Limited duration of the effect of methylprednisolone on changes on MRI in multiple sclerosis.

Treatment with methylprednisolone reduces the duration and severity of clinical relapses in multiple sclerosis (MS), while reducing the number of gadolinium-enhancing lesions on T1-weighted MRI. We performed serial MRI imaging after methylprednisolone treatment to see whether suppression of enhancement persists and whether related abnormalities on T2-weighted images disappear at follow-up. Thirteen patients with definite MS received a total of 31 courses of methylprednisolone over an average period of 50 weeks. Gadolinium-enhanced MRI was obtained before and after treatment, then at monthly intervals, using a standardised repositioning and imaging protocol. Two experienced readers in conference defined the number of active (gadolinium-enhancing and new or enlarging nonenhancing) lesions. We detected 609 active lesions on 195 examinations. Directly after treatment the reduction in the number of enhancing lesions was 78%, indicating restoration of the BBB and suppression of inflammation. It was uncommon for a lesion which stopped enhancing to show enhancement on a subsequent examination. No beneficial effect was observed on the rate of disappearance of related abnormalities on T2-weighted images, indicating persistent change such as oedema, cellular infiltration or demyelination. Moreover, in 89% of cases, an increase in the number of active lesions was observed before new clinical activity, if any, was observed (on average 52% earlier). MRI enabled us to demonstrate that the duration of the effect of methylprednisolone treatment is temporary (on average 9.7 weeks).