The Role of Simpson Grading System in Spinal Meningioma Surgery: Institutional Case Series, Systematic Review and Meta-Analysis

Abstract

Background: Although its validity has recently been questioned since its introduction, the Simpson grade has remained one of the most relevant factors in estimating the recurrence risk of intracranial meningiomas. This study aims to assess its role in spinal meningiomas through a retrospective analysis of a mono-institutional surgical series and literature meta-analysis.

Methods: We conducted a systematic review and meta-analysis of the literature from 1980 to 2023, complemented by a mono-institutional series of 74 patients treated at "Santa Maria delle Grazie" hospital. Demographic, clinical, neuroradiological, pathological, surgical, and outcome data of case series were analyzed. For the meta-analysis, studies were selected based on predefined inclusion criteria, and a fixed-effects model was used to synthesize data due to assumed homogeneity among included studies. Statistical analyses included odds ratios (OR) for recurrence risk and assessment of publication bias using Peter's test.

Results: Mono-institutional sample included 74 patients, most of whom were women (85%) with a median age of 61.9 years. The thoracic spine was the most common tumor location (81%). Recurrences occurred in patients with Simpson grade II and III resections. The meta-analysis involved 2142 patients from 25 studies and revealed a significantly higher recurrence rate for Simpson grades III-V compared to grades I-II (OR 0.10; CI95 0.06-0.16). Additionally, Simpson grade II had a higher recurrence risk than grade I (OR 0.42; CI95 0.20-0.90).

Conclusions: The Simpson grading remains a valid predictor of recurrence also for spinal meningiomas. Our findings revealed a significant increase in recurrence rate with higher Simpson grades. These results support the need to strive for Simpson grade I resection when feasible.

Keywords: intradural extramedullary tumor; meningioma recurrence; meta-analysis; simpson grade; spinal meningioma; systematic review.

Figure 1

Three illustrative cases from our series of 74 spinal meningiomas: left, preoperative T1-weighted MRI scans; right, intraoperative images. (A) T1 transitional meningioma with anterior growth. (B) T7–T8 psammomatous/calcific meningioma with posterolateral extension. (C) T7 fibroblastic meningioma with right lateral extension.

Figure 2

PRISMA flowchart for study selection.

Figure 3

Forest plot comparing Simpson I vs. Simpson II resections. This plot presents a meta-analysis of recurrence rates for patients with Simpson grade I versus Simpson grade II resections. Each study’s odds ratio (OR) and 95% confidence interval (CI) are shown, with the overall OR calculated using a Mantel–Haenszel random-effects model. The pooled OR is 0.42 (95% CI: 0.20–0.90), indicating a statistically significant advantage for Simpson grade I resections in reducing recurrence rates (p < 0.05). The heterogeneity assessment shows no significant variability among studies (I² = 0%), supporting the consistency of effect sizes across studies [1,3,6,8,12,19,20,22,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38].

Figure 4

Forest plot comparing Simpson I and II vs. Simpson III, IV, and V resections. This plot illustrates a meta-analysis comparing recurrence rates for combined Simpson grades I and II versus Simpson grades III, IV, and V resections. Individual study ORs and 95% CIs are provided, with an overall pooled OR of 0.10 (95% CI: 0.06–0.16), suggesting a substantial reduction in recurrence risk for grades I and II compared to grades III, IV, and V (p < 0.01). Significant heterogeneity was detected (I² = 21%), indicating variability in effect sizes across studies [1,6,19,20,21,22,23,24,25,26].