicky Uhland

Vicky Uhland is a writer and editor in Lafayette, Colorado.

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Everything You Need to Know About the Updated MS Diagnostic Criteria

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