Overview: the epidemiology of neurodevelopmental disorders

Psychosocial correlates of neurodevelopmental disabilities in 2- to 3-year-olds

RATIONALE

Canada's National Longitudinal Study of Children and Youth survey data provide insights into chronic health conditions in children. Children with neurodevelopmental disabilities (NDD) are at increased risk for adverse behavioral outcomes.

METHODS

We examined data from 3 cycles of Canada's National Longitudinal Survey of Children and Youth for the presence of epilepsy (Epi), cerebral palsy (CP), and intellectual disability (ID) in 2- to 3-year-olds. We then examined the relationship of NDD to composite measures of behavior: hyperactivity-inattention (HI), prosocial behaviors (PS), emotional disorder-anxiety (EA), physical aggression oppositional behavior (AO), and separation anxiety (SA).

RESULTS

There were 15 children with Epi, 25 with CP and 28 with ID in a sample of 10,879, which represented a population of 756,848 2- to 3-year-old Canadian children. Comparison of mean scores of the NDD groups and controls (Welch's ANOVA), indicated statistically significant differences in HI, PS, EA, and SA at the p < 0.001 level. Post hoc analysis showed significant intergroup differences. Children with epilepsy did not differ from controls on any of the behavioral measures. However, in comparison to controls, children with intellectual disability had higher EA and SA scores and lower PS scores, and those with cerebral palsy had lower PS scores.

CONCLUSIONS

Children with NDD show differences in behavioral outcomes at a very early age when compared with controls. Screening for these behaviors and early intervention programs may help avoid longer term psychiatric comorbidity associated with these disabilities.

Language Assessment for Children With a Range of Neurodevelopmental Disorders Across Four Languages in South Africa

PURPOSE

The purpose of this study is (a) to examine the applicability of a culturally and linguistically adapted measure to assess the receptive and expressive language skills of children with neurodevelopmental disorders (NDDs) in South Africa and then (b) to explore the contributions of 2 additional language measures.

METHOD

In Part 1, 100 children with NDD who spoke Afrikaans, isiZulu, Setswana, or South African English were assessed on the culturally and linguistically adapted Mullen Scales of Early Learning (MSEL). Clinicians independently rated the children's language skills on a 3-point scale. In Part 2, the final 20 children to be recruited participated in a caregiver-led interaction, after which the caregiver completed a rating scale about their perceptions of their children's language.

RESULTS

Performance on the MSEL was consistent with clinician-rated child language skills. The 2 additional measures confirmed and enriched the description of the child's performance on the MSEL.

CONCLUSIONS

The translated MSEL and the supplemental measures successfully characterize the language profiles and related skills in children with NDD in multilingual South Africa. Together, these assessment tools can serve a valuable function in guiding the choice of intervention and also may serve as a way to monitor progress.

From Learning to Memory: What Flies Can Tell Us about Intellectual Disability Treatment

Intellectual disability (ID), previously known as mental retardation, affects 3% of the population and remains without pharmacological treatment. ID is characterized by impaired general mental abilities associated with defects in adaptive function in which onset occurs before 18 years of age. Genetic factors are increasing and being recognized as the causes of severe ID due to increased use of genome-wide screening tools. Unfortunately drug discovery for treatment of ID has not followed the same pace as gene discovery, leaving clinicians, patients, and families without the ability to ameliorate symptoms. Despite this, several model organisms have proven valuable in developing and screening candidate drugs. One such model organism is the fruit fly Drosophila. First, we review the current understanding of memory in human and its model in Drosophila. Second, we describe key signaling pathways involved in ID and memory such as the cyclic adenosine 3',5'-monophosphate (cAMP)-cAMP response element binding protein (CREB) pathway, the regulation of protein synthesis, the role of receptors and anchoring proteins, the role of neuronal proliferation, and finally the role of neurotransmitters. Third, we characterize the types of memory defects found in patients with ID. Finally, we discuss how important insights gained from Drosophila learning and memory could be translated in clinical research to lead to better treatment development.

