Intractable singultus: a diagnostic and therapeutic challenge.

Hiccup or singultus is a repeated involuntary, spasmodic contraction of the diaphragm accompanied by a sudden closure of the glottis mediated by sensory branches of the phrenic and vagus nerves as well as dorsal sympathetic afferents. The principle efferent limb and diaphragmatic spasms are mediated by motor fibers of the phrenic nerve. Hiccup has been classified as a respiratory reflex and the central connection probably consists an interaction among the brainstem respiratory centers, phrenic nerve nuclei, medullary reticular formation and the hypothalamus. Chronic intractable hiccup may be due to brainstem seizures, and baclofen may be the long-awaited remedy for intractable hiccup as demonstrated in three illustrative cases.