Foramen Magnum Meningiomas: Results of Surgical Management and Risks Predicting Poor Outcomes Based on a Modified Classification

Objectives: The study aimed to evaluate neurological functional and recurrence outcome of foramen magnum meningioma (FMM) based on a modified classification.

Methods: This study included 185 consecutive cases of FMMs (124 females, 67.0%). We classified the FMMs into 4 types according to the previous classification of Bruneau and George as follows: Type A (n = 49, 26.5%), the dural attachment of lesion grew below the VA; Type B (n = 39, 21.1%), the dural attachment of lesion grew above the VA; Type C1 (n = 84, 45.4%), VA courses across the lesion with or without VA encasement; and Type C2 (n = 13, 7.0%), that was defined as Type C1 plus partial/total encasement of VA and extradural growth via dural penetration of VA.

Results: The mean age on admission was 49.4 years, the mean of preoperative KPS was 78.1, and the mean size was 3.3 cm. Type C2 lesions inherently harbored significantly larger size (p = 0.001), higher percentage of ventrolateral location (p = 0.009) and VA encasement (p < 0.001), lower rate of GTR (p < 0.001), and more time-consumption (p = 0.015) compared with other types. GTR and STR were achieved in 154 (83.2%) and 31 (16.8%), respectively. Type A lesions suffered lower surgical morbidity rate than other types. After a mean follow-up duration of 103.8 months (6.2–268.2 months), most recent follow-up was obtained in 163 patients (88.1%). Progression/recurrence (P/R) was observed in 13 patients (7.2%). Multivariate Cox proportional hazard regression model demonstrated type C2 (hazard ratio [HR] 3.94, 95% confidence interval [CI] 1.04–15.0, p = 0.044), non-total resection (HR 6.30, 95%CI 1.91–20.8, p = 0.003), and pathological mitosis (HR 7.11, 95%CI 1.96–25.8, p = 0.003) as independent adverse predictors for tumor P/R. Mean of follow-up KPS was 80.6. Compared with preoperative status, recent neurological status was improved in 91 (49.2%), stabilized in 76 (41.1%), and worsened in 18 (9.7%) patients. Multivariate Logistic regression analysis identified age (per 1 year increase)(OR 1.08, 95%CI 1.03–1.14, p = 0.004), male gender (OR 2.95, 95%CI 1.04–8.38, p = 0.042), preoperative KPS (per 10 point decrease) (OR 3.39, 95%CI 1.99–5.75, p < 0.001), non-total resection (OR 4.06, 95%CI 1.16–14.2, p = 0.029), and pathological mitosis (OR 6.29, 95%CI 1.47–27.0, p = 0.013) as independent risk for poor outcome (KPS<80).

Conclusions: The modified classification was useful in predicting surgical outcome and recurrence. Preoperative radiologic films and neurological function should be reviewed carefully to establish individualized management strategy to improve long-term outcome.