gms | German Medical Science

Objective: Functional pituitary adenomas (FPA) represent a special sub-entity among pituitary adenomas which come with characteristic challenges for imaging diagnostics, medical and surgical treatment. Transsphenoidal surgery (TSS) is an established treatment option for FPAs aiming at better hormone remission associated with complete resections. In this series we evaluated the role of intraoperative 1.5 tesla MRI for resection of FPAs emphasizing on intraoperative findings, the extent of resection and postoperative hormone function.

Methods: From 01/2010 to 12/2017 a total of 114 consecutive FPAs with TSS were retrospectively reviewed. All cases had excess hormone secretion on preoperative endocrinological evaluation. IMRI findings were analysed focussing on intraoperative decision making. Extent of resection was evaluated on postoperative MRI and compared to iMRI findings. Postoperative hormonal remission was evaluated according to consensus criteria. Variables of incomplete resections and persistent hormone excess was evaluated in binary regression analysis.

Results: We included 23 cases with hypercortisolism (20%), 56 with acromegaly (49%) and 35 with prolactinoma after failed medical therapy (31%). Preoperative MRI showed 81 macroadenomas (71%) with a median Knosp grade 1 (range 0-4) and involvement of optic chiasm in 41 cases (36%). After iMRI, re-inspection of the cavity helped to clear equivocal iMRI findings in 19 cases (17%). Additional tumor was removed in 22 (20%) leading to complete resections in all but 4 cases. Overall, complete resection was achieved in 82%. IMRI had no direct effect on surgical results in 2/3 of cases but exhibited excellent agreement with postoperative MRI. Hormonal remission was achieved in 59%. Supra- and parasellar invasion and preoperative visual impairment were significant predictors for incomplete resections. Risk for persistent hormone excess was increased 7-fold after incomplete resections.

Conclusion: While the strong impact of complete adenoma resections was corroborated particularly for treatment of excess hormone secretion in this series, we observed a manifold value for iMRI in resections of FPAs. It expectedly assisted to detect remnants in large and invasive tumors but also helped to rule out residual tumor by allowing for focused re-inspection of equivocal findings. High diagnostic quality might repeal the need for postoperative MRI which supports use of iMRI in FPA resections.