The effect of lip strengthening exercises in children and adolescents with myotonic dystrophy type 1

Objective: Myotonic dystrophy type 1 (DM1) is a slowly progressive neuromuscular disease. Most children and adolescents with DM1 have weak lips and impaired lip function. The primary aim of the present study was to investigate if regular training with an oral screen could strengthen the lip muscles in children and adolescents with DM1. If lip strength improved, a secondary aim would be to see if this could have an immediate effect on lip functions such as lip mobility, eating and drinking ability, saliva control, and lip articulation.

Methods: Eight school aged children and adolescents (7-19 years) with DM1 were enrolled in an intervention study with a single group counterbalanced design. After three baseline measurements four children (Subgroup A) were randomly chosen to start 16 weeks therapy while the others (Subgroup B) acted as controls without therapy. After 16 weeks the subgroups changed roles. During treatment the participants exercised lip strength with an oral screen for 16 min, 5 days/week. Lip force, grip force (control variable), and lip articulation were followed-up every fourth week. At baseline, after treatment, and after maintenance, the assessment protocol was completed with measurements of lip mobility using 3D motion analysis and parental reports concerning eating ability and saliva control.

Results: Seven of eight participants improved maximal lip strength and endurance but only four showed significant change. Increased lip strength did not automatically lead to improved function. There was a wide intra-individual variation concerning speech and eating ability within and between assessments. The treatment programme could be carried out without major problems but the frequency and the effect of training were affected by recurrent infections in some.

Conclusions: Maximal lip force and lip force endurance can improve in school aged children and adolescents with DM1. Improved lip strength alone cannot be expected to have an effect on lip articulation, saliva control, or eating and drinking ability in this population. Lip strengthening exercises can be a complement but not a replacement for speech therapy and dysphagia treatment. A prefabricated oral screen is an easy to use tool suitable for strengthening lip exercises.