Use of Dalfampridine in Primary Lateral Sclerosis

This study will comprise an 18-week open label safety and tolerability trial. In this study, a total of 35 subjects with primary lateral sclerosis PLS or upper motor neuron predominate ALS will be enrolled. At the initial screening evaluation, a baseline T25FW will be obtained. This baseline test will be repeated at weeks 2, 4, 6, 10, 14 18. The validity of this measure was shown in MS studies when compared to the MSWS-12 (12 item walking scale) and CGI (clinical global impression) scales (35-37). A consistent responder will be defined as improvement in 3 of 4 Timed 25Foot Walk while on medication, compared with the baseline results while off medication.