Bilateral Endoscopic Posterior Clinoidectomies with Separation of Kissing Carotids: A Technical Report

Background: Posterior clinoidectomies are often performed during endoscopic endonasal approaches, either because the posterior clinoids are directly involvement with tumor, or as a means to gain access to the interpeduncular cistern. When the parasellar carotid arteries are very close to one another (i.e., “kissing carotids”), posterior clinoidectomies with preservation of pituitary gland function become very challenging. We describe a novel technique for performing bilateral posterior clinoidectomies in the setting of “kissing carotids.” The technique is presented in the context of an illustrative case.

Case Presentation: The case refers to a 41-year-old male patient with a clival chordoma, who was previously operated on at another institution. Imaging revealed progression of a residual tumor within the left medial petrous apex, and extending into the left posterior clinoid and dorsum sellae. The parasellar carotids were less than 4 mm apart. Given the tumor location, bilateral posterior clinoidectomies were essential for the complete resection of the tumor. Notably, the patient did not have any evidence of pituitary dysfunction preoperatively. Because of the fairly tall posterior clinoids, an extradural pituitary transposition would not provide adequate exposure. Furthermore, given the absence of a reasonable window in the anterior wall of the cavernous sinus (between the parasellar carotids and the medial wall of the cavernous sinus) an interdural pituitary transposition was thought to be a dangerous undertaking. On the other hand, a true intradural pituitary transposition would have placed the patient at a significant risk for hypopituitarism. Given the above we chose to perform a modified intra/interdural pituitary transposition: After wide exposure of the sella and the parasellar carotids, both the periosteal and meningeal layers of the sellar dura were incised in the midline. The incision was carried over from the anterior sella, all the way to the posterior intercavernous sinus, which was coagulated and divided. This incision released the connection between the two carotids, facilitating their lateralization. Subsequently, after gentle packing of the cavernous sinus posteriorly, and following the now widened interdural transcavernous compartment (between the meningeal dural layer of the pituitary gland and the periosteal layer of the cavernous sinus), we performed the posterior clinoidectomies as previously described with an interdural pituitary transposition. This exposure allowed complete resection of the tumor. In effect, despite the midline incision of the meningeal dural layer of the pituitary gland, no dura was actually stripped from the gland superiorly and posteriorly, thus allowing preservation of its venous outflow. Postoperative pituitary lab work revealed no evidence of pituitary dysfunction.

Conclusion: The proposed technique of a modified intra/interdural pituitary transposition appears to be safe and effective for performing posterior clinoidectomies in the setting of very medial parasellar carotid arteries. Further experience with this technique in a larger cohort of patients will help define its true advantages, risks, and limitations.