The Simpson Grading: Is It Still Valid in the Imaging Era?

Meningiomas represent the most common primary tumors within the central nervous system, with primary modality of treatment being gross total resection. The Simpson grade, described in 1957, was the first attempt to characterize extent of resection for purposes of prognostication, though discordant recurrence rates have demonstrated that the Simpson grade may not completely characterize meningioma biology. The WHO classification of meningiomas historically included histopathologic features key for prognostication; however, broadening availability of genetic and epigenetic sequencing in the past decade has significantly improved delineation of meningioma recurrence, and is now starting to be included within the WHO classification. In this chapter, we will describe the historic histopathologic classification of meningioma and provide contemporary data detailing key genetic and epigenetic factors found to predict recurrence. In this context, we will discuss the relevance of the Simpson grade in the current management of meningioma with potential avenues for future research.