Multiple sclerosis: Should MR criteria for dissemination in time be less stringent

for diagnosis of MS. 1 Among those, Dalton and colleagues 2 have suggested an addition to the Panel’s recommendation for imaging to determine “dissemination in time” when the initial presentation is a monosymptomatic, clinically isolated syndrome consistent with demyelinating disease and a first image is done within 3 months of presentation. From a retrospective analysis of 56 patients in whom optic neuritis was the most common presentation, the appearance of a new T2weighted lesion at a 3-month follow-up scan is more sensitive and just as specific for predicting a clinical diagnosis of multiple sclerosis as a new gadolinium-enhancing lesion (the recommended criterion.) The authors suggest expanding the International Panel magnetic resonance imaging criteria to include T2 lesions at the 3-month follow-up in these patients. The International Panel originally considered, but rejected, the inclusion of new T2 lesions at a 3-month imaging follow-up. The point of this criterion was to identify lesions that clearly represent new pathology. T2 lesions, as Dalton and colleagues note, can arise at any time and thus do not necessarily represent new disease activity since presentation. At this moment, the generalizability of these new results is not clear. The Queen Square MS Research Center is among the world’s most experienced at comparing scans from different time points, using highly standardized protocols with a minimum of repositioning error. They have great expertise, which may not be in place at all centers, at defining what is, and what is not, a new T2 lesion. Their baseline scans were performed a median of 5 (range, 1–12) weeks after onset of visual symptoms. This delay will vary in different practices and countries and has considerable bearing on whether an increase in T2 lesion load at 3 months reflects lesions that developed around the time of initial symptoms or truly occurred separated in time from the clinical finding. This problem may be greater still for initial isolated clinical presentations other than optic neuritis. Despite the demonstrated sensitivity and specificity of including T2 lesions at a 3-month follow-up scan at Queen Square, for most diagnosticians gadolinium-enhancing lesions at that point likely still provide the most unequivocal demonstration of new pathology. The “McDonald criteria” were intended to be revised as additional data became available. We are grateful for the contribution of Dalton and colleagues and look forward to guidance to ensure that, if incorporated, their suggestion can enhance multiple sclerosis diagnosis in everyday clinical practice.