Deep Brain Stimulation for Spasmodic Dysphonia: A Blinded Comparison of Unilateral and Bilateral Stimulation in Two Patients

Abstract

Deep brain stimulation (DBS) is a promising new therapy for patients with spasmodic dysphonia (SD). The preliminary results from our randomized controlled trial showed good clinical effects with unilateral left thalamic stimulation in 6 righthanded patients. This suggests that the pathological process underpinning SD may have a "hemisphere dominant" pathway. We describe 2 patients with concurrent essential tremor and SD who had previously undergone bilateral thalamic DBS for their limb tremor. Both patients experienced an unanticipated improvement of their SD symptoms. One patient was right-handed, and the other was mixed left-handed. To investigate the amount of SD improvement following DBS therapy in each hemisphere, 4 different settings were tested: both sides on, left side on, right side on, and both sides off. Both patients most improved following bilateral stimulation. There was, however, a powerful unilateral benefit in both patients with only a small additional benefit from bilateral stimulation. The right-handed patient improved most with left-hemisphere stimulation whereas the mixed left-handed patient improved most with right hemisphere stimulation. There was some discrepancy between the two tests applied in the second patient reflecting the known difficulties to evaluate vocal symptom improvement in SD. We discuss the possible correlation of handedness and speech hemisphere dominance as well as the need for more reliable tests to measure SD severity. Ultimately, we recommend a bilateral approach for future studies, using a patient perception test as the primary outcome and functional imaging to further investigate the correlation of handedness and the amount of hemisphere dominance in SD.

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

“… 13 , 20 Recent work has shown that bilateral surgery may add a small but additional benefit to the voice. 21 …”

Adductor Spasmodic Dysphonia Improves with Bilateral Thalamic Deep Brain Stimulation: Report of 3 Cases Done Asleep and Review of Literature

“…Stimulating the left VIM was only slightly better than stimulating the right VIM, though handedness of the patient was not specified. Kruger et al compared unilateral versus bilateral VIM stimulation in two patients, as well as side to side difference [13]. They too concluded that bilateral stimulation was superior to unilateral stimulation, but further observed that unilateral stimulation of the dominant hemisphere was superior to stimulation of the nondominant hemisphere.…”

“…Second, we did not characterize the effect of unilateral versus bilateral stimulation nor compare dominant hemisphere versus nondominant hemisphere stimulation, though may be able to do so in future evaluations of case 2 who is still actively being seen in our clinic. Third, our study was retrospective, though the ongoing phase 1 DEBUSSY sham-controlled trial involving six SD patients will be the first to furnish prospective data [13]. Lastly, some of the improvement in the vocal quality and USDRS scores post-DBS could be from improvement of vocal tremor given that severe vocal tremor can also lead to voice breaks which can mimic SD.…”

“…Awake DBS offers the intended benefit of intraoperative test stimulation to verify therapeutic effect, allowing the surgeon the opportunity to reposition the lead if intended benefits are not observed. Since then, there have been five other published reports of SD that have undergone awake DBS surgery [10][11][12][13]. Herein, we report on three additional cases of patients with SD who have responded favorably to bilateral VIM DBS done under general anesthesia, without the use of intraoperative test stimulation.…”

The Patho-Neurophysiological Basis and Treatment of Focal Laryngeal Dystonia: A Narrative Review and Two Case Reports Applying TMS over the Laryngeal Motor Cortex

“…Table 1 presents findings of BoNT treatments of LD and an overview of the literature on invasive brain modulation with deep brain stimulation (DBS) [ 77 , 78 , 79 , 80 , 81 ]. The efficacy and safety of BoNT were established for the treatment of LD, and this approach is considered by most to be the treatment of choice for spasmodic dysphonia/LD, particularly adLD [ 16 ].…”