ESOPHAGEAL BALLOON DISTENSION AND CEREBRAL EVOKED-POTENTIAL RECORDING IN THE EVALUATION OF UNEXPLAINED CHEST PAIN

A minority of patients presenting with the common clinical challenge of unexplained chest pain can be diagnosed as having an esophageal etiology for their pain using conventional manometric and provocative (acid infusion and edrophonium) testing. Esophageal balloon distention may provide an important adjuvant to routine testing. Most pain from the esophagus is mediated by visceral sensory receptors located near the myenteric plexus; these receptors respond to movements of the organ wall in response to contractions or distention. Balloon distention can be used to simulate this wall movement. Early clinical studies have been expanded by recent investigations demonstrating a lowered pain threshold in response to balloon distention in patients with both unexplained chest pain and nonobstructive dysphagia. The physiologic basis for this increased sensitivity is not clear. Balloon distention has several effects on esophageal motility that may play a role in producing pain. The recording of cerebral evoked potentials is a technique newly developed to provide an objective measurement of the subjective sensation of pain. Electrical and mechanical stimulation of the esophagus has been shown to produce cerebral evoked potentials. Recent investigations of cerebral potentials evoked by balloon-induced esophageal stimulation have confirmed that this response depends on pain production, have clarified the appropriate stimulus parameters, and have localized the site of origin of the evoked potential to the balloon site. Balloon distention may prove to be an important addition to current esophageal provocative testing, although widespread applicability has been hampered by the lack of a commercially available standardized balloon. Recording evoked potentials produced by esophageal stimulation may provide additional clues in unraveling the mystery of unexplained chest pain.