Routine MRI Assessment Immediately Following Transsphenoidal Resection of Nonfunctional Pituitary Macroadenomas Does Not Alter the Course of Clinical Management

Introduction: Postoperative magnetic resonance imaging (MRI) following transsphenoidal resection of pituitary macroadenomas is frequently performed in a delayed manner due to difficulties in assessing for residual tumor related to the presence of blood products and intrasellar reconstruction materials such as autologous fat or muscle. Since 2006, our practice has been to avoid intrasellar reconstruction with such materials, and we sought to determine whether obtaining an MRI in the “immediate” (1-3 days) postoperative period provided clinically meaningful information regarding extent of resection or surgical complication compared with delayed MRI obtained in the “early” (1-4 months) period following surgery.

Methods: Between 2006 and 2012, 125 patients were identified who had undergone endoscopic transsphenoidal resection of a nonfunctional pituitary macroadenoma and obtained postoperative MR imaging in both the “immediate” (1-3 days) and “early” (1-4 months) periods following surgery. Surgical technique was notable for dural closure using a synthetic dural substitute inlay graft with placement of no intrasellar packing materials. Assessment for extent of tumor resection was based on T1-weighted gadolinium-enhanced and nonenhanced scans obtained in the immediate and early time periods, with any nodular tissue interpreted as intrasellar, suprasellar, or cavernous sinus residual adenoma. Radiographic interpretation regarding the presence and location of residual adenoma was compared between the two MRI time periods.

Results: Based on the early MRI findings, gross total resection was achieved in 79/125 (63.2%) patients. Of those cases with residual adenoma, 30/46 (65.2%) patients demonstrated residual tumor entirely within the cavernous sinus, and 7 patients had intrasellar or suprasellar remnants in addition to cavernous sinus residual disease. Five patients demonstrated persistent disease in the suprasellar location and four patients had residuum entirely within the sella. The immediate MRI revealed a 100% sensitivity and 89.7% specificity for the presence of residual adenoma compared with the early MRI. The positive predictive value for residual adenoma was 85.1%. In 6/125 (4.8%) patients, the immediate MRI was determined to provide helpful radiographic information regarding the location of residual disease. In all six patients, residual tumor in the suprasellar location was observed on the immediate postoperative MRI and accurate determination of the anatomic location of tumor residua would not have been possible based solely on the early MRI due to recession of the tumor into the intrasellar space.

Conclusions: Obtainment of MR imaging in the immediate postoperative period demonstrates excellent sensitivity for the detection of residual adenoma. However, despite the absence of intrasellar packing material, the diminished specificity and positive predictive value remain limiting. In only 4.8% of patients did the immediate MRI provide disparate information regarding the location of residual adenoma compared with the more conventional early study, and in no cases did this information alter the course of patient management. Our findings demonstrate that MRI evaluation immediately following transsphenoidal resection of pituitary macroadenomas provides the most accurate determination of the anatomic location of residual adenoma; however, these data are unlikely to affect clinical management, and routine use of MRI in the immediate postoperative period should be avoided.