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

Abstract

Objective: 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. Materials and Methods: Simulations with a 3-dimensional computer model of the vibrating vocal folds. Results and Conclusion: (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.

Description of patients consulting the voice clinic regarding gender, age, occupational status, and diagnosis

“…Each patient underwent the following evaluations on the same day: subjective self-evaluations using the Voice Handicap Index [13], perceptual evaluations using the GRBAS Nodules appear as small, bilateral, mostly symmetric mass lesions (thickenings) of the inferior lip of the vocal folds and result in an hourglass closure glottal configuration [17]. Their localization at the mid portion of the vibrating edge of both vocal folds is due to maximu m collisional impacts at that level [18].…”

“…However, the difference in mean speaking frequency provides only a partial explanation [17]. Higher prevalence of nodules in females may also be explained by intrinsic differences in laryngeal anatomy and phonatory physiology, including differences in phonatory air pressure, in posterior glottis closure and in the ability of the membranous vocal fold to absorb phonotrauma [31].…”

A computational study of systemic hydration in vocal fold collision

“…However, complexities in modeling the multi-physics nature of the flow-structure interaction problem has led to research that mostly incorporates simplifications like two-dimensional (2D) geometry, longitudinal uncoupling of VF sections and non-linear stiffening of VF tissue for modeling contact (Dejonckere and Kob 2009; Horáček et al 2005, 2009; Luo et al 2008, 2009; Zheng et al 2009). A related challenge is in solving the glottal airflow.…”

Simulation of tremulous voices using a biomechanical model

“…This voice production model belongs to the class of discrete, high-dimensional, biomechanical models. It is based on previous works carried out by Kob et al [29,30], and it has been successfully employed for analyzing the pathogenesis of vocal fold nodules [31] and for simulating laryngeal disorders [28]; a resembling model was also used by Wong et al [32] for a similar purpose.…”