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Abstract
Irritable bowel syndrome (IBS) is characterized by visceral hypersensitivity, possibly
related to abnormal brain-gut communication. Positron emission tomography imaging
has suggested specific central nervous system (CNS) abnormalities in visceral pain
processing in IBS. This study aimed to determine (1) if functional magnetic resonance
imaging (fMRI) detects CNS activity during painful and nonpainful visceral stimulation;
and (2) if CNS pain centers in IBS respond abnormally.
fMRI was performed during nonpainful and painful rectal distention in 18 patients
with IBS and 16 controls.
Rectal stimulation increased the activity of anterior cingulate (33/34), prefrontal
(32/34), insular cortices (33/34), and thalamus (32/34) in most subjects. In IBS subjects,
but not controls, pain led to greater activation of the anterior cingulate cortex
(ACC) than did nonpainful 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.
IBS patients activate the ACC, a critical CNS pain center, to a greater extent than
controls in response to a painful rectal stimulus. Contrary to previous reports, these
data suggest heightened pain sensitivity of the brain-gut axis in IBS, with a normal
pattern of activation.