Early developmental outcome in Dravet syndrome: A scoping review of cognitive, language, behavioural and motor development in the first six years of life

Dravet syndrome (DS) is a severe developmental and epileptic encephalopathy. In the vast majority of the patients DS is associated with a mutation in the SCN1A gene. As a substantial number of children with an SCN1A mutation do not develop DS, but a less severe phenotype it is crucial to find early prognostic developmental biomarkers for developing DS. At present, little research has been conducted into early developmental biomarkers in DS in the first few years of life. The current scoping review provides an overview of developmental delay in the first six years of life in children with DS. Information is presented on four developmental domains: cognitive development, language and speech development, behavior and motor development. A systematic literature search in PubMed yielded ten articles which met the in- and exclusion criteria. Nine studies investigated cognition, four assessed language and speech development, five assessed behavior and five evaluated motor development. Some studies were based on retrospective data from medical records, some used parental surveys and others actually applied developmental assessments. Altogether, our findings suggest that developmental delay in DS already starts before the age of two years in the majority of children and is present in several developmental domains. It is first visible in the domain of motor development where it already appears after the first half year of life in part of the children, and is becoming apparent in the cognitive, language and behavioural domain after the age of one year in most children. Data available are limited.