The Simpson’s Grading Scale Continues to Hold Strong Prognostic Value in Modern Meningioma Surgery: 10-Year Single-Institution Experience

Background: Over the past 10 years, the relevance of the Simpson’s resection grading scale has been called into question in modern meningioma surgery. We have continued to pursue Simpson’s grade I resection when safe and possible over this time period. Considering this surgical strategy, we aimed to analyze the relationship between Simpson’s resection grade and meningioma recurrence in our institutional experience.

Methods: This is a retrospective review of all patients who underwent surgical resection of a WHO grade I intracranial meningioma at our institution from 2008 to 2017. Tumor recurrence was defined by radiographic growth on serial MRI in comparison to the immediate postoperative MRI. Logistic regression analysis was utilized to assess predictors of Simpson’s grade IV resection. Kaplan–Meier analysis and Log-Rank tests were utilized to assess and compare progression-free survival (PFS) of Simpson’s resection grades, respectively.

Results: A total of 498 patients with evaluable data were included for analysis, including 398 females (79.9%) and 100 males (20.1%) with a mean age of 58.7 ± 12.9 years. The tumors were most commonly located at the skull base (n = 307; 61.6%) or the convexity (n = 132; 26.5%), and the mean tumor volume was 13.8 ± 19.5 cm³. Ninety-seven tumors (19.5%) invaded into a major dural sinus, and 50 tumors (10%) encased the internal cerebral, middle cerebral, or basilar artery. Simpson’s grade I, II, III, or IV resections was achieved in 106 (21.3%), 154 (30.9%), 50 (10%), and 188 (37.8%) patients, respectively. In multivariate analysis, larger tumor volume (p = 0.04), sinus invasion (p < 0.01), and higher preoperative mRS score (p = 0.01) predicted Simpson’s grade IV resection. Tumor recurrence occurred in 60 patients (12%) at a mean duration of 41.4 ± 33 months from surgery. Simpson’s grade I resection resulted in superior PFS compared with both Simpson’s grade II (p = 0.02) and grade III resections (p < 0.01). Simpson’s grade I to III resections resulted in superior PFS compared with Simpson’s grade IV resection (p < 0.01).

Conclusion: In this large, single-institution experience of WHO grade I intracranial meningioma resection, there was a strong correlation between Simpson’s resection grade and tumor recurrence. Simpson’s grade I resection resulted in superior PFS to both Simpson’s grade II and III resection, and, when safe, should remain the goal of intracranial meningioma surgery. The Simpson’s resection grading scale continues to hold strong prognostic value in the modern neurosurgical era.