Abstract
The goal of this study is to quantify the effects of vocal fold nodules on vibratory motion in children using high-speed videoendoscopy. Differences in vibratory motion were evaluated in 20 children with vocal fold nodules (5–11 years) and 20 age and gender matched typically developing children (5–11 years) during sustained phonation at typical pitch and loudness. Normalized kinematic features of vocal fold displacements from the mid-membranous vocal fold point were extracted from the steady-state high-speed video. A total of 12 kinematic features representing spatial and temporal characteristics of vibratory motion were calculated. Average values and standard deviations (cycle-to-cycle variability) of the following kinematic features were computed: normalized peak displacement, normalized average opening velocity, normalized average closing velocity, normalized peak closing velocity, speed quotient, and open quotient. Group differences between children with and without vocal fold nodules were statistically investigated. While a moderate effect size was observed for the spatial feature of speed quotient, and the temporal feature of normalized average closing velocity in children with nodules compared to vocally normal children, none of the features were statistically significant between the groups after Bonferroni correction. The kinematic analysis of the mid-membranous vocal fold displacement revealed that children with nodules primarily differ from typically developing children in closing phase kinematics of the glottal cycle, whereas the opening phase kinematics are similar. Higher speed quotients and similar opening phase velocities suggest greater relative forces are acting on vocal fold in the closing phase. These findings suggest that future large-scale studies should focus on spatial and temporal features related to the closing phase of the glottal cycle for differentiating the kinematics of children with and without vocal fold nodules.
Highlights
Mechanical trauma on vocal fold tissues resulting from vocal hyperfunction has an important role in the pathogenesis of vocal nodules. [1, 2]
We propose to quantify the effects of vocal fold nodules on vocal fold vibrations in pre-pubertal children with the use of high-speed videoendoscopy and normalized kinematic features that quantify the opening and closing phases of the glottal cycle [17]
A small effect size was observed for the normalized average closing velocity (H(2) = 2.86, p = 0.09, d = 0.267), normalized peak closing velocity (H(2) = 2.42, p = 0.12, d = 0.245), and normalized peak displacement (H(2) = 0.726, p = 0.39, d = 0.135) (Table 3)
Summary
Mechanical trauma on vocal fold tissues resulting from vocal hyperfunction has an important role in the pathogenesis of vocal nodules. [1, 2]. Mechanical trauma on vocal fold tissues resulting from vocal hyperfunction has an important role in the pathogenesis of vocal nodules. Vocal nodules occur in 38–78% [3,4,5] of children and are thought to result from mechanical influences of vocal hyperfunction [1, 2] resulting in chronic hoarseness in 2% [6] to 23.4% [4] of children. Dysphonia can be detrimental to children both psychologically [8, 9] and academically [10]. Evaluation of dysphonia is multidimensional involving a battery of tests, like acoustics, aerodynamics, perceptual evaluation, outcome measurements, and laryngeal imaging. Accurate evaluation of the cause of dysphonia is typically dependent on assessment of vocal fold structure and the resulting vibratory motion through techniques of laryngeal imaging
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