Language impairment in the 22q11.2 deletion syndrome: A comparison with Developmental Language Disorder
The 22q11.2 deletion syndrome is a relatively common genetic syndrome with large phenotypical variation. Symptoms include, but are not limited to, congenital heart diseases, cleft palate, velopharyngeal insufficiency, hypotonia, and below average intelligence. Furthermore, there are indications that the language development of children with 22q11DS is delayed or impaired. However, detailed information regarding the language profile of these children is scarce, and most available knowledge concerns children in the school age. In this research program, we will therefore thoroughly examine the language profile of young children (3 to 7 years) and adolescents (14-18 years) with 22q11DS.This knowledge can help researchers and clinicians to identify 22q11DS more accurately, especially when physical symptoms are absent, and develop adequate interventions and treatment programs. Additionally, the results of this study will specifically enhance our understanding of the 22q11DS phenotype, and are also expected to be an impetus for improving speech-language diagnostics and prognostics in this population. We expect the results to be conducive to improving advising parents/caretakers, and managing their expectations with regard to their child’s condition.
Moreover, the homogeneous genetic etiology of 22q11DS provides us with a unique opportunity to learn more about the causal chain from genes to behavior underlying the behavioral phenotype of other children with language problems. Indeed, some children experience language difficulties in the absence of a clear cause. This latter group of children, estimated at 5-7% of the population, is diagnosed with a developmental language disorder (DLD). The etiology of DLD, in particular the role of neurocognitive processes such as learning and information processing, is poorly understood, partly due to the genetic heterogeneity of this population. We propose to address this issue by comparing children with DLD to children with 22q11DS, who have a developmental language impairment resulting from a uniform etiology. By examining both language and cognitive skills, we aim to learn more about the underlying neurocognitive deficits of language impairment.
Finally, we aim to gain more knowledge on the relation between language and (developing) psychopathology. Individuals with 22q11DS have an elevated genetic predisposition for schizophrenia (25-30% as compared to 1% in the general population) and there are indications that the development of schizophrenia is foreshadowed by language difficulties at a younger age. The identification of linguistic markers that are present before the onset of psychiatric disorders will help timely diagnosis and intervention for the 22q11DS population and help shine light on the general relationship between language use and mental health. Moreover, DLD also often co-occurs with social-emotional and psychiatric problems. By associating the mental health of adolescents with severity and domain of language impairment, we hope to gain insight into which children have a high risk of developing mental problems and we hope to contribute to prevention and early diagnosis and treatment of schizophrenia and other psychiatric disorders.
To summarize, our program has three interrelated objectives:
(1) to provide a detailed description of language development in 3-7-year old children with 22q11DS. A secondary objective is to provide a detailed comparison of early language development in children with 22q11DS and DLD, comprising expressive and receptive abilities, covering language structure (sounds, words, grammar), and use (pragmatics).
(2) to examine neurocognitive mechanisms associated with language acquisition in children with 22q11DS and DLD, with special reference to implicit learning and executive functions. We aim to assess the degree to which deficiencies in these domains are related to language impairments in these populations.
(3) to describe the language skills of adolescents with 22q11DS in comparison with adolescents with DLD and investigate the possible relationship between language skills/use and psychopathology in these populations.
We aim to achieve the first two objectives by using a longitudinal study design, involving three groups of children. The following three groups of participants (N = +/- 70 per group) will be involved: children with 22q11DS, children with DLD, and typically developing controls. All children will be between 3-6 years of age at the start of the study. We aim to achieve the third objective by using a cross-sectional design in which adolescents with 22q11DS are compared to adolescents with DLD. Participants will be between 14 and 18 years old.