"Intellectual developmental disorders": reflections on the international consensus document for redefining "mental retardation-intellectual disability" in ICD-11

RNA-Seq data analysis reveals novel nonsense mutations in the NPR3 gene leading to the progression of intellectual disability disorder

Intellectual disability (ID) is a progressive disorder that affects around 1-3% of the world's population. The heterogeneity of intellectual disability makes it difficult to diagnose as a complete disease. Genetic factors and major mutations play a noticeable role in the development and progression of ID. There is a high need to explore novel variants that may lead to new insights into the progressive aspects of ID. In the current course of study, 31 samples of ID from different studies available on GEO (GSE77742, GSE74263, GSE90682, GSE98476, GSE108887, GSE145710, and PRJEB21964) datasets were taken for the study. These datasets were analyzed for differential gene expression and single nucleotide polymorphism (SNPs). The SNPs of high impact were compared with the differentially expressed genes. Comparison leads to the identification of the priority gene ie NPR3 gene. The identified priority gene further was evaluated for the effect of the mutation using a Mutation Taster. Structure comparison analysis of the wild and mutated proteins of the NPR3 gene was further carried out by UCSF Chimera. Structural analysis reveals the anomalies in protein expression affecting the regulations of the NPR3 gene. These findings identified a novel nonsense mutation (E222*) in the downregulated NPR3 gene that leads to anomalies in the regulation of its protein expression. This missense mutation reveals a major role in causing ID. Our study concludes that the decrease in the expression of the NPR3 gene causes delayed sensory, motor, and physiological functions of the human brain leading to neurodevelopmental delay that causes ID.

Success and Pitfalls of Genetic Testing in Undiagnosed Diseases: Whole Exome Sequencing and Beyond

Novel approaches to uncover the molecular etiology of neurodevelopmental disorders (NDD) are highly needed. Even using a powerful tool such as whole exome sequencing (WES), the diagnostic process may still prove long and arduous due to the high clinical and genetic heterogeneity of these conditions. The main strategies to improve the diagnostic rate are based on family segregation, re-evaluation of the clinical features by reverse-phenotyping, re-analysis of unsolved NGS-based cases and epigenetic functional studies. In this article, we described three selected cases from a cohort of patients with NDD in which trio WES was applied, in order to underline the typical challenges encountered during the diagnostic process: (1) an ultra-rare condition caused by a missense variant in MEIS2, identified through the updated Solve-RD re-analysis; (2) a patient with Noonan-like features in which the NGS analysis revealed a novel variant in NIPBL causing Cornelia de Lange syndrome; and (3) a case with de novo variants in genes involved in the chromatin-remodeling complex, for which the study of the epigenetic signature excluded a pathogenic role. In this perspective, we aimed to (i) provide an example of the relevance of the genetic re-analysis of all unsolved cases through network projects on rare diseases; (ii) point out the role and the uncertainties of the reverse phenotyping in the interpretation of the genetic results; and (iii) describe the use of methylation signatures in neurodevelopmental syndromes for the validation of the variants of uncertain significance.

Glycosylation and behavioral symptoms in neurological disorders

Glycosylation, the addition of glycans or carbohydrates to proteins, lipids, or other glycans, is a complex post-translational modification that plays a crucial role in cellular function. It is estimated that at least half of all mammalian proteins undergo glycosylation, underscoring its importance in the functioning of cells. This is reflected in the fact that a significant portion of the human genome, around 2%, is devoted to encoding enzymes involved in glycosylation. Changes in glycosylation have been linked to various neurological disorders, including Alzheimer's disease, Parkinson's disease, autism spectrum disorder, and schizophrenia. Despite its widespread occurrence, the role of glycosylation in the central nervous system remains largely unknown, particularly with regard to its impact on behavioral abnormalities in brain diseases. This review focuses on examining the role of three types of glycosylation: N-glycosylation, O-glycosylation, and O-GlcNAcylation, in the manifestation of behavioral and neurological symptoms in neurodevelopmental, neurodegenerative, and neuropsychiatric disorders.

Paradoxical effects of levetiracetam in people with epilepsy with rhythmic epileptiform discharges

OBJECTIVE

To elucidate the incidence and risk factors for paradoxical effects (i.e., increased seizure frequency, increased seizure severity, or onset of new seizure types) of levetiracetam (LEV) in people with epilepsy (PWE) and identify the usefulness of electroencephalography (EEG) in predicting these effects.

