Longitudinal Ultrasound Kinematic Evaluation of Digastric Muscles

Ultrasound applied to the upper aerodigestive tract for the assessment of swallowing disorders has been the subject of numerous publications in recent years. Changes in the range of motion or muscular characteristics of the structures involved in swallowing are associated with the presence of swallowing disorders. However, current assessment remains limited to morphological parameters at rest, whereas the combined analysis of measurements at rest and during contraction is a recognised indicator of muscle activity and recruitment capacity in other areas (diaphragm, pelvic floor). For the anterior bellies of the digastric muscles, which are central to hyo-laryngeal kinematics during swallowing, the conventional transverse ultrasound approach yields a non-interpretability rate of approximately 30% at rest and exceeding 50% during dynamic assessment, along with insufficient reproducibility. These limitations prevent reliable access to functional muscle parameters such as thickness variation during contraction and pennation angle. This single-centre, cross-over study aims to evaluate whether a proposed new ultrasound approach (NAEP), based on a longitudinal (sagittal) probe positioning, achieves a significantly higher rate of interpretable measurements compared to the conventional approach. The study enrolls 35 healthy volunteers and 35 patients with dysphagia. Both approaches are applied during the same session for each participant, across four swallowing conditions (dry swallow, 5, 10, and 20 mL water boluses). Secondary objectives include assessment of intra- and inter-rater reliability of the NAEP, analysis of the impact of bolus volume on muscle contraction and hyoid movement, and comparison of morphometric parameters between healthy subjects and dysphagic patients.