The Genetic and Molecular Basis of Developmental Language Disorder: A Review

The Emergence and Development of Palestinian Arabic Lexicon and Morphosyntax From 18 to 36 Months: A Communicative Development Inventory Study

PURPOSE

This study presents a comprehensive exploration of lexical and grammatical development in Palestinian Arabic (PA). The study aims to test the validity of the Palestinian Arabic Communicative Development Inventory (PA-CDI) as well as generate growth curves for lexical and morphosyntactic development, examine the order of emergence of both lexical and morphosyntactic categories, and explore the contribution of demographic and developmental factors to language development.

METHOD

Data were collected from 1,399 parents of PA children aged 18-36 months using an online PA-CDI.

RESULTS

The results show that as age increased, so did lexical and morphosyntactic production, along with considerable variability across individuals. While lexical development in PA resembles the order observed in other languages with nouns preceding verbs and adjectives, morphosyntactic development indicates early emergence of verbal inflectional morphology prior to noun pluralization or negation. Age of word combination and health problems are predictive of lexical and morphosyntactic development, and so are parental concerns.

CONCLUSIONS

Our findings indicate the potential of the PA-CDI as an assessment tool for lexical and morphosyntactic development among PA-speaking children in Israel. Our developmental growth curves may also be used to identify children at risk for developmental language disorder, particularly those falling below the 10th percentile, thus allowing for early identification and early intervention. The use of background variables, specifically parental concerns, health issues, and word combinations, along with the PA-CDI, could potentially enhance the precision of language delay assessment.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.26026777.

Differences in Cortical Surface Area in Developmental Language Disorder

Approximately 7% of children have developmental language disorder (DLD), a neurodevelopmental condition associated with persistent language learning difficulties without a known cause. Our understanding of the neurobiological basis of DLD is limited. Here, we used FreeSurfer to investigate cortical surface area and thickness in a large cohort of 156 children and adolescents aged 10-16 years with a range of language abilities, including 54 with DLD, 28 with a history of speech-language difficulties who did not meet criteria for DLD, and 74 age-matched controls with typical language development (TD). We also examined cortical asymmetries in DLD using an automated surface-based technique. Relative to the TD group, those with DLD showed smaller surface area bilaterally in the inferior frontal gyrus extending to the anterior insula, in the posterior temporal and ventral occipito-temporal cortex, and in portions of the anterior cingulate and superior frontal cortex. Analysis of the whole cohort using a language proficiency factor revealed that language ability correlated positively with surface area in similar regions. There were no differences in cortical thickness, nor in asymmetry of these cortical metrics between TD and DLD. This study highlights the importance of distinguishing between surface area and cortical thickness in investigating the brain basis of neurodevelopmental disorders and suggests the development of cortical surface area to be of importance to DLD. Future longitudinal studies are required to understand the developmental trajectory of these cortical differences in DLD and how they relate to language maturation.

Lexical-semantic processing in preschoolers with Developmental Language Disorder: an eye tracking study

This study examined lexical-semantic processing in children with Developmental Language Disorder (DLD) during visually situated comprehension of real-time spoken words. Existing evidence suggests that children with DLD may experience challenges in lexical access and retrieval, as well as greater lexical competition compared to their peers with Typical Development (TD). However, the specific nature of these difficulties remains unclear. Using eye-tracking methodology, the study investigated the real-time comprehension of semantic relationships in children with DLD and their age-matched peers. The results revealed that, for relatively frequent nouns, both groups demonstrated similar comprehension of semantic relationships. Both groups favored the semantic competitor when it appeared with an unrelated visual referent. In turn, when the semantic competitor appeared with the visual referent of the spoken word, both groups disregarded the competitor. This finding shows that, although children with DLD usually present a relatively impoverished vocabulary, frequent nouns may not pose greater difficulties for them. While the temporal course of preference for the competitor or the referent was similar between the two groups, numerical, though non-significant, differences in the extension of the clusters were observed. In summary, this research demonstrates that monolingual preschoolers with DLD exhibit similar lexical access to frequent words compared to their peers with TD. Future studies should investigate the performance of children with DLD on less frequent words to provide a comprehensive understanding of their lexical-semantic abilities.

