We retrospectively reviewed all imaging data and reports from our patients for the extent of the resection, the evidence of post-operative ischemia, defined by hyperintense area in diffusion weighted images (DWI, b1000) with hypointensities within spatially matched apparent diffusion coefficient (ADC) maps, and for the pattern of recurrence. We defined gross total resection (GTR) as resection of at least 99% of the contrast enhancing tumor. Subtotal resection was defined as evidence of contrast enhancing tumor after resection while resection of less than 20% of the tumor mass were defined as biopsy. Progression was defined according to the RANO-HGG criteria .