Multiparametric laryngeal assessment of the effect of thalamic deep brain stimulation on essential vocal tremor

Effect of Ventral Intermediate Nucleus Deep Brain Stimulation on Vocal Tremor in Essential Tremor

Background

There is a paucity of literature examining the effect of Ventral Intermediate Nucleus (VIM) deep brain stimulation (DBS) on voice in patients with vocal tremor (VT).

Objective

Investigate the effect of unilateral and bilateral VIM DBS on voice in patients with Essential Tremor (ET) and VT.

Methods

All patients receiving VIM DBS surgery underwent voice evaluation pre- and six-months post-operatively. We collected patient-reported quality-of-life outcome measures and acoustic voice measures of sustained phonation and connected speech. Acoustic measures specific to VT included amplitude tremor intensity index (ATRI), frequency tremor intensity index (FTRI), rate and extent of F0 modulation, and rate and extent of intensity modulation.

Results

Five patients, age 72.8 ± 2.6 years, 4 female, 1 male with mean disease duration of 29 ± 26.2 years met the inclusion criteria and were included. Two subjects had bilateral procedure and three had unilateral. We observed significant improvements in measures of vocal tremor including ATRI, FTRI, rate of F0 modulation, rate of intensity modulation, and extent of intensity modulation, as well as patient reported voice-related quality of life measured by VHI-10. Bilateral VIM DBS cases showed greater improvement in VT than unilateral cases.

Conclusion

Both unilateral and bilateral VIM DBS resulted in significant improvement of VT, with more improvement demonstrated in patients having bilateral as compared to unilateral VIM DBS. In addition, patients also reported significant improvements in voice-related quality of life. If larger studies confirm our results, VIM DBS has the potential to become a treatment specifically for disabling VT.

How can we make better decisions about dystonic voice management?

PURPOSE OF REVIEW

The optimal diagnosis and management of dystonic voice disorders are rooted in the nuanced understanding of their phenomenology. Distinguishing between subtypes of vocal dystonia is challenging, not only because the audible and physical presentations of these dystonia's can seem similar, but also because there is a lack of scientific consensus regarding the diagnostic criteria for these conditions. To help improve the clinician's acumen we focus on outlining the classification of the top three neurological voice disorders, notably: spasmodic dysphonia, (2) spasmodic dysphonia with tremor, and essential tremor of the voice. We also provide an algorithmic approach based on current evidence-based literature to guide practitioners through the clinical diagnosis and management of each possible etiology.

RECENT FINDINGS

Much remains unknown about the subtypes of vocal dystonia, and this gap in our knowledge likely limits our ability to advance clinical management. Still, continued experience evaluating and treating these patients yields refined clinical evaluations and decision making.

SUMMARY

Improvements in our clinical decision-making can be made by acknowledging that our limited understanding of vocal dystonia may hinder what therapeutic interventions we can offer, yet our ability to accurately diagnose the dystonia is central to providing optimal patient management.