--This is a randomized, double-blind placebo controlled cross-over study. All subjects will receive a baseline evaluation and have their dystonia assessed by the eyes, mouth, speech and swallowing subscores of the Burke-Fahn-Marsden (BFM) dystonia scale, and the eyes and upper and lower face, jaw, and tongue subscores of the Global Dystonia Severity (GDS) rating scale. They will then be randomized into two groups. Either LVT or placebo with a titration schedule up to a total daily dose of 4000 mg will be prescribed for six weeks. After week 6, all subjects will undergo tapering and a wash-out period (one week for tapering off and one week for the washout). The two groups will then be switched to the opposite intervention (LVT or placebo), following the same titration and tapering pattern. We will evaluate both groups at weeks 3, 6, 11 and 14 using the same scales. This study requires six outpatient visits to the NIH CC; the total duration of this study will be 15 weeks.