Autism spectrum disorder in a term birth neonatal intensive care unit population

BACKGROUND

Nonspecific perinatal risk factors have been revealed to be associated with the development of autism spectrum disorder. However, term at-risk infants, as a distinct population, are underrepresented in the literature. This study examines the incidence and neonatal risk factors for autism spectrum disorder in term neonatal intensive care unit survivors.

METHODS

We performed a retrospective analysis from a single university-practice database of neonates admitted to the neonatal intensive care unit and followed by a single pediatric neurologist. Term infants (≥ 37 weeks), born between 1991 and 2011, with at least 2 years (or 1 year if found to be neurologically normal) of follow-up were included. Principle outcomes were autism spectrum disorder, cerebral palsy, global developmental delay, and epilepsy.

RESULTS

One hundred eighty infants were included from a database of 564 neonates. Twelve (6.6%) developed autism spectrum disorder, 53 (29.4%) cerebral palsy, 77 (42.7%) global developmental delay, and 47 (26.1%) epilepsy. Seventy-one (39.4%) developed no adverse outcomes. Nine patients with autism spectrum disorder (75%) were diagnosed with at least one other adverse outcome. No neonatal or perinatal variables were evident to be significantly associated with later autism spectrum disorder.

CONCLUSIONS

In term neonatal intensive care unit survivors, autism spectrum disorder occurs at a greater frequency than in the general population and often develops alongside comorbid conditions. This highlights the importance of screening term neonatal intensive care unit survivors for autism spectrum disorder, particularly when comorbidities are present.

Recent challenges to the psychiatric diagnostic nosology: a focus on the genetics and genomics of neurodevelopmental disorders

Recent advances in the genetics of neurodevelopmental disorder (NDD) have demonstrated that rare mutations play a role not only in Mendelian syndromes, but in complex, common forms of NDDs as well. Strikingly, both common polymorphisms and rare variations in a single gene or genetic locus have been found to carry risk for conditions previously considered to be clinically and aetiologically distinct. Recent developments in the methods and tools available for studying complex NDDs have led to systematic and reliable genome-wide variant discovery. Both common as well as rare, and structural as well as sequence, genetic variations have been identified as contributing to NDDs. There are multiple examples in which the identical variant had been found to contribute to a wide range of formerly distinct diagnoses, including autism, schizophrenia, epilepsy, intellectual disability and language disorders. These include variations in chromosomal structure at 16p11.2, rare de novo point mutations at the gene SCN2A, and common single nucleotide polymorphisms (SNPs) mapping near loci encoding the genes ITIH3, AS3MT, CACNA1C and CACNB2. These selected examples point to the challenges to current diagnostic approaches. Widely used categorical schema have been adequate to provide an entré into molecular mechanisms of NDDs, but there is a need to develop an alternative, more biologically-relevant nosology. Thus recent advances in gene discovery in the area of NDDs are leading to a re-conceptualization of diagnostic boundaries. Findings suggest that epidemiological samples may provide important new insights into the genetics and diagnosis of NDDs and that other areas of medicine may provide useful models for developing a new diagnostic nosology, one that simultaneously integrates categorical diagnoses, biomarkers and dimensional variables.

Longitudinal analyses of geographic differences in utilization rates of children with developmental delays who participation in early intervention services