METHODS

We examined data for consecutive PWE treated with LEV. All PWE underwent EEG and magnetic resonance imaging (MRI) before LEV administration. We also evaluated the incidence of paradoxical LEV effects and conducted multivariate logistic regression analyses to identify the associated factors.

RESULTS

In total, 210 (66.2%) of 317 PWEs treated in our department had a history of LEV use. The incidence of paradoxical LEV effects was 5.2% (n = 11) and was significantly associated with a high LEV dose (p = 0.029), high seizure frequency (p = 0.005), temporal lobe epilepsy (p = 0.004), focal awareness seizure (p = 0.004), focal impaired awareness seizure (p = 0.007), spike (p = 0.015), rhythmic epileptiform discharges (REDs; p = 0.003), and MRI-identified focal cortical dysplasia (FCD; p < 0.0001). Multivariate analyses revealed that REDs (odds ratio [OR] = 5.35, p = 0.048, 95% confidence interval [CI]: 1.01-28.21) were independently associated with paradoxical LEV effects.

CONCLUSIONS

Paradoxical LEV effects occurred in PWE, particularly in those with drug-resistant focal epilepsy. Furthermore, the occurrence of REDs in EEG was an independent factor associated with the paradoxical effects of LEV in PWE.

Survey results on training in developmental disabilities in Canadian psychiatry residency programs

Objective

Mental health problems in children, adolescents, and adults with developmental disabilities (DD) are an underserviced clinical area. Although the Royal College of Physicians and Surgeons of Canada requires that experiences with patients with DD must be included during psychiatry residency training, the type and extent of this experience is not specified. The purpose of this study was to examine the current educational opportunities regarding DD in Canadian psychiatry residency programs.

Methods

A survey asking about training in DD was sent to psychiatry residency directors at all 17 medical schools in Canada. The survey consisted of three sections focused on didactic teaching and clinical rotations (required and elective) in DD for residents.

Results

Program directors of all psychiatry residency programs noted that their program included didactic teaching specific to DD, although the time dedicated to this differed greatly, ranging from 2 to 20 hours. Although 13 programs offered electives in DD, only five programs required residents to complete a clinical rotation specific to DD. Two programs did not have required or elective rotations in DD.

Conclusion

These results suggest that training specific to DD is probably inadequate for most residents. This is likely to result in limitations in knowledge and skills required to assess and treat people with DD, decreased comfort working with them, and ultimately reduced quality and availability of psychiatric care for this underserved population. More specific and comprehensive training requirements and opportunities are needed to ensure that residents receive appropriate training in this area.

Rare EIF4A2 variants are associated with a neurodevelopmental disorder characterized by intellectual disability, hypotonia, and epilepsy

Eukaryotic initiation factor-4A2 (EIF4A2) is an ATP-dependent RNA helicase and a member of the DEAD-box protein family that recognizes the 5' cap structure of mRNAs, allows mRNA to bind to the ribosome, and plays an important role in microRNA-regulated gene repression. Here, we report on 15 individuals from 14 families presenting with global developmental delay, intellectual disability, hypotonia, epilepsy, and structural brain anomalies, all of whom have extremely rare de novo mono-allelic or inherited bi-allelic variants in EIF4A2. Neurodegeneration was predominantly reported in individuals with bi-allelic variants. Molecular modeling predicts these variants would perturb structural interactions in key protein domains. To determine the pathogenicity of the EIF4A2 variants in vivo, we examined the mono-allelic variants in Drosophila melanogaster (fruit fly) and identified variant-specific behavioral and developmental defects. The fruit fly homolog of EIF4A2 is eIF4A, a negative regulator of decapentaplegic (dpp) signaling that regulates embryo patterning, eye and wing morphogenesis, and stem cell identity determination. Our loss-of-function (LOF) rescue assay demonstrated a pupal lethality phenotype induced by loss of eIF4A, which was fully rescued with human EIF4A2 wild-type (WT) cDNA expression. In comparison, the EIF4A2 variant cDNAs failed or incompletely rescued the lethality. Overall, our findings reveal that EIF4A2 variants cause a genetic neurodevelopmental syndrome with both LOF and gain of function as underlying mechanisms.

The exploration of genetic aetiology and diagnostic strategy for 321 Chinese individuals with intellectual disability

BACKGROUND

Intellectual disability is a heterogeneous neurodevelopmental disorder with complex genetic architectures. Different sequential methodologies are usually applied to identify the genetic aetiologies of ID patients.

