The Role of the Glymphatic System in Perioperative Neurocognitive Disorders.

Background: The glymphatic system plays a crucial role in clearing metabolic waste from the central nervous system and is most active during sleep. Patients with obstructive sleep apnea (OSA) have a dysfunctional glymphatic system that correlates with disease severity. In addition, these patients have worse outcomes after surgery. The status of the glymphatic system during the perioperative period is unclear and can be examined with magnetic resonance imaging (MRI)-based diffusion tensor imaging (DTI). This study assessed perioperative glymphatic system changes in OSA surgical patients and possible relationships with perioperative neurocognitive disorders.

Methods: DTI data from 13 OSA patients having laparoscopic abdominal surgery with general anesthesia were acquired and analyzed using a 3.0-T MRI scanner. Diffusivity maps in the x-axis (Dxx), y-axis (Dyy), z-axis (Dzz), x-y axis (Dxy), y-z axis (Dyz), and x-z axis (Dxz) were calculated. Diffusion values for the projection and association fibers were extracted, and DTI analysis along the perivascular space (ALPS) was performed. The patients' cognition was assessed using the Montreal Cognitive Assessment tool. Evaluations were carried out within 5 days before surgery and within the first 48 hours after surgery.

Results: The ALPS index decreased after surgery, and this correlated with a decrease in general cognition scores and specific memory domains, including visuospatial and delayed recall.

Conclusions: The glymphatic system in OSA patients is worsened after surgery and this may contribute to an increased risk for long-term postoperative cognitive disorders. This study suggest that the glymphatic system might play a role in the pathophysiology of perioperative neurocognitive disorders and be a potential therapeutic target.