The purposes of the present study were to describe the longitudinal utilization rates of participation in early intervention services of children with developmental delays, and to examine the geographical difference of services in this vulnerable population. We analyzed service utilization of the developmentally delayed children based on data of governmental reported early intervention services from year 2003 to 2009 in Taiwan. Results show that, the utilization rate of early intervention services was 9.18‰ (range=6.96-12.09‰) of children in 0-5 years during the past 7 years. Mean utilization rate in age group of 0-2 years was 8.32‰ (range=5.73-10.93‰), and age group of 3-5 years was 9.92‰ (range=7.78-13.78‰). We found that the utilization rate in all children aged 0-5 years (R(2)=0.93; p<0.001), boy group (R(2)=0.93; p<0.001) and girl group (R(2)=0.92; p=0.001) were significant increased gradually. The higher utilization rate of early intervention services (aged 0-5 years) were more likely to locate in the north cities (Keelung City=14.65‰; Taipei City=13.49‰), east areas--Hualien County (14.03‰), Taitung County (11.76‰) and central or south counties such as, Chiayi City (14.05‰), Tainan City (12.47‰), and Miaoli County (12.38‰). Hsinchu County (5.97‰), Kaohsiung City (6.21‰), Taichung County (6.74‰), Taipei County (6.95‰) have lower utilization rates of early intervention in Taiwan. The study highlights that the health care system should close the gaps in geographic disparities of early intervention services for children with developmental delays, and respond timely to the needs of these vulnerable children and their families.

Comparison of the ASQ and PEDS in screening for developmental delay in children presenting for primary care

OBJECTIVES

This study investigated the sensitivity and specificity of two brief, parent-completed developmental screening measures-the Ages and Stages Questionnaire (ASQ) and the Parents' Evaluation of Developmental Status (PEDS)-in children presenting to their primary care providers.

METHOD

A sample of 334 children aged 12 to 60 months was recruited. Parents completed the PEDS and the ASQ in their home or the primary care clinic of one of the investigators. The presence of ≥ 1 predictive concerns or abnormal domains was considered a positive screen. All children underwent evaluation (administered by a psychologist) with the following criterion measures: the Bayley Scales of Infant Development-Third Edition or the Wechsler Preschool and Primary Scale of Intelligence-Third Edition, the Preschool Language Scale-Fourth Edition, and the Vineland Adaptive Behavior Scales-Second Edition.

RESULTS

The mean age of children was 32.3 months. Developmental delay was identified in 34 children (10%). The PEDS had moderate sensitivity (74%) but low specificity (64%); comparatively, the ASQ had significantly higher sensitivity (82%) and specificity (78%). The ASQ had moderate sensitivity and specificity across age subgroups, whereas the PEDS had either low sensitivity or specificity in each of the age subgroups, except for the ≤ 30 month group, where there was moderate sensitivity (78%) and specificity (75%). Using ≥ 2 predictive concerns on the PEDS or ≥ 2 abnormal domains on the ASQ significantly improved specificity of both tests (89% and 94%, respectively) but resulted in very low sensitivity (41% and 47%, respectively).

CONCLUSIONS

These findings support the guidelines of the American Academy of Pediatrics, demonstrating that both the ASQ and, to a lesser extent, the PEDS have reasonable test characteristics for developmental screening in primary care settings. Although the ASQ seems to have higher sensitivity and specificity across a variety of age groups, the choice of which measure to use should be determined by the practice setting, population served, and preference of the physician.

The risk of intellectual disability in children born to mothers with preeclampsia or eclampsia with partial mediation by low birth weight

OBJECTIVE

Preeclampsia and eclampsia (PE) are potentially modifiable risk factors for maternofetal complications. Owing to a paucity of research connecting PE to the risk of intellectual disability (ID) in the offspring, this study examined this relationship. Furthermore, we explored how low birth weight (LBW) mediates the effect of PE on ID.

METHODS

Data related to South Carolina Medicaid births from 1996 to 2002 were comprised of linked data from maternal Medicaid records, delivery records, birth certificates, Department of Education (DOE), and the Department of Disabilities and Special Needs (DDSNs). After exclusions such as nonidiopathic etiologies of ID, multiple gestations, subsequent siblings in the cohort, pregnancy losses, births under 20 weeks' gestation, and children neither in DOE nor DDSN records, 80,866 maternal-child dyads remained. After adjusting for five covariates of maternal age, race, and education as well as the child's birth year and sex, the effect of PE on ID was examined.

RESULTS

The rates of PE and ID were 6.4 and 2.0%, respectively. The rates of ID among children exposed and not exposed to PE were 3.0 and 2.0%, respectively. The crude odds ratio (OR) was 1.549 (95% CI 1.310, 1.832) and the adjusted OR was 1.58 (95% CI 1.334, 1.870). LBW was a significant mediator of the relationship accounting for approximately half of the association.

