Getting a diagnosis of multiple sclerosis (MS) can feel like a long, confusing journey. Symptoms come and go, test results are sometimes unclear, and many people wait months or even years for certainty.
But there is good news. In 2024, an international expert panel revised the official McDonald Criteria, the rules doctors use to diagnose MS. These updated criteria make it possible to confirm MS earlier and with greater confidence, so that treatment can begin sooner — a step that can change the long-term course of the disease.
The new recommendations were developed by the International Panel on the Diagnosis of Multiple Sclerosis, a group of neurologists, radiologists, and other specialists from around the world. Their work was published in The Lancet Neurology in October 2025.
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Why the Criteria Keep Changing
Medicine evolves, and so does our understanding of MS. Since the first version of the McDonald Criteria was introduced in 2001, researchers have continued to learn more about how MS develops, how it appears on MRI scans, and which biological markers help confirm it.
Each revision — in 2005, 2010, 2017, and now 2024 — has had the same goal:
👉 to make diagnosis faster, more accurate, and less dependent on waiting for multiple attacks.
The 2024 update is the most patient-centered so far. It integrates new scientific evidence, better MRI technology, and clear rules for rare cases. It also acknowledges that sometimes, MS can be detected even before a second clinical episode occurs — if other strong indicators are present.
How Doctors Diagnose MS – Step by Step
Although every patient’s story is unique, the process of diagnosing MS usually follows several key steps. Let’s go through them one by one — in plain language.
1. Clinical Symptoms
It all starts with neurological symptoms that suggest inflammation in the central nervous system — for example, vision problems, numbness, weakness, dizziness, or balance issues.
Doctors call the first episode of neurological symptoms lasting more than 24 hours a Clinically Isolated Syndrome (CIS).
2. MRI Evidence
Magnetic Resonance Imaging (MRI) is the cornerstone of MS diagnosis. It helps visualize lesions — small areas of inflammation and tissue damage in the brain or spinal cord.
To confirm MS, doctors look for signs of:
Dissemination in Space (DIS): lesions in different parts of the central nervous system (e.g. brain and spinal cord).
Dissemination in Time (DIT): lesions that appeared at different moments, meaning ongoing activity.
3. Cerebrospinal Fluid (CSF) Analysis
A lumbar puncture (spinal tap) can show oligoclonal bands (OCBs) — specific antibodies that indicate immune activity in the central nervous system. Their presence supports an MS diagnosis, even if MRI findings are borderline.
4. Ruling Out Other Causes
MS is a diagnosis of exclusion — doctors must rule out other causes such as neuromyelitis optica spectrum disorder (NMOSD), MOG-antibody disease, or certain infections.
What’s New in the 2024 McDonald Criteria
The 2024 revision makes several important changes aimed at identifying MS earlier, but still safely. Here are the key updates:
1. Stronger Role of CSF Findings
If a person has only one clinical event but MRI shows lesions typical for MS, the presence of oligoclonal bands in the CSF can now be enough to confirm the diagnosis — without waiting for another attack.
This is a major step forward, because it allows earlier treatment when the biological evidence is already clear.
2. Radiologically Isolated Syndrome (RIS)
This is one of the most discussed changes.
RIS means that someone has MRI lesions typical of MS, but no clinical symptoms yet.
In earlier versions of the criteria, RIS was not considered MS — doctors had to wait until symptoms appeared.
Now, under the 2024 criteria, a subset of RIS patients can be diagnosed with MS if additional evidence supports it — for example:
lesions in multiple typical locations (periventricular, juxtacortical, infratentorial, or spinal cord),
the presence of CSF oligoclonal bands, and
specific MRI features that predict progression.
This change acknowledges what researchers have observed for years: some people with RIS already have silent inflammatory activity that will almost certainly lead to MS.
3. Better Integration of Optic Nerve and Spinal Cord Findings
The new criteria explicitly recognize that lesions in the optic nerve and spinal cord count as evidence for dissemination in space.
This helps in cases where visual or spinal symptoms were previously “not enough” to confirm MS.
4. Clarified Definitions and Standardized Imaging
The panel introduced clearer MRI protocols, minimum lesion numbers for interpretation, and better definitions of what counts as a “typical MS lesion.”
This should improve consistency between hospitals and radiologists worldwide.
What Hasn’t Changed
The foundation remains the same:
Objective evidence from MRI or CSF is required,
Alternative explanations must be excluded,
Clinical judgment remains essential — no algorithm replaces experience.
But overall, the balance has shifted slightly toward earlier recognition rather than long waiting periods.
Why Early Diagnosis Makes a Difference
The earlier MS is diagnosed, the sooner treatment can begin — and that can make all the difference for long-term outcomes.
Disease-modifying therapies (DMTs) don’t just reduce relapses; they can also slow or even prevent the accumulation of disability. Studies have shown that people who start treatment soon after their first event often stay active, mobile, and independent for much longer.
Equally important, an early and confident diagnosis provides clarity and emotional relief. It ends the uncertainty that many people experience while “waiting for the second attack.”
What About People With CIS or RIS?
If you were told in the past that you have a Clinically Isolated Syndrome (CIS) or a Radiologically Isolated Syndrome (RIS), it might be worth revisiting your diagnosis.
The new 2024 criteria could mean that some of these cases now meet the definition of MS.
That doesn’t automatically mean treatment is required — but it does mean it’s worth discussing again with your neurologist, especially if you have new MRI findings or if your last evaluation was several years ago.
Emerging Biomarkers and Imaging Features
Beyond the official updates, researchers are exploring new markers that could further improve MS diagnosis in the near future.
Two of the most promising are Iron Rim Lesions (IRLs) and Kappa Free Light Chains (κ-FLCs).
Iron Rim Lesions are dark-rimmed spots on advanced MRI scans that indicate ongoing inflammation in older MS plaques. They are highly specific for MS but not yet part of the diagnostic criteria, since they require high-field MRI and standardized imaging protocols.
In CSF testing, κ-FLCs may soon complement or even replace oligoclonal bands as a faster, more standardized marker of immune activity.
For now, both are recognized as emerging tools that will likely influence the next generation of diagnostic criteria.
Other MRI markers — such as the Central Vein Sign, leptomeningeal enhancement, and cortical lesions — are also under investigation for their potential to improve diagnostic accuracy and help identify MS-specific patterns of inflammation.
In Summary
The 2024 McDonald Criteria allow earlier and more precise diagnosis of MS.
CSF findings now play an even stronger role.
Some people with RIS may already meet the definition of MS.
Early diagnosis = earlier treatment = better long-term outcomes.
MS remains a complex disease, but these updates mark a major step forward toward timely care and improved quality of life.
Closing Words
Knowledge empowers patients. If you or someone you know is living with CIS, RIS, or early signs of MS, consider talking to your neurologist about the new diagnostic guidelines.
Medicine is always evolving — and thanks to ongoing international collaboration, people with MS today have a better chance than ever to get the right diagnosis, at the right time, and start treatment that truly makes a difference.
Source
The Lancet Neurology (October 2025) — Diagnosis of multiple sclerosis: 2024 revisions of the McDonald criteria by the International Panel on the Diagnosis of Multiple Sclerosis.
Read more on PubMed
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Nele
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