Cerebral evoked potentials. A method of quantification of central nervous system response to esophageal pain

Cerebral evoked potentials (EPs) represent a new technique for the evaluation of afferent outflow from the gastrointestinal tract. We compared EPs obtained with distension of the distal and proximal esophagus. Responses were recorded with the balloon 5 cm proximal to the lower esophageal sphincter and 3 cm distal to the upper esophageal sphincter. Balloon stimulation resulted in cortical responses recorded by midline scalp electrodes (CZ', PZ, and OZ by the International 10-20 system) in normal volunteers. EP responses consisted of two negative (N1, N2) and one positive (P1) deflections. The proximal esophageal latency of N1 was shorter in all three leads. The latency to P1 was shorter with proximal stimulation in lead CZ' only, and N2 latencies were not different. Amplitudes expressed as the difference between N1 and P1, and P1 and N2 were not different. When two sets of potentials several minutes apart from the proximal position were compared, a decrease in amplitude with the second set of stimulations was noted. Esophageal EP recording is a new technique that may provide information about the integrity and function of the sensory innervation of the esophagus.