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Background and aims: Many patients with irritable bowel syndrome (IBS) show in testinal hypersensitivity to distension and sensitisation after repeated intestinal distensions. Abnormalities in endogenous pain inhibitory mechanisms, such as diffuse noxious inhibitory controls (DNIC), may be implicated and were investig ated during brain functional magnetic resonance imaging (fMRI). Patients and methods: fMRI was performed in 10 female patients with IBS (five constipated (IBS-C) and five with diarrhoea (IBS-D)) and 10 female healthy controls during rectal balloon distension alone or during activation of DNIC by painful heterotopic stimulation of the foot with ice water. Rectal pain was scored with and without heterotopic stimulation (0 = none, 10 = maximal). Results: Heterotopic stimulation decreased median rectal pain scores significantly in healthy controls (-1.5 ( interquartile range -2 to -1); p = 0.001) but not in IBS-C (-0.7 (-1 to 0.5 )), IBS-D (-0.5 (-1.5 to 0.5)), or in all IBS patients (0 (-1.5 to 1.3)). Brain activation changes during heterotopic stimulation differed highly significan tly between IBS-C, IBS-D, and controls. The main centres affected were the amy gdala, anterior cingulate cortex, hippocampus, insula, periaqueductal gray, and prefrontal cortex, which form part of the matrix controlling emotional, autonomic, and descending modulatory responses to pain. Conclusions: IBS-C and IBS-D appear to have differing abnormal endogenous pain inhibitory mechanisms, involving DNIC and other supraspinal modulatory pathways.
Background and aims: Many patients with irritable bowel syndrome (IBS) show in testinal hypersensitivity to distension and sensitisation after repeated intestinal distensions. Abnormalities in endogenous pain inhibitory mechanisms, such as diffuse noxious inhibitory controls (DNIC), may be implicated and were investigating ated during brain functional magnetic resonance imaging (fMRI). Patients and methods: fMRI was performed in 10 female patients with IBS (five constipated (IBS-C) and five with diarrhea (IBS-D)) and 10 female healthy controls during rectal balloon distension alone or during activation of DNIC by painful heterotopic stimulation of the foot with ice water. Rectal pain was scored with and without heterotopic stimulation (0 = none, 10 = maximal). Results: Heterotopic stimulation of median rectal pain scores significantly in healthy controls -1.5 (interquartile range -2 to -1); p = 0.001) but not in IBS-C (-0.7 (-1 to 0.5)), IBS- IBS Brain activation changes during heterotopic stimulation differed significantly significantly between IBS-C, IBS-D, and controls. The main centers affected were the amy gdala, anterior cingulate cortex, hippocampus, insula, periaqueductal gray, and prefrontal cortex, which form part of the matrix controlling emotional, autonomic, and descending modulatory responses to pain. Conclusions: IBS-C and IBS-D appear to have differing abnormal endogenous pain inhibitory mechanisms, involving DNIC and other supraspinal modulatory pathways.