Assessment of motor outcomes in multiple sclerosis patients with walking impairment treated with Fampridine using motor evoked potentials

Abstract

Backgound : the purpose of the study is to consider the utility of Transcranial Magnetic Stimulation (TMS) in patients with Multiple Sclerosis (MS) and walking impairment, treated with Fampridine, as correlated with the 25-Foot-Walk test (T25-FW). It is known that clinical benefits should be identified within two to four weeks after starting the treatment; otherwise, if there is no benefit reported by patients, it should be discontinued. Methods: 15 MS patients with walking impairment, ranked between 3.5 and 7 on the Expanded Disability Status Scale (EDSS), were investigated by T25-FW and TMS. Evaluations were performed prior to Fampridine 10 mg twice daily administration, 5 and 12 days afterwards, and also 1 and 3 months later. The medium age was 42.8 years and an average duration of the disease was 12.06 years. Results: we assessed an improvement of walking by 2.1 seconds measured on the T25-FW after the first 12 days in 9 patients, which correlated with a 2 miliseconds improvement of the Central Motor Conduction Time (CMCT). For the other 6 patients there was no visible clinical improvement. Nevertheless, CMCT dropped by 0.5 ms and the motor conduction speed by 1 millisecond in 4 of these 6 patients. Fampridine administration was continued in the 4 cases. At the end of the 3 months period, their walking speed measured as on the T25-FW also improved by 2 sec. Conclusions: the amelioration of TMS parameters anticipated the improvement of speed on the T25-FW. In spite of the early false negative clinical response, electrophysiological findings could predict a future clinical improvement if treatment is continued.