Fig. 1.

The evolution of diagnostic criteria for multiple sclerosis. ∗In the 1983 Poser criteria, the inclusion of CSF IgG OCB or IgG index was necessary to establish the definition of laboratory supported definite MS. This designation was considered a more conservative level of diagnosis when compared to clinically definite MS. For the latter, fulfilment of the criteria required either two distinct attacks with clinical evidence of two separate lesions or two attacks with clinical evidence of one lesion and paraclinical evidence of another separate lesion. In contrast, the former necessitated any of the following combinations: i) two attacks with either clinical or paraclinical evidence of one lesion along with CSF OCB/IgG index; ii) one attack with clinical evidence of two separate lesions and CSF OCB/IgG index; iii) one attack with clinical evidence of one lesion and paraclinical evidence of another separate lesion, along with CSF OCB/IgG index. In cases where two attacks and CSF OCB or IgG index were present, a diagnosis of laboratory-supported probable MS was permissible, even in the absence of MRI data. ∗∗ According to the 2001 and 2005 McDonald criteria, abnormalities in CSF analysis could offer supportive evidence of the immune and inflammatory nature of lesion(s). This became particularly valuable when imaging criteria proved insufficient, lacked specificity (as in the case of older patients), or when the clinical presentation was atypical. DIS had to be demonstrated by the presence of three of the following: i) One gadolinium-enhancing lesion or nine T2-hyperintense lesions if no gadolinium-enhancing lesion was present; ii) At least one infratentorial lesion; iii) At least one juxtacortical lesion; iv) At least three periventricular lesions. Alternatively, dissemination in space could also be established by two MRI lesions consistent with the suspicion of MS and CSF IgG OCB or IgG index. ∗∗∗ According to the 2001 McDonald criteria, the presence of abnormalities in CSF analysis was mandatory to diagnose MS in cases of insidious neurological progression suggestive of MS. § According to the 2005 revision of the McDonald criteria, in cases of insidious neurological progression suggestive of MS, MS could be diagnosed if there was one year of disease progression (retrospectively or prospectively determined) and two of the following: i) positive brain MRI (nine T2 lesions or four or more T2 lesions with positive VEP); ii) positive spinal cord MRI (two focal T2 lesions); iii) CSF IgG OCB or IgG index. CSF was therefore not necessary for the diagnosis of progressive MS. §§ According to the 2010 and 2017 revisions of the McDonald criteria, in cases of insidious neurological progression suggestive of MS, MS could be diagnosed it there was one year of disease progression (retrospectively or prospectively determined) and two of the following: i) evidence for DIS in the brain based on ≥ 1 T2 lesions in at least 1 area characteristic for MS (periventricular, juxtacortical, or infratentorial); ii) evidence for DIS in the spinal cord based on ≥ 1 T2 lesions in the cord; iii) positive CSF (isoelectric focusing evidence of IgG OCB and/or elevated IgG index). CSF was therefore not necessary for the diagnosis of progressive MS. # According to the 2017 revision of the McDonald criteria, the evidence of CSF IgG OCB and/or elevated IgG index could substitute for the evidence of DIT. Abbreviations. CSF: Cerebrospinal fluid. DIS: Dissemination in space. DIT: Dissemination in time. IgG: Immunoglobulin G. MRI: Magnetic resonance imaging. MS: Multiple sclerosis. OCB: Oligoclonal bands. VEP: Visual evoked potentials.