Patterns of excitability in human esophageal sensorimotor cortex to painful and nonpainful visceral stimulation

To better understand the relationship between cortical plasticity and visceral pain, we developed a pain-induced model of altered esophageal corticobulbar excitability. In eight healthy volunteers, corticoesophageal electromyographic responses were recorded via an intraluminal catheter, following magnetic stimulation of the right sensorimotor cortex using perithreshold intensities. Corticothenar responses were used as control. Responses were assessed both before and for up to 1 h after either painful or nonpainful balloon distension of the esophagus (frequency = 1 Hz, dwell time = 200 ms, duration = 10 min), each being delivered to each subject in random order. Painful esophageal distension (mean volume = 11 ± 3 ml) induced a profound increase in esophageal responses compared with baseline levels (at 30 min: 141 ± vs. 101 ± 9 μV, P <0.01), whereas nonpainful esophageal distension (mean volume = 4 ± 2 ml) showed a decrease (at 30 min: 72 ± 8 vs. 88 ± 12 μV, P <0.03). Thenar responses were unaffected. The results show that painful and nonpainful stimuli induce different patterns of esophageal corticobulbar excitability, suggesting a physiological link between cortical plasticity and visceral pain.