gms | German Medical Science

Objective: We hypothesized that invasion of the cortex and increased peritumoral edema facilitate seizures in brain-invasive meningiomas.

Methods: Correlations of microscopic brain invasion with tumor and edema volume and pre- and postoperative seizures were analyzed in uni- and multivariate analyses.

Results: Analyzes included 176 patients with 92 grade I (52%), 79 grade II (45%) and 5 grade III (3%) tumors. Brain invasion was found in 38 individuals (22%). Tumors were located at the convexity in 41% (N=72), the falx in 15% (N=26), the skull base in 39% (N=69), in the posterior fossa in 4% (N=7) and intraventricular in 1% (N=2), with median tumor and edema volumes of 13.73ccm (range: .81-162.22ccm) and 1.38ccm (range: .00-355.80ccm), respectively. Brain invasion was strongly correlated with edema volume (p<.001). Thus, mean edema volume was 33.0ccm in non-invasive but 130.7ccm in invasive tumors (p=.008). Incidence of preoperative seizures was independent of patients age, sex and tumor location but 32% (N=12) in invasive vs. 15% (N=21) in non-invasive meningiomas (p=.033). Vice versa, probability of detecting brain invasion was increased in patients with history of preoperative seizures (OR: 2.57, 95%CI 1.13-5.88; p=.025). Rate of preoperative seizures correlated with tumor (p=.049) and edema volume (p=.014), while semiology was found to be independent of brain invasion (p=.211). In multivariate analyses, rising tumor volume (OR: 1.02, p=.042) and brain invasion were identified as independent predictors of preoperative seizures (OR: 5.26, p=.009). 9 patients (5%) developed new seizures after surgery within a median follow-up of 15 months. Development of postoperative epilepsy was independent of all clinical variables including Simpson grade (p=.133), tumor location (0=.936), brain invasion (p=.408) and preoperative edema volume (p=.081), but was correlated with increasing preoperative tumor volume (p=.004). Rates of postoperative seizure-free patients were similar in invasive and non-invasive meningiomas (p=.372).

Conclusion: Brain invasion was identified as a new and strong predictor for pre- but not for postoperative seizures. Although also associated with increased peritumoral edema, seizures in patients with invasive meningiomas might be substantially facilitated by cortical invasion itself. Consideration of seizures in communication between the neurosurgeon and neuropathologist can improve the microscopical detection of brain invasion.