Background & aims: To characterize the cerebral processing of noxious visceral events, changes in regional cerebral blood flow associated with perception of intestinal pain were examined.
Methods: The effects of rectal pressure stimuli on regional cerebral blood flow were assessed with 15O-water positron emission tomography (PET) in 12 subjects, half with irritable bowel syndrome (IBS). PET scans were obtained at baseline and during both actual and simulated delivery of anticipated stimuli. Changes in regional cerebral blood flow were interpreted using statistical parametric mapping and region of interest methods of analysis.
Results: In healthy subjects, perception of pain during actual or simulated delivery of painful stimuli was significantly associated (P < 0.01) with activity of the anterior cingulate cortex (ACC; Brodmann's areas 24 and 32), whereas no ACC response to perception of nonpainful stimuli was observed. In patients with IBS, the ACC failed to respond to the same stimuli, whereas significant activation (P < 0.01) of the left prefrontal cortex (maximal in Brodmann's area 10) was seen.
Conclusions: The perception of acute rectal pain is associated with activation of the ACC in healthy subjects, and patients with IBS show an aberrant brain activation pattern both during noxious rectal distention and during the anticipation of rectal pain.