Abstracts

Adults with temporal lobe epilepsy (TLE) and partial epilepsy have significant hippocampal volume reduction ipsilateral as well as contralateral to the epileptic focus. Although consistently associated with lateralization of the seizure focus, hippocampal volume loss has been inconsistently related to longer duration of illness, earlier age of onset, and distribution of epileptic discharges at anterior temporal electrodes. Among the few childhood epilepsy morphometric studies, there have been none to date on hippocampal volume in children with childhood absence epilepsy (CAE) and in children with medically controlled complex partial seizures (CPS) who have average intelligence. The purpose of our study was to compare hippocampal volume in children with CPS, CAE, and age and gender matched normal children controlling for between group differences in IQ and demographic variables (e.g., age, gender, ethnicity, socioeconomic status). We hypothesized that the children with CPS would have significantly smaller hippocampi and greater hippocampal asymmetry than the children with CAE and the normal children. In contrast, we predicted no significant differences in hippocampal morphometry between the CAE and normal children. Using quantitative magnetic resonance imaging (MRI), we compared the hippocampal volumes of 24 medically treated children with CPS and 9 with CAE, aged 5-16 years with average intelligence, to 21 age and gender matched normal children. To compare hippocampal volumes in the CPS, CAE, and normal groups, we computed ANOVAs controlling for total brain volume without and with demographic (i.e., age, gender, socioeconomic status, ethnicity) and cognitive variables in the model. Within the patient groups, we examined the relationship of hippocampal volumes to seizure, cognitive, and perinatal variables. The study found significantly smaller left and right anterior hippocampal volumes in the CPS and CAE groups compared to the normal group controlling for demographic, total brain, and IQ variables. Although the CAE group had mean anterior hippocampal volumes between the smaller CPS and the larger normal volumes, there were no significant differences in the hippocampal volumes of the two patient groups. A composite of EEG findings, but no other seizure variables, was significantly associated with reduced hippocampal volumes in the patients. Our findings imply a vulnerability of the anterior but not posterior hippocampus in children with medically controlled CPS and CAE compared to normal children. In addition, seizure propagation appears to be related to hippocampal development in children with these seizure disorders. (Supported by grant NS32070 (R.C.) and MH067187 (R.C.).)