Quantitative electromyography-guided botulinum toxin treatment of cervical dystonia.

The purpose of this study was to investigate the clinical and electromyographic effect of turn/amplitude analysis (TAA)-guided botulinum toxin administration in patients with cervical dystonia. Involuntary electromyographic activity was recorded from both sternocleidomastoidei, both splenii capites, and both trapezii muscles of 13 torticollis patients, aged 34-73 years, before and after botulinum toxin A (Dysport) application. Dystonic muscles were selected for the injection if mean turns/s exceeded a level of 200. Four weeks after treatment with a mean dose of 223 mu/subject, clinical improvement was observed in 12 patients (92%) and only one patient reported no effect. Electromyographic improvement could be observed in 10 patients (77%). Both turns/s and the amplitude/turn decreased by 27% on the average after treatment. The electromyographic toxin effect showed a good correlation with the clinical toxin effect (r = 0.6). No dose dependency of the changes in turn/amplitude parameters could be observed. We found TAA a valuable modality for targeting and selecting dystonic muscles and for assessing the therapeutic benefit of the toxin.