The Vagoaccessory Triangle (VAT): The Arena of ELITE

Introduction  Lesions in the cerebellomedullary angle, anterolateral aspect of lower brainstem, and anterior foramen magnum can be accessed through far lateral approach and extreme lateral infrajugular transcondylar exposure. Detailed anatomical knowledge of this region is of paramount importance to avoid untoward complications. Objectives  Comprehensive anatomy of this microsurgical corridor is sparse. Our aim was to define the anatomy of this region with relevance to the surgical approach, which would enable the surgeon to navigate this region with ease during surgery. Materials and Methods  Cadaveric dissection was performed with focus on the various anatomical structures, which are of relevance to the operating surgeon. The same was correlated with the computerized scan and magnetic resonance imaging brain findings and intraoperative findings. The observations are presented. Discussion  Through the far lateral approach, the vagoaccessory triangle (VAT) and three subtriangles within it are exposed. Lateral boundary of the VAT is formed by the spinal accessory nerve, which follows a superolateral trajectory toward the jugular foramen. Medial boundary is formed by the medulla oblongata. Superior boundary is formed by the vagus nerve, which courses horizontally toward the jugular foramen. Rootlets of the hypoglossal nerve divide the VAT into infra-hypoglossal, supra-hypoglossal, and hypoglossal-hypoglossal subtriangles. The floor is formed by the inferior clivus, anterior foramen magnum, occipital condyle, and jugular tubercle. The roof is formed by the dura covering the lower part of the posterior fossa, biventral lobule, and tonsil of the cerebellum. The VAT contains three cisterns compartmentalized by three membranes, three nerves, and a fourth segment of vertebral artery (V4) with its three branches, in three subtriangles. Cisterns are the premedullary, lateral cerebellomedullary, and posterior cerebellomedullary. Membranes are the medial pontomedullary membrane, lateral pontomedullary membrane, and denticulate ligament. Nerves are the rootlets of hypoglossal, cranial accessory, and first cervical nerve. Posterior inferior cerebellar artery, anterior spinal artery, and posterior spinal artery are the three branches of V4. Conclusion  Detailed knowledge of each anatomical structure and its relationship would enable the surgeon to operate safely within the corridors naturally present in this region.