A new update of the McDonald criteria, the international reference tool for the diagnosis of multiple sclerosis (MS) first published in 2001, introduces changes that will help identify the disease at earlier stages. The work has been led by Dr. Xavier Montalban, Director of the Multiple Sclerosis Centre of Catalonia (Cemcat) and Head of the Clinical Neuroimmunology Group at the Vall d’Hebron Research Institute (VHIR), and has been published inThe Lancet Neurology. The update has also involved Dr. Mar Tintoré, Dr. Jaume Sastre-Garriga, Dr. Susana Otero, Dr. Georgina Arrambide and Dr. Alex Rovira, members of Cemcat, the Preventive Medicine and Neuroradiology Services at Vall d’Hebron University Hospital, and the Epidemiology and Public Health and Neuroradiology groups at VHIR.

This is the first update of the criteria since 2017 and are consolidated with their scientific publication, following an international consensus process that brought together experts from 16 countries. These updates have been made possible largely thanks to research published by Cemcat-Vall d’Hebron University Hospital-VHIR.

“The McDonald 2024 criteria are the result of an international consensus aimed at achieving diagnosis as early as possible. This allows us to start treatment at even earlier stages of the disease, which is essential to reduce disability in the medium and long term”, explains Dr. Xavier Montalban.

Update of the criteria for the diagnosis of MS

Among the main novelties of the 2024 McDonald criteria is the inclusion of the optic nerve as a fifth anatomical location to demonstrate dissemination in space, determined through the performance of an MRI scan of the optic nerves, visual evoked potentials and/or an OCT. Until now, only lesions in four areas of the central nervous system (periventricular, cortical or juxtacortical, infratentorial and spinal cord) could be considered. Adding the optic nerve is particularly relevant, as approximately one quarter of patients with MS present with optic neuritis as their first symptom and most show involvement of this nerve.

Another fundamental change is that dissemination in time is no longer a mandatory requirement. Previously, to confirm the diagnosis it was necessary to demonstrate that lesions occurred at different points in time. With the new criteria, this condition is no longer required in cases where there are characteristic biomarkers of the disease in the cerebrospinal fluid or specific findings on MRI.

The new criteria also allow MS to be diagnosed in patients with radiologically isolated syndrome (RIS), that is, people without clinical symptoms but with typical lesions on MRI. Until now, these cases, often detected by chance, were considered possible preclinical stages of the disease, and treatment was not usually initiated as usual. With the 2024 revision, these patients can receive a formal diagnosis and earlier access to therapy.

The McDonald 2024 criteria also provide guidance for special populations, such as children, adolescents, people over 50 years of age and patients with vascular risk factors, in whom the risk of misdiagnosis is higher. For the first time, a single diagnostic framework is proposed for all forms of the disease, both relapsing and progressive.

This paradigm shift is crucial. As Dr. Xavier Montalban points out: “We are moving towards a biological diagnosis of MS, as already happens in other neurodegenerative diseases such as Alzheimer’s or Parkinson’s. It will no longer be necessary to wait for new clinical symptoms or new MRI lesions to confirm the disease. We will be able to rely on objective markers that allow us to act earlier and improve patient outcomes.”