A combined physiological, psychophysical, and functional neuroimaging study of rectal function in patients with irritable bowel syndrome
By: by Chun Leung Kwan.
Published: 2006
Language: eng
Number of pages: 257
ISBN-13: 9780494158784
Description: Introduction and aims. A key feature of irritable bowel syndrome (IBS) is rectal hypersensitivity exemplified by a reduced pain threshold to rectal stimuli. However, it is contentious whether abnormalities in rectal motor physiology and/or the activity of specific brain regions contribute to IBS symptomology. To gain insight into the underlying peripheral and/or central dysfunction in IBS, the aim of this thesis was to determine whether IBS patients have abnormal rectal, psychophysical or brain responses to low (urge producing) or high (pain producing) rectal pressures. Methods.  IBS patients and healthy control subjects were assessed in two sessions. The first session assessed rectal physiology and psychophysical responses during: (a) ascending stepwise distensions terminating upon report of moderate pain, (b) phasic or (c) tonic distensions at a single pressure eliciting moderate urge or moderate pain intensity. Qualities of the pain experience during single pressure distensions were assessed with the McGill Pain Questionnaire (MPQ). In the second session, participants underwent percept-related functional magnetic resonance imaging (fMRI) evoked by rectal pressure distensions eliciting either moderate urge or moderate pain intensity. Results.  Rectal physiology abnormalities in IBS included a lower volume-pressure ratio during phasic single-pressure distensions and a slower rate of rectal relaxation during urge- versus pain-eliciting tonic distensions. Psychophysical abnormalities in IBS included an altered relationship between the three rectal distension-evoked percepts of urge, unpleasantness and pain, the lingering of distension-evoked percepts, and higher scores on the affective/evaluative dimension of the MPQ evoked by painful rectal distension. Percept-related fMRI revealed that IBS patients, but not controls had rectal-evoked activation of primary somatosensory cortex during low-pressure distension, and medial thalamus and hippocampus during painful distension. However, activations in rostral anterior cingulate cortex and dorsal right anterior insula during low- and high-pressure distension were present in the control group but not IBS group. Conclusions. This thesis demonstrated abnormal rectal and psychophysical responses to distension in IBS. Furthermore, abnormal brain responses in IBS may reflect rectal hypersensitivity, abnormal processing of attentional and affective aspects of pain, and abnormal interoception and/or visceromotor integration.
Notes: Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3617.

Thesis (Ph.D.)--University of Toronto, 2006.

Includes bibliographic references.

Electronic version licensed for access by U. of T. users.