Re-Evaluating Simpson Grade I, II, and III Resections in Neurosurgical Treatment of World Health Organization Grade I Meningiomas

Background Since 1957, the Simpson grading system has been considered a predictive system for meningioma recurrence. However, since then, surgical equipment and neurosurgical technique have developed extensively, so this grading system should be re-evaluated. This study aims to assess if the recurrence rate and recurrence-free survival (RFS) are different after Simpson grade I, II, and III resections in World Health Organization (WHO) grade I meningiomas. Methods We retrospectively reviewed the data of patients who underwent surgical treatment of WHO grade I meningiomas located in the convexity (group 1), falx/parasagittal (group 2), skull base, and tentorium (group 3) between June 1991 and December 2011. We compared the recurrence rates and RFSs between Simpson grade I, II, and III resections in both overall cases and tumor subsets according to their localization. Results A total of 224 meningiomas were included in this study. There were no significant differences in recurrence rates and RFSs between Simpson grades I, II, and III. In each of the location groups, no significant differences were noted between the different degrees of Simpson. Conclusions We have shown that complete resection of WHO grade I meningiomas achieves excellent tumor control, regardless of Simpson grades. More aggressive attempts at tumor resection (ie, Simpson grade I) must be balanced against the risks of removing dura or damaging critical neurovascular structures.