EEG and Neuroimaging Studies in Young Children Having Epilepsy Surgery Maria Hnojcikova ´ *, Katherine C. Nickels, MD † , Nicholas M. Wetjen, MD ‡ , Jeffrey R. Buchhalter, MD §k , Corey Raffel, MD ¶ , and Elaine C. Wirrell, MD † The aim of this study was to evaluate the yield of electroen- cephalography and structural and functional neuroimag- ing in children having resective epilepsy surgery before 5 years of age. Charts of all 28 children (54% male) having resective surgery before 60 months of age at the Mayo Clinic between January 2002 and June 2009 were re- viewed. Mean age at seizure onset was 9.6 months (S.D. 12.7); mean age at surgery was 28.8 months (S.D. 17.7). Sixteen children (57%) had partial-onset seizures, 8 (29%) had partial-onset seizures and spasms, and 4 (14%) had spasms alone. Initial surgery type was hemi- spherectomy in 6 cases, multilobar resection in 8, temporal in 7, and extratemporal in 7. Only 10 of the 25 children (40%) with recorded seizures preoperatively had a well- localized, single ictal focus. Ictal discharge was generalized in 8/25 cases (32%), both generalized and focal in 1 case (4%), hemispheric in 4 cases (16%), and absent in 1 case (4%). Findings from magnetic resonance imaging were abnormal in 27 cases, and revealed focal pathology in 20. Surgical outcome was favorable, with 18 of the 27 survi- vors (67%) being free, or nearly free, of disabling seizures. In summary, electroencephalography frequently failed to indicate a single ictal focus in young children having epilepsy surgery. In contrast, magnetic resonance imaging was more helpful, revealing focal abnormalities in 74% of patients. Ó 2010 by Elsevier Inc. All rights reserved. Hnojcikova ´ M, Nickels KC, Wetjen NM, Buchhalter JR, Raffel C, Wirrell EC. EEG and neuroimaging studies in young children having epilepsy surgery. Pediatr Neurol 2010;43:335-340. Introduction Population-based studies in children with epilepsy indi- cate that approximately 8-22% will have persistent seizures despite adequate trials of antiepileptic medications, and will meet the criteria for medical intractability [1-3]. Intractable epilepsy is even more common among those whose seizures begin in the first year [4,5]. Uncontrolled seizures adversely affect quality of life and neurodevelopmental outcome, and a significant proportion of children with medically intractable seizures exhibit cognitive impairment [6]. Some of these children have a surgically remediable focus and may achieve seizure freedom or significant reduction with epilepsy surgery. Pediatric epilepsy surgery is not simply an extension of adult procedures. Compared with adults, children are more likely to have malformations of cortical development, tumors, and perinatal injury, and are less likely to have mesial temporal sclerosis [7,8]. Additional factors to be considered include the detrimental effects of seizures and antiepileptic drugs on the developing brain and the greater capacity for functional plasticity in younger patients. In contrast to adults, extratemporal resection, including multilobar resection and hemispherectomy, is the most common type of surgery in this age group, comprising 90% of surgeries in infants [9] and 52% of surgeries in chil- dren between birth and age 4 years [8]. The decision to perform resective surgery for epilepsy requires localization of a focal epileptogenic region, using a combination of EEG and structural or functional neuroi- maging (either or both), because completeness of resection of the epileptogenic zone is the most significant predictor of outcome [10,11]. In very young children, however, defining such a region can be more challenging. Focal brain lesions may manifest generalized or diffuse ictal EEG changes [12], and incomplete myelination of the brain may limit de- tection and appreciation of the extent of focal cortical dys- plasias by magnetic resonance imaging (MRI) [13]. In the present retrospective study of children who had resective surgery for medically intractable epilepsy before 5 years From *Masaryk University, Brno, Czech Republic; † Child and Adolescent Neurology and ‡ Neurosurgery, Mayo Clinic, Rochester, Minnesota; § Division of Neurology, Phoenix Children’s Hospital, and k Clinical Pediatrics & Neurology, University of Arizona College of Medicine, Phoenix, Arizona; and ¶ Neurological Surgery, The Ohio State University College of Medicine, Columbus, Ohio. Communications should be addressed to: Dr. Wirrell; Child and Adolescent Neurology; Mayo Clinic; 200 First St SW; Rochester MN 55905. E-mail: wirrell.elaine@mayo.edu Received March 8, 2010; accepted June 8, 2010. Ó 2010 by Elsevier Inc. All rights reserved. doi:10.1016/j.pediatrneurol.2010.06.002  0887-8994/$—see front matter Hnojcikova ´ et al: Epilepsy Surgery Under 5 Years of Age 335