Does Low-Field Intraoperative Magnetic Resonance Improve the Results of Endoscopic Pituitary Surgery? Experience of the Implementation of a New Device in a Referral Center.

Objective: To assess the contribution of low-field intraoperative magnetic resonance (iMRI) to endoscopic pituitary surgery.

Methods: We analyzed a prospective series of patients undergoing endoscopic endonasal surgery for pituitary macroadenomas assisted with a low-field iMRI (PoleStarN30, 0.15 T [Medtronic]). Clinical, radiologic, and surgical variables were analyzed and compared with our fully endoscopic historic cohort operated on without iMRI assistance. A bibliographic review of pituitary surgery assisted with iMRI was conducted.

Results: Thirty patients (57% female; mean age, 55 years) were prospectively analyzed. The most frequent tumor subtype was nonfunctioning macroadenoma (50%). The average Knosp grade was 2.3 and mean tumor size was 18 mm. Surgical and positioning time were 102 and 47 minutes, respectively. Hospital stay and complication rates were similar to our historical cohort for pituitary surgery. Mean follow-up was 10 months. Complete resection (CR) was achieved in 83% of patients. Seven patients (23%) benefited from iMRI assistance and achieved a CR in their surgeries. All patients except 1 experienced hormonal activity remission. iMRI sensitivity and specificity was 0.8 and 1, respectively. Although not statistically significant, CR rates were globally 11.5% superior in iMRI series compared with our historical cohort. This difference was independent of cavernous sinus invasiveness grade (CR rate increased 12.5% for Knosp grade 0-2 and 8.1% for Knosp grade 3-4).

Conclusions: Low-field iMRI is a useful and safe assistance even in advanced surgical techniques such as endoscopy. Its contribution is limited by the intrinsic features of the tumor. Further randomized studies are required to confirm the cost-effectiveness of iMRI in pituitary surgery.