Maintaining vowel distinctiveness in children with Steinert Myotonic Dystrophy: An ultrasound study

Abstract

Speech production entails appropriately timed contractions of many muscles. Steinert myotonic dystrophy, a neurodegenerative disease that causes muscle weakness and difficulties in muscle relaxation after muscle contraction, frequently affects orofacial articulatory dynamics leading to decreased speech intelligibility. We aimed to investigate the articulatory and acoustic characteristics of cardinal vowels produced by children with Steinert disease. We recruited fourteen 6- to 14-year-old French-speaking children diagnosed with Steinert disease and 14 aged-matched typically developing children. They were asked to produce repetitions of the vowels /i a u/ in consonant-vowel (CV) contexts. A synchronized ultrasound, Optotrak motion tracking system, and audio recording system was used to track lip and jaw displacement as well as tongue shape and position. Duration and formant values were also extracted. The Euclidean distance between vowels, in the formant space, was reduced in children with Steinert disease compared to the control children. Different patterns of articulatory contrasts were observed among the children, with some of them using more tongue contrasts than lip contrasts. Intelligibility tests conducted with adult listeners on a subset of the data show that some patterns are related to higher intelligibility scores than others.