Extent of Resection during Endoscopic Trans-sphenoidal Pituitary Surgery with Intraoperative Magnetic Resonance Imaging

Introduction: The surgical goal of pituitary surgery is gross total resection (GTR) of macroadenomas. Our group has previously reported that intraoperative magnetic resonance imaging (iMRI) may reveal unrecognized unacceptable residual tumor in 66% of patients undergoing trans-sphenoidal resection. A recent study demonstrated the feasibility of endoscopic trans-sphenoidal surgery with iMRI, with post-iMRI endoscopic confirmation of residual tumor location. We set out to evaluate the potential benefit of endoscopy on better visualization and pre-iMRI prediction accuracy of residual tumor presence and location during trans-sphenoidal surgery.

Methods: We performed endoscopic, endonasal resection of pituitary macroadenomas in 11 patients with the use of iMRI in a 0.3 Tesla vertical-field open magnet (Hitachi AIRIS II). We report on the extent of resection and location of residual tumor as predicted by the surgeon, based on intrasellar endoscopy prior to iMRI, and as demonstrated by the intraoperative imaging.

Results: The combination of endoscopic trans-sphenoidal pituitary surgery and iMRI was performed successfully in all patients. There were seven nonsecreting tumors, three growth hormone-secreting tumors, and one prolactin-secreting tumor. Average maximal tumor diameter was 2.4 cm (1 to 3.6 cm). Prior to iMRI, surgeon predictions based on intrasellar endoscopy were correct in 10/11 patients, GTR in 7 patients and residual tumor in 3 patients (2 supradiaphragmatic with a mostly intact diaphragma sella and 1 in the cavernous sinus with an intact medial wall of the cavernous sinus). One patient had unacceptable residual tumor superiorly through a widened diaphragma sella that was incorrectly predicted and was re-explored for complete resection, confirmed by a second iMRI.

Conclusions: Our experience indicates that the use of intrasellar endoscopy may allow for better visualization of residual tumor. Endoscopy can be a useful adjunct to pituitary surgery and may allow us in the future to improve the rate of GTR even in the absence of iMRI.