Combined use of minimal access craniotomy, intraoperative magnetic resonance imaging, and awake functional mapping for the resection of gliomas in 61 patients

Abstract

Objective: Current management of gliomas involves a multidisciplinary approach, including a combination of maximal safe resection, radiotherapy, and chemotherapy. The use of intraoperative MRI (iMRI) helps to maximize extent of resection (EOR), and use of awake functional mapping supports preservation of eloquent areas of the brain. This study reports on the combined use of these surgical adjuncts.

Methods: The authors performed a retrospective review of patients with gliomas who underwent minimal access craniotomy in their iMRI suite (IMRIS) with awake functional mapping between 2010 and 2017. Patient demographics, tumor characteristics, intraoperative and postoperative adverse events, and treatment details were obtained. Volumetric analysis of preoperative tumor volume as well as intraoperative and postoperative residual volumes was performed.

Results: A total of 61 patients requiring 62 tumor resections met the inclusion criteria. Of the tumors resected, 45.9% were WHO grade I or II and 54.1% were WHO grade III or IV. Intraoperative neurophysiological monitoring modalities included speech alone in 23 cases (37.1%), motor alone in 24 (38.7%), and both speech and motor in 15 (24.2%). Intraoperative MRI demonstrated residual tumor in 48 cases (77.4%), 41 (85.4%) of whom underwent further resection. Median EOR on iMRI and postoperative MRI was 86.0% and 98.5%, respectively, with a mean difference of 10% and a median difference of 10.5% (p < 0.001). Seventeen of 62 cases achieved an increased EOR > 15% related to use of iMRI. Seventeen (60.7%) of 28 low-grade gliomas and 10 (30.3%) of 33 high-grade gliomas achieved complete resection. Significant intraoperative events included at least temporary new or worsened speech alteration in 7 of 38 cases who underwent speech mapping (18.4%), new or worsened weakness in 7 of 39 cases who underwent motor mapping (18.0%), numbness in 2 cases (3.2%), agitation in 2 (3.2%), and seizures in 2 (3.2%). Among the patients with new intraoperative deficits, 2 had residual speech difficulty, and 2 had weakness postoperatively, which improved to baseline strength by 6 months.

Conclusions: In this retrospective case series, the combined use of iMRI and awake functional mapping was demonstrated to be safe and feasible. This combined approach allows one to achieve the dual goals of maximal tumor removal and minimal functional consequences in patients undergoing glioma resection.

Keywords: awake craniotomy; awake functional mapping; glioma resection; iMRI; intraoperative magnetic resonance imaging; minimal access craniotomy; oncology; surgical technique.