Simpson Grading System

The Simpson grading scale 1), developed in 1957 by Donald Simpson, has been considered the gold standard for defining the surgical extent of resection World Health Organization grade 1 meningiomas. Since its introduction, the scale and its modifications have generated enormous controversy. The Simpson grade is based on an intraoperative visual assessment of resection, which is subjective and notoriously inaccurate. The majority of studies in which the grading system was used were performed before routine postoperative MRI surveillance was employed, rendering assessments of extent of resection and the definition of recurrence inconsistent. The infiltration and proliferation potential of tumor components such as hyperostotic bone and dural tail vary widely based on tumor location, as does the molecular biology of the tumor, rendering a universal scale for all meningiomas unfeasible. While extent of resection is clearly important at reducing recurrence rates, achieving the highest Simpson grade resection should not always be the goal of surgery.Donald Simpson's name and his scale deserve to be recognized and preserved in the historical pantheon of pioneering and transformative neurosurgical concepts. Nevertheless, his eponymous scale is no longer relevant in modern meningioma surgery. While his message of maximizing extent of resection and minimizing morbidity is still germane, a single measure using subjective criteria cannot be applied universally to all meningiomas, regardless of location. Meningioma surgery should be performed with the goal of achieving maximal safe resection, ideally guided by molecularly tagged fluorescent labeling and assessed using objective criteria, including postoperative MRI as well as molecularly tagged scans such as 68Ga-DOTATATE PET 2).

Simpson Grading System for removal of meningiomas.

Simpson Grading System 1.


Macroscopically complete removal of tumour and its visible extensions with coagulation of its dural attachment.


Macroscopically complete removal of the intradural tumour, without resection or coagulation of its dural attachment or its extradural extensions.


Partial removal, leaving intradural tumour in situ.


Simple decompression, with or without biopsy 3),

The clinical significance of the Simpson grading system of extent of meningioma resection and its role as a predictor for recurrence of World Health Organization grade 1 meningiomas has been questioned in the past, as microsurgery and knowledge of pathological details have advanced.

The relevance of Simpson grading system grade I and II resection as a sole predictor of recurrence in meningiomas surgery was diminished in the work of Sughrue et al. 4).

When histological grade is fixed, Simpson's grading system is the prime predictor for recurrence of meningioma after resection. Grade 0-I resection is also beneficial to cut off anti-epileptic medication in patients with convexity meningiomas. Although complete tumor resection (grade 0-I) is the goal, surgical approach should be tailored to each patient depending on the risks and surgical morbidity 5).

A Simpson Grade II rather than Grade I resection more than doubled the risk of recurrence at 10 years in the overall series (18.8% vs 8.5%). The impact of aggressive resections was much stronger in higher grade meningiomas.

A policy of maximal safe resections for meningiomas prolongs progression free survival (PFS) and is not associated with increased morbidity 6).

1) , 3)
SIMPSON D. The recurrence of intracranial meningiomas after surgical treatment. J Neurol Neurosurg Psychiatry. 1957 Feb;20(1):22-39. doi: 10.1136/jnnp.20.1.22. PMID: 13406590; PMCID: PMC497230.
Schwartz TH, McDermott MW. The Simpson grade: abandon the scale but preserve the message. J Neurosurg. 2020 Oct 9:1-8. doi: 10.3171/2020.6.JNS201904. Epub ahead of print. PMID: 33035995.
Sughrue ME, Kane AJ, Shangari G, Rutkowski MJ, McDermott MW, Berger MS, et al. The relevance of Simpson Grade I and II resection in modern neurosurgical treatment of World Health Organization Grade I meningiomas. J Neurosurg. 2010;113:1029–35.
Nanda A, Bir SC, Konar S, Maiti TK, Bollam P. World Health Organization Grade I Convexity Meningiomas: Study on Outcomes, Complications and Recurrence Rates. World Neurosurg. 2015 Dec 15. pii: S1878-8750(15)01651-4. doi: 10.1016/j.wneu.2015.11.050. [Epub ahead of print] PubMed PMID: 26704204.
Gousias K, Schramm J, Simon M. The Simpson grading revisited: aggressive surgery and its place in modern meningioma management. J Neurosurg. 2016 Sep;125(3):551-60. doi: 10.3171/2015.9.JNS15754. Epub 2016 Jan 29. PubMed PMID: 26824369.
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