The course of multiple sclerosis (MS) is unpredictable, and the mechanisms leading to permanent disability are poorly understood. The number of lesions on a T2 weighted MRI scan at presentation bears some prognostic significance, certainly in the first decade of the disease,1 but what determines whether patients will have a benign or secondary progressive (SP) course thereafter is difficult to foresee based on the number of cerebral T2 lesions. To a certain extent this reflects the definition of “benign disease” which depends on the cut-offs required in terms of Expanded Disability Status Scale (EDSS) score and disease duration. Use of the EDSS biases the definition towards spinal …