Abstracts

Rationale: Intermittent rhythmic delta activity (IRDA) has been recognized by many electroencephalographers in children with childhood absence epilepsy (CAE). Some suggest that it carries a favorable prognosis. We assessed the predictive presence of IRDA in a large cohort of children whose clinical and EEG features meet diagnostic criteria for CAE as it is currently defined by the International League Against Epilepsy. Methods: Patients were identified by a keyword search ( IRDA, CAE, absence, and staring spells ) in the database of all EEG recordings performed at our center from 2003-2011. The diagnosis of CAE was confirmed by a review of all clinical information. We also extracted data regarding age at seizure onset, medications used, presence of convulsive seizures, individual education plan (IEP), length of follow-up, length of seizure remission at last visit, EEG (normal-abnormal) at last visit. Multiple EEGs were often available for an individual child. The initial EEG performed at our center was used to assess the presence of IRDA. Only children followed for at least 6 months were included in the analysis. A good seizure outcome was defined as seizure remission for at least 6 months at last follow-up. The chi-square and t-tests were used for assessing the relationship of IRDA with other clinical factors and outcomes. Results: Of 13,428 EEGs searched, 135 children met criteria for CAE (average age at onset = 6.5, average age at EEG = 8.2, 64 (47%) girls. IRDA was present in 24 (18%) initial EEG tracings. Age at onset was a bit younger in the IRDA (5.8 vs 6.7y, p=0.09) group. Length of follow-up was about the same. 11/24 (46%) of children with IRDA and 62/103 (60%) without IRDA were seizure-free at last contact (p=0.20). Children in the IRDA group were somewhat less likely to develop convulsive seizures (8% vs 21%, p=0.16) and significantly less likely to have an IEP (4% vs 21%, p=0.03).Conclusions: Seizure remission does not appear to be improved in children whose EEGs demonstrate IRDA; however, longer-term outcomes were not studied here. There are fewer children with convulsions (a finding consistent with others) and also fewer in need of special education resources at school. Our findings in general support the concept that IRDA may identify a subset of children with CAE who have better outcomes in general.