METHODS

We collected 321 consecutive ID patients. All patients underwent karyotyping, while 293 and 164 cases further received copy number variation sequencing (CNV-seq) and whole-exome sequencing (WES). The updated WES technology can detect CNVs simultaneously. The diagnostic data from 137 patients who received WES and CNV-seq were used to define the approach that could be recommended as the first-tier test.

RESULTS

WES obtains the highest diagnostic yield of 50% (82/164), compared with karyotyping (7.79%, 25/321) and CNV-seq (19.80%, 58/293). Among the variants detected by WES, 66.67% (44/66) de novo and 57.58% (38/66) novel pathogenic/likely pathogenic (P/LP) variants were identified in patients with ID. Besides, 24 out of 25P/LP CNVs discovered by CNV-seq can also be accurately identified using WES in 137 patients who received WES and CNV-seq. Thus, genetic abnormalities found through karyotyping, CNV-seq, and WES can be completely detected by combined karyotyping and WES.

CONCLUSIONS

This study illustrates the genetic aberrations of a Chinese ID cohort and expands the mutation spectrum of ID-related genes. Compared with the conventional diagnostic strategy, a combination of karyotype analysis and WES could be recommended as the first-tier diagnostic strategy for ID patients.

Bringing machine learning to research on intellectual and developmental disabilities: taking inspiration from neurological diseases

Intellectual and Developmental Disabilities (IDDs), such as Down syndrome, Fragile X syndrome, Rett syndrome, and autism spectrum disorder, usually manifest at birth or early childhood. IDDs are characterized by significant impairment in intellectual and adaptive functioning, and both genetic and environmental factors underpin IDD biology. Molecular and genetic stratification of IDDs remain challenging mainly due to overlapping factors and comorbidity. Advances in high throughput sequencing, imaging, and tools to record behavioral data at scale have greatly enhanced our understanding of the molecular, cellular, structural, and environmental basis of some IDDs. Fueled by the "big data" revolution, artificial intelligence (AI) and machine learning (ML) technologies have brought a whole new paradigm shift in computational biology. Evidently, the ML-driven approach to clinical diagnoses has the potential to augment classical methods that use symptoms and external observations, hoping to push the personalized treatment plan forward. Therefore, integrative analyses and applications of ML technology have a direct bearing on discoveries in IDDs. The application of ML to IDDs can potentially improve screening and early diagnosis, advance our understanding of the complexity of comorbidity, and accelerate the identification of biomarkers for clinical research and drug development. For more than five decades, the IDDRC network has supported a nexus of investigators at centers across the USA, all striving to understand the interplay between various factors underlying IDDs. In this review, we introduced fast-increasing multi-modal data types, highlighted example studies that employed ML technologies to illuminate factors and biological mechanisms underlying IDDs, as well as recent advances in ML technologies and their applications to IDDs and other neurological diseases. We discussed various molecular, clinical, and environmental data collection modes, including genetic, imaging, phenotypical, and behavioral data types, along with multiple repositories that store and share such data. Furthermore, we outlined some fundamental concepts of machine learning algorithms and presented our opinion on specific gaps that will need to be filled to accomplish, for example, reliable implementation of ML-based diagnosis technology in IDD clinics. We anticipate that this review will guide researchers to formulate AI and ML-based approaches to investigate IDDs and related conditions.

Diagnostic yield of patients with undiagnosed intellectual disability, global developmental delay and multiples congenital anomalies using karyotype, microarray analysis, whole exome sequencing from Central Brazil

Intellectual Disability (ID) is a neurodevelopmental disorder that affects approximately 3% of children and adolescents worldwide. It is a heterogeneous and multifactorial clinical condition. Several methodologies have been used to identify the genetic causes of ID and in recent years new generation sequencing techniques, such as exome sequencing, have enabled an increase in the detection of new pathogenic variants and new genes associated with ID. The aim of this study was to evaluate exome sequencing with analysis of the ID gene panel as a tool to increase the diagnostic yield of patients with ID/GDD/MCA in Central Brazil, together with karyotype and CMA tests. A retrospective cohort study was carried out with 369 patients encompassing both sexes. Karyotype analysis was performed for all patients. CMA was performed for patients who did not present structural and or numerical alterations in the karyotype. Cases that were not diagnosed after performing karyotyping and CMA were referred for exome sequencing using a gene panel for ID that included 1,252 genes. The karyotype identified chromosomal alterations in 34.7% (128/369). CMA was performed in 83 patients who had normal karyotype results resulting in a diagnostic yield of 21.7% (18/83). Exome sequencing with analysis of the ID gene panel was performed in 19 trios of families that had negative results with previous methodologies. With the ID gene panel analysis, we identified mutations in 63.1% (12/19) of the cases of which 75% (9/12) were pathogenic variants,8.3% (1/12) likely pathogenic and in 16.7% (2/12) it concerned a Variant of Uncertain Significance. With the three methodologies applied, it was possible to identify the genetic cause of ID in 42.3% (156/369) of the patients. In conclusion, our studies show the different methodologies that can be useful in diagnosing ID/GDD/MCA and that whole exome sequencing followed by gene panel analysis, when combined with clinical and laboratory screening, is an efficient diagnostic strategy.

