Abstracts

Rationale: The objective of this study is to determine if visual responses to simple visual stimuli differ in children with absence epilepsy compared to age-matched controls. Visual-evoked potentials (VEPs) to stimuli changing contrast over time give us important information about how the balance between excitation and inhibition is maintained in the brain. In doing this, we hope to gain a better understanding of how children with absence epilepsy process visual stimuli and how this may affect attention and learning. Methods: A prospective study of twelve patients with childhood absence epilepsy between the ages of 7-12 years and twelve age-matched control subjects was conducted. All of the patients were receiving treatment with anti-seizure medications. Six of the patients had well-controlled seizures while six had clinical concern for ongoing seizures and evidence of epileptiform discharges on EEG. We recorded sweep VEPs in response to random 5.14Hz checkerboard patterns changing contrast over time. We plotted the response function at the stimuli frequency against stimulus contrast. Results: At a group level, children with absence epilepsy demonstrate a trend toward a lower response threshold. The shape of the function for the two groups appears different with early saturation for the control group and a more linear appearance for the absence epilepsy group. These results suggest that contrast normalization processes are somehow affected in children with absence epilepsy. Conclusions: Visual evoked responses reveal differences in excitability in children with absence epilepsy. Visual evoked responses may serve as a biomarker for cortical excitability in absence and other forms of epilepsy. Altered visual cortex responses appeared even in children treated with anti-seizure medications and normal EEGs at the time of the study. Further studies are underway to explore the effects of epileptiform discharges and treatment responses on VEPs.