Development of vocal tract length during early childhood: A magnetic resonance imaging study

TLDR

Speech development in children depends partly on growth and anatomical restructuring of the vocal tract. The study investigates how hard and soft vocal tract structures grow and relate to vocal tract length using MRI. MRI measurements of lip, palate, tongue, pharyngeal lengths, mandibular dimensions, and hyoid/larynx positions were taken from 63 children (birth to 6 y 9 m) and 12 adults. All oral and pharyngeal structures grow continuously with no sex differences, accelerating between birth and 18 months, and their growth patterns—driven by region and orientation—determine vocal tract length changes, with pharyngeal growth dominating overall length but oral growth contributing significantly in the first 18 months, providing normative data for vocal tract development models.

Abstract

Speech development in children is predicated partly on the growth and anatomic restructuring of the vocal tract. This study examines the growth pattern of the various hard and soft tissue vocal tract structures as visualized by magnetic resonance imaging (MRI), and assesses their relational growth with vocal tract length (VTL). Measurements on lip thickness, hard- and soft-palate length, tongue length, naso-oro-pharyngeal length, mandibular length and depth, and distance of the hyoid bone and larynx from the posterior nasal spine were used from 63 pediatric cases (ages birth to 6 years and 9 months) and 12 adults. Results indicate (a) ongoing growth of all oral and pharyngeal vocal tract structures with no sexual dimorphism, and a period of accelerated growth between birth and 18 months; (b) vocal tract structure's region (oral/anterior versus pharyngeal/posterior) and orientation (horizontal versus vertical) determine its growth pattern; and (c) the relational growth of the different structures with VTL changes with development-while the increase in VTL throughout development is predominantly due to growth of pharyngeal/posterior structures, VTL is also substantially affected by the growth of oral/anterior structures during the first 18 months of life. Findings provide normative data that can be used for modeling the development of the vocal tract.