De Novo Mutation in KMT2C Manifesting as Kleefstra Syndrome 2: Case Report and Literature Review

Diagnosis of pediatric intellectual disability (ID) can be difficult because it is due to a vast number of established and novel causes. Here, we described a full-term female infant affected by Kleefstra syndrome-2 presenting with neurodevelopmental disorder, a history of hypotonia and minor face anomalies. A systematic literature review was also performed. The patient was a 6-year-old Caucasian female. In the family history there was no intellectual disability or genetic conditions. Auxological parameters at birth were adequate for gestational age. Clinical evaluation at 6 months revealed hypotonia and, successively, delay in the acquisition of the stages of psychomotor development. Auditory, visual, somatosensory, and motor-evoked potentials were normal. A brain MRI, performed at 9 months, showed minimal gliotic changes in bilateral occipital periventricular white matter. Neuropsychiatric control, performed at 5 years, established a definitive diagnosis of childhood autism and developmental delay. Molecular analysis of the exome revealed a novel KMT2C missense variant: c.9244C > T (p.Pro3082Ser) at a heterozygous state, giving her a diagnosis of Kleefstra syndrome 2. Parents did not show the variant. Literature review (four retrieved eligible studies, 10 patients) showed that all individuals had mild, moderate, or severe ID; language and motor delay; and autism. Short stature, microcephaly, childhood hypotonia and plagiocephaly were also present. Conclusion. Kleefstra syndrome 2 is a difficult diagnosis of a rare condition with a high clinical phenotypic heterogeneity. This study suggests that it must be taken in account in the work-up of an orphan diagnosis of intellectual disability and/or autism spectrum disorder.

Web Simplification Prototype for Cognitive Disabled Users

Information and communication technology (ICT) and World Wide Web (WWW) are increasingly being used in daily life and becoming important in community, business, personal performance, and improvement of livelihood. people with disabilities (PWDs) can easily perform many tasks using WWW which might be difficult or impossible for them. However, many websites applications such as e-learning, e-commerce, and e-government are not specifically designed keeping in view PWD users. Through the web accessibility guidelines, web developers can build a web program accessible to PWDs. In this paper, we have investigated the issues related to website design that make it unavailable for PWDs. Keeping in view these issues, we have built a framework to make the web easier for PWDs. In addition, these issues are assessed using the GTmetrix, Netcraft, and WAVE accessibility tools and the results are generated using Google Analytics. Based on these results, we have proposed a simplified web version to improve website access for people with disabilities. The proposed prototype is also implemented on a website called Easywebcare by incorporating our recommendations for resolving the investigated issues. Analytics shows that the proposed type surpasses all existing activities in improving website accessibility for people with disabilities.

Reciprocal Xp11.4p11.3 microdeletion/microduplication spanning USP9X, DDX3X, and CASK genes in two patients with syndromic intellectual disability

Only a few patients with deletions or duplications at Xp11.4, bridging USP9X, DDX3X, and CASK genes, have been described so far. Here, we report on a female harboring a de novo Xp11.4p11.3 deletion and a male with an overlapping duplication inherited from an unaffected mother, presenting with syndromic intellectual disability. We discuss the role of USP9X, DDX3X, and CASK genes in human development and describe the effects of Xp11.4 deletion and duplications in female and male patients, respectively.

