A Quantitative Volumetric MRI Analysis of the Immediate Effects of Meningioma Embolization on Tumor Size and Surrounding Edema

Introduction: There is increasing adoption of preoperative endovascular embolization for patients undergoing meningioma resection as a surgical adjunct. It remains, however, largely unclear what effects embolization has on tumor size and surrounding brain edema, and the time course of the possible changes.

Objectives: To investigate the effects of embolization on tumor size and surrounding brain edema within the immediate post procedural period.

Methods: Medical records of all patients who underwent MRI following tumor embolization prior to resection were retrospectively analyzed. Total tumor volume, tumor enhancement volume, and surrounding brain edema volume pre- and postembolization were generated by using semi-automated segmentation on the Slicer3D software. Embolization extent was quantified as the ratio of residual non–contrast-enhancing tumor volume to post-embolization total tumor volume. Edema index was calculated as (tumor volume + edema volume) / tumor volume.

Results: There were 28 patients included in the study. The mean tumor size pre-embolization was 60 cm³, with no statistically significant change postembolization (p = 0.16). 7/28 (25%) patients had an increase in total tumor volume, and 21/28 (75%) had a decrease. The mean embolization extent was 0.34 with a range of 0 to 0.94. 7/28 (25%) patients had extent of embolization greater than 75%, 6/28 (21%) had between 25 and 75%, and 15/28 (54%) had less than 25%. The mean preembolization edema index is 1.97, with a range of 1 to 9.68. There was no significant change in edema index postembolization (p = 0.29). 7/28 (25%) patients had an increase in edema index postprocedure, 8/28 (29%) had a decrease, and 13/28 (46%) were unchanged. The mean extent of midline shift preembolization was 4.2 mm, with a range of 0 to 17 mm, with no statistically significant change postembolization (p = 0.48). 7/28 (25%) patients had an increase in midline shift postembolization, 4/28 (14%) had a decrease, and 17/28 (61%) stayed unchanged. 11/28 patients had gotten their MRIs within 24 hours of the embolization procedure, 15/28 between 24 and 48 hours, and 2/28 over 48 hours. There were no statistically significant correlations between time to MRI with changes in total tumor volume, edema index, midline shift, and embolization extent.

Conclusion: This is the first study using quantitative volumetric analysis to characterize changes in tumor and surrounding edema in preoperatively embolized meningiomas in the immediate postembolization period. In our cohort we did not find any direct correlations between timing to imaging and changes in tumor characteristics. Further investigations with larger cohorts and interval imaging at more and longer time points will be needed to reveal the subacute and long term effects of meningioma embolization.

Publication History

Article published online:
01 February 2023