Abstracts

Rationale: Polymicrogyria (PMG) is one of the most common malformations of cortical development. Epilepsy affects up to 75% of patients with PMG and can often be medically refractory. A subset of these patients with drug-resistant epilepsy may benefit from epilepsy-surgery. To date, there are few published series describing epilepsy surgery outcomes in children with PMG. Furthermore, there is limited data regarding seizure outcomes in those who undergo complete versus partial PMG resection. We aimed to describe the seizure outcomes in children with PMG who underwent epilepsy surgery at our center. Methods: Consecutive children with unilateral PMG (based on radiological and/or pathological findings) and epilepsy who underwent epilepsy surgery at our institution from January 2002 – May 2017 were enrolled. Records were reviewed for patient demographics, clinical features, investigations, surgical intervention and clinical outcomes.   Results: A total of 12 children (67% boys) with PMG underwent epilepsy surgery. The mean age at surgery was 8.9 years (Standard deviation [SD] 4.3). The median duration of epilepsy at the time of surgery was 6 years (SD 2.8). Eight children (67%) had global developmental delay. The median number of anti-epileptics at the time of surgery was 2 (Inter-Quartile Range [IQR] 2-3). Eight children had magnetoencephalography (MEG) and 6 had MRI concordant MEG dipole clusters. Five children (42%) underwent invasive EEG monitoring using subdural grid electrodes. Five children had functional hemispherectomy, and seven children had lesionectomy: 2 had complete PMG lesion resection and 5 had partial PMG resection. The median duration of follow up was 2.1 years after surgery (IQR 0.9 – 3.7 years). Nine children had an ILAE class 1 seizure outcome (4 with hemispherectomy, 3 with partial resections, 2 complete resections), 2 had a class 5 outcome (2 partial resections) and 1 had a class 4 outcome (1 hemispherectomy) at last follow up. In children who underwent partial resection, 4/5 (80%) had MEG dipole clusters, and these were included within resection margins (2 had class 1 & 2 class 5 outcome).  Conclusions: All children with PMG had medically refractory epilepsy and most were globally delayed. Those who underwent complete resection or hemispherectomy had favourable seizure outcomes. Subtotal resection may still be successful in a subset of patients. The presence of ictal invasive EEG data, MEG cluster and the risk of creating/worsening neurologic functional deficits may influence the final surgical resection. Larger studies are needed to further improve the seizure outcomes in children with PMG. Funding: None