The Effects of Integrated Step Training into the Physical Education Curriculum of Children with Intellectual Disabilities

(1) Background: This study investigated the changes in step frequency, walking ability, and standing posture of students with intellectual disabilities by integrating step training into the students' physical education curriculum; (2) Methods: The centroid formula was used to estimate the geometric center of the students' bodies in video footage of each participant. Each participant's stepping frequency per minute was recorded. After training, the teachers involved were interviewed regarding the participants' everyday activities in school. Each step training session was recorded by two video cameras. Each step training session was observed and photographed by a senior physical education teacher with special education qualifications; (3) Results: The step training increased the stability of the participants' body axes. The participants' average steps per minute of the participants significantly improved from 24.200 ± 7.554 to 28.700 ± 8.629. Additionally, despite the students exhibiting anxious behavior (e.g., squeezing their hands and grasping at their clothes) at baseline, the frequency of these behaviors decreased significantly from week 4. Overall, the students' daily activities, motivation, interpersonal interaction, self-confidence, and anxiety behaviors improved; (4) Conclusions: After the 8-week step program, the participants with intellectual disabilities improved their step frequency, movement stability, ability to perform daily activities, walking speed, motivation, interpersonal interaction, and self-confidence, and they exhibited a lower level of anxiety-related behaviors.

Children and adolescents with neurodevelopmental disorders show cognitive heterogeneity and require a person-centered approach

We aimed to identify patterns of cognitive differences and characterize subgroups of Mexican children and adolescents with three neurodevelopmental disorders (NDD): intellectual disability (ID), autism spectrum disorders (ASD) and attention deficit/hyperactivity disorder (ADHD). The sample included 74 children and adolescents 6–15 years; 34% had ID, ASD or ADHD, 47% had ID in comorbidity with ASD, ADHD or both, 11% had ASD + ADHD, 8% were children without NDD. We applied WISC-IV, Autism Diagnostic Interview-Revised, Mini-International Neuropsychiatric Structured Interview, Child Behavior Checklist, and UNICEF Child Functioning Module. We evaluated the normality of the WISC-IV sub-scales using the Shapiro-Francia test, then conducted a latent class analysis and assessed inter-class differences in terms of household, parent and child characteristics. The following four-class solution best fit the data: “Lower Cognitive Profile” (LCP), “Lower Working Memory” (LWM), “Higher Working Memory” (HWM), “Higher Cognitive Profile” (HCP). LCP included most of the children with ID, who had a low Working Memory (WM) index score. LWM included mainly children with ASD or ID + ADHD; their Perceptual Reasoning (PR) and Processing Speed (PS) index scores were much higher than those for Verbal Comprehension (VC) and WM. HWM included children with ASD or ADHD; their scores for PR, PS and VC were high with lower WM (although higher than for LWM). HCP included children without NDD and with ASD or ADHD or both and had the highest scores on all indices. Children with NDD show cognitive heterogeneity and thus require individualized treatment plans.

Next-generation gene panel testing in adolescents and adults in a medical neuropsychiatric genetics clinic

Intellectual disability (ID) encompasses a clinically and genetically heterogeneous group of neurodevelopmental disorders that may present with psychiatric illness in up to 40% of cases. Despite the evidence for clinical utility of genetic panels in pediatrics, there are no published studies in adolescents/adults with ID or autism spectrum disorder (ASD). This study was approved by our institutional research ethics board. We retrospectively reviewed the medical charts of all patients evaluated between January 2017 and December 2019 in our adult neuropsychiatric genetics clinic at the McGill University Health Centre (MUHC), who had undergone a comprehensive ID/ASD gene panel. Thirty-four patients aged > 16 years, affected by ID/ASD and/or other neuropsychiatric/behavioral disorders, were identified. Pathogenic or likely pathogenic variants were identified in one-third of our cohort (32%): 8 single-nucleotide variants in 8 genes (CASK, SHANK3, IQSEC2, CHD2, ZBTB20, TREX1, SON, and TUBB2A) and 3 copy number variants (17p13.3, 16p13.12p13.11, and 9p24.3p24.1). The presence of psychiatric/behavioral disorders, regardless of the co-occurrence of ID, and, at a borderline level, the presence of ID alone were associated with positive genetic findings (p = 0.024 and p = 0.054, respectively). Moreover, seizures were associated with positive genetic results (p = 0.024). One-third of individuals presenting with psychiatric illness who met our red flags for Mendelian diseases have pathogenic or likely pathogenic variants which can be identified using a comprehensive ID/ASD gene panel (~ 2500 genes) performed on an exome backbone.

