Introduction: Surgical treatment of intractable epilepsy in children is an accepted treatment option in properly selected patients. Seizure outcome is greater when an identifiable epileptic lesion can be identified on pre surgical MR imaging. The purpose of this study was to review our results of the surgical treatment of epilepsy in pediatric patients with normal MR imaging.

Methods: We retrospectively identified patients that had surgery for intractable epilepsy between 2001 and 2011 at the Alberta Children’s Hospital and who had normal MR imaging. The patients’ medical charts were reviewed for demographic data, pre-surgical evaluation [which included any combination of: EEG, Video/EEG, MRI, ictal/interictal SPECT, MEG and neuropsychogical assessment], surgical procedure and pathology. All but 1 patient had invasive monitoring prior to surgery. 5 patients had frontal resection, 4 had temporal resection and 5 had multilobar resection. Seizure outcome was assessed using the Engel Classification.

Results: 16 patients were identified for the study. The average patient age at surgery was 10years (range: 1-17 yrs) and they were followed for 0.5-5 years (mean of 2yrs) post surgery. After the first procedure 39.6% of patients had favorable outcome (Engel Class 1&II). Following additional resections 50.0% of patients had a favorable outcome (Engel Class 1&2), 16.7% had Engel Class 3 and 33.3% had Engel Class 4 outcome. Histopathology of surgical specimens reported 7(46.7%) of the specimen however had no abnormal findings and 9(53.3%) had positive pathology including gliosis, cortical dysplasia and malformation of cortical development. Favorable outcome was correlated with temporal/frontal resections as well as negative pathology.

Conclusions: Surgical treatment of intractable epilepsy in children with normal MR imaging can result in good seizure outcome in up to one half of patients.. While malformations of cortical development can be identified, the majority of surgical specimens exhibit normal or non-specific pathological abnormalities.

Patient Care: We hope to show surgery has a significant benefit in the setting of refractory epilepsy.

Learning Objectives: 1) Investigating postsurgical seizure outcome in children with intractable epilepsy with normal pre-surgical MR imaging findings. 2) What factors influence the outcome of patients with non-lesional epilepsy after surgical treatment. Factors such as the type pathology, time between age of onset and surgery, the use of either non-invasive or invasive evaluations to localize the seizure foci preoperatively can be valuable to outcomes.

References: 1. Fisher RS, van Emde Boas W, Blume W, Elger C, Genton P, Lee P, Engel J, Jr.: Epileptic seizures and epilepsy: Definitions proposed by the international league against epilepsy (ilae) and the international bureau for epilepsy (ibe). Epilepsia 2005;46:470-472. 2. Forsgren L, Beghi E, Oun A, Sillanpaa M: The epidemiology of epilepsy in europe - a systematic review. Eur J Neurol 2005;12:245-253.