Thalamic Deep Brain Stimulation for Spasmodic Dysphonia: A Phase I Prospective Randomized Double-Blind Crossover Trial

BACKGROUND: Adductor spasmodic dysphonia (SD) is a dystonia of the vocal folds causing difficulty with speech. The current standard of care is repeated botulinum toxin injections to weaken the adductor muscles. We sought to ameliorate the underlying neurological cause of SD with a novel therapy—deep brain stimulation (DBS). OBJECTIVE: To assess the safety of DBS in SD through phase I trial, and to quantify the magnitude of any benefit. METHODS: Six patients had left ventral intermediate nucleus (Vim) thalamic DBS and were randomized to 3 mo blinded-DBS “on” or “off” followed by a crossover. Primary outcomes were quality of life and quality of voice during the blinded phase. Patients continued with open-DBS “on.” Secondary outcomes were comparisons of pre- and 1-yr cognitive, mood, and quality of life. This trial was registered with ClinicalTrials.gov (NCT02558634). RESULTS: There were no complications. Every patient reported an improvement in quality of life (P = .07) and had an improvement in quality of their voice (P = .06) when their blinded DBS was “on” versus “off.” The trend did not reach statistical significance with the small sample size. Secondary outcomes showed no difference in cognition, an improvement in mood, and quality of life at 1 yr. CONCLUSION: This phase I randomized controlled trial confirmed that DBS can be performed safely in patients with SD. Blinded DBS produced a strong trend toward improved quality of life and objective quality of voice despite the small sample size. The cerebellar circuit, not the pallidal circuit, appears to be crucial for motor control of the vocal folds.