A separation of innate and learned vocal behaviors defines the symptomatology of spasmodic dysphonia
Samantha Guiry BA  Alexis Worthley BA  Kristina Simonyan MD, PhD
First published: 24 December 2018 https://doi.org/10.1002/lary.27617 Cited by: 1
This study was supported by the National Institute on Deafness and Other Communication Disorders, the National Institutes of Health (grants R01DC011805 and R01NS088160 to k.s.). The authors have no other funding, financial relationships, or conflicts of interest to disclose.
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Abstract
Objective
Spasmodic dysphonia (SD) is a neurological disorder characterized by involuntary spasms in the laryngeal muscles. It is thought to selectively affect speaking; other vocal behaviors remain intact. However, the patients' own perspective on their symptoms is largely missing, leading to partial understanding of the full spectrum of voice alterations in SD.

Methods
A cohort of 178 SD patients rated their symptoms on the visual analog scale based on the level of effort required for speaking, singing, shouting, whispering, crying, laughing, and yawning. Statistical differences between the effort for speaking and the effort for other vocal behaviors were assessed using nonparametric Wilcoxon rank‐sum tests within the overall SD cohort as well as within different subgroups of SD.

Results
Speech production was found to be the most impaired behavior, ranking as the most effortful type of voice production in all SD patients. In addition, singing required nearly similar effort as speaking, ranking as the second most altered vocal behavior. Shouting showed a range of variability in its alterations, being especially difficult to produce for patients with adductor form, co‐occurring voice tremor, late onset of disorder, and familial history of dystonia. Other vocal behaviors, such as crying, laughing, whispering, and yawning, were within the normal ranges across all SD patients.

Conclusion
Our findings widen the symptomatology of SD, which has predominantly been focused on selective speech impairments. We suggest that a separation of SD symptoms is rooted in selective aberrations of the neural circuitry controlling learned but not innate vocal behaviors.

Level of Evidence
4

Laryngoscope, 129:1627–1633, 2019