Endoscopic Endonasal Surgical Approach to the Oculomotor Trigone from the Cavernous Sinus

Abstract

Knowledge of anatomy visualized endoscopically is necessary to perform endoscopic surgical procedures safely. The cavernous sinuses are complicated structures with major blood vessels and nerves seated deeply in the center of the skull base. Anatomical orientation during surgery is essential for deep and narrow skull base surgery. While performing surgery involving the cavernous sinuses, understanding of the structures identifiable via a transsphenoidal view can allow comprehension of the relationship between a lesion and the surrounding structures, thus preventing intraoperative complications. The objective of this study was to dissect the neurovascular structures in the cavernous sinus deeply inside the oculomotor trigone through a transsphenoidal view, and to determine the relationships among anatomical landmarks in the path of surgery. Ten fresh silicone-injected cadaveric heads were evaluated. Four millimeter-diameter rigid endoscopes with 0° and 30° rod-lenses were utilized to perform an endonasal transsphenoidal approach. The detailed position and course of the major components in each cavernous sinus were assessed under panoramic view. We also validated the utility of this approach by successfully excising a huge pituitary adenoma.

Pituitary macroadenomas with oculomotor cistern extension and tracking: implications for surgical management

“…Hidden posterolateral to the posterior clinoid process and within the lateral wall of the cavernous sinus, the oculomotor triangle must be approached in a fashion that requires a direct endoscopic endonasal transcavernous approach or indirect endonasal posterior clinoidectomy in order to access the basal cisterns. 1,2,6,37 In their endoscopic study of the oculomotor nerve, Abuzayed et al 1 were able to visualize the courses of the interpeduncular and intercavernous segments via extended endonasal suprasellar and endonasal ethmoidopterygosphenoidal approaches, respectively, but found exposing the cisternal segment to be extremely difficult because of its hidden location in the superior part of the cavernous sinus, forming a posteroinferior border with the anterior clinoid process that is anterolateral to the posterior clinoid process. They noted that endoscopic exposure of the cistern would lead to reduced maneuverability because of the positioning of the endoscope within the constricted chiasmatic cistern required for the endonasal suprasellar approach.…”

“…This required meticulous dissection of the interdural plane separating the cavernous sinus and lateral mobilization of the ICA in order to expose the posterior clinoid and dorsum sellae. Wakuta et al 37 described an endoscopic endonasal transcavernous dissection and approach to the oculomotor trigone. They accessed the oculomotor trigone after medial mobilization of the intracavernous ICA and identified a triangular area defined by the abducens nerve, occulomotor nerve, and posterior vertical segment of the ICA, which lead to the oculomotor trigone.…”

Endoscopic endonasal surgery for pituitary adenomas extending to the oculomotor cistern

“…Anatomically, the nerve enters the oculomotor cistern at the roof of the cavernous sinus and courses laterally along the cavernous sinus lateral wall . Thus, the nerve is rarely encountered when approaching the tumor at the oculomotor cistern through the medial corridor of the cavernous sinus . Confirmation of the nerve's absence on the way to the tumor by negative response on electrical stimulation is another important measure.…”

“…13 Thus, the nerve is rarely encountered when approaching the tumor at the oculomotor cistern through the medial corridor of the cavernous sinus. 7 Confirmation of the nerve's absence on the way to the tumor by negative response on electrical stimulation is another important measure. Although a small tumor within the cistern can be removed by simple aspiration by a suction tube inserted into the dural opening of the oculomotor cistern, excessive blind suctioning should be withheld.…”

“…2 The recent evolution of the endoscopic endonasal surgical technique, however, provides a new aspect in the treatment of pituitary adenomas within the cavernous sinus, 3,4 and management of the tumor compartment within the oculomotor and interpeduncular cisterns is expected to become feasible. [5][6][7] The present study intends to demonstrate the role and results of the endoscopic endonasal surgery in treating the pituitary adenomas with extension to the oculomotor cistern, paying special attention to the oculomotor nerve function and removal rate of the tumor compartment within the oculomotor cistern and lateral recess of the interpeduncular cistern.…”