Abstracts

Rationale: Drug resistant epilepsy (DRE) is common in pediatric population affecting up to one third of individuals with epilepsy1. Several factors play a role in delaying epilepsy surgery evaluation in some of these drug resistance patients; including non-lesional cases, genetic etiologies, multifocal or diffuse structural abnormalities whether inherited or acquired. Through our case series we aimed to analyze the role of stereo- encephalography (SEEG) in patients with broad epileptogenic networks or with multifocal ictal onset zones.

Methods: Retrospective chart review was performed to obtain electroclinical information to assess the efficacy and safety of SEEG in 13 patients with multifocal DRE. 13 patients were reviewed. One patient was excluded due to loss to follow up.

Results: The mean age of seizure onset was 5.03 and the mean age at SEEG was 11.05 years. MRI lesions were identified in 5 out of 12 patients, among them 2 patients had neonatal stroke and 3 had malformation of cortical development. Seizure types for 75% of patients were focal motor with impaired awareness and 25% patients had generalized types of seizure with atonic seizures, myoclonic seizures and spasms. Two patients had also developed epileptic encephalopathy with spike wave activation in sleep syndrome. Scalp EEG showed a multifocal hemispheric discharge in 5 patients, mixed focal and generalized discharges in 5 and generalized discharges in 2 patient. SEEG was pursued based on hypothesis after a detailed review of scalp EEG, clinical and radiographic data. SEEG implantation scheme was bilateral in 7/12 patients with a median of 12 depth electrodes. SEEG showed multi-lobar onset or broad ictal onset zones in all patients. Different palliative surgical interventions were performed in 9/12 patients, including broader resection (7), radiofrequency ablation (1) and neurostimulation with implantation of VNS (2). 22% (2/9) patients were seizure free with Engel I outcome, 44.4 % (4/9) patients had Engel II outcome, and 33.3% (3/9) had Engel IV outcome, up to 1 year post-intervention. Out of 7 patients who underwent broader resection, 29% had Engel I outcome, and 42% had Engel II outcome. The patient who underwent RF ablation had Engel IV outcome. 3 patients had no intervention, of those 2 had Engel IV outcome. None of the patients had any postoperative functional deficit.

Conclusions: There remains hesitancy in pursuing epilepsy surgery in children with features of focal epilepsy with diffuse networks or developmental and epileptic encephalopathies. SEEG is a safe way to study the three-dimensional organization of epileptogenic zone in multifocal DRE pediatric epilepsy. In patients with a multilobar ictal onset zones recorded on SEEG, palliative surgical interventions could be pursued without any harm, rendering greater than 50% seizure improvement. Further studies are needed to help with meticulous surgical evaluation of patients with multifocal DRE to offer the best outcomes.

Funding: None