gms | German Medical Science

Objective: Recent series analysing the utility of intraoperative MRI (iMRI) in transsphenoidal pituitary surgery suggest that the rate of complete resections can be significantly increased while the rate of pituitary insufficiency remains unaffected. Since iMRI is time-consuming and costly however, it would be desirable to better identify and characterize patients in whom iMRI would result in additional resections.

Methods: From 01/2010 to 10/2017, a total of 438 consecutive patients were prospectively assessed in a registry. The series comprises all Knosp grades (0-4), micro-(17.3%) and macroadenomas (82.7%), hormone-active (38.8%) and inactive tumors (61.2%), primary surgeries (n=396, 90.5%) and secondary interventions for recurrencies (n=42, 9.5%). Intraoperatively, a 1.5Tesla scanner was used. Intraoperative scans were conjointly evaluated by neuroradiologists and neurosurgeons. Univariate regression was calculated to identify variables of additional adenoma resection after iMRI.

Results: The iMRI suspected tumor remnants of 174/438 cases (39.7%). Transsphenoidal re-inspection resulted in an additional curettage of adenomas in only 73 cases, however (16.7%). In 61 patients (13.9%), no remnants could be identified. In 40 patients (9.1%), tumour remnants could not be reached due to their para- or suprasellar location. E.g. adenoma satellites already recognized preoperatively, could often not be resected transsphenoidally (18 pts., 4.0%). In univariate regression, adenoma size, parasellar location and recurrent surgery increased the likelihood for an additional adenoma resection after iMRI. Further analysis revealed that an increasing surgical experience is associated with better prediction of tumour remnants, indicating that iMRI is especially valuable in training.

Conclusion: In the majority of cases in this series, pituitary adenomas were completely removed transsphenoidally without the adjunct of iMRI. Thus, iMRI for resection control in microsurgical transsphenoidal pituitary surgery offers limited benefits. Particularly in recurrent surgeries and in large adenomas with para- and suprasellar extension, however, iMRI is a valuable tool to increase the rate of complete adenoma removal. Stratification of cases according to these preconditions can assist to efficiently use iMRI in pituitary surgery.