CONCLUSION

Because of the association of PE, ID, and LBW, additional research is needed to explain mechanisms and to investigate possible impacts of different PE treatment.

The contribution of rare diseases to understanding the epidemiology of neurodevelopmental disabilities

Our objective is to describe the contribution of rare diseases to our understanding of the epidemiology of neurodevelopmental disabilities (NDDs) by comparing and contrasting the epidemiologic features of NDDs classified according to key characteristics of developmental delay or deviance in such areas as behavior or cognition (the phenotypic approach; autism spectrum disorders and intellectual disability as examples) versus classification based on the identification of an etiologic diagnosis (the etiologic approach; 22q11.2 deletion syndrome and fragile X syndrome as examples). We suggest specific applications in which consideration of rare etiology-based NDDs might further our understanding of NDD epidemiology overall; what is needed to integrate the two classification approaches; and identify practical challenges in achieving that integration. Understanding commonalities and differences in the epidemiologic features of the phenotypically and etiologically defined NDD classifications provides a useful framework for furthering our understanding of the prevalence, distribution, and causes of NDDs, as well as delivering appropriate diagnostic resources, appropriate treatments, accurate prognostic information, and estimates of recurrence risk for these disorders.

Neurodevelopmental disorders: cluster 2 of the proposed meta-structure for DSM-V and ICD-11

BACKGROUND

DSM-IV and ICD-10 are atheoretical and largely descriptive. Although this achieves good reliability, the validity of diagnoses can be increased by an understanding of risk factors and other clinical features. In an effort to group mental disorders on this basis, five clusters have been proposed. We now consider the second cluster, namely neurodevelopmental disorders.

METHOD

We reviewed the literature in relation to 11 validating criteria proposed by a DSM-V Task Force Study Group.

RESULTS

This cluster reflects disorders of neurodevelopment rather than a 'childhood' disorders cluster. It comprises disorders subcategorized in DSM-IV and ICD-10 as Mental Retardation; Learning, Motor, and Communication Disorders; and Pervasive Developmental Disorders. Although these disorders seem to be heterogeneous, they share similarities on some risk and clinical factors. There is evidence of a neurodevelopmental genetic phenotype, the disorders have an early emerging and continuing course, and all have salient cognitive symptoms. Within-cluster co-morbidity also supports grouping these disorders together. Other childhood disorders currently listed in DSM-IV share similarities with the Externalizing and Emotional clusters. These include Conduct Disorder, Attention Deficit Hyperactivity Disorder and Separation Anxiety Disorder. The Tic, Eating/Feeding and Elimination disorders, and Selective Mutisms were allocated to the 'Not Yet Assigned' group.

CONCLUSION

Neurodevelopmental disorders meet some of the salient criteria proposed by the American Psychiatric Association (APA) to suggest a classification cluster.

PEDS and ASQ developmental screening tests may not identify the same children

OBJECTIVE

In analyzing data from a larger study, we noticed significant disagreement between results of 2 commonly used developmental screening tools (Parents' Evaluation of Developmental Status [PEDS; parent concern questionnaire] and Ages & Stages Questionnaires [ASQ; parent report of developmental skills]) delivered to children at the same visit in primary care. The screens have favorable reported psychometric properties and can be efficient to use in practice; however, there is little comparative information about the relative performance of these tools in primary care. We sought to describe the agreement between the 2 screens in this setting.

METHODS

Parents of 60 children aged 9 to 31 months completed PEDS and ASQ screens at the same visit. Concordance (PEDS and ASQ results agree) and discordance (results differ) for the 2 screens were determined.

RESULTS

The mean age of children was 17.6 months, 77% received Medicaid, and 50% of parents had a high school education or less. Overall, 37% failed the PEDS and 27% failed the ASQ. Thirty-one children passed (52%) both screens; 9 (15%) failed both; and 20 (33%) failed 1 but not the other (13 PEDS and 7 ASQ). Agreement between the 2 screening tests was only fair, statistically no different from agreement by chance.