Whole exome sequencing and polygenic assessment of a Swedish cohort with severe developmental language disorder

Developmental language disorder (DLD) overlaps clinically, genetically, and pathologically with other neurodevelopmental disorders (NDD), corroborating the concept of the NDD continuum. There is a lack of studies to understand the whole genetic spectrum in individuals with DLD. Previously, we recruited 61 probands with severe DLD from 59 families and examined 59 of them and their families using microarray genotyping with a 6.8% diagnostic yield. Herein, we investigated 53 of those probands using whole exome sequencing (WES). Additionally, we used polygenic risk scores (PRS) to understand the within family enrichment of neurodevelopmental difficulties and examine the associations between the results of language-related tests in the probands and language-related PRS. We identified clinically significant variants in four probands, resulting in a 7.5% (4/53) molecular diagnostic yield. Those variants were in PAK2, MED13, PLCB4, and TNRC6B. We also prioritized additional variants for future studies for their role in DLD, including high-impact variants in PARD3 and DIP2C. PRS did not explain the aggregation of neurodevelopmental difficulties in these families. We did not detect significant associations between the language-related tests and language-related PRS. Our results support using WES as the first-tier genetic test for DLD as it can identify monogenic DLD forms. Large-scale sequencing studies for DLD are needed to identify new genes and investigate the polygenic contribution to the condition.

Genetic outcomes in children with developmental language disorder: a systematic review

Introduction

Developmental language disorder (DLD) is a common childhood condition negatively influencing communication and psychosocial development. An increasing number of pathogenic variants or chromosomal anomalies possibly related to DLD have been identified. To provide a base for accurate clinical genetic diagnostic work-up for DLD patients, understanding the specific genetic background is crucial. This study aims to give a systematic literature overview of pathogenic variants or chromosomal anomalies causative for DLD in children.

Methods

We conducted a systematic search in PubMed and Embase on available literature related to the genetic background of diagnosed DLD in children. Included papers were critically appraised before data extraction. An additional search in OMIM was performed to see if the described DLD genes are associated with a broader clinical spectrum.

Results

The search resulted in 15,842 papers. After assessing eligibility, 47 studies remained, of which 25 studies related to sex chromosome aneuploidies and 15 papers concerned other chromosomal anomalies (SCAs) and/or Copy Number Variants (CNVs), including del15q13.1-13.3 and del16p11.2. The remaining 7 studies displayed a variety of gene variants. 45 (candidate) genes related to language development, including FOXP2, GRIN2A, ERC1, and ATP2C2. After an additional search in the OMIM database, 22 of these genes were associated with a genetic disorder with a broader clinical spectrum, including intellectual disability, epilepsy, and/or autism.

Conclusion

Our study illustrates that DLD can be related to SCAs and specific CNV's. The reported (candidate) genes (n = 45) in the latter category reflect the genetic heterogeneity and support DLD without any comorbidities and syndromic language disorder have an overlapping genetic etiology.

Perampanel effectiveness in treating ROGDI-related Kohlschütter-Tönz syndrome: first reported case in China and literature review

PURPOSE

This study reported the first case of Kohlschütter-Tönz syndrome (KTS) in China and reviewed the literature of the reported cases.

METHODS

This patient was registered at the Children's Hospital of Chongqing Medical University. The patient's symptoms and treatments were recorded in detail, and the patient was monitored for six years. We employed a combination of the following search terms and Boolean operators in our search strategy: Kohlschütter-Tönz syndrome, KTS, and ROGDI. These terms were carefully selected to capture a broad range of relevant publications in PubMed, Web of Science, WHO Global Health Library, and China National Knowledge Infrastructure, including synonyms, variations, and specific terms related to KTS. The pathogenicity of the variants was predicted using SpliceAI and MutationTaster, and the structures of the ROGDI mutations were constructed using I-TASSER.

RESULTS

This is the first case report of KTS in China. Our patient presented with epilepsy, global developmental delay, and amelogenesis imperfecta. A trio-WES revealed homozygous mutations in ROGDI (c.46-37_46-30del). The brain magnetic resonance imaging (MRI) and video electroencephalogram (VEEG) were normal. The efficacy of perampanel (PMP) in treating seizures and intellectual disability was apparent. Furthermore, 43 cases of ROGDI-related KTS were retrieved. 100% exhibited epilepsy, global developmental delay, and amelogenesis imperfecta. 17.2% received a diagnosis of attention deficit hyperactivity disorder (ADHD), and 3.4% were under suspicion of autism spectrum disorder (ASD). Language disorders were observed in all patients. Emotional disorders, notably self-harm behaviors (9.1%), were also reported.

