De Novo Skull Base Atypical Meningioma: Incidence and Outcome.

 Atypical meningiomas are uncommon in skull base practice and present a management challenge. We aimed to review all de novo atypical skull base meningioma cases within a single unit to analyze presentation and outcome.  A retrospective review of all patients undergoing surgery for intracranial meningioma identified consecutive cases of de novo atypical skull base meningioma. Electronic case records were analyzed for patient demographics, tumor location and size, extent of resection, and outcome. Tumor grading is based on the 2016 WHO criteria.  Eighteen patients with de novo atypical skull base meningiomas were identified. The most common tumor location was the sphenoid wing in 10 patients (56%). Gross total resection (GTR) was achieved in 13 patients (72%) and subtotal resection (STR) in 5 patients (28%). There was no tumor recurrence recorded in patients who had undergone GTR. Patients with tumors >6 cm were more likely to undergo a STR as opposed to a GTR (  < 0.01). Patients who had undergone a STR were more likely to have postoperative tumor progression and be referred for radiotherapy (  = 0.02 and <0.01, respectively). On multiple regression analysis, tumor size is the only significant factor correlating with overall survival (  = 0.048).  The incidence of de novo atypical skull base meningioma is higher in our series than currently published data. Tumor size was a significant indicator for patient outcome and extent of resection. Those undergoing a STR were more likely to have tumor recurrence. Multicenter studies of skull base meningiomas with associated molecular genetics are needed to guide management.