Rapid balloon distension as a tool to study cortical processing of visceral sensations and pain

The processing of discomfort and pain in the central nervous system is normally studied with experimental methods, but it is mandatory that they are reliable over time to ensure that any interventions will result in valid results. We investigated reliability of rapid balloon distension in the rectum to elicit cortical evoked potentials (CEPs) to study the reliability of central processing of visceral sensation and discomfort/pain.

Eighteen healthy volunteers had two series of rectal balloon distensions performed on two separate days. Individualized balloon pressure, corresponding to pain detection threshold or to the maximum possible distension (30 psi), was used. Within- and between days reliability was measured in terms of amplitudes and latencies of the CEP global field power, topography and underlying brain networks.

There were two prominent peaks in the CEP recordings at mean latencies of 157 and 322 ms. There were no differences in latencies or amplitudes (p = 0.3) and they passed the Bland-Altman test for reproducibility. There were no differences in topographies (p > 0.7). Brain source connectivity revealed the cingulate-operculum network as the most consistent network within and between subjects. There were no differences in the location of brain sources in this network (p = 0.9) and the source coordinates were reproducible. Finally, the cingulate source generally had higher strength than operculum source (p < 0.001).

A reliable method to study central mechanisms underlying visceral sensation and pain was established. The method may improve our understanding of visceral pain and could be an objective method for studying efficacy of analgesics on visceral pain.