Cerebral response to electric stimulation of the colon and abdominal skin in healthy subjects and patients with irritable bowel syndrome

Background: Visceral hyperalgesia may play an important part in the pathoph ysiology of the irritable bowel syndrome (IBS). We investigated the neurona l afferent pathways in healthy volunteers and IBS patients by recording evo ked potentials (EPs) elicited by electrical stimulation of the colon and ab dominal skin inside and outside the referred pain area. Methods: Six health y subjects and nine IBS patients met the inclusion criteria. Morphology and topography of EPs to painful electrical stimuli were estimated in the rect osigmoid junction and on the skin inside/outside the referred pain areas. R esults: The EPs to painful stimuli of the gut showed a shorter latency and a smaller amplitude of the first positive peak (PI) in the IBS group. The c ontrols had a mid-latency frontal positive component after 100 ms, whereas no reliable early activation was seen in the IBS patients. In controls, a s ingle late (> 150 ms) positive component was seen, whereas the late compone nt was biphasic in the IBS group. The EPs to painful stimuli of the two ski n areas differed in IBS patients, but not in controls. Conclusion: Differen ces in the EPs to electrical painful stimulation of the sigmoid colon and s kin inside/outside the experimentally evoked referred pain area were seen c omparing healthy subjects and IBS patients. The results indicate altered ce ntral nervous system responses.