Brief Report: Delayed Diagnosis of Treatable Inborn Errors of Metabolism in Children with Autism and Other Neurodevelopmental Disorders

The objective of our study was to evaluate the frequency of treatable inborn errors of metabolism (IEM) in a clinical sample of Mexican children and adolescents with neurodevelopmental disorders (NDD). Amino acids and acylcarnitines in blood samples of 51 unrelated children and adolescents were analyzed by tandem mass spectrometry to detect treatable IEM of small molecules. One patient with isovaleric acidemia and autism spectrum disorder (ASD) and another with beta-ketothiolase deficiency and ASD/intellectual disability/attention-deficit/hyperactivity disorder (ADHD) were diagnosed, indicating an IEM frequency of 3.9% (1:26 subjects). The high frequency of treatable IEM indicates the need to perform a minimum metabolic screening as part of the diagnostic approach for patient with NDD, particularly when newborn screening programs are limited to a few disorders.

A bio-behavioral intervention combining task analysis with skill-based training to train toothbrushing among children with intellectual disability

AIMS

Individuals with intellectual disability (ID) have special health care needs. Teaching self-care behaviors like toothbrushing helps reduce their dependence on adult caregivers. We present a bio-behavioral intervention combining task analysis with skill-based teaching of toothbrushing behavior aimed to promote autonomy in children with various types of ID.

METHODS

One hundred twenty children with ID enrolled at a special school in the State were included in the study. After baseline measurements using task analysis, four methods were used to train the children - instruction, three-phase modeling, physical guidance, and descriptive praise. The caregiver was trained and given instructional videos for reinforcement. After 4 weeks, the children were asked to brush their teeth and performance was evaluated.

RESULTS

There was increased independence in the performance of toothbrushing behavior, the mild and moderate ID groups showing the most improvement. Steps like oral manipulation of the toothbrush showed the greatest improvement in these groups. The severe ID group showed improvement in certain skills, while requiring assistance for others that demanded dexterity.

CONCLUSION

This intervention can be implemented by special schools and special care dentistry centers to foster autonomy in oral self-care skills in the mild and moderate ID children, and complemented with other methods for severe ID children.

Individuals With Intellectual Disabilities Rely on Somatosensory Information Rather Than Visual Information to Catch a Ball

According to the literature, persons with intellectual disabilities have poor motor control in tasks in which motor anticipation is needed. Our study aimed to assess their motor behavior during interceptive tasks (a tennis ball interception with external-and-oneself throw conditions). A stick-bar was used as a reference or to support cloth to occlude a ball's trajectory. Catch performance and interceptive behavior were analyzed (26 persons). The results show that high/low values of the initial approaching movement led to successful/successful catches, respectively. Our results are in line with the literature about the impact of poor motor control on performance in those with intellectual disabilities. We suggest that low anticipation may relate to problems in real-life situations.

Genetic and phenotypic analysis of 101 patients with developmental delay or intellectual disability using whole-exome sequencing

Whole-exome sequencing (WES) enables identification of pathogenic variants, including copy number variants (CNVs). In this study, we performed WES in 101 Japanese patients with unexplained developmental delay (DD) or intellectual disability (ID) (63 males and 38 females), 98 of them with trio-WES. Pathogenic variants were identified in 54 cases (53.5%), including four cases with pathogenic CNVs. In one case, a pathogenic variant was identified by reanalysis of exome data; and in two cases, two molecular diagnoses were identified. Among 58 pathogenic variants, 49 variants occurred de novo in 48 patients, including two somatic variants. The accompanying autism spectrum disorder and external ear anomalies were associated with detection of pathogenic variants with odds ratios of 11.88 (95% confidence interval [CI] 2.52-56.00) and 3.46 (95% CI 1.23-9.73), respectively. These findings revealed the importance of reanalysis of WES data and detection of CNVs and somatic variants in increasing the diagnostic yield for unexplained DD/ID. In addition, genetic testing is recommended when patients suffer from the autism spectrum disorder or external ear anomalies, which potentially suggests the involvement of genetic factors associated with gene expression regulation.

Validity of DSM-5 Oppositional Defiant Disorder Symptoms in Children with Intellectual Disability

Oppositional defiant disorder (ODD) is one of the most frequently diagnosed disorders in children with intellectual disabilities (ID). However, the high variability of results in prevalence studies suggests problems that should be investigated further, such as the possible overlap between some ODD symptoms and challenging behaviors that are especially prevalent in children with ID. The study aimed to investigate whether there are differences in the functioning of ODD symptoms between children with (n = 189) and without (n = 474) intellectual disabilities. To do so, we analyzed the extent to which parental ratings on DSM-5 ODD symptoms were metrically invariant between groups using models based on item response theory. The results indicated that two symptoms were non-invariant, with degrees of bias ranging from moderately high ("annoys others on purpose") to moderately low ("argues with adults"). Caution is advised in the use of these symptoms for the assessment and diagnosis of ODD in children with ID. Once the bias was controlled, the measurement model suggested prevalences of 8.4% (children with ID) and 3% (typically developing children). Theoretical and practical implications are discussed.

Developmental Perspectives on the Study of Persons with Intellectual Disability

Developmental approaches provide inclusive, universal, and methodologically rigorous frameworks for studying persons with intellectual disability (ID). This is an exceptionally heterogeneous group with regard to etiology, genotype, and phenotype that simply shares the traditional diagnostic criteria, typically a score of two standard deviations below the population mean of 100 on standardized IQ tests and deficits in adaptive behavior. We trace the foundational, conceptual, and methodological roots of developmental approaches and highlight ways that these and more recent iterations continue to be central to advances in the increasingly nuanced study of persons with ID. This work is premised on the consideration of specific etiological groupings and subgroupings across and between different domains of functioning within the context of familial and complex environments throughout the life span. We highlight the potential contributions of advances in behavioral methodologies, genomics, and neuroscience when considered within universal and hierarchic frameworks based on development.

The moderating effect of types of child's neurodevelopmental disorder on the relationship between Indonesian mothers' perception of child's maladaptive behaviour and maternal parenting stress

This study aimed to examine the effect of mother's perception of child's maladaptive behaviour and types of child's neurodevelopment disorder on maternal parenting stress, and examine the role of types of child's neurodevelopmental disorder in moderating the relationship between mother' perception of child's maladaptive behaviours and maternal parenting stress. The mother' perception of child's maladaptive behaviours tested included internalizing and externalizing maladaptive behaviours, while the types of child's neurodevelopmental disorder included intellectual disability (ID), attention-deficit/hyperactivity disorder (ADHD), and autism spectrum disorder (ASD). A total of 163 mothers of children with different types of neurodevelopmental disorders were included in this study. The data were analysed with regression analysis, t-test, and ANOVA. The results showed that 1) there is an influence of the mother's perception of child's maladaptive behaviours and types of neurodevelopmental disorders on parenting stress; 2) types of child neurodevelopmental disorders moderate the relationship between the mother's perception of child's maladaptive behaviour and maternal parenting stress; 3) mothers of children with ASD experience higher levels parenting stress than mothers of children with ADHD and ID.

The genetics of intellectual disability: advancing technology and gene editing

Intellectual disability (ID) is a neurodevelopmental condition affecting 1–3% of the world’s population. Genetic factors play a key role causing the congenital limitations in intellectual functioning and adaptive behavior. The heterogeneity of ID makes it more challenging for genetic and clinical diagnosis, but the advent of large-scale genome sequencing projects in a trio approach has proven very effective. However, many variants are still difficult to interpret. A combined approach of next-generation sequencing and functional, electrophysiological, and bioinformatics analysis has identified new ways to understand the causes of ID and help to interpret novel ID-causing genes. This approach offers new targets for ID therapy and increases the efficiency of ID diagnosis. The most recent functional advancements and new gene editing techniques involving the use of CRISPR–Cas9 allow for targeted editing of DNA in in vitro and more effective mammalian and human tissue-derived disease models. The expansion of genomic analysis of ID patients in diverse and ancient populations can reveal rare novel disease-causing genes.

Neurocognition in childhood epilepsy: Impact on mortality and complete seizure remission 50 years later

OBJECTIVE

To study associations of the severity of impairment in childhood neurocognition (NC) with long-term mortality and complete seizure remission.

METHODS

A population-based cohort of 245 subjects with childhood onset epilepsy was followed up for 50 years (median = 45, range = 2-50). Childhood NC before age 18 years was assessed as a combination of formal intelligence quotient scores and functional criteria (school achievement, working history, and psychoneurological development). Impaired NC was categorized with respect to definitions of intellectual functioning in International Classification of Diseases, 10th revision (R41.83, F70-F73). The outcome variables, defined as all-cause mortality and 10-year terminal remission with the 5 past years off medication (10YTR), were analyzed with Cox regression models.

RESULTS

Of the 245 subjects, 119 (49%) had normal childhood NC, whereas 126 (51%) had various degrees of neurocognitive impairment. During the 50-year observation period, 71 (29%) of the subjects died, 13% of those with normal and 44% of those with impaired NC. The hazard of death increased gradually in line with more impaired cognition, reaching significance in moderate, severe, and profound impairment versus normal NC (hazard ratio [Bonferroni corrected 95% confidence interval] = 3.3 [1.2-9.2], 4.2 [1.2-14.2], and 5.5 [2.4-12.3], respectively). The chance for 10YTR was highest among subjects with normal NC (61%), whereas none of those with profound impairment reached 10YTR. In the intermediate categories, the chance was, however, not directly related to the increasing severity of impairment.

SIGNIFICANCE

The severity of neurocognitive impairment during childhood shows a parallel increase in the risk of death. In comparison with normal NC, subjects with lower childhood NC are less likely to enter seizure remission. However, normal NC does not guarantee complete remission or prevent premature death in some individuals with childhood onset epilepsy.

The road to 11th edition of the International Classification of Diseases: trajectories of scientific consensus and contested science in the classification of intellectual disability/intellectual developmental disorders

PURPOSE OF REVIEW

To increase the expert knowledge-base on intellectual developmental disorders (IDDs) by investigating the typology trajectories of consensus formation in the classification systems up to the 11th edition of the International Classification of Diseases (ICD-11). This expert review combines an analysis of key recent literature and the revision of the consensus formation and contestation in the expert committees contributing to the classification systems since the 1950s.

RECENT FINDINGS

Historically two main approaches have contributed to the development of this knowledge-base: a neurodevelopmental-clinical approach and a psychoeducational-social approach. These approaches show a complex interaction throughout the history of IDD and have had a diverse influence on its classification. Although in theory Diagnostic and Statistical Manual (DSM)-5 and ICD adhere to the neurodevelopmental-clinical model, the new definition in the ICD-11 follows a restrictive normality approach to intellectual quotient and to the measurement of adaptive behaviour. On the contrary DSM-5 is closer to the recommendations made by the WHO 'Working Group on Mental Retardation' for ICD-11 for an integrative approach.

SUMMARY

A cyclical pattern of consensus formation has been identified in IDD. The revision of the three major classification systems in the last decade has increased the terminological and conceptual variability and the overall scientific contestation on IDD.

Intelligence and specific cognitive functions in intellectual disability: implications for assessment and classification

PURPOSE OF REVIEW

Current diagnostic criteria for intellectual disability categorize ability as measured by IQ tests. However, this does not suit the new conceptualization of intellectual disability, which refers to a range of neuropsychiatric syndromes that have in common early onset, cognitive impairments, and consequent deficits in learning and adaptive functioning. A literature review was undertaken on the concept of intelligence and whether it encompasses a range of specific cognitive functions to solve problems, which might be better reported as a profile, instead of an IQ, with implications for diagnosis and classification of intellectual disability.

RECENT FINDINGS

Data support a model of intelligence consisting of distinct but related processes. Persons with intellectual disability with the same IQ level have different cognitive profiles, based on varying factors involved in aetiopathogenesis. Limitations of functioning and many biopsychological factors associated with intellectual disability are more highly correlated with impairments of specific cognitive functions than with overall IQ.

SUMMARY

The current model of intelligence, based on IQ, is of limited utility for intellectual disability, given the wide range and variability of cognitive functions and adaptive capacities. Assessing level of individual impairment in executive and specific cognitive functions may be a more useful alternative. This has considerable implications for the revision of the International Classification of Diseases and for the cultural attitude towards intellectual disability in general.

From the EBM pyramid to the Greek temple: a new conceptual approach to Guidelines as implementation tools in mental health

Guideline methods to develop recommendations dedicate most effort around organising discovery and corroboration knowledge following the evidence-based medicine (EBM) framework. Guidelines typically use a single dimension of information, and generally discard contextual evidence and formal expert knowledge and consumer's experiences in the process. In recognition of the limitations of guidelines in complex cases, complex interventions and systems research, there has been significant effort to develop new tools, guides, resources and structures to use alongside EBM methods of guideline development. In addition to these advances, a new framework based on the philosophy of science is required. Guidelines should be defined as implementation decision support tools for improving the decision-making process in real-world practice and not only as a procedure to optimise the knowledge base of scientific discovery and corroboration. A shift from the model of the EBM pyramid of corroboration of evidence to the use of broader multi-domain perspective graphically depicted as 'Greek temple' could be considered. This model takes into account the different stages of scientific knowledge (discovery, corroboration and implementation), the sources of knowledge relevant to guideline development (experimental, observational, contextual, expert-based and experiential); their underlying inference mechanisms (deduction, induction, abduction, means-end inferences) and a more precise definition of evidence and related terms. The applicability of this broader approach is presented for the development of the Canadian Consensus Guidelines for the Primary Care of People with Developmental Disabilities.