Cortical evoked responses following esophageal balloon distension and electrical stimulation in healthy volunteers

Recording of evoked potential responses represents an objective and quantifiable method to study visceral afferent sensory pathways in humans. We examined the evoked responses to mechanical distension (balloon) and electrical stimulation of the proximal and distal esophagus. A standard manometric catheter with a latex balloon and an additional electrode attached to its body was placed in the lower esophagus in 15 healthy 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 distension produced a reproducible triphasic response at both sites. Peak latencies 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). Electrical stimulation produced a triphasic response with significantly shorter peak latencies at both 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 with distal stimulation (P < 0.01). The calculated conduction velocities for both modes of stimulation (balloon: 1.73 +/- 0.9 m/sec vs electrical: 10.1 +/- 3.4 m/sec) are compatible with conduction through C fibers and A delta fibers, respectively. Both modes of stimulation produce characteristic brain responses that are conveyed through different types of afferent fibers. The respective contributions of both types of fibers to esophageal function and symptomatology can be specifically addressed using this approach in both normal and pathologic conditions.