This review takes the 2024 McDonald criteria not as a consensus document to be summarised but as an intervention in clinical behaviour, and asks what happens when they are applied outside expert centres. Each revision since 1965 has broadened the evidence that can support a diagnosis of multiple sclerosis while trying to preserve specificity; the 2024 version brings in the optic nerve as a topography, and admits the central vein sign and paramagnetic rim lesions as supporting evidence.
The concern is operational rather than conceptual. The central vein sign and paramagnetic rim lesions need specific sequences, adequate field strength and a radiologist practised in reading them. Where those conditions are not met, a criterion intended to increase specificity can do the opposite — and more routes to a diagnosis means more heterogeneity in how the diagnosis is actually reached. Misdiagnosis in multiple sclerosis is not an academic harm: it commits a patient to a disease-modifying therapy with real risks, for a disease they do not have.
The practical response is to decide locally which of the new criteria your service can actually support. If your scanner and reporting pathway cannot produce a reliable central vein sign, say so explicitly and do not use it, rather than recording it as absent. And where a diagnosis rests entirely on one of the new elements, that is the case to discuss with a subspecialist before starting treatment.
- Audit which 2024 criteria your imaging and reporting pathway can actually deliver, and document the ones it cannot
- Do not record a central vein sign or paramagnetic rim lesion as absent when the sequence to detect it was not acquired
- Where the diagnosis depends on a single new criterion, get a second specialist opinion before starting disease-modifying therapy
- Re-examine the alternative diagnoses explicitly; broader criteria make it easier to stop looking
- In services without 3T imaging or susceptibility-weighted sequences — which is much of Indian neurology outside tertiary centres — the older criteria may be the safer instrument
Why it matters
Broader criteria applied in centres without the imaging to support them produce misdiagnosis and unnecessary disease-modifying therapy, not earlier diagnosis.
Don't overread it
This is an expert appraisal of implementation risk, not evidence that misdiagnosis rates have in fact risen.
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