MKI67 and Atypical Meningioma: Ki-67 LI provides insight into the proliferative nature of tumors, and while it has been used as a prognostic factor for postoperative recurrence in atypical meningiomas [13, 27, 28, 30, 31], few studies have evaluated Ki-67 LI as a prognosticator for atypical meningioma SRS outcomes.