Abstracts

Rationale: Children with refractory epilepsy due to early brain lesions may have seizure free outcome after epilepsy surgery, despite generalized or bilateral interictal epileptiform abnormalities. The goal of our study was to explore the predictive value of seizure semiology for surgical outcome in such patients. Methods: From a previously published cohort of 50 children in whom 30-100% of the preoperative interictal epileptiform abnormalities were generalized or contralateral to the side of surgery, 26 patients in whom videos were available for review formed the study group. Another cohort of 26 children in whom the interictal EEG abnormalities were predominantly ipsilateral to the side of surgery formed the control group. The control group was closely matched for age at surgery (median 8 years), MRI abnormality (predominantly cortical malformation or encephalomalacia), and type of surgery. Two independent blinded observers reviewed archived seizure videos to classify seizure type and to identify lateralizing signs. Seizure semiology and outcome were compared between the groups. Results: 379 seizures (194 in study group and 185 in controls) were reviewed. 50% of children in study group and 80% in controls had only focal seizures; 42% of children in study group and 12% of controls had generalized and focal seizure types (p-0.02); 2 (8%) in each group had generalized seizure types only. Lateralizing signs concordant to the side of surgery were seen in 22 (85%) study patients and 14 (54%) controls (p-0.01). Discordant (to the side of surgery) lateralizing signs including clonic or tonic features involving face or limbs, head version and asymmetric spasm were seen in 12 study patients (46%) and 4 controls (15%) (p-0.03). At a median follow up of 21 months, in study group (versus controls), 62% (versus 73%) were seizure free, 23% (versus 8%) had major improvement, and 15% (versus 19%) had no improvement. Post operative seizure freedom was not significantly different between the groups. In patients with only focal seizures, 9/13 study patients (69%) and 15/21 controls (71%) were seizure free. In patients with generalized seizures with or without focal seizures, 7/13 (54%) study patients and 4/5 (80%) controls were seizure free. In patients with concordant lateralizing signs, 8/12 study patients and 7/10 controls were seizure free. In patients with discordant signs, seizure free outcome was obtained for 7/12 study patients (58%) and 3/4 controls (75%). In the study group, seizure free outcome tended to be less frequent among children with generalized seizures or discordant signs, but the difference was not significant. Conclusions: Selected patients with early brain lesions may benefit from epilepsy surgery despite generalized clinical seizures or discordant lateralizing signs, with or without generalized EEG findings. In these complicated cases, surgical strategy is based on a global assessment of the MRI lesion, side of hemiparesis and other features, in addition to EEG and seizure semiology.