Regional cerebral activation in irritable bowel syndrome and control subjects with painful and nonpainful rectal distention

Background & Aims: Irritable bowel syndrome (IBS) is characterized by visce ral hypersensitivity, possibly related to abnormal brain-gut communication, Positron emission tomography imaging has suggested specific central nervou s system (CNS) abnormalities in visceral pain processing in IBS, This study aimed to determine (1) if functional magnetic resonance imaging (fMRI) det ects CNS activity during painful and nonpainful visceral stimulation; and ( 2) if CNS pain centers in IBS respond abnormally. Methods: fMRI was perform ed during nonpainful and painful rectal distention in 18 patients with IBS and 16 controls. Results: Rectal stimulation increased the activity of ante rior cingulate (33/34), prefrontal (32/34), insular cortices (33/34), and t halamus (32/34) in most subjects. In IBS subjects, but not controls, pain l ed to greater activation of the anterior cingulate cortex (ACC) than did no npainful stimuli. IBS patients had a greater number of pixels activated in the ACC and reported greater intensity of pain at 55-mm Hg distention than controls, Conclusions: IBS patients activate the ACC, a critical CNS pain c enter, to a greater extent than controls in response to a painful rectal st imulus. Contrary to previous reports, these data suggest heightened pain se nsitivity of the brain-gut axis in IBS, with a normal pattern of activation .