CONCLUSION

ROGDI-related KTS is a rare neurodegenerative disorder, characterized by three classic clinical manifestations: epilepsy, global developmental delay, and amelogenesis imperfecta. Moreover, patients could present comorbidities, including ADHD, ASD, emotional disorders, and language disorders. PMP may be a potential drug with relatively good efficacy, but long-term clinical trials are still needed.

Creating the conditions for robust early language development for all-Part 1: Evidence-informed child language surveillance in the early years

BACKGROUND

The emergence of language in the early years is a major developmental accomplishment that underpins learning, enables social interaction and, later, is an indicator of well-being. Learning language is an effortless process for most, but can be challenging for others. There is a need to act early. First, because there are several social, environmental and family factors known to influence how language develops during the critical early years. Second, there is a robust association between a child's socio-economic circumstances and language outcomes. Put simply, children living in less advantaged circumstance have poorer language outcomes, which are apparent very early and persist across the lifespan. Third, children with demonstrated weaknesses in language learning in early childhood have poorer educational, employment, mental health and quality-of-life outcomes across the lifespan. Acting early to counter these impacts is important; however, there are several well-documented challenges in accurately identifying in the early years children who are at later risk of developmental language disorder (DLD) and to deliver prevention and intervention programmes to scale. This is critical because many services do not currently reach those who need them most; as many as 50% of children in need may not be receiving support.

AIM

To determine whether an improved surveillance system, based on best evidence, could be developed for the early years.

METHODS & PROCEDURES

We summarised findings from longitudinal, population or community studies that: (1) adopted bioecological models, (2) repeatedly measured language (including the early years) and (3) adopted similar methodologies, to identify factors that influence language outcomes.

MAIN CONTRIBUTION

The evidence confirmed that language development is not always stable but is characterized by distinct trajectories and each has distinguishing social, environmental features. Children in the change or fluctuating groups tend to live in less advantageous circumstances that may not always support and enable language development. Risk factors tend to cluster and accumulate across the early years and beyond, thereby markedly increasing the likelihood of poorer language outcomes later in life.

CONCLUSIONS & IMPLICATIONS

In this the first of two papers, designed to be read together, we integrate research on the social determinants of child language and propose they be embedded into surveillance models. This has the potential to reach more children and those living in disadvantaged circumstances. In the accompanying paper we combine this information with evidence-informed early prevention/intervention approaches and propose the design and implementation of an early language public health framework.

WHAT THIS PAPER ADDS

What is already known on the subject There are several well-documented challenges in accurately identifying in the early years children who are at later risk of DLD and reaching those most in need of language support. What this study adds to existing knowledge A combination of child, family and environmental determinants, collectively and cumulatively, play out over time and dramatically increase the risk of later language problems, in particular those children living in disadvantaged circumstances. We propose an improved surveillance system that incorporates these determinants be developed and that this be part of a whole of system approach to child language in the early years. What are the potential or actual clinical implications of this work? Clinicians intuitively act to prioritize children with multiple features or risks; however, they can only do so for those who present or are identified to be at risk. Given many children with language problems are not being reached by many early language services, it is reasonable to ask if this knowledge can be integrated to improve reach. Or is a different surveillance model required?

Children With Developmental Language Disorder Have Lower Quality of Life Than Children With Typical Development and Children With Cochlear Implants

PURPOSE

The purpose of this study was to examine quality of life (QOL) and its relation to language skills in children with developmental language disorder (DLD). This was examined by comparing QOL to a control group of children with typical development (TD), as well as children with cochlear implants (CIs), who potentially struggle with language for language, although for a different reason than children with DLD.

METHOD

Two groups of children, a group with TD (n = 29) and a group of children with CIs (n = 29), were matched to the DLD group (n = 29) on chronological age, gender, nonverbal IQ, and parental educational level through a propensity matching procedure. A third group consisting of children with CIs was also matched to the DLD group but additionally matched on language abilities. QOL scores were compared across groups, and the association between language skills and QOL was examined in the DLD group.