CONCLUSIONS

There was substantial discordance between PEDS and ASQ developmental screens. Although these are preliminary data, clinicians need to be aware that in implementing revised American Academy of Pediatrics screening guidelines, the choice of screening instrument may affect which children are likely to be identified for additional evaluation.

Fruit flies and intellectual disability

Mental retardation--known more commonly nowadays as intellectual disability--is a severe neurological condition affecting up to 3% of the general population. As a result of the analysis of familial cases and recent advances in clinical genetic testing, great strides have been made in our understanding of the genetic etiologies of mental retardation. Nonetheless, no treatment is currently clinically available to patients suffering from intellectual disability. Several animal models have been used in the study of memory and cognition. Established paradigms in Drosophila have recently captured cognitive defects in fly mutants for orthologs of genes involved in human intellectual disability. We review here three protocols designed to understand the molecular genetic basis of learning and memory in Drosophila and the genes identified so far with relation to mental retardation. In addition, we explore the mental retardation genes for which evidence of neuronal dysfunction other than memory has been established in Drosophila. Finally, we summarize the findings in Drosophila for mental retardation genes for which no neuronal information is yet available. All in all, this review illustrates the impressive overlap between genes identified in human mental retardation and genes involved in physiological learning and memory.

Determining paralysis prevalence in the United States

BACKGROUND

Estimates of paralysis vary widely, largely owing to a lack of standard definition and nontargeted survey approaches. Like other poorly understood conditions such as fibromyalgia, chronic fatigue, or chronic pain, paralysis falls outside the scope of clearly defined medical diagnosis, further complicating surveillance efforts. This inability to identify accurate prevalence makes developing policy interventions around the needs of many persons with these disabilities problematic. The objectives were to investigate how paralysis is being measured in the United States and to examine the validity of prevalence estimates based on current approaches.

METHODS

We reviewed existing measurement instruments and surveyed 139 agencies and organizations to determine how they capture paralysis data.

RESULTS

There is a widespread reliance on ICD coding or broad functional capabilities for most state or federal agencies. Many organizations serving consumers depend on state registries for discrete conditions in which paralysis is not directly measured.

CONCLUSIONS

Improved paralysis prevalence data will benefit from a more functional definition consistent with ICF guidelines, which can be part of future surveillance efforts at state and federal levels.

Epidemiology and Etiology of Mental Retardation

Mental retardation (MR) is a manifestation of a heterogeneous set of impairments and conditions that result in cognitive limitation. It is a condition of medical, educational, and social importance. Physicians identify profound, severe, and moderate MR but rarely diagnose mild MR unless it is associated with a genetic or medical syndrome. From a medical perspective, the quest for etiology and the possibility of medical or surgical intervention to minimize deterioration are paramount. Educators, on the other hand are less concerned with causation than with academic achievement and school success. The majority of cases of mild MR is identified in school settings. Finally, the public uses the label to describe poor adaptive skills. Adults with MR who hold jobs, live independently, and participate in society are not always described as having MR. Thus some individuals characterized in childhood or adolescence as having mild MR become indistinguishable from the general population in adulthood.

Prevalence and psychosocial correlates of global developmental delay in 3-year-old children in the United Arab Emirates

OBJECTIVE

Developmental disabilities are lifelong conditions with considerable public health impact, incurring substantial financial and societal costs. Data on prevalence and associated factors can provide the basis for setting priorities and designing interventions.

METHODS

A representative random sample of 694 United Arab Emirates national children aged 3 years were evaluated in a two-stage epidemiological study.

RESULTS

Stage 1 screening using the Denver Developmental Screening Test found that 8.4% [confidence interval (CI): 6.4-10.7] had global developmental delay (GDD). Using clinical diagnostic interview in Stage 2, the weighted prevalence for clinically significant developmental disability was estimated to be 2.44% (CI: 1.28-3.56). GDD was associated with pregnancy and birth complications, poor maternal education, family history of developmental problems, and major traumatic life events, as well as behavioral problems in children.

