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Neurostimulation with Laryngeal Pacemaker Does Not Affect Vocal Quality

by Amy E. Hamaker •

What are the voice quality and respiratory function effects of neurostimulation with the laryngeal pacemaker (LP) system in patients with bilateral vocal fold paralysis (BVFP)?

Bottom line
LP system neurostimulation results in an immediate and stable peak expiratory flow (PEF) improvement, without negative effects on the voice quality.

Background: Although transoral laser surgical glottic enlargement is considered the gold-standard treatment for BVFP, respiratory function improvement often correlates with voice quality deterioration due to the irreversible and static modification of the vocal fold conformation. Selective neurostimulation could be a promising BVFP therapy based on the dynamic restoration of vocal fold mobility.

Study design: Feasibility study, first-in-human, single-arm, open-label, prospective, multicenter study with group-sequential design and six-month post-implantation period of nine symptomatic BVFP subjects.

Synopsis: The evaluated voice quality parameters (MPT [glottal competence]; F0 range in semitones and the sound pressure level [SPL] range in decibels [correlation between changes in the vocal fold tension and subglottal air pressure]; jitter analysis [fundamental frequency perturbation of a sustained vowel]; and the Dysphonia Severity Index [a combination of objective measures of vocal performance]) did not change significantly from the pre- to the six-month post-implantation visit. The SPL range was the only parameter to show a significant improvement six months post-implantation.

Effects of the continuous LP system stimulation during and in absence of phonation. (A) Aligned vocal folds during phonation of the vowel [eee]. The position of both arytenoid cartilages is symmetric and the vocal folds show the same length and tension. The adduction required to phonate overrides the abduction elicited by the LP system. (B) Abduction of the right vocal fold caused by electrical posterior cricoarytenoid muscle stimulation via the LP system in absence of phonation. The right arytenoid cartilage shows dorsolateral shifting, whereas the vocal fold is driven into a position that can be classified between paramedian and intermedial. Accordingly, the stimulation mediated by the LP system results in the formation of a clearly visible glottal gap of about 3 to 4 mm. Credit: Copyright 2017 The American Laryngological, Rhinological and Otological Society, Inc.

Effects of the continuous LP system stimulation during and in absence of phonation. (A) Aligned vocal folds during phonation of the vowel [eee]. The position of both arytenoid cartilages is symmetric and the vocal folds show the same length and tension. The adduction required to phonate overrides the abduction elicited by the LP system. (B) Abduction of the right vocal fold caused by electrical posterior cricoarytenoid muscle stimulation via the LP system in absence of phonation. The right arytenoid cartilage shows dorsolateral shifting, whereas the vocal fold is driven into a position that can be classified between paramedian and intermedial. Accordingly, the stimulation mediated by the LP system results in the formation of a clearly visible glottal gap of about 3 to 4 mm.
Credit: Copyright 2017 The American Laryngological, Rhinological and Otological Society, Inc.

At the post-implantation visit, videolaryngoscopy descriptive evaluation showed that the targeted vocal fold responded to the neurostimulation by shifting from a paramedian to a lateral position (abduction), resulting in a dynamic and transient enlargement of the glottal gap nearly mimicking the physiological situation of a healthy vocal fold during respiration. During phonation, the physiological adduction overrode the stimulated abduction, and both vocal folds were driven back in a median position. Weekly self-assessment with a PEF meter showed significant improvement a week after LP system activation.

Limitations included a limited sample size, and previous contralateral glottic enlargement in four of seven participants.

Citation: Mueller AH, Hagen R, Pototschnig C. Laryngeal pacing for bilateral vocal fold paralysis: voice and respiratory aspects. Laryngoscope. 2017;127:1838–1844.