Resting-state functional MRI activity and connectivity in inflammatory bowel disease: a systematic review.

Purpose: Inflammatory bowel disease (IBD), encompassing Crohn's disease (CD) and ulcerative colitis (UC), primarily affects the gastrointestinal tract but can also present with systemic manifestations, including those affecting the central nervous system (CNS). Resting-state functional MRI (rs-fMRI) provides insights into alterations in brain activity and connectivity. This review aims to evaluate rs-fMRI findings in IBD patients compared to healthy controls and to explore potential differences between CD and UC.

Methods: A systematic search of PubMed/MEDLINE and SCOPUS identified rs-fMRI studies in neurologically asymptomatic IBD patients. Observational rs-fMRI studies assessing local neural activity and/or functional connectivity, were included.

Results: Twenty-seven studies met eligibility criteria and findings were summarized descriptively based on rs-fMRI analysis technique, given the methodological variability. UC patients showed reduced neural activity in the hippocampus and altered functional connectivity in the visual and cerebellar networks, highlighting memory and motor control disruptions. CD patients exhibited increased neural activity in the anterior cingulate cortex and frontal regions, alongside altered connectivity in multiple sensory and higher-order cognitive networks. Both IBD types displayed disruptions in key networks, including the default mode, salience, and cerebellar networks, associated with emotional processing, pain perception and stress response regulation.

Conclusion: Despite shared rs-fMRI disruptions, UC is primarily associated with decreased neural activity in areas linked to memory and motor coordination, whereas CD exhibits increased activity in regions regulating emotion and cognition. Connectivity disruptions underscore the broader impact of IBD on brain function, emphasizing the role of the brain-gut axis in emotional and sensory impairments.