Multiple sclerosis, or MS, can be difficult to diagnose because its early signs are not the same for everyone.
Some people first notice blurred vision, numbness, weakness, or problems with balance, while others may have changes in the brain before they feel anything unusual.
A new study from Hannover Medical School in Germany suggests that updated diagnostic rules can identify more people with MS during their first medical assessment.
MS is a long-term disease in which the immune system mistakenly attacks parts of the central nervous system, which includes the brain, spinal cord, and optic nerves.
This attack damages myelin, the protective covering around nerve fibers.
When myelin and the nerves underneath are injured, messages traveling between the brain and the rest of the body can become slower or disrupted.
There is no single simple test that proves a person has MS. Doctors usually combine a patient’s symptoms and medical history with neurological examinations, MRI scans, and sometimes tests of the fluid surrounding the brain and spinal cord.
They also need to rule out other conditions that can produce similar symptoms or scan results.
To make diagnosis more consistent, experts introduced the McDonald criteria in 2001. These international rules have been updated several times as scientists have learned more about MS and developed better tests.
The goal is to diagnose the disease early without incorrectly labeling people who have another condition.
The criteria were revised again in 2024. One important change was the addition of the optic nerve as another location where MS-related damage can help support a diagnosis. The updated criteria also allow some people with highly typical MRI findings to be diagnosed even before clear neurological symptoms appear.
Researchers from the Department of Neurology and Clinical Neurophysiology at Hannover Medical School compared the revised criteria with the earlier version. They wanted to know whether the changes would make a practical difference when doctors used tests already available in routine clinical care. Their analysis found that the 2024 rules increased first-time diagnoses by almost 10 percentage points.
The optic nerve accounted for much of this increase. Earlier criteria focused heavily on typical areas of the brain and spinal cord where MS lesions, or areas of damage, tend to appear. The new rules recognize that inflammation and injury to the optic nerve can provide another important piece of evidence.
This makes biological and clinical sense because optic neuritis is a common early sign of MS. It can cause blurred or reduced vision, pain when moving an eye, and colors that appear less bright than usual. In some people, optic nerve problems may provide one of the earliest clues that inflammation is affecting the central nervous system.
Doctors have several ways to examine the optic nerve and visual pathway. MRI can reveal some changes, while optical coherence tomography can measure layers at the back of the eye and detect signs of nerve damage. Another test measures how quickly visual signals travel from the eyes to the brain.
The revised criteria also change how doctors can approach radiologically isolated syndrome, or RIS. This term describes people who have MRI abnormalities that look strongly like MS even though they have not experienced the usual clinical symptoms. Such findings may be discovered unexpectedly when a person has a brain scan for an unrelated reason.
Under the newer framework, some of these people may now meet the requirements for an MS diagnosis earlier. That could allow closer monitoring and, in appropriate cases, earlier discussion of treatment. However, diagnosing a disease before symptoms develop also makes careful interpretation especially important because doctors must avoid confusing MS-like MRI changes with other causes.
Another important change involves cerebrospinal fluid, the clear liquid surrounding the brain and spinal cord. Doctors can test this fluid for signs of immune activity inside the central nervous system. Traditionally, oligoclonal bands have been an important clue supporting an MS diagnosis.
The revised criteria also recognize a measure called the kappa index. It provides another way of detecting abnormal antibody-related activity and can be measured automatically in a laboratory. The researchers found that cerebrospinal fluid testing remained extremely important even under the expanded rules.
In fact, the study reported that without cerebrospinal fluid testing, about one quarter of patients diagnosed under the revised 2024 criteria would not have received a diagnosis. This finding suggests that newer imaging rules do not make traditional laboratory testing unnecessary. Instead, several forms of evidence continue to work together.
The 2024 criteria include additional advanced MRI signs as well, but the Hannover team did not use them in this analysis. The researchers deliberately relied on conventional tools that are already widely used in routine practice. This makes the results particularly relevant to hospitals that may not have highly specialized imaging equipment or expert neuroradiology services.
The study was published in eClinicalMedicine. Overall, the findings suggest that the revised McDonald criteria can help doctors identify more patients at an earlier stage using tests that many neurological clinics already have. Earlier diagnosis may allow treatment and monitoring to begin sooner, potentially reducing future nerve damage.
Still, faster diagnosis is useful only if it remains accurate. The study supports the practical value of the new criteria, but further research is needed to understand how they perform in different populations and healthcare systems and how often earlier diagnoses change long-term outcomes.
Future studies should also determine whether the newer specialized MRI markers add enough benefit to justify the extra equipment, expertise, and cost.
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