Gastroenterology

Gastroenterology

Volume 118, Issue 5, May 2000, Pages 842-848
Gastroenterology

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

https://doi.org/10.1016/S0016-5085(00)70170-3Get rights and content

Abstract

Background & Aims: 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. Methods: fMRI was performed during nonpainful and painful rectal distention in 18 patients with IBS and 16 controls. Results: 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. Conclusions: 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.

GASTROENTEROLOGY 2000;118:842-848

Section snippets

Subjects

Sixteen normal right-handed control subjects (14 women and 2 men; age, 20–52 years; average age, 33 years) and 18 right-handed patients with IBS (16 women and 2 men; age, 24–49 years; average age, 34 years) participated in the study. All volunteers were free of any gastrointestinal complaint. The IBS patients were all seen in the Vanderbilt GI clinic, and met the Rome criteria for IBS, which includes at least 3 months of recurrent abdominal pain and bowel dysfunction.11 Each underwent a basic

Subjective stimulus responses

At 15–mm Hg rectal distention, subjects generally sensed a very-low-intensity stimulation, using the terms “gas,” “barely felt,” or “mild pressure.” At 30–mm Hg rectal distention, both IBS and control subjects expressed nonpainful sensations such as “stool,” “pressure,” or “needed to defecate.” No subject reported pain. At 55–mm Hg rectal distention, all subjects reported painful sensations. Patients with IBS rated this pain significantly higher than control subjects and occurring in an

Discussion

fMRI is a useful technology to measure changes in regional CNS blood oxygenation, which is known to parallel regional metabolic activity.9, 12, 13 We now show that fMRI has adequate sensitivity to measure regional CNS blood flow changes in response to visceral—in this case rectal—stimulation. Activity in the 4 selected CNS pain centers, ACC (BA 24, 32), PFC (BA 10), thalamus, and insular cortex (BA 13–15), promptly increases with nonpainful and painful visceral stimulation. Deactivation occurs

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    Address requests for reprints to: Howard R. Mertz, M.D., 1501 TVC, Vanderbilt University Medical Center, Nashville, Tennessee 37232-5340. e-mail: [email protected]; fax: (615) 343-8174.

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