journalsPermissions.nav MULTIPLE SCLEROSIS MSJ JOURNAL

Treatment with natalizumab is a double-edged sword: profound efficacy meets the medical need especially for patients with highly active relapsing multiple scle-rosis (MS) but is also accompanied by the potential to induce possibly fatal progressive multifocal leukoen-cephalopathy (PML).1 Whereas the PML risk is virtu-ally absent during the first treatment year, it increases in the second year; after 24 months the risk is as high as 1:90 for specific patient groups.2 If natalizumab is stopped after this interval, disease activity may resume shortly after treatment cessation. Unfortu-nately, there is considerable uncertainty about suitable follow up therapy. In view of this clinical dilemma, refined measures of individual risk stratification are urgently needed. In addition to treatment dura