FAQs about McDonald criteria

Yes. The McDonald criteria are a formal set of guidelines that enable an accurate diagnosis of MS as early as possible. Depending on the clinical presentation of each patient, or the symptoms the person experiences, the criteria determine which additional tests should be performed before a formal diagnosis can be made. Therefore, using the criteria can allow MS to be diagnosed as quickly as possible.

Dissemination in time means that there is MS-like neurological damage that is occurring at multiple points in time. Similarly, dissemination in space means that the damage is affecting multiple parts of the brain and/or spinal cord. Under the McDonald criteria, only patients meeting both of these requirements can receive a formal MS diagnosis.

Relapses are important clinical factors that help establish a formal MS diagnosis. For example, tracking relapses can be useful for telling whether or not a person meets the criterion of dissemination in time: If a person has had at least two relapses, this is clear evidence of inflammatory brain damage happening at multiple points in time. The symptoms that appear during relapses also may indicate damage to different parts of the central nervous system, which can be used to fulfill the criterion of dissemination in space.

Optic neuritis refers to inflammation in the optic nerves, which transmit information from the eyeballs to the brain. According to the 2017 McDonald criteria, the optic nerves are not one of the regions that can be considered when determining whether or not a person with optic neuritis fulfills the criterion of dissemination in space.

The 2017 updates to the McDonald criteria aimed to simplify and clarify elements of older versions of the criteria, to help facilitate an earlier diagnosis of MS. A key update was the inclusion of oligoclonal bands in the cerebrospinal fluid as a possible surrogate of dissemination in time. That inclusion takes into account both symptomatic and asymptomatic lesions when determining dissemination in space or time. The updated version also counts lesions in the brain’s cortex, in addition to juxtacortical ones, when assessing for dissemination in space.

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