Diagnosis of multiple sclerosis

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Diagnosis of multiple sclerosis
Animation showing dissemination of brain lesions in time and space as demonstrated by monthly MRI studies along a year
Purpose	diagnosis via lab test, imaging and symptoms

Current standards for diagnosing multiple sclerosis (MS) are based on the 2018 revision of McDonald criteria. They rely on MRI detection (or clinical demonstration) of demyelinating lesions in the CNS, which are distributed in space (DIS) and in time (DIT). It is also a requirement that any possible known disease that produces demyelinating lesions is ruled out before applying McDonald's criteria.^{[citation needed]}

This last requirement makes MS an ill-defined entity, whose borders change every time that a new disease is set apart. Some cases previously considered MS are now considered distinct conditions, like Neuromyelitis optica or antiMOG associated encephalomyelitis. Because of the requirement of distributed lesions, a single lesion (RIS) is not considered MS. For the same reason, the prodromal stage of MS (the unknown condition that causes the lesions) would not be considered as MS if it could be found.^{[citation needed]}

Sometimes the diagnosis must be retrospective, relying on gradual worsening of neurological signs/symptoms, due to the lack of understanding of the pathogenicity driving disease progression.^[1] However, the only definite diagnosis of MS is post-mortem autopsy, where lesions typical of MS can be detected through histopathological techniques.^[2][3]