Brain Regional Activities In Patients With Irritable Bowel Syndrome With Diarrhea In Different Episodic Status During The Rectal Balloon Distention

Objective Patients with irritable bowel syndrome (IBS) have fluctuated symptoms. IBS with diarrhea (IBS-D) is the most common subgroup of IBS in China. The central pathogenesis is still unclear, the brain-gut interactions are currently thought to play an important role in IBS pathophysiology. This study aims to identify the brain regional activities of functional magnetic resonance imaging (fMRI) in patients with IBS-D in different episodic symptoms status during rectal balloon distention, to explore the correlation between psychological abnormalitis and the activated brain regions.Methods IBS-D patients met the Rome III criteria and matched healthy subjects(HS) were enrolled in this study. Patients completed symptoms questionnaires, diary records and HAMD, HAMA evaluation. IBS-D patients were divided as onset group (having typical symptoms onset in the 3 days), remission group (having no symptoms over 10 days) and persistence group (having symptoms more than 2/3 of days during the past 3 months) according to the symptoms status. All the subjects underwent the anorectal manometry to abtain the sensation thresholds. Rest and task fMRI were performed in the prime study. Block design was adopted in the task fMRI, subject was stimulated with rectal balloon distention of 3 sensation thresholds. The data of were processed and analyzed with SPM, REST, GraphPad Prism software to find the significant activated brain regions, one-way analysis of variance (ANOVA) and two independent sample t test were used to compare the significant activated brain areas between two groups, Pearson correlation analysis was used to analyze the correlations between HAMD, HAMA and activated areas.Results In the prime study,32 subjects participated fMRI study. Considering strict quality of images,24 subjects’ data of task fMRI (including 7 cases in onset group,5 cases in remission group, each 6 cases in persistence group and HS) were enrolled in this analysis study. There were no significant differences in the anorectal sensation thresholds among the four groups (P>0.05).The significant activated brain regions during the rectal balloon distention were anterior cingulate cortex (ACC), inferior parietal lobe and midfrontal gyrus (P<0.05, AlphaSim corrcted). Patients in onset group had lower activities in ACC, inferior parietal lobe and midfrontal gyrus (P<0.01, P<0.01 and P<0.05, respectively) comparing with HS; patients in persistence group had higher activities in inferior parietal lobe, midfrontal gyrus (both P<0.05) comparing with patients in the onset group. The activated brain regions in task fMRI are different from the spontaneous activated brain regions in resting-state fMRI in prime analysis by Xin. There is a negative correlation between HAMD score and the activited inferior parietal lobe in onset group patients, and also negative correlations between HAMD score the activited inferior parietal lobe and midfrontal gyrus in persistence group patients (both P<0.05).Conclusions Three brain regions were activated during the rectal balloon distention in IBS-D patients and HS, and the differences were identified among the different episodic status of IBS-D symptoms in task fMRI, and between the stimulated activation and the spontaneous brain activities in the resting state. Depression might be involved in the activities of specific brain regions during rectal stimulation in IBS-D patients, which play an important role in IBS symptom onset and persisitence.