Range of motion (ROM) in the lips and jaw during vowels assessed with 3D motion analysis in Swedish children with typical speech development and children with speech sound disorders.

Purpose: The aim was to compare movement patterns of lips and jaw in lateral, vertical and anteroposterior directions during vowel production in children with typical speech development (TSD) and in children with speech sound disorders (SSD) persisting after the age of six.

Methods: A total of 93 children were included, 42 children with TSD (6:0-12:2 years, mean age 8:9 ± 1:5, 19 girls and 23 boys) and 51 children with SSD (6:0-16:7 years, mean age 8:5 ± 3:0, 14 girls and 37 boys). Range of motion (ROM) in lips and jaw in the vowels [a, ʊ, ɪ] produced in a syllable repetition task and median values in resting position were measured with a system for 3D motion analysis. The analysis was based on the coordinates for the mouth corners and the chin centre.

Results: There were significant differences between the groups on movements in lateral direction in both lips and jaw. Children with TSD had generally smaller and more, symmetrical movements in the lips and jaw, in all three dimensions compared to children with SSD. There were no significant differences between the groups in resting position.

Conclusion: Children with SSD persisting after the age of six years show more asymmetrical and more variable movement patterns in lips and jaw during vowel production compared with children with TSD in a simple syllable repetition task. Differences were more pronounced in lateral direction in both lips and jaw.