Thalamic Deep Brain Stimulation Ameliorates Mixed and Abductor Spasmodic Dysphonia: Case Reports and Proof of Concept

Spasmodic dysphonia (SD) is a dystonia of the vocal folds causing difficulty with speech. A recent randomized controlled trial showed that thalamic deep brain stimulation (DBS) was safe and could improve this condition in the most common subtype—adductor SD. We investigated if thalamic DBS could also improve the other subtypes of abductor SD and mixed SD. These prospective blinded trials of 1 were designed to assess the safety of thalamic DBS in mixed and abductor SD and to quantify the magnitude of any benefit from unilateral or bilateral thalamic stimulation. One patient with mixed SD and one patient with abductor SD received bilateral thalamic DBS. After optimizing their DBS settings for vocal improvement, they were blinded and prospectively randomized to receive 1 mo of left, right, both, or neither hemisphere stimulation. Outcome was assessed by a speech language pathologist, blinded to the settings, rating voice recordings with the Unified Spasmodic Dysphonia Rating Scale, and by patient self-reported quality-of-life questionnaires. Additional outcomes included scores of mood and cognition. There were no complications. Both patients reported a subjective improvement of their voice and quality of life with blinded left thalamic DBS. The quality of their voice was also objectively rated as improved with blinded left thalamic DBS. This small proof-of-concept study suggests that left thalamic DBS can improve the quality of voice and quality of life of patients with mixed SD and abductor SD.