RESULT

The DLD group was reported by parents to have statistically significantly poorer QOL scores than peers with TD or CIs. When controlling for language skills, either statistically or through an additional CI group matched on language abilities, there were no statistically significant differences in QOL scores across groups. In the DLD group, language skills explained 16% of the variation in QOL.

CONCLUSION

DLD is associated with the children's overall QOL, and the degree of reduced QOL relates to the severity of the language impairment.

An Investigation of Barriers and Enablers for Genetics in Speech-Language Pathology Explored Through a Case Study of Childhood Apraxia of Speech

PURPOSE

Advancements in genetic testing and analysis have allowed improved identification of the genetic basis of childhood apraxia of speech, a rare speech presentation. This study aimed to understand speech-language pathologists' (SLPs') consideration of incorporation of genetics in clinical practice using a theory-informed qualitative approach.

METHOD

Semistructured interviews were conducted with 12 pediatric SLPs using a behavior change theory (Theoretical Domains Framework [TDF]) within a case study describing a child with complex co-occurring features, including childhood apraxia of speech. Interviews focused on three stages of the patient journey (prereferral, referral, and postreferral). Interviews were analyzed to identify barriers and enablers to considering incorporation of genetics in current clinical practice. Barriers and enablers were grouped and mapped onto a contextually relevant TDF-coded analysis framework.

RESULTS

Barriers were identified across several TDF domains, through all stages of the patient journey. Lack of confidence, relevance, and level of experience were most common prereferral, and connection to and awareness of genetics services and contextual factors were barriers in the referral stage. Perception of professional role, knowledge, and beliefs about effects on families were barriers postreferral. Associated enablers were also identified, including seeing value in genetic diagnosis, support from other health care professionals, supervision, and relationships with genetics services.

CONCLUSIONS

Results of this qualitative study highlight barriers and enablers to incorporating genetics into speech-language pathology clinical practice. These findings will assist in the development of theory-informed implementation strategies to support SLPs into the future.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.24112800.

Redefining cerebral palsies as a diverse group of neurodevelopmental disorders with genetic aetiology

Cerebral palsy is a clinical descriptor covering a diverse group of permanent, non-degenerative disorders of motor function. Around one-third of cases have now been shown to have an underlying genetic aetiology, with the genetic landscape overlapping with those of neurodevelopmental disorders including intellectual disability, epilepsy, speech and language disorders and autism. Here we review the current state of genomic testing in cerebral palsy, highlighting the benefits for personalized medicine and the imperative to consider aetiology during clinical diagnosis. With earlier clinical diagnosis now possible, we emphasize the opportunity for comprehensive and early genomic testing as a crucial component of the routine diagnostic work-up in people with cerebral palsy.

Using machine-learning methods to identify early-life predictors of 11-year language outcome

BACKGROUND

Language is foundational for neurodevelopment and quality of life, but an estimated 10% of children have a language disorder at age 5. Many children shift between classifications of typical and low language if assessed at multiple times in the early years, making it difficult to identify which children will have persisting difficulties and benefit most from support. This study aims to identify a parsimonious set of preschool indicators that predict language outcomes in late childhood, using data from the population-based Early Language in Victoria Study (n = 839).

METHODS

Parents completed surveys about their children at ages 8, 12, 24, and 36 months. At 11 years, children were assessed using the Clinical Evaluation of Language Fundamentals 4th Edition (CELF-4). We used random forests to identify which of the 1990 parent-reported questions best predict children's 11-year language outcome (CELF-4 score ≤81 representing low language) and used SuperLearner to estimate the accuracy of the constrained sets of questions.

RESULTS

At 24 months, seven predictors relating to vocabulary, symbolic play, pragmatics and behavior yielded 73% sensitivity (95% CI: 57, 85) and 77% specificity (95% CI: 74, 80) for predicting low language at 11 years. [Corrections made on 5 May 2023, after first online publication: In the preceding sentence 'motor skills' has been corrected to 'behavior' in this version.] At 36 months, 7 predictors relating to morphosyntax, vocabulary, parent-child interactions, and parental stress yielded 75% sensitivity (95% CI: 58, 88) and 85% specificity (95% CI: 81, 87). Measures at 8 and 12 months yielded unsatisfactory accuracy.

CONCLUSIONS

We identified two short sets of questions that predict language outcomes at age 11 with fair accuracy. Future research should seek to replicate results in a separate cohort.

