Pathogenesis of vocal fold nodules: new insights from a modelling approach.
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.


METHODS
Simulations with a 3-dimensional computer model of the vibrating vocal folds.


CONCLUSIONS
(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.
Dejonckere
Philippe H
PH
Institute of Phoniatrics, University Medical Centre, Utrecht, The Netherlands. ph.dejonckere@umcutrecht.nl
Kob
Malte
M
D003198:Computer Simulation; D020820:Dyskinesias / Q000150:complications / Q000473:pathology / Q000503:physiopathology; D004548:Elasticity; D005260:Female; D006801:Humans; D007818:Laryngeal Diseases / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D008954:Models, Biological; D018763:Muscle Fatigue; D009129:Muscle Tonus; D010699:Phonation / Q000502:physiology; D011312:Pressure; D012727:Sex Characteristics; D014732:Vibration; D014826:Vocal Cord Paralysis / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D014827:Vocal Cords / Q000473:pathology / Q000503:physiopathology*