Botulinum toxin in cervical dystonia: low dosage with electromyographic guidance.

Sixty patients with idiopathic cervical dystonia were treated a total of 240 times with botulinum toxin type A (BTA). Selected muscles were injected with BTA under electromyographic (EMG) guidance. The clinical effect was measured on the Tsui scale and a 10-point anchored visual analogue scale. A dosage of 150-300 mouse units was used in 77% of the treatments (mean 204 mouse units). Based on the Tsui scale, 45% of 240 treatments were still effective at the moment of reinjection (median improvement 2 points). Based on the 10-point anchored visual analogue scale, 73% of treatments were successful (median improvement 3 points). Forty-eight patients (80%) responded favourably to the treatment. Side-effects were mild and transient. Dysphagia occurred in 9% of treatments. Antibody production was investigated in 41 patients and was negative in all. A striking difference from previous reports is the lower dosage used in this study. The clinical response, however, was similar to that of other studies. We conclude that a dosage of 200-400 mouse units BTA (Dysport) may also be effective in the treatment of cervical dystonia, but with fewer side effects. EMG guidance and application of BTA into deep cervical muscles may further improve the clinical effect.