Changes in vocal fold contact across the voice field after injection laryngoplasty.

Abstract

Rationale: Unilateral vocal fold paralysis (UVFP) causes glottic insufficiency that varies in severity across the phonation range, yet treatment outcomes are typically evaluated through perceptual ratings or acoustic indices obtained at a single vocal effort level. This study used voice mapping, a method that computes acoustic and electroglottographic metrics cycle-by-cycle across the fundamental frequency-sound pressure level plane, to characterise the effects of injection laryngoplasty across the voice field in patients affected by UVFP.

Methods: Two complementary cohorts were studied: eight patients assessed before and immediately after injection with hyaluronic acid or calcium hydroxyapatite, and five patients injected with autologous fat and followed at one and three months.

Results: Difference maps and phonation-type cluster analyses consistently showed that the predominant effect of glottic medialisation was a reduction in cycle-by-cycle irregularity, suggesting that improved vibratory regularity, rather than a simple increase in contact magnitude, may be the primary mechanism underlying clinical vocal improvement.

Conclusions: These findings offer a spatially resolved perspective on the physiology of injection laryngoplasty that is not accessible through conventional assessments, and support further development of voice mapping as an objective monitoring tool in the management of UVFP.