Understanding postoperative cognitive dysfunction after cardiac surgery: an integrated narrative review of neuropsychological, neuroimaging, and rehabilitative perspectives

Postoperative cognitive dysfunction (POCD) is a common and severe complication after cardiac surgery, characterized by declines in memory, attention, executive function, and processing speed. This narrative review synthesizes current evidence on POCD from neuropsychological, neuroimaging, and rehabilitative perspectives. The underlying mechanisms are multifactorial and include cerebral microembolization, systemic inflammation from cardiopulmonary bypass, hypoperfusion, and patient-specific risk factors such as advanced age and mild cognitive impairment. Neuroimaging studies have identified structural changes, such as new ischemic lesions on diffusion-weighted magnetic resonance imaging (MRI), and functional disruptions within the Default Mode Network and frontoparietal connections, which are associated with neuroinflammation as shown by positron emission tomography (PET). Neuropsychological assessment is limited by the absence of standardized diagnostic criteria and the use of diverse testing protocols, resulting in considerable variability in reported incidence rates. Although formal guidelines are lacking, cognitive rehabilitation interventions, including computerized cognitive training, multitasking exercises, and virtual reality, demonstrate potential for reducing cognitive decline, particularly when implemented before surgery. A significant gap persists in connecting these functional improvements to underlying neurobiological changes. Future research should integrate longitudinal neuropsychological, biomarker, and neuroimaging data within standardized frameworks to clarify POCD mechanisms and to develop effective, individualized prevention and rehabilitation strategies. These efforts are essential for improving long-term patient outcomes and quality of life.