Abnormal electroencephalogram in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a functional bowel disorder characterized by abdominal pain and abnormal bowel habits. IBS patients sometimes complain of sleep disturbance, depression, and various autonomic symptoms. Our hypothesis is that the central nervous system (CNS) might play a role in the pathogenesis of IBS.

We conducted two experiments using an electroencephalogram (EEG) to evaluate brain activity while at rest and during mental arithmetic stress with pharmacologic neostigmine administered to IBS patients. The first experiment was conducted on 48 conscious and relaxed patients (24 IBS patients and 24 normal controls). EEG recordings were evaluated for visual and power spectrum data. In the second experiment colonic manometric studies combined with EEG recordings were performed in 21 of 24 IBS patients and 8 of 24 normal controls under mental arithmetic stress and the administration of neostigmine.

Inspection of the EEG showed significantly greater EEG abnormality in the IBS patients (29.2%) than in the controls (4.2%) (P < 0.02). In the power spectrum analysis of the EEG the IBS patients showed significantly greater beta power percentage than did the normal subjects (P < 0.02). A significant positive correlation was observed between the colonic motility index and beta power percentage after the administration of neostigmine, 10 microg/kg, only in the IBS patients (P < 0.05).

A brain dysfunction as indexed by the EEG suggests an electrophysiologic brain-gut interaction in IBS.