10219- NI-18 FUNCTIONAL RESECTION BOUNDARY INDICATED BY THE T2-FLAIR MISMATCH SIGN IN IDH-MUTANT GLIOMAS

Abstract INTRODUCTION In IDH-mutant gliomas, the T2-FLAIR mismatch sign is a characteristic imaging marker suggestive of astrocytoma. Recently, it has been reported that IDH-mutant astrocytoma showing this feature have a good prognosis; however, the reason for this is still unclear. In this study, we investigated factors associated with gross-total resection of IDH-mutant gliomas in which awake surgery was performed, and validated the characteristics obtained from T2-FLAIR mismatch sign with results of functional mapping. METHODS From 2014 to 2023, 60 patients who underwent awake surgery and were diagnosed with IDH-mutant gliomas (WHO grade 2-3; 22 astrocytoma and 38 oligodendroglioma) were included in this study. T2-FLAIR mismatch sign, gross-total resection (GTR), and the following background factors that might have effects on the extent of resection in previous reports were extracted; primary or recurrent tumor, existence of positive functional mapping on the resection boundary of white matter, laterality and localization of the lesion, histopathological diagnosis, and WHO grading. First, statistical analysis of the relationship between GTR, T2-FLAIR mismatch sign, and background factors was performed using stepwise regression analysis. Second, neuroimaging analysis was performed to determine the spatial relationship between lesions and white matter mapping in cases with T2-FLAIR mismatch sign. RESULTS Twenty-six cases had no residual lesion after surgery, nine of which had T2-FLAIR mismatch sign and were diagnosed with astrocytoma. Analysis of GTR and background factors showed that T2-FLAIR mismatch sign (p=0.0043), no positive white matter mapping (p=0.0059), and WHO grade 2 (p=0.0182) were statistically significant factors that contributed to GTR. Furthermore, in 7 of the 9 cases with T2-FLAIR mismatch sign, GTR on postoperative neuroimaging was obtained with positive mappings on the normal white matter as the resection boundary. CONCLUSION IDH-mutant gliomas with T2-FLAIR mismatch sign may achieve GTR by awake surgery due to the absence of functional regions within the tumor.