A New Perspective on the Cavernous Sinus as Seen through Multiple Surgical Corridors: Anatomical Study Comparing the Transorbital, Endonasal, and Transcranial Routes and the Relative Coterminous Spatial Regions.

Background: The cavernous sinus (CS) is a highly vulnerable anatomical space, mainly due to the neurovascular structures that it contains; therefore, a detailed knowledge of its anatomy is mandatory for surgical unlocking. In this study, we compared the anatomy of this region from different endoscopic and microsurgical operative corridors, further focusing on the corresponding anatomic landmarks encountered along these routes. Furthermore, we tried to define the safe entry zones to this venous space from these three different operative corridors, and to provide indications regarding the optimal approach according to the lesion's location. Methods: Five embalmed and injected adult cadaveric specimens (10 sides) separately underwent dissection and exposure of the CS via superior eyelid endoscopic transorbital (SETOA), extended endoscopic endonasal transsphenoidal-transethmoidal (EEEA), and microsurgical transcranial fronto-temporo-orbito-zygomatic (FTOZ) approaches. The anatomical landmarks and the content of this venous space were described and compared from these surgical perspectives. Results: The oculomotor triangle can be clearly exposed only by the FTOZ approach. Unlike EEEA, for the exposure of the clinoid triangle content, the anterior clinoid process removal is required for FTOZ and SETOA. The supra- and infratrochlear as well as the anteromedial and anterolateral triangles can be exposed by all three corridors. The most recently introduced SETOA allowed for the exposure of the entire lateral wall of the CS without entering its neurovascular structures and part of the posterior wall; furthermore, thanks to its anteroposterior trajectory, it allowed for the disclosure of the posterior ascending segment of the cavernous ICA with the related sympathetic plexus through the Mullan's triangle, in a minimally invasive fashion. Through the anterolateral triangle, the transorbital corridor allowed us to expose the lateral 180 degrees of the Vidian nerve and artery in the homonymous canal, the anterolateral aspect of the lacerum segment of the ICA at the transition zone from the petrous horizontal to the ascending posterior cavernous segment, surrounded by the carotid sympathetic plexus, and the medial Meckel's cave. Conclusions: Different regions of the cavernous sinus are better exposed by different surgical corridors. The relationship of the tumor with cranial nerves in the lateral wall guides the selection of the approach to cavernous sinus lesions. The transorbital endoscopic approach can be considered to be a safe and minimally invasive complementary surgical corridor to the well-established transcranial and endoscopic endonasal routes for the exposure of selected lesions of the cavernous sinus. Nevertheless, peer knowledge of the anatomy and a surgical learning curve are required.

Magnetic resonance imaging finding of coexistence of bilateral paraclinoid aneurysms in a patient with a nonfunctioning macroadenoma, simultaneous resection, and clipping: illustrative case.

BACKGROUND: Unruptured incidental intracranial aneurysm can coexist with pituitary adenoma, however, the occurrence is extremely rare. Timely diagnosis of asymptomatic intracranial aneurysms with pituitary adenoma may lead to planning a tailored surgical strategy to deal with both pathologies simultaneously. A case of a patient who underwent transcranial resection of a pituitary adenoma with clipping of two mirror aneurysms is reported. OBSERVATIONS: A 55-year-old female presented with deterioration of visual acuity that progressed over 1 year, as well as presence of right eyelid ptosis. Magnetic resonance imaging of the head showed the presence of an intrasellar pituitary macroadenoma. Bilateral paraclinoid aneurysms were documented to be in contact with the pituitary tumor. The patient underwent surgery with simultaneous aneurysm clipping and tumor resection through a standard pterional approach with intradural clinoidectomy. The aneurysms were successfully clipped after the tumoral debulking. After clipping, the pseudocapsule was fully resected. LESSONS: Various treatment options are available. Although endovascular securing of the aneurysms prior to the tumor resection would be ideal, in cases in which this resource is not readily available at all times, the surgeon must be prepared to solve pathologies with an elevated level of complexity.