Abstracts

Rationale: Infantile spasms (IS) is a rare, catastrophic epileptic encephalopathy of infancy, often characterized by the triad of epileptic spasms, hypsarrhythmia on EEG and developmental delay. Hypsarrhythmia or modified hypsarrhythmia on EEG is an essential component for diagnosis and evaluating treatment responses. This may impact decisions to initiate, continue or change therapy. Medication commonly used to treat IS including vigabatrin, adrenocorticotropic hormone (ACTH) or prednisolone, have the potential to cause significant side effects and should not be prescribed unnecessarily. Several studies have reported poor inter-rater reliability for the assessment of hypsarrhythmia. The use of objective EEG criteria may improve the accuracy of diagnosis and evaluation of treatment response rates or relapse. Methods: A single centre, retrospective health record analysis of children with IS at McMaster Children's Hospital between January 2009-July 2015. All patients were followed for at least 6 months from diagnosis. Demographic and epidemiological data was collected. The EEG reports at diagnosis, treatment changes and relapse were de-identified and reanalyzed using objective criteria of hypsarrhythmia and modified hypsarrhythmia. The results were compared to the original reports to determine the impact that objective assessment criteria may make on the diagnosis and evaluation of treatment response or relapse of IS. Results: 30 children met inclusion criteria. The numbers of EEG's positive for hypsarrhythmia/ modified hypsarrhythmia on the original vs reviewed reports were: Diagnosis 30/30 vs 25/30 (p=0.052), Response at first follow up 9/29 vs 5/29 (p=0.36), Response at 2nd follow up with medication change 9/27 vs 10/27 ( p =1)and Total relapse 17/30 vs 15/30 (p=0.8). There was no statistically significant difference in the diagnosis and evaluation of response or relapse rates using standard methods vs objective criteria for the assessment of hypsarrhythmia/ modified hypsarhythmia on EEG. Conclusions: The utilization of objective EEG criteria compared the standard method of hypsarrhythmia evaluation in IS at diagnosis, response to treatment and relapse did not significantly alter the diagnosis or medical management. This suggests standard EEG evaluation methods are effective to diagnose and manage IS. The objective criteria may be useful in some patients, with a trend towards decreased diagnosis rate and decreased response rate at first follow up in this cohort. This study contradicts recent studies that showed high inter-rater variability in evaluation of hypsarrhythmia. This information may guide clinical practice and the design of IS clinical trials in the future. Funding: The abstract did not receive financial support.