Abstracts

Rationale: Focal cortical dysplasia is one of the common causes for refractory epilepsy requiring epilepsy surgery. Preoperatively delineation of presumed epileptogenic zone is a challenging task and requires multimodal noninvasive and sometimes invasive monitoring.  MEG (Magnetoencephalography) is a noninvasive presurgical tool with high spatial and temporal resolution for localization of interictal discharges. There is inadequate data on the role of MEG in the evaluation of patients with focal cortical dysplasia. This study tried to describe the MEG profile of patients who had histologically confirmed FCD and its the correlation with outcome. Methods: Retrospective review of case records of patients with histopathology of focal cortical dysplasia who underwent epilepsy surgery from 2014-2017 was done. The clinical, MRI, VEEG and other available presurgical details and MEG characteristics were collected. The postoperative seizure outcome was assessed by Engel outcome scale (good- Engel 1a, b, c; poor- Engel 2 or more) with minimum of 12 months follow up. The MEG characteristics were described in the cohort by descriptive statistics. MEG concordance with presumed epileptogenic zone in patients with good and poor outcome was assessed at four levels, i.e., concordant and specific region, concordant and region nonspecific, concordant lateralization only, discordant lateralization. Results: A total of 21 patients were recruited who had histopathology of FCD and a minimum follow up of 12 months postoperatively. M: F (15:6), age range:6-37 yrs, mean duration of epilepsy: 12 years, mean MRI brain findings: normal in 1 and abnormal in 20. MEG: inconclusive-2/21 (95.23 %). Seizure outcome was good in 13/21(61.90%) and poor in 8/21(38.09%) with minimum follow up of 12months postoperatively. MEG concordance between good and poor seizure outcome respectively- concordant and specific region: 0 &1, concordant and region nonspecific: nil, concordant lateralization only:12&6, discordant lateralization: 1&0. Conclusions: MEG characteristics between the two groups (good and poor seizure outcome) were similar. This may be due to small sample size. Future studies with large sample size may provide better evidence for the role of MEG in presurgical evaluation. Funding: No funding