Association between pain sensitivity and gray matter properties in the sensorimotor network in women with irritable bowel syndrome

Background Enhanced perception of visceral stimuli is an important feature of Irritable Bowel Syndrome (IBS), but it is not known whether visceral sensitivity is associated with regional structural brain properties in IBS. Methods Structural brain magnetic resonance imaging data from 216 women with IBS and 138 healthy women were parcellated with FreeSurfer to define regional gray matter morphometry (volume, cortical thickness, surface area and mean curvature) in the sensorimotor network. General linear models were used to detect group differences between IBS and health. In a second set of 48 female IBS patients, pain threshold, pain intensity ratings during rectal balloon distension, and reported levels of abdominal pain and bloating were correlated with brain regions that showed differences between IBS and health in the first data set. Key Results Several statistically significant differences between IBS patients and healthy controls were found, mainly higher gray matter volume and cortical thickness in primary somatosensory cortex, secondary somatosensory cortex, and subcortical regions, and lesser gray matter volume, surface area and cortical thickness in posterior insula and superior frontal gyrus. Pain intensity ratings during rectal distension were associated with left primary somatosensory cortical thickness, and pain threshold was associated with right nucleus accumbens volume. Conclusions and Inferences Regional gray matter differences in sensorimotor network are associated with visceral sensitivity and may represent neuroplastic changes in female IBS patients.

Automated summary

This study found several regional gray matter differences between IBS patients and healthy controls, with higher gray matter volume and cortical thickness in primary somatosensory cortex, secondary somatosensory cortex, and subcortical regions in IBS patients, and lower gray matter volume, surface area, and cortical thickness in posterior insula and superior frontal gyrus. Pain intensity during rectal distension was associated with cortical thickness in the left primary somatosensory cortex, while pain threshold was associated with volume in the right nucleus accumbens. These findings suggest that regional gray matter differences in the sensorimotor network are linked to visceral sensitivity in female IBS patients.