The relevance of Simpson grade I and II resection in modern neurosurgical treatment of World Health Organization grade I meningiomas

Object. In 1957, Simpson published a seminal paper defining the risk factors for recurrence following surgical treatment of intracranial meningiomas. Given that Simpson's study was published more than 50 years ago, preceding image guidance technology and MR imaging, the authors reviewed their own experience with surgical treatment of Grade I meningiomas to determine if Simpson's grading scale is still relevant to modern neurosurgical practice. Methods. From this cohort, the authors evaluated all patients undergoing craniotomy for resection of a histologically proven WHO Grade I meningioma as their initial therapy. Clinical information was retrospectively reconstructed using patient medical records and radiological data. Recurrence analysis was performed using the Kaplan-Meier method. Results. The 5-year recurrence/progression-free survival for all patients receiving a Simpson Grade I, II, III, or IV resection was 95, 85, 88, and 81%, respectively (p = not significant, log-rank test). Kaplan-Meier analysis revealed no significant difference in recurrence-free survival between patients receiving a Simpson Grade I, II, III, or IV resection. Analysis limited to meningiomas arising from the skull base (excluding the cavernous sinus) similarly found no significant benefit to Simpson Grade I or II resection, and the survival curves were nearly superimposed. Conclusions. 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.