Dravet syndrome in Sweden: a population‐based study

AIM: To assess the prevalence and incidence of Dravet syndrome in children diagnosed in Sweden between 2007 and 2011, and to describe neurological comorbidity, disease course, phenotypes, and treatment effects. METHOD: All neuropaediatricians at university and county hospitals were asked to supply information for patients that matched the electro-clinical profile of Dravet syndrome. Genetic laboratories and referral clinicians were also contacted and requested to supply information. RESULTS: The estimated incidence was one in 33 000 live births (95% CI 1:20 400-1:56 200) and prevalence on December 31, 2011 was one in 45 700 children aged less than 18 years of age (95% CI 1:33 800-1:63 400). The median age of the 42 children (18 males, 24 females) was 7 years (range 1-17y), the median age at seizure onset was 6 months (range 0-12mo), and the median age at diagnosis was 3 years (range 1-14y). A mutation in the SCN1A gene was found in 37 patients (88%), four were familial. Intellectual disability was diagnosed in 28 (67%) children, and 18 out of 30 patients investigated had autism spectrum disorder. Thirty participants had neurological deficits. Stiripentol, as an add-on medication, was used in 18 patients. Among these patients, seven were seizure free, six had >50% seizure reduction, and five <50% seizure reduction. INTERPRETATION: This is the first population-based study of Dravet syndrome in Sweden. Our data confirm international findings of incidence and highlights the severe and progressive course of this genetic epilepsy syndrome.