gms | German Medical Science

Objective: Maximizing the extent of resection (EOR) while preserving functional integrity is a mainstay of modern glioma surgery. Resection guidance tools such as intraoperative MRI (iMRI) help to augment the EOR. However, in eloquently located gliomas the significance of iMRI is controversial since the EOR is limited by functional rather than image-based boundaries. Thus, we set out to determine the impact of iMRI in our series of awake glioma resections.

Methods: Our institutional database was searched for all awake glioma resections within or adjacent to eloquent (language, motor, sensory) areas since the implementation of a 1.5 Tesla iMRI in 2009. Demographic, tumor- and procedure-related data and functional outcome were assessed through medical charts review. The EOR was determined semi-quantitatively on intra- and early postoperative T1 contrast-enhanced (CE) and FLAIR MR images.

Results: In a 7-year period, awake surgery was performed in 97 glioma patients of whom 81 had iMRI-guided surgery with concurrent language (n=67) and/or motor (n=36) mapping. The iMRI group consisted of 50 lower-grade gliomas and 31 glioblastomas with a median age of 46 years (range 12-74), mainly located in left-sided language or motor areas (n=71; 88%). iMRI was well tolerated by all patients and was done when functional boundaries were reached (n=24; 30%), for resection control (n=50; 62%) or for other reasons (n=7). Additional resection after iMRI (AR) was performed in 60 cases (74%); otherwise resection was terminated because eitherthe targeted EOR or functional boundaries were reached. New or deteriorated neurological deficits occurred in 17 patients prior (21%) and 14 patients post (17%) iMRI; however, all but 2 resolved within 6 months (2%). Median EOR significantly increased after AR from 98% to 100% (range 0-15%; p<0.0001) when CE was the target volume and from 85% to 95% (range 0-25%; p<0.0001) in non-enhancing tumors. Remarkably, the reason to perform iMRI, either for resection control or because of functional limitations, did not affect the frequency of AR, deficits acquired post iMRI or the increase in EOR after AR.

Conclusion: IMRI is feasible in awake surgery of eloquently located gliomas and is a valuable adjunct to maximize the EOR without increasing the risk for functional impairment, particularly in non-enhancing tumors. Importantly, iMRI contributes to a maximized EOR even in cases where the resection has to be stopped because functional boundaries were reached.