Grade I—complete microscopic removal of tumor & dural attachment w/ any abnormal bone

Grade II—complete microscopic removal of tumor w/ diathermy coagulation of its dural attachment

Grade IIIA—complete microscopic removal of intra- & extradural tumor w/o resection or coagulation of its dural attachment

Grade IIIB—complete microscopic removal of intradural tumor w/o resection or coagulation of its dural attachment or any of its extradural extensions

Grade IVA—intentional subtotal removal to preserve CNs or blood vessels w/ complete microscopic removal of attachment

Grade IVB—partial removal leaving tumor ≤10% in vol

Grade V—partial removal leaving tumor >10% in vol, or decompression w/ or w/o biopsy

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