Changing patterns of intellectual strengths and weaknesses in males with fragile X syndrome

Cognitive and Behavioural Development of Israeli Males with Fragile X and Down Syndrome

Hebrew translations of the Kaufman Assessment Battery for Children (KABC) and the Vineland Adaptive Behaviour Scales (VABS) were administered to 17 Israeli males with fragile X and 17 with Down syndrome matched for chronological and mental ages. When differences in the initial baselines were considered, the pattern of findings was generally consistent with previous reports. On the K-ABC, the males with fragile X scored higher on some subtests of the Simultaneous Domain but not on any of those of the Sequential Domain. On the VABS, superior scores of the males with fragile X on the Daily Living Skills and Communication domains is consistent with prior evidence of their relative strength on the former and the specific weakness of persons with Down syndrome on the latter. These differences between the males with fragile X and Down syndrome with regard to functioning on various domains and subdomains highlight the need to carefully examine the profiles of aetiologically homogeneous groups of persons.

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

PURPOSE

The debate as to whether intellectual disability (ID) should be conceptualized as a health condition or as a disability has intensified as the revision of World Health Organization's (WHO's) International Classification of Diseases (ICD) is being finalized. Defining ID as a health condition is central to retaining it in ICD, with significant implications for health policy and access to health services. The purpose of this paper is to include some reflections on the consensus document produced by the first WHO Working Group on the Classification of MR (WHO WG-MR) and on the process that was followed to realize it. The consensus report was the basis for the development of official recommendations sent to the WHO Advisory Group for ICD-11.

DESIGN/METHODOLOGY/APPROACH

A mixed qualitative approach was followed in a series of meetings leading to the final consensus report submitted to the WHO Advisory group. These recommendations combined prior expert knowledge with available evidence; a nominal approach was followed throughout with face-to-face conferences.

FINDINGS

The WG recommended a synonym set ("synset") ontological approach to the conceptualisation of this health condition underlying a clinical rationale for its diagnosis. It proposed replacing MR with Intellectual Developmental Disorders (IDD) in ICD-11, defined as "a group of developmental conditions characterized by a significant impairment of cognitive functions, which are associated with limitations of learning, adaptive behaviour and skills". The WG further advised that IDD be included under the parent category of neurodevelopmental disorders, that current distinctions (mild, moderate, severe and profound) be continued as severity qualifiers, and that problem behaviours removed from its core classification structure and instead described as associated features.

ORIGINALITY/VALUE

Within the ID/IDD synset two different names combine distinct aspects under a single construct that describes its clinical as well as social, educational and policy utilities. The single construct incorporates IDD as a clinical meta-syndrome, and ID as its functioning and disability counterpart. IDD and ID are not synonymous or mirror concepts as they have different scientific, social and policy applications. New diagnostic criteria for IDD should be based on a developmental approach, which accounts for the complex causal factors known to impact the acquisition of specific cognitive abilities and adaptive behaviours. The paper focuses on a new clinical framework for the diagnosis of IDD that also includes and complements the existing social, educational and policy components inherent in ID.

Phonological awareness and reading in boys with fragile X syndrome

BACKGROUND

Reading delays are well documented in children with fragile X syndrome (FXS), but few studies have examined linguistic precursors of reading in this population. This study examined the longitudinal development of phