Simpson's Grading Scale for WHO Grade I Meningioma Resection in the Modern Neurosurgical Era: Are We Really Asking the Right Question?

Abstract

The Simpson grading scale for the classification of the extent of meningioma resection provided a tremendous movement forward in 1957 suggesting increasing the extent of resection improves recurrence rates. However, equal, if not greater, movements forward have been made in the neurosurgical community over the last half a century owing to improvements in neuroimaging capabilities, microsurgical techniques, and radiotherapeutic strategies. Sughrue et al proposed the idea that these advancements have altered what a "recurrence" and "subtotal resection" truly means in modern neurosurgery compared with Simpson's era, and that a mandated use of the Simpson Scale is likely less clinically relevant today. A subsequent period of debate ensued in the literature which sought to re-examine the clinical value of using the Simpson Scale in modern neurosurgery. While a large body of evidence has recently been provided, these data generally continue to support the clinical importance of gross tumor resection as well as the value of adjuvant radiation therapy and the importance of recently updated World Health Organization classifications. However, there remains a negligible interval benefit in performing overly aggressive surgery and heroic maneuvers to remove the last bit of tumor, dura, and/or bone just for the simple act of achieving a lower Simpson score. Ultimately, meningioma surgery may be better contextualized as a continuous set of weighted risk-benefit decisions throughout the entire operation.

Keywords: Simpson Scale; gross total resection; meningiomas; neuroimaging; neurosurgery; recurrence; subtotal resection.

Fig. 1

Superimposed trend of the discussions on the Simpson grading scale for WHO grade I meningiomas following the Sughrue et al publication in 2010. Solid blue lines represent approximate publication counts of the Simpson Scale for WHO grade I meningiomas captured from a PubMed search utilizing the string (“meningioma” AND “simpson” AND “grade 1”). Dotted blue lines represent a 2-year moving average of solid blue line reference counts. Solid orange lines represent citations of the Sughrue et al's paper starting with its introduction.

Fig. 2

Kaplan–Meier curves demonstrating recurrence-free survival rates of patients with WHO grade I meningiomas: ( A ) recurrence-free survival for all patients according to Simpson grades I–IV resection. ( B ) Recurrence-free survival for patients with more than 4 years of postoperative follow-up ( n  = 126) according to Simpson grades I ( n  = 24), II ( n  = 37), III ( n  = 19), IV ( n  = 46). No statistically significant difference was noted between Simpson grades in both figures. Figures taken from Sughrue et al, published in the Journal of Neurosurgery , Volume 113, “The relevance of Simpson grade I and II resection in modern neurosurgical treatment of World Health Organization Grade I meningiomas,” pp. 1029–35, with permission from the Journal of Neurosurgery .

Fig. 3

Kaplan–Meier curves demonstrating recurrence-free survival rates according to tumor location for patients with WHO grade I meningiomas: ( A ) patients with convexity meningiomas ( n  = 77) undergoing Simpson grade I–IV resections. ( B ) Patients with falcine or parasagittal meningiomas ( n  = 58) undergoing Simpson grade I–IV resections. ( C ) Patients with skull base meningiomas ( n  = 189) undergoing Simpson grade I–IV resections. No statistically significant difference was noted between Simpson grades in any location. Figures taken from Sughrue et al, published in the Journal of Neurosurgery , Volume 113, “The relevance of Simpson grade I and II resection in modern neurosurgical treatment of World Health Organization Grade Imeningiomas,” pp. 1029–35, with permission from the Journal of Neurosurgery .