Full-Endoscopic Minimally-Invasive Trans-Magendie Approach to the Fourth Ventricle: An Anatomical Feasibility Study

Background: The telovelar approach provides access to the caudal two-thirds of the fourth ventricle without requiring vermian splitting. Indeed, the traditional microsurgical approach is often limited by a restricted cranial angle of attack and visualization, making it challenging to evaluate the patency of the aqueduct. To address this limitation, resection of the posterior arch of C1 is frequently performed. This study aims to describe and evaluate the feasibility of a full-endoscopic, retractorless, trans-Magendie approach to the inferior third of the fourth ventricle, avoiding removal of the posterior arch of C1 through a minimally invasive burr-hole suboccipital craniotomy. Methods: Four formalin-fixed, injected cadaveric heads were investigated. A step-by-step anatomic description of the proposed approach is provided. Results: Adequate cranial and lateral visualization of the aqueduct and fourth ventricle floor was achieved without removing the posterior arch of C1. Conclusions: The full-endoscopic trans-Magendie approach enables adequate visualization of the inferior two-thirds of the fourth ventricle and the caudalmost portion of the aqueduct while avoiding the need for a C1 laminectomy and significantly reducing the craniotomy size.