The Hyoid Bone Kinematics in Dysphagic Stroke Patients: Instantaneous Velocity, Acceleration and Temporal Sequence Matters.

Hyoid bone excursion (HBE) is one of the most critical events in the pharyngeal phase of swallowing. Most previous studies focused on the total displacement and average velocity of HBE. However, HBE during swallowing is not one-dimensional, and the change of velocity and acceleration is not linear. This study aims to elucidate the relationship between the instantaneous kinematics parameters of HBE and the severity of penetration/aspiration and pharyngeal residue in patients with stroke. A total of 132 sets of video-fluoroscopic swallowing study images collected from 72 dysphagic stroke patients were analyzed. The maximal instantaneous velocity, acceleration, displacement, and the time required to reach these values in the horizontal and vertical axes were measured. Patients were grouped according to the severity of the Penetration-Aspiration Scale and the Modified Barium Swallow Impairment Profile- Pharyngeal Residue. The outcome was then stratified according to the consistencies of swallowing materials. Stroke patients with aspiration were associated with a lower maximal horizontal instantaneous velocity and acceleration of HBE, a shorter horizontal displacement, and prolonged time to maximal vertical instantaneous velocity compared to the non-aspirators. In patients with pharyngeal residue, the maximal horizontal displacement of HBE was decreased. After stratification according to bolus consistencies, the temporal parameters of HBE were more significantly associated with aspiration severity when swallowing thin bolus. Meanwhile spatial parameters such as displacement had a bigger influence on aspiration severity when swallowing viscous bolus. These novel kinematic parameters of HBE could provide important reference for estimating swallowing function and outcomes in dysphagic stroke patients.