Abstracts

Rationale: Typical Childhood Absence Epilepsy (CAE) is characterized by absence seizures with 3 – 4 Hz spike-wave discharge on EEG. The seizures behaviorally manifest as blank staring and unresponsiveness (lasting 5 – 10 seconds). In the CAE child’s daily living environment seizure episodes can be mistakenly identified as daydreaming, as these periods can be brief and mimic attention deficit hyperactivity disorder symptoms. Previous studies have tried to better understand “inattention” in CAE both during and between seizures (interictal). However, to our knowledge none have studied CAE patients while not on antiepileptic (AEDs) medication. The present study investigates dimensions of attention in a sample of typical CAE patients compared with normal controls.Methods: Typical CAE patients (diagnosed by an epileptologist) were recruited from EEG centers and area neurologists. Normal controls were recruited via advertisements. All participants were administered a brief cognitive/behavioral battery including the Continuous Performance Test (CPT). After screening and training, a subset participated in simultaneous fMRI (3T) and EEG recording (standard 10-20 system), while performing the CPT. Patients remained off antiepileptic medications for 48 hours prior to the study session. The sample included 14 CAE and 10 controls, with a combined mean age of 12 years. The majority of CAE patients were female (60%) and controls were male (80%). Both groups were primarily right-hand dominant (92%).Results: One-way ANOVA indicates a significant mean difference in the interictal omission (non-response to target; inattentive pattern) error rate (p < .02); the CAE group having higher error rates. While there was no significant difference in mean reaction time (RT), the standard deviation of the reaction time was different in the two groups (p < .04), with the CAE group having more variability in RT compared to controls. There was also a significant difference in d’ or detectability scores, with the CAE group performing more poorly than controls (p < .01).Conclusions: CAE patients make a greater number of errors on sustained attention testing when compared to controls. They fail to respond to targets at a higher rate. Further analysis of these errors suggests variability in their response speed to visual stimuli, as well as their discriminative power or ability to distinguish between target and non-targets. These findings indicate that attention problems are not just ictal, and that CAE patients experience considerable attention problems interictally. These problems occur even while off medications, suggesting that they may be related to underlying impairment of attentional networks associated with CAE.