Specificities of phonation biomechanics in Down Syndrome children

Abstract

Down Syndrome (DS) has been the aim of numerous studies, although its phonation specificities have not received much attention. DS is a genetic disorder caused by the presence of a third copy of chromosome 21, being the explanation of different behavioral and clinical anomalies: developmental disorders, hearing, speech and language impairments and neuromotor and morphological alterations of the oro-naso-pharyngeal (ONP) and laryngeal (ONL) structures. The goal of the current study is to carry on a first approach to the biomechanics of phonation in DS children from an acoustic perspective, trying to describe its specificities and to establish a link with the syndrome. A specific application designed to analyze the glottal source and its relationship to vocal fold biomechanics has been used. Nineteen biomechanical features from vocal fold dynamics have been used, related to fundamental frequency, jitter, shimmer, noise-to-harmonic ratio, mass and stiffness profiles, unbalance, contact gaps, and tremor. On one hand, the non-normophonic corpus is composed of eight children with DS with age range between five and six years old. On the other hand, a normative or normophonic population was taken. The last group consisted of eight children with similar ages to the previous ones. The results achieved show relevant differences (p < .05) in larynx biomechanics regarding the following features: deviations in the fundamental frequency, vocal fold tension (regarding musculus vocalis), and phonation tremor. These distortions could be directly related with the neuromotor alterations known to be associated to DS and could reflect underlying factors of DS phonation features.