Botulinum toxin in tremor

Twenty-five patients with hand tremor of 2+ (moderate) to 4+ (severe) on the tremor severity rating scale were randomized to receive either 50 units of Botulinum toxin (BTX) type A (allergan, Inc., Irvine, CA) or placebo injections into the wrist flexors and extensors of the dominant limb. If patients failed to respond to the initial injection, they were eligible to receive another injection of 100 units 4 weeks later. Rest, postural and kinetic tremor were evaluated at 2-4 week intervals over a 16-week study period, using tremor severity rating scales, accelerometry, and assessments of improvement and disability. A significant improvement (p < 0.05) was observed on the tremor severity rating scale 4 weeks after injection in patients treated with BTX as compared to placebo, and this effect was maintained for the duration of the study. Four weeks after injection, 75% of BTX treated patients vs 27% of placebo treated patients (p < 0.05) reported mild to moderate improvement (peak effect rating greater than or equal to 2). There were no significant improvements in functional rating scales although trends were observed for some items. Postural accelerometry measurements showed a greater than or equal to 30% reduction in amplitude in 9 of 12 BTX treated subjects and in 1 of 9 placebo heated subjects (p < 0.05). Although all patients heated with BTX reported some degree of finger weakness, no severe, irreversible, or unexpected adverse events occurred. Chemodenervation with BTX may significantly ameliorate essential hand tremor in patients who fail to improve with conventional pharmacologic therapy.