From Above and Below: The Microsurgical Anatomy of Endoscopic Endonasal and Transcranial Microsurgical Approaches to the Parasellar Region

Abstract

The parasellar region is one of the most complex of the skull base. In this study, we review the anatomy and approaches to this region through a 360° perspective, correlating microsurgical and endoscopic anatomic nuances of this area. An endoscopic endonasal approach (EEA) and microsurgical dissections were performed. The parasellar anatomy is reviewed and common areas of tumor extensions are assessed. Surgical approaches are discussed based on the anatomic nuances of those regions. The cavernous sinus (CS) can be divided into 2 spaces: posterosuperior, above and behind the internal carotid artery (ICA); and anterior, in front of the cavernous ICA. Those spaces can be approached through the CS walls: anterior and/or medial wall via EEA; or superior and/or lateral wall via transcranial approaches. The relationship of the Meckel cave, adjacent to the lateral and posterior wall of the CS, is relevant for surgical planning. Areas often affected by tumor extension can be divided into 6 regions: superior (cisternal), superolateral (parapeduncular), posterolateral (Meckel cave and petrous bone), medial (sella), anterior (superior orbital fissure), and anterior inferior (pterygopalatine fossa). Anatomic and technical nuances of each of those regions should be taken into consideration when dealing with tumors in the parasellar space. A transcranial approach and EEA provide effective access to the parasellar region. Management of cavernous sinus and Meckel cave tumors requires familiarity with those approaches. Understanding of the surgical anatomy of the parasellar region, from above and below, is therefore necessary for adequate surgical planning and execution.