Dalfampridine for Imbalance in Multiple Sclerosis

Dalfampridine is a new medication that was FDA approved in 2010 to improve walking speed in people with Multiple Sclerosis (MS). People with MS walk slowly in part because MS damages the myelin insulation around nerves which slows conduction of messages from the brain to the leg muscles. Dalfampridine works by improving conduction in nerves with damaged myelin. Recent research indicates that imbalance in MS is in large part caused by poor conduction by the nerves that transmit information about the position of the legs to the brain. It is therefore likely that, by improving nerve conduction, dalfampridine will also improve imbalance in people with MS. Dalfampridine will be administered in this study by the same route (oral), dosage (10mg), and frequency (every 12 hours) approved by the FDA to improve walking speed in people with MS. The proposed pilot study will examine the effects of dalfampridine on imbalance in 24 subjects with Multiple Sclerosis (MS) and imbalance. This small pilot study will help to show if dalfampridine improves imbalance in MS and will guide the design and implementation of a larger full scale study to definitively determine if dalfampridine improves balance and prevents falls in people with MS.

Automatic Postural Response (APR) latencies will be measured by Computerized Dynamic Posturography (CDP). The restoration of balance after an unexpected movement by Computerized Dynamic Posturography relies on automated postural responses in the upper and lower legs, trunk, shoulders, and neck muscles. APR latency is the reaction- time response to movements of the support surface on which the subject stands. These responses typically occur at onset latencies of ~100 milliseconds. In response to a change, both feet-in-place and stepping strategies can be used to recover balance, with the incidence of stepping responses becoming larger as the change magnitude increases voluntary movements in human subjects.

The ABC is an 11-point scale and subjects are asked to indicate personal level of confidence in doing specific activities without losing balance or becoming unsteady on a scale from 0% to 100%. The ratings are added (possible range =0 -1600) and divide by 16 to get each subject's ABC score. A high ABC score indicates a high degree of confidence and a low ABC score indicates a low degree of confidence.

Inclusion Criteria: Age 20- 59 years, Able to walk at least 100m without an aide or with unilateral assistance Prolonged APR latencies (≥ 1SD > mean for healthy people in this age range) OR, Reduced balance-related activity (ABC scores ≤ 85%), Abnormal trunk range of motion (horizontal), trunk range of motion (frontal), turning duration, cadence, double support time, stride length or gait cycle time (outside 1SD of the average for healthy people in this age range) Exclusion Criteria: Currently taking dalfampridine (any within the last 2 weeks), Cause(s) of imbalance other than MS, Impaired renal function (creatinine clearance ≤50mL/min), Seizure disorder Pregnancy or breast feeding