Charlotte Tye

Aim To characterize early changes in developmental ability, language, and adaptive behaviour in infants diagnosed with tuberous sclerosis complex (TSC), and determine whether clinical features of epilepsy influence this pathway. Method Prospective, longitudinal data were collected within the Early Development in Tuberous Sclerosis (EDiTS) Study to track development of infants with TSC ( n = 32) and typically developing infants ( n = 33) between 3 and 24 months of age. Questionnaire and observational measures were used at up to seven timepoints to assess infants' adaptive behaviour, developmental ability, language, and epilepsy. Results A significant group by age interaction effect showed that infants with TSC had lower adaptive functioning at 18 to 24 months old (intercept = 88.12, slope estimate = −0.82, p < 0.001) and lower developmental ability scores from 10 months old (intercept = 83.33, slope estimate = −1.44, p < 0.001) compared to typically developing infants. Early epilepsy severity was a significant predictor of these emerging developmental ( R 2 = 0.35, p = 0.004, 95% confidence interval [CI] –0.08 to −0.01) and adaptive behaviour delays (R 2 = 0.34, p = 0.004, 95% CI –0.05 to −0.01]). Lower vocabulary production (intercept = −1.25, slope = −0.12, p < 0.001) and comprehension scores (intercept = 2.39, slope estimate = −0.05, p < 0.001) in infants with TSC at 24 months old were not associated with epilepsy severity. Interpretation Divergence of developmental ability and adaptive functioning skills occur in infants with TSC from 10 and 18 months, respectively. Associations between early epilepsy severity and impaired development supports the importance of early intervention to reduce seizure severity.