Endoscopic Contralateral Occipital Interhemispheric Transtentorial Superior Transvelar Approach to Pontomesencephalic Cavernous Malformations: Cadaveric Anatomy and Clinical Illustration.

Abstract

Neurosurgical management of dorsal pontomesencephalic junction lesions is inherently complex and challenging. We introduce a novel endoscopic technique for resection of such lesions: the contralateral occipital interhemispheric transtentorial superior transvelar approach. A meticulous dissection of 5 formalin-fixed cadaveric specimens was conducted to simulate the contralateral occipital interhemispheric transtentorial superior transvelar approach, with a focus on exposing the pontomesencephalic junction and the upper fourth ventricle. Each key anatomical landmark was thoroughly evaluated. We present a detailed clinical case to demonstrate the effective and safe removal of a pontomesencephalic cavernous malformation using this innovative surgical approach. No cortical veins draining into the superior sagittal sinus were found in the field of view behind 1 cm superior to the lambdoid suture. The critical surgical procedures included unilateral occipital craniotomy, identification and lateral incision of the tentorium, arachnoid dissection to reveal the cerebellomesencephalic fissure, superior medullary velum exposure, and opening to unveil the upper fourth ventricle and the dorsal pontomesencephalic junction. Using this surgical approach, we achieved complete resection of a cavernous malformation located at the dorsal pontomesencephalic junction. The surgical trajectory provided ample exposure, enhancing the precision of the surgical manipulation and offering a significant advantage in visualizing the contralateral lateral region. This study validates the practicality and efficacy of the endoscopic contralateral occipital interhemispheric transtentorial superior transvelar approach for resection of pontomesencephalic CMs. This approach affords optimal entry to the upper fourth ventricle and the dorsal pontomesencephalic junction, strategically broadening the surgical reach laterally via a pioneering "cross-court" corridor.