The antiepileptic drug topiramate has been reported to improve essential tremor, but clinical trials have been small and of unsatisfactory design. We undertook a double-blind, placebo-controlled crossover study of topiramate in essential tremor, using accelerometry, spirography, and an activities of daily living questionnaire.1
Sixteen subjects were recruited between January and June 2002. Three withdrew consent, 13 commenced the study, and 10 finished it. Subjects were assessed at baseline and after 2, 4, and 6 weeks of treatment (placebo or topiramate doses 25, 50, and 100 mg daily). Following a washout period of 1 week, patients crossed over to the alternate arm of the study. Statistical analysis followed the method described by Altman.2
There was no period effect or treatment-period interaction. No outcome measure improved significantly in the active treatment period as compared with the placebo control period, although 4 of the 10 patients improved in at least 2 of the 3 outcome measures during the active treatment phase, and none during the control treatment phase.
This study provided no evidence of therapeutic benefit of topiramate in essential tremor. A marginally larger study would be required formally to exclude a useful therapeutic effect. To achieve a study with a power of 80% to exclude the null hypothesis, at least 17 patients would be required using accelerometry, 19 using spirography, and 2100 using an activities of daily living questionnaire.