Abilities and Disabilities Among Children With Developmental Language Disorder

PURPOSE

The aim of this study was to situate developmental language disorder (DLD) within the impairment and disability framework of the International Classification of Functioning, Disability, and Health (ICF); describe the functional strengths and weaknesses of a cohort of first-grade children with DLD and their peers; and explore the ways that language-related disabilities relate to language impairment, developmental risk, and receipt of language services.

METHOD

We queried the caregivers of 35 children with DLD and 44 peers with typical language development about their children's language-related functions, developmental risks, and language services using mixed quantitative and qualitative methods.

RESULTS

The children with DLD presented with weaknesses in domains that are highly dependent upon language skill, including communication, community function, interpersonal relationships, and academics. They presented with strengths in domestic and personal aspects of daily living, play and coping aspects of socialization, and gross motor function. Caregivers of children with DLD expressed pride in their children's agentive and prosocial qualities. Consistent with the ICF, what distinguished children with DLD who had functional weaknesses and disabilities from those who had healthy function was not the severity of language impairment as measured by decontextualized tests of language skill, but the presence of cumulative developmental risks. Compared to those with healthy function, a larger portion of children with weaknesses and disabilities were receiving language services; however, two girls who had disabilities despite mild levels of impairment were without services.

CONCLUSIONS

Children with DLD present with predictable strengths and weaknesses in everyday language-related functioning. For some children, the weaknesses are mild, but for others, they limit function to a greater extent and should be considered disabilities. The severity of language impairment is not a strong indicator of language-related function and, therefore, is not a good metric for determining service qualification.

Innovative Family-Based Genetically Informed Series of Analyses of Whole-Exome Data Supports Likely Inheritance for Grammar in Children with Specific Language Impairment

Individuals with specific language impairment (SLI) struggle with language acquisition despite average non-verbal intelligence and otherwise typical development. One SLI account focuses on grammar acquisition delay. The current study aimed to detect novel rare genetic variants associated with performance on a grammar assessment, the Test of Early Grammatical Impairment (TEGI), in English-speaking children. The TEGI was selected due to its sensitivity and specificity, consistently high heritability estimates, and its absence from all but one molecular genetic study. We performed whole exome sequencing (WES) in eight families with SLI (n = 74 total) and follow-up Sanger sequencing in additional unrelated probands (n = 146). We prioritized rare exonic variants shared by individuals with low TEGI performance (n = 34) from at least two families under two filtering workflows: (1) novel and (2) previously reported candidate genes. Candidate variants were observed on six new genes (PDHA2, PCDHB3, FURIN, NOL6, IQGAP3, and BAHCC1), and two genes previously reported for overall language ability (GLI3 and FLNB). We specifically suggest PCDHB3, a protocadherin gene, and NOL6 are critical for ribosome synthesis, as they are important targets of SLI investigation. The proposed SLI candidate genes associated with TEGI performance emphasize the utility of precise phenotyping and family-based genetic study.

Quantitative MRI reveals differences in striatal myelin in children with DLD

Developmental language disorder (DLD) is a common neurodevelopmental disorder characterised by receptive or expressive language difficulties or both. While theoretical frameworks and empirical studies support the idea that there may be neural correlates of DLD in frontostriatal loops, findings are inconsistent across studies. Here, we use a novel semiquantitative imaging protocol - multi-parameter mapping (MPM) - to investigate microstructural neural differences in children with DLD. The MPM protocol allows us to reproducibly map specific indices of tissue microstructure. In 56 typically developing children and 33 children with DLD, we derived maps of (1) longitudinal relaxation rate R1 (1/T1), (2) transverse relaxation rate R2* (1/T2*), and (3) Magnetization Transfer saturation (MTsat). R1 and MTsat predominantly index myelin, while R2* is sensitive to iron content. Children with DLD showed reductions in MTsat values in the caudate nucleus bilaterally, as well as in the left ventral sensorimotor cortex and Heschl's gyrus. They also had globally lower R1 values. No group differences were noted in R2* maps. Differences in MTsat and R1 were coincident in the caudate nucleus bilaterally. These findings support our hypothesis of corticostriatal abnormalities in DLD and indicate abnormal levels of myelin in the dorsal striatum in children with DLD.