Usefulness of opening the diaphragma sellae before transecting interclinoidal ligament for endoscopic endonasal transoculomotor triangle approach: technical nuances and surgical outcomes.

OBJECT: Opening the oculomotor triangle and removing the posterior fossa lesion by endoscopic endonasal approach (EEA) is challenging for even an experienced endoscopic neurosurgeon. We summarize the treatment experience and technical nuances with EEA for resection of pituitary neuroendocrine tumors and cavernous sinus (CS) meningiomas invading through the oculomotor triangle (OT).

METHOD: Between 2018 and 2022, eight cases, including five pituitary neuroendocrine tumors (PitNET) including three nonfunctioning and two somatotroph tumors with elevated growth hormone, and 3 CS meningiomas were treated using an endoscopic endonasal transoculomotor triangle approach. The critical surgical technique is continuously opening the diaphragma sellae from medial to lateral towards the interclinoidal ligament (ICL) and transecting it to enlarge the OT. We evaluated preoperative tumor size, previous surgical history, preoperative symptoms, extent of tumor resection, histopathology, and postoperative complications for all patients.

RESULTS: The GTR(gross total resection)- defined as complete removal in 3 patients (38%), near-total resection(NTR) - defined as >95% removal in 4 patients (50%), and subtotal resection (STR)- defined as up to 90 % removal in one patient (12%)and gross-total resection of tumor invading through the OT was achieved in all patients through pure EEA. Two of three patients with visual deficit in Non-Functioning-PitNET improved, and the other remained stable postoperatively. One patient showed transient oculomotor nerve palsy. The Growth Hormone level of the two patients with somatotroph tumors declined to normal. For three patients with CS meningiomas, cranial nerve palsy improved in two patients, while the other patient developed increased facial numbness after surgery.

CONCLUSION: Endoscopic endonasal transoculomotor triangle approach is an efficient surgical option for the tumor with CS invasion and OT penetration.