Abstract
The present study was undertaken to validate how descent of the hyoid position, considered as a pathological condition of dysphagia, affect swallowing function by evaluating spatial and temporal hyoid excursion, hyoid position and bolus transmission in healthy volunteers and patients with dysphagia.
All subjects, including 65 patients with dysphagia and 10 normal volunteers, were examined using videofluorographic images. These images were analyzed to measure the time series of hyoid movement and bolus transmission based on the moment the tip of the tongue starts to move. The hyoid position was also investigated, and the origin was defined on the anterior ridge of the fourth cervical vertebra. Statistical comparison between both groups was then performed.
The oral and pharyngeal transit times were prolonged in the patient group; in addition, entry of the bolus head into the pharynx was significantly earlier than the start of pharyngeal swallowing (start of the rapid hyoid elevation). There was no significant difference in the hyoid position between the two groups when the origin was defined on the anterior ridge of the fourth cervical vertebra. Further evaluation was performed by classifying patients with dysphagia by the diseases causing their dysphagia. A similar hyoid trajectory among the classified groups was observed after the onset of the swallowing reflex; in contrast, the hyoid bone showed complicated movement before the swallowing reflex occurred. The hyoid position may affect the delay in the swallowing onset because positive correlation between the distance and time of hyoid movement was observed before swallowing reflex in some diseases.
