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Visceral afferent hypersensitivity in irritable bowel syndrome--evaluation by cerebral evoked potential after rectal
P Sinhamahapatra1, S P Saha, A Chowdhury
1Department of Medicine and Gastroenterology, Institute of Post Graduate Medical Education and Research, Calcutta, India.
Objectives:
Gut hypersensitivity has been shown to be present in irritable bowel syndrome. The current study sought to determine the involvement or hypersensitivity of the gut afferents, objectively, by recording cerebral evoked potential after rectal stimulation.
Methods:
In 13 patients with irritable bowel syndrome and nine healthy controls, rectal perception thresholds to electrical stimulation were measured, and cerebral evoked potentials were recorded from 2 cm behind vertex (Cz') after rectal stimulation electrically (frequency 1 Hz, duration 0.5 ms) at an intensity 50% above perception threshold and with filter setting 1-250 Hz.
Results:
Perception thresholds to rectal electrical stimuli in patients with irritable bowel syndrome were lower than controls (p < 0.05). Rectal stimulation led to recognizable and reproducible cerebral evoked potentials. P1, N1, P2 latencies in patients with irritable bowel syndrome were shorter than that in controls (p < 0.05). P1/N1 amplitude was greater in patients with irritable bowel syndrome than in controls (p < 0.05).
Conclusions:
The shorter latency and increased amplitude of cerebral evoked potential after rectal stimulation in patients with irritable bowel syndrome compared to controls provide objective evidence supporting visceral afferent hypersensitivity as the underlying mechanism in irritable bowel syndrome.