The Simpson grade of meningioma resection was described in 1957 and correlated the degree of surgical resection completeness with symptomatic recurrence 1.
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grade I
- complete removal including resection of the underlying bone and associated dura
- 9% symptomatic recurrence at 10 years
-
grade II
- complete removal and coagulation of dural attachment
- 19% symptomatic recurrence at 10 years
-
grade III
- complete removal without resection of dura or coagulation
- 29% symptomatic recurrence at 10 years
-
grade IV
- subtotal resection
- 44% symptomatic recurrence at 10 years
-
grade V
- simple decompression with or without biopsy
- 100% symptomatic recurrence at 10 years (small sample in the original paper)
Validation
In the conception of the Simpson grade, it was unclear whether meningiomas were surgically curable tumors, and the grade was created based on the assumption that there is a direct correlation between the degree of resection and recurrence of the tumor 2.
The advent of routine post-operative MRI, molecular classifications of meningiomas, and improvements in surgical techniques have put the validity of the Simpson grading into debate 2. Several recent studies found no difference in recurrence in Simpson grade I-III resections, and there also appears to be variability in recurrence within Simpson grade IV resections 3-4. The location of the tumor (convexity vs skull base vs others) also appears to influence the validity of the Simpson grade 5.
Several other grading systems have been proposed, including the MEGA (Meningioma Group Amsterdam Grading System of Meningioma Removal Based on Postoperative Magnetic Resonance Imaging) scale and the Okudesa-Kobayashi grade; however, these have not been widely validated 6,7.
History and etymology
The Simpson grade was described in 1957 by Australian neurosurgeon Donald Simpson (1927-2017) while he worked at the Royal Adelaide Hospital.