Twenty spinocerebellar ataxia patients will be randomized to receive either Dalfampridine or placebo over a total period of 10 weeks. After entering the study, patients will return every 2 weeks for evaluation. After four weeks, intervention will be stopped and patient will enter a 2-week wash out period where they do not take any drug. Then, patients will be given the opposite treatment (Dalfampridine or placebo) and this "crossover" study will be performed for another 4 weeks. Investigators expect there will be improvement in walking speed and steadiness after taking Dalfampridine, thereby improving activities of daily living and enhancing social and occupational functions.
