Survival implications of postoperative restricted diffusion in high-grade glioma and limitations of intraoperative MRI detection.

Purpose: Here we assess whether the volume of cerebral ischemia induced during glioma surgery may negatively impact survival independently of neurological function. We also evaluate the sensitivity of intraoperative MRI (iMRI) in detecting cerebral ischemia during surgery.

Methods: We retrospectively reviewed 361 cranial surgeries that used a 3 Tesla iMRI. 165 patients met all inclusion criteria and were included in the final analysis. Diffusion weighted imaging (DWI) obtained during iMRI was compared to postoperative DWI obtained within 7 days of the operation in cases where no further resection occurred after the iMRI.

Results: 42 of 165 patients (25%) showed at least some evidence of restricted diffusion on postoperative (poMRI). 37 of these 42 (88%) cases lacked evidence of restricted diffusion on iMRI, meaning iMRI had a false-negative rate of 88% and a sensitivity of 12% in assessing the extent of ischemic brain after surgery. In high-grade gliomas, the volume of restricted diffusion on poMRI was predictive of overall survival, independent of new functional deficits acquired during surgery (p = 0.011).

Conclusion: This study presents the largest case series to date analyzing the sensitivity of iMRI in detecting surgical ischemia. In high-grade gliomas, increased volume of ischemia correlated with worsening median overall survival (OS) irrespective of postoperative neurologic deficits. Future work will focus on improving intraoperative detection of ischemia during the hyperacute phase when interventions such as blood pressure modulation or direct application of vasodilator agents may be effective.