CORTICAL EVOKED-RESPONSES FOLLOWING ESOPHAGEAL BALLOON DISTENSION ANDELECTRICAL-STIMULATION IN HEALTHY-VOLUNTEERS

Recording of evoked potential responses represents an objective and qu antifiable method to study visceral afferent sensory pathways in human s. We examined the evoked responses to mechanical distension (balloon) and electrical stimulation of the proximal and distal esophagus. A st andard manometric catheter with a latex balloon and an additional elec trode attached to its body was placed in the lower esophagus in 15 hea lthy young volunteers. Repeated nonpainful balloon distension stimuli above the individual sensation threshold (0.17 Hz, 12-20 mi) or short electrical impulses (0.2 Hz, 12-16 mA) were delivered in an alternate fashion at 23 and 33 cm from the nares. Evoked potential responses (EP ) were recorded through 22 scalp surface electrodes using the standard 10/20 International EEG system of electrode placement. Balloon disten sion produced a reproducible triphasic response at both sites. Peak la tencies of three negative EP peaks were 92 +/- 17, 229 +/- 40, and 339 +/- 36 msec with proximal stimulation versus 154 +/- 24, 275 +/- 24, and 384 +/- 30 msec obtained with distal stimulation (P < 0.001). Elec trical stimulation produced a triphasic response with significantly sh orter peak latencies at both sites when compared to mechanical stimula tion (P < 0.001). Peak latencies were 74 +/- 12, 137 +/- 11, and 245 /- 27 msec proximal versus 83 +/- 12, 148 +/- 32, and 247 +/- 51 msec with distal stimulation (P < 0.01). The calculated conduction velociti es for both modes of stimulation (balloon: 1.73 +/- 0.9 m/sec vs elect rical: 10.1 +/- 3.4 m/sec) are compatible with conduction through C fi bers and A delta fibers, respectively. Both modes of stimulation produ ce characteristic brain responses that are conveyed through different types of afferent fibers. The respective contributions of both types o f fibers to esophageal function and symptomatology can be specifically addressed using this approach in both normal and pathologic condition s.