Brain structural and functional alterations in patients following cardiopulmonary bypass: a short-term longitudinal fMRI study

Objective While cross-sectional studies have identified brain abnormalities after cardiopulmonary bypass (CPB), the early dynamic trajectory of these alterations from the preoperative state remains to be fully characterized. This longitudinal study investigates the within-subject evolution of brain structure and function following CPB. Methods Sixty-eight patients undergoing CPB were scanned twice (preoperatively and 15 days post-surgery) using resting-state fMRI and T1-weighted MRI. We assessed changes in regional homogeneity (ReHo) for local neural activity, graph-based network topology, and surface-based morphometry (SBM). Results Comparison of pre- and postoperative scans revealed a coordinated pattern of brain reorganization. Functionally, ReHo decreased within default mode network (DMN) hubs, specifically the posterior cingulate cortex and right angular gyrus, while increasing in fronto-parietal network (FPN) regions (bilateral inferior frontal gyri) and the right temporal lobe. Network analysis showed altered functional segregation (reduced clustering coefficient and local efficiency) alongside enhanced integration (increased global efficiency), raising the possibility of network-level reorganization. Structurally, these functional shifts paralleled gray matter loss, cortical thinning, and sulcal shallowing in fronto-temporal regions and the right precuneus, accompanied by reduced cortical complexity (fractal dimension, gyrification index) in temporal, frontal, and occipital areas. Conclusion This longitudinal study provides preliminary evidence suggesting that CPB is associated with dynamic and coordinated remodeling of brain structure and function. The DMN-FPN imbalance and right temporal lobe alteration may represent candidate neural correlates for future investigations into postoperative cognitive dysfunction.