Pathogenesis of Vocal Fold Nodules: New Insights from a Modelling Approach

TLDR

The adult female larynx has an anatomical characteristic that predisposes to nodules, with decreased active stress from fatigue and increased subglottal pressure from effort compensation. The study aims to explain the extreme female/male ratio, the origin of hourglass‑shaped vibration patterns, and the roles of muscular tension imbalance and behavioral factors in vocal fold nodule pathogenesis. The authors used 3‑D computer simulations of vibrating vocal folds. The model shows that incomplete dorsal adduction, a small ventral curvature, and sufficient vibration amplitude—achieved by higher subglottal pressure or lower active stress—create a localized impact, linking muscular tension imbalance and behavioral factors to nodule formation.

Abstract

<i>Objective:</i> To give new insights into the pathogenesis of vocal fold nodules: (a) why the female/male ratio is so extreme, (b) how an hourglass-shaped vibration pattern – eliciting a localized microtrauma – originates, and (c) what the roles of muscular tension imbalance and of behavioral aspects are. <i>Materials and Methods:</i> Simulations with a 3-dimensional computer model of the vibrating vocal folds. <i>Results and Conclusion:</i> (1) A slightly incomplete dorsal vocal fold adduction is a first condition for inducing an hourglass vibration pattern. (2) A limited collision zone is only possible with a small degree of curving of the rest position of the vocal fold edges in their ventral portion. This is an anatomical characteristic of the adult female larynx. Muscular fatigue and resulting hypotonia seem to enhance this curving. (3) If both these conditions are fulfilled, a sufficient vibration amplitude is required to achieve a localized impact. (4) This third condition can be obtained by an increased subglottal pressure and/or by a decrease in active stress of the tension forces between the neighboring vocalis masses. These last aspects incorporate muscular tension imbalance (dyskinesia) and behavioral aspects in the modelling process. Decrease in active stress is a possible effect of fatigue, and increase in subglottal pressure a result of effort compensation.