Dysphagia in a patient with lateral medullary syndrome: Insight into the central control of swallowing

Background & Aims: Central control of swallowing is regulated by a central pattern generator (CPG) positioned dorsally in the solitary tract nucleus and neighboring medullary reticular formation. The CPG serially activates the cranial nerve motor neurons, including the nucleus ambiguus and vagal dorsal motor nucleus, which then innervate the muscles of deglutition. This case provides insight into the central control of swallowing. Methods: A 65-year-old man with a right superior lateral medullary syndrome presented with a constellation of symptoms, including dysphagia. The swallow was characterized using videofluoroscopy and esophageal motility and the results were compared with magnetic resonance imaging (MRI) findings. Results: Videofluoroscopy showed intact lingual propulsion and volitional movements of the larynx. Distal pharyngeal peristalsis was absent, and the bolus did not pass the upper esophageal sphincter. Manometry showed proximal pharyngeal contraction and normal peristaltic activity in the lower esophagus (smooth muscle), but motor activity of the upper esophageal sphincter and proximal esophagus (striated muscle) was absent. MRI showed a lesion of the dorsal medulla. Conclusions: These findings are compatible with a specific lesion of the connections from a programming CPG in the solitary tract nucleus to nucleus ambiguus neurons, which supply the distal pharynx, upper esophageal sphincter, and proximal esophagus. There is functional preservation of the CPG control center in the solitary tract nucleus and of the vagal dorsal motor nucleus neurons innervating the smooth muscle esophagus.