CONCLUSION

Our findings suggest the need for comprehensive and early screening programs for developmental problems, and the importance of training medical and child care professionals accordingly.

Clinical genetic evaluation of the child with mental retardation or developmental delays

This clinical report describes the clinical genetic evaluation of the child with developmental delays or mental retardation. The purpose of this report is to describe the optimal clinical genetics diagnostic evaluation to assist pediatricians in providing a medical home for children with developmental delays or mental retardation and their families. The literature supports the benefit of expert clinical judgment by a consulting clinical geneticist in the diagnostic evaluation. However, it is recognized that local factors may preclude this particular option. No single approach to the diagnostic process is supported by the literature. This report addresses the diagnostic importance of clinical history, 3-generation family history, dysmorphologic examination, neurologic examination, chromosome analysis (> or =650 bands), fragile X molecular genetic testing, fluorescence in situ hybridization studies for subtelomere chromosome rearrangements, molecular genetic testing for typical and atypical presentations of known syndromes, computed tomography and/or magnetic resonance brain imaging, and targeted studies for metabolic disorders.

Maternal health in pregnancy and intellectual disability in the offspring: a population-based study

PURPOSE

The aim of the study is to investigate the relationship between common maternal conditions and intellectual disability (ID) of unknown cause in the offspring.

METHODS

Information about the maternal health of children with and without ID was obtained by using record linkage. For mothers with specific medical conditions, proportions of children with mild to moderate ID, severe ID, and autism spectrum disorder (ASD) with ID were compared with those who did not have ID.

RESULTS

There was an increased risk for mild to moderate ID in children of mothers with asthma (odds ratio [OR], 1.52; confidence interval [CI], 1.26-1.83]), diabetes (OR, 1.69; CI, 1.26-2.27), a renal or urinary condition (OR, 2.09; CI, 1.39-3.14), and epilepsy (OR, 3.53; CI, 2.56-4.84). ASD risk was increased for children of women with diabetes (OR, 2.89; CI, 1.28-6.51) and epilepsy (OR, 4.57; CI, 1.69-12.31). For anemia (n = 1101), there was an increased risk for severe ID (OR, 5.26; CI, 2.16-12.80).

CONCLUSIONS

The increased risk for ID in offspring of mothers with such conditions as asthma and diabetes is particularly important for disadvantaged or ethnic populations, for whom these conditions are more prevalent and may be less well managed.

Normalization in families raising a child who is medically fragile/technology dependent and developmentally delayed

The authors combined and analyzed parent data from two field studies examining family experiences in raising children who were both medically fragile and developmentally delayed or disabled to compare these families' experiences to published attributes of normalization. Normalization is usually considered a useful conceptual and coping strategy for families of children with chronic conditions, but it has not been examined in families whose children have both complex physical and developmental disabilities. Developmental delays compounded the effects of the children's physical chronic conditions, severely affecting how families organized and managed their daily lives, with the result that families did not fit currently established attributes of normalization. Instead, parents recognized normal and positive aspects of their lives while acknowledging the profound challenges that their families faced. Parents concluded that it was possible to have a good life that was not necessarily normal by usual standards.

Imaging data in autism: from structure to malfunction

During the last two decades, neuroimaging studies have improved our knowledge of brain development and contributed to our understanding of disorders involving the developing brain. Differences in cerebral anatomy have been determined in autism spectrum disorder (ASD). Morphological studies by magnetic resonance imaging have provided evidence of structural differences in ASD compared with the normal population. This has enhanced our view of autism as a neurobiological disorder corresponding with different stages and events in brain development. Alterations in volume of the total brain and specifically the cerebellum, frontal lobe, and limbic system have been identified. There appears to be a pattern of increased and then decreased rate of brain growth over time. We integrate these observations with neurobehavioral findings to provide a developmental hypothesis of the pathophysiology of autism.