Dravet syndrome in children—A population-based study

OBJECTIVE: The aim was to describe age at diagnosis, cumulative incidence, SCN1A variants, mortality, seizure types and treatments in children with Dravet Syndrome (DS) in Sweden. METHODS: Children diagnosed with DS, born between January 1st 2000 and December 31st 2018 were included in a population-based study. Clinical data, frequency of seizure types and treatments were collected from caregivers and medical records in 42 children. Age at diagnosis, cumulative incidence and treatment were compared between children born in Sweden 2000-2009 and 2010-2018. RESULTS: We identified 55 children with DS, 53 were born in Sweden. Three children had died of definite, probable, or possible sudden unexpected death in epilepsy, one of acute anoxic brain injury and three of pneumonia or pneumonitis. Median age at death was 4.7 (range 3.3-11) years. In 49/53 children with known SCN1A status, a pathogenic/likely pathogenic variant of SCN1A was detected. In two a SCN1A variant of unknown significance was found. For children born in Sweden 2010-2018, median age at DS diagnosis was lower (1.6 vs 4.5 years, p = 0.001) and cumulative incidence higher (1/33,000 vs 1/46,000 live-born children, p = 0.03), compared to children born in 2000-2009. The most common seizure types were focal to bilateral tonic clonic (n = 41/42) and myoclonic (n = 35/42). Tonic seizures were reported in 25/42 children. Sodium-channel inhibitors had been used in 9/24 children born in 2010-2018 and 17/18 children born in 2000-2009 (p = 0.001). SIGNIFICANCE: A SCN1A variant that could explain the syndrome was found in over 90% of children. Tonic seizures seem to be more frequent than earlier described. Median age at diagnosis was lower, cumulative incidence higher and use of contra-indicated sodium-channel inhibitors less common for children born in 2010-2018 compared with children born in 2000-2009. This could indicate an increased awareness of DS.