**6. Avoiding dysphagia as an adverse effect of treatment for dystonia**

Radiologic findings show that in patients with dysphagia prior to treatment with BoNT-A, the condition did not worsen following treatment [8].

Careful choice of the correct muscle groups with the aid of electromyography before applica‐ tion of BoNT and the use of low dosages may prevent adverse effects [29]. In a study by Jankovic et al. [37], in which higher average doses of BoNT were used without electromyog‐ raphy guidance, 24 % of CD patients experienced adverse effects, and of these 23 % suffered from dysphagia. In a study by Barbosa et al. [43], who used an average dose of 191 U and did not use electromyography, slightly under half (47 %) of the patients developed dysphagia.

Other factors may have contributed to the low dysphagia indexes found in most studies. For example, the use of a larger number of injection points in each muscle and application in only one sternocleidomastoid (thus reducing diffusion of BoNT-A to the pharynx) can reduce the incidence of dysphagia [29]. Denervation has been shown to occur within a definable area that crosses anatomic barriers, including fascia and bone. Nevertheless, clinical and laboratory data suggest that dysphagia secondary to BoNT therapy is the result of toxin spreading from the sternocleidomastoid injection site to the pharyngeal musculature. Ensuring the injection dose in the sternomastoid does not exceed 100 IU leads to a substantially reduced incidence of this complication [12].
