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.