In this study of a cohort of patients undergoing surgery for WHO Grade I meningiomas, the authors demonstrate that the benefit of more aggressive attempts to resect the tumor with dura and underlying bone was negligible compared with simply removing the entire tumor, or even leaving small amounts of tumor attached to critical structures. The authors believe that these data reflect an evolution in the nature of meningioma surgery over the past 2 decades, and bring into question the relevance of using Simpson's grading system as the sole predictor of recurrence.

Background Grade II and III meningiomas have higher rates of tumor recurrence than grade I meningiomas after surgery and/or external irradiation. As the utility of non-invasive treatments for brain tumors increases, it is becoming increasingly important to assess the likelihood that a tumor is not benign before treatment initiation. Hence, we have reviewed a large-series of our patients to determine risk-factors for higher-grade pathology with particular interest paid towards tumor location. Methods We reviewed 378 patients presenting to our institution from 2000 to 2007 with: histologically confirmed meningioma, central pathology grading according to the WHO 2000 guidelines, and tumor location confirmed with preoperative imaging. We performed univariate and multivariate logistic regression on potential risk-factors for high-grade pathology. Results Risk-factors for grade II/III pathology included non-skull base location (twofold) and male gender (two-fold). Patients with prior surgery had a three-fold increased incidence of higher-grade meningiomas at presentation to our center. We controlled for this referral bias by performing a multivariate regression, and analysis without patients receiving prior treatment. 97% of operations were performed for tumor size and clinical symptoms, while less than 3% for interval growth or features concerning of higher-grade pathology. Conclusion Non-skull-base meningiomas, male gender, and prior surgery impart increased risk for grade II or III pathology. This increased risk translates to probable poorer prognosis and increased likelihood of recurrence after treatment. Thus, it is prudent to take these specific variables into consideration in conjunction with the complete clinical presentation when advising patients regarding their prognosis.

Abbreviations used in this paper: EBRT = external-beam radiation therapy; GTR = gross-total resection; KPS = Karnofsky Performance Scale; NS = not significant; NTR = near-total resection; SRS = stereotactic radiosurgery; UCSF = University of California at San Francisco.See the corresponding editorial in this issue, pp 199-201.

Importantly, these data provide a more modern estimate of the expected outcomes that can be obtained with treatment of these tumors, in which a combination of image guidance, advanced microsurgical tools, and conformal radiation treatments is used.

Object. Although meningiomas are commonly found along the supratentorial convexity, the risk profile associated with this subset of lesions in the modern neurosurgical era is unknown.Methods. The authors retrospectively reviewed the clinical course of patients with supratentorial convexity meningiomas treated during the past 10 years. All patients had undergone MR imaging within 72 hours after surgery and at least 1 year of clinical follow-up. Patients with multiple meningiomas, hemangiopericytomas, malignant meningiomas, or tumor-prone syndromes were excluded from analysis.Results. Between 1997 and 2007, 141 consecutive patients (median age 48 years, range 18-95 years) underwent resection of a supratentorial convexity meningioma. The most common signs or symptoms at presentation were headache (48%), seizures (34%), and weakness (21%). The mean tumor volume was 146.3 cm 3 (range 1-512 cm 3). There were no intraoperative complications or deaths. Medical or neurosurgical morbidity was noted in the postoperative course of 14 patients, equating to a 10% overall complication rate. Postoperative surgical complications included hematoma requiring evacuation, CSF leakage, and operative site infection. Medical complications included pulmonary embolus and deep vein thrombosis requiring treatment. A Simpson Grade 0 or 1 resection was achieved in 122 patients (87%). One hundred six tumors (75%) were WHO Grade I, whereas 35 (25%) were WHO Grade II. The median clinical follow-up was 2.9 years (range 1-10 years), and the median radiographic follow-up was 3.7 years (range 1-10 years). Six patients (4%) had radiographic evidence of tumor recurrence, with 3 (2%) undergoing repeat resection.Conclusions. With the conservative recommendations for surgery for asymptomatic meningiomas and the advent of radiosurgery during the past 10 years, microsurgically treated convexity meningiomas are now typically large in size. Nevertheless, the patient's clinical course following microsurgical removal of these lesions is expected to be uncomplicated. The authors' findings provide a defined risk profile associated with the resection of supratentorial convexity meningiomas in the modern neurosurgical era.