Cortical Evoked Responses Following Esophageal Balloon Distension and Electrical Stimulation in Healthy Volunteers

Recording of evoked potential responsesrepresents an objective and quantifiable method to studyvisceral afferent sensory pathways in humans. Weexamined the evoked responses to mechanical distension(balloon) and electrical stimulation of the proximal anddistal esophagus. A standard manometric catheter with alatex balloon and an additional electrode attached toits body was placed in the lower esophagus in 15 healthy young volunteers. Repeatednonpainful balloon distension stimuli above theindividual sensation threshold (0.17 Hz, 12-20 ml) orshort electrical impulses (0.2 Hz, 12-16 mA) weredelivered in an alternate fashion at 23 and 33 cm from thenares. Evoked potential responses (EP) were recordedthrough 22 scalp surface electrodes using the standard10/20 International EEG system of electrode placement. Balloon distension produced a reproducibletriphasic response at both sites. Peak latencies ofthree negative EP peaks were 92 ± 17, 229± 40, and 339 ± 36 msec with proximalstimulation versus 154 ± 24, 275 ± 24, and384 ± 30 msec obtained with distal stimulation (P< 0.001). Electrical stimulation produced a triphasicresponse with significantly shorter peak latencies atboth sites when compared to mechanical stimulation (P <0.001). Peak latencies were 74 ± 12, 137 ±11, and 245 ± 27 msec proximal versus 83 ±12, 148 ± 32, and 247 ± 51 msec withdistal stimulation (P < 0.01). The calculated conduction velocities forboth modes of stimulation (balloon: 1.73 ± 0.9m/sec vs electrical: 10.1 ± 3.4 m/sec) arecompatible with conduction through C fibers and Adeltafibers, respectively. Both modes of stimulation producecharacteristic brain responses that are conveyed throughdifferent types of afferent fibers. The respectivecontributions of both types of fibers to esophageal function and symptomatology can be specificallyaddressed using this approach in both normal andpathologic conditions.