The Simpson grade: abandon the scale but preserve the message

Abstract

The Simpson grading scale, developed in 1957 by Donald Simpson, has been considered the gold standard for defining the surgical extent of resection for WHO grade I 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.

Lateral Ventricular Meningiomas: Clinical Features, Radiological Findings and Long-Term Outcomes

“… 27 However, some scholars believe that the Simpson classification cannot be used as a predictive indicator. 28 Voß K et al proved that Simpson grade is not related to the recurrence of intraventricular meningioma. 29 Due to the uniqueness of lateral ventricle anatomy and improvements at surgical technique, the GTR rate is higher than the other locations.…”

Improved Detection of Postoperative Residual Meningioma with [68Ga]Ga-DOTA-TOC PET Imaging Using a High-resolution Research Tomograph PET Scanner

“…Second, the Simpson grade was not available in all cases and determined on the basis of the surgical reports. Although the majority of procedures were performed by the coauthors (K. Fugleholm and M. Ziebell), the Simpson grading scale is not used consistently by all surgeons at our institution owing to its controversy and the numerous revolutions in imaging, molecular biology, and stereotactic radiotherapy since its introduction in 1957 (1)(2)(3)44). Third, the results were not confirmed directly by biopsy in all cases, but relied on identification of progression on subsequent MRI scans of tumors with variable growth rates (with histologic verification in a subgroup) and PET scans with confirmation of [ 68 Ga]Ga-DOTA-TOC-avid lesions, as the former would neither be medically indicated nor ethical.…”

The applicability of established clinical and histopathological risk factors for tumor recurrence during long-term postoperative care in meningioma patients

“…Despite the limited number of patients in this subcohort, these findings clearly support the thesis of a minor prognostic role of the extent of resection for long-term tumor control in meningioma patients. Within the last years, several studies revealed shortcomings of the Simpson classification system and raised doubts about its prognostic value for the estimation of the risk of postoperative tumor recurrence [22]. Recent series reported a less favorable extent of resection in a considerable portion of meningioma patients comparing the intraoperatively assessed Simpson grade with results from postoperative MRI [26,27].…”

“…As the consequence, the Simpson grading system is frequently applied when indicating adjuvant irradiation therapy or scheduling follow-up intervals. However, recent studies increasingly discuss fundamental shortcomings of the Simpson classification system, including both the assessment by the neurosurgeon and its value for the prediction of prognosis [22]. Moreover, the value of the Simpson grading system for the prediction of long-term tumor control is largely unexplored, and most analyses are restricted to small cohorts and/or patients with tumors in distinct locations [12,17,19,28].…”