Influence of bolus volume on swallow-induced hyoid movement in normal subjects.

Swallowing normally elicits a superior-anterior excursion of the hyoid that contributes to elevation of the larynx and opening of the upper esophageal sphincter. The magnitude of hyoid movements, however, has not been quantitated with respect to the volume of the swallowed bolus. In this study, we determined the magnitude of superior and anterior movements of the hyoid associated with swallows of barium of different volumes. Lateral videoradiographic images of 2- to 20-ml boluses of barium were obtained in 15 subjects who had no pharyngoesophageal symptoms and had normal pharyngoesophageal motor function. Analysis indicated that a significant direct correlation existed between the volume of the swallowed bolus and the magnitude of the superior and anterior movements of the hyoid. For example, the mean values for these respective movements were 13.0 +/- 5 mm and 13.5 +/- 6 mm for a 2-ml bolus, compared with 14.8 +/- 5 mm and 16.7 +/- 5 mm for a 10-ml bolus. The findings indicate that values of deglutitive movement of the hyoid need to be indexed to the volume of the swallowed bolus. The results imply that the neural program in the brainstem that generates the oral and pharyngeal phases of swallowing is not completely stereotyped, but rather is modulated by volume-dependent sensory feedback.