Early Vocal Development in Tuberous Sclerosis Complex Predicts Language but Not Autism Outcomes

Language impairments impact 72% of individuals with tuberous sclerosis complex (TSC). Nevertheless, evaluations are often delayed until children are 7 years old or older. Earlier prediction of language impairment is needed. Infant vocal behavior is a predictor of language development in typically developing children, but early vocal development had not been studied in TSC until recent research on 38 infants. In this study, the canonical babbling ratio (CBR) and volubility, key indicators of infant vocal behavior, were low. CBR reflects the proportion of syllables that are canonical and volubility reflects either production of utterances or syllables per minute. The present study has the following three goals: (1) To expand CBR and volubility characterization, (2) To evaluate predictiveness of CBR and volubility for autism spectrum disorder (ASD) and language outcomes, and (3) To determine if the contribution of CBR to prediction is independent of other known predictors.

We analyzed 202 recordings at 12 months for infants with TSC. Linear regression predicted language outcomes from vocal measures. Then, stepwise multiple regression compared the relative predictiveness for language outcomes of CBR and other measures known to predict language outcomes. Finally, logistic regression tested for ASD prediction.

CBR and volubility were lower in TSC than in prior typically developing data. CBR was predictive of language outcomes at 24 months for infants with TSC even when competing against other known predictors, but neither CBR nor volubility predicted ASD.

CBR may have utility for early identification of language impairments in TSC.