Botulinum toxin treatment for functional disability induced by essential tremor.

This study aimed to improve botulinum toxin's (BTX) efficacy and to reduce its unwanted effects in the treatment of functional disability due to essential tremor (ET) of the hand. Twenty patients with disabling ET, not responding to conventional pharmacological therapy, were enrolled in this open-label study. Activities of daily living self-questionnaire (ADLS) and severity tremor scale (STS) were used to establish patients' functional disability and tremor severity. Accelerometry and surface electromyography were used to identify the arm muscles with tremorogenic activity during impaired positions. Global rating was used to measure treatment efficacy and unwanted effects. BTX type A was injected into the muscles principally responsible for impaired positions. After BTX treatment, there was a significant reduction in both severity and functional rating scales scores (ADLS and STS) and of tremor amplitude as measured with accelerometry and EMG. Adverse effects were limited to a slight third finger extension weakness in 15\% of patients. BTX injections are effective and safe in reducing disability due to ET, if based on the criterion of functional selection.