Epidemiology and outcome of infantile spasms in Denmark in 1996-2019

Purpose: To investigate the treatment of infantile epileptic spasm syndrome (IESS) in Denmark. Methods: National retrospective cohort study of all patients born 1996-2019 who had a diagnosis of IESS in the National Patient Registry. Medical records were reviewed to evaluate the diagnosis. Patients were included if semiology was compatible with IESS, or if unclear semiology if there was an abnormal EEG or EEG with hypsarrhythmia. Results: Number of cases with a register based IESS diagnosis was 538. Medical records were unavailable in 48 and 164 did not fulfil the inclusion criteria. Thereby the cohort consisted of 326 children. Mean age at onset of IESS was 5.9 months and mean lead time to treatment was 26.6 days (SD= 63.5). Consistent with the Danish treatment guidelines most patients received vigabatrin as first treatment. In the cohort 44.7 % of patients solely received vigabatrin, whereas combined vigabatrin and corticosteroid was given to 28.3 % (either hydrocortisone or prednisolone). Other anti-seizure medication was given to 28.4 % within 90 days of IESS onset. Aetiology was prenatal (40.3 %), perinatal (10.5 %), postnatal (3.7 %), with unknown timing (10.2 %) or with unknown aetiology (33.5 %). The cohort was followed to a mean age of 8.2 years. At latest follow-up severe neurodevelopmental outcome was seen in 44.2 % and 76.4 % still had epilepsy. The incidence of IESS was 22 per 100.000 live births. Conclusion: In Denmark treatment algorithm is based on start of treatment with vigabatrin. A total of 44.7 % became seizure free by vigabatrin. Neurodevelopmental outcome was severe. A national incidence could be established.