MRI features of benign multiple sclerosis: toward a new definition of this disease phenotype.

It is well known that the current classification of patients with benign multiple sclerosis (BMS), i.e., those with absent or minimal locomotor disability several years after disease onset, suffers from not having any prognostic value for the subsequent evolution of multiple sclerosis (MS). The identification of markers predictive of the longer-term course of MS will help define BMS more reliably and would allow better counseling of patients, particularly when advising on the initiation of a disease-modifying treatment. MRI-based evidence suggests that there are three potential, but not mutually exclusive, explanations for the scarce clinical impact of BMS: 1) the paucity of tissue damage within and outside MS lesions; 2) the relative sparing of clinically eloquent regions; and 3) the presence of effective compensatory mechanisms. In addition, the results of correlative MRI/neuropsychology studies underpin the need for a new definition of BMS, which should consider the maintenance of a normal cognitive profile as an additional criterion.