Abstract
Background: Surgical management of third ventricular tumors is challenging due to the narrow operative corridor and the critical importance of maintaining ventricular anatomy. In microsurgical approaches, cerebrospinal fluid (CSF) aspiration is commonly performed to improve exposure; however, this may lead to ventricular collapse and functional narrowing or closure of the foramen of Monro. In contrast, endoscopic techniques utilize continuous irrigation, allowing surgery under a fluid medium and potentially preserving ventricular volume and patency. Methods: Between August 2006 and April 2026, a total of 247 third ventricular procedures were performed using different surgical techniques, including 17 microsurgical interhemispheric transcallosal approaches, 210 endoscope-assisted tubular transcortical approaches, and 20 purely endoscopic procedures. Intraoperative observations focused on ventricular volume dynamics and the behavior of the foramen of Monro under different CSF management strategies. Results: In microsurgical procedures, CSF aspiration frequently resulted in ventricular volume reduction, approximation of the ventricular walls, and transient narrowing or collapse of the foramen of Monro, thereby limiting visualization and maneuverability. In contrast, endoscopic and endoscope-assisted tubular approaches performed under continuous irrigation maintained ventricular distension through hydrostatic pressure, preserving patency of the foramen of Monro and providing a stable operative corridor. Restoration of ventricular volume was consistently observed after fluid reintroduction, supporting the role of continuous irrigation in maintaining operative space and visualization. Conclusion: Continuous irrigation in endoscopic third ventricular surgery offers a significant technical advantage by maintaining ventricular volume and preventing collapse of the foramen of Monro. The hydrostatic effect improves visualization, facilitates instrument maneuverability, and enhances surgical safety. These findings support the preferential use of endoscopic approaches in selected third ventricular lesions.