Polymicrogyria Related Epilepsy: Heterogeneous Epileptogenicity, 2001-2018

Abstract

Objective: We aimed to study the heterogeneity of epileptogenicity in polymicrogyria (PMG) by analyzing the intracranial electroencephalography (icEEG) ictal onset in relation to PMG as well as the extent of surgical resection. We also compare seizure outcome between the surgical group and the medical management group. Methods: Thirty-five PMG related epilepsy patients (19 – adult, 16 – pediatric, 20 unilateral, 15 bilateral) were studied. Seizure freedom (SF) was defined as Engel class 1A at the last visit. Result: 52% achieved SF in the surgical group ( mean 41 months follow up) whereas none achieved SF in the medical group (mean 39.3 months follow up). Similar to prior literature, our result also suggested that epileptogenicity in PMG is heterogeneous. In the icEEG surgical group, only 17% of the patients achieved SF if ictal onset in icEEG was confined to the PMG region only. 57% and 67% SF were achieved if the icEEG onset was noted from both the PMG and nonPMG region, and only from the nonPMG region, respectively. Thus, one should not focus only on the PMG regions for electrode implantation while developing epilepsy pre-surgical hypotheses in the particular patient population. Conclusion: Surgical treatment seems to be superior to medical treatment in the preselected group of drug-resistant epilepsy patients related to PMG. SF is still plausible even in bilateral or extensive unilateral PMG. In addition, our study suggested that epileptogenicity in PMG is heterogeneous, and thus complete PMG resection does not guarantee SF. Extensive non-invasive and invasive pre-surgical evaluation is warranted, especially in patients with a co-existent functional cortex, for a higher SF chance.