EFFICIENT and effortless swallowing at the upper end of the esophagus requires, among other events, coordinated and powerful contraction of the pharyngeal constrictors coupled with relaxation of the cricopharyngeus muscle, or upper esophageal sphincter, at the precise moment of arrival of the bolus from above. This highly coordinated sequence of events in normal persons has been demonstrated by a number of investigators using pressure recording,1,2 routine radiographic,3,4 and cineradiographic techniques.5-8
The peristaltic wave begun by the pharyngeal constrictors is propagated into the esophagus proper but first must traverse the zone of increased pressure at the level of the cricopharyngeal sphincter. Code and his associates have shown in normal swallowing that there is a precisely timed and pronounced relaxation of the sphincter beginning immediately prior to pharyngeal contraction, "ensuring that the doorway to the esophagus is open as the swallowed material is forced toward it" (Fig 1). The