Meningioma seizures and oedema

Meningiomas are common dural based tumours that are associated with oedema and epilepsy. Meningiomas are heterogenous and the mechanisms that underpin oedema and epilepsy are complex and poorly understood. Furthermore, the strength and nature of this association is uncertain.
A systematic review of 51 studies was performed which identified oedema to be a key prognostic factor for preoperative seizure (k = 28, n = 7,725, OR 3.5, 95% CI = 3.1-4.0, I2 = 0%, p < .001). An additional adjusted analysis for preoperative seizures was also significant (k = 3, n = 2,241, OR 3.9, CI = 2.4–6.3, I2 = 0%, p = .007). There is a weaker association with early postoperative seizure (k = 9, n = 2,929, OR 1.5, CI = 1.1–1.9, I2 = 0%, p = .011). There is an association between preoperative oedema and late postoperative seizure (k = 9, n = 2,150, OR 1.9, CI = 1.5–2.2, I2 = 0%, p < .001). The literature is limited to surgical populations and a lack of focus on oedema volumes and seizure outcomes.
A retrospective observational study explored the relationship between oedema and seizures further. Presence of oedema (not oedema volume) was a significant predictor of seizure (in conservative or pre-treatment meningioma) in multivariable testing (n = 400, OR 7.3, CI= 2.7-79.7, p<.001). Oedema (not volume) was associated with late postoperative seizure in univariable testing (n = 158, OR 5.5, CI= 1.6-19.1, p=.007) but non-significant on multivariable testing. There was no association between oedema and early post-operative seizure or late post-radiotherapy seizure. Oedema was not predictive of anti-seizure medication use or of seizure freedom at last follow up.
Oedema is a key risk factor for developing seizures, especially prior to treatment, but it does not signal adverse seizure outcomes. Oedema is unlikely to be epileptogenic, but could signal increased seizure risk through other factors, such as tumour location and parenchymal disruption. The role of tumour growth rate and cytogenetic profiling remains to be explored.