Deep Brain Stimulation (DBS)Original ArticleHow Does GPi-DBS Affect Speech in Primary Dystonia?

- The precise prevalence and character of speech disorders following GPI DBS is unknown.
- Speech was systematically evaluated in 15 patients with predominant torticollis and GPi-DBS.
- Patients with dystonia showed slight speech impairment which was independent of stimulation.
- Two patients showed re-occurrence of stuttering and one patient dysarthria due to stimulation spread to the internal capsula.
- Speech disorders are not generally seen as a consequence of GPI DBS.

BackgroundGlobus pallidus internus deep brain stimulation (GPi-DBS) can be an effective treatment for primary dystonia. However, speech disorders have previously been reported as a common possible side effect of the treatment.ObjectivesTo study possible deterioration of speech after GPi-DBS and describe this in different dimensions.MethodsSpeech was systematically evaluated in 15 patients with predominant torticollis and GPi-DBS. Each patient was tested twice within one day in two stimulation conditions: ON-DBS vs. OFF-DBS. Speech analyses comprised both function-oriented (perceptual scales, acoustic analyses) and communication-related measures (intelligibility, naturalness). A control sample of 15 healthy speakers underwent the same speech assessment.ResultsOn the group level, patients with dystonia showed mild but significant impairment on the overall dysarthria scale, the intelligibility score, and the naturalness ratings in both stimulation conditions (Mann-Whitney, P < .05). No stimulation-induced deterioration was found. A slight increase in articulation rate was measured in the ON condition.On the single-case level, effects of GPi-DBS on speech were heterogenous. In one patient we observed a deterioration of speech (dysarthria), in a second patient with a history of childhood stuttering we found an aggravation of dysfluency. Impressive benefits could be documented in another patient who also suffered from spasmodic dysphonia.ConclusionsThe study provides evidence that speech impairment is not a necessary side-effect of GPi-DBS in primary dystonia. Both, recurring of stuttering and a worsening of dysarthria may be seen in individual patients. The positive effects of GPi-DBS on the symptoms of spasmodic dysphonia merits further research as DBS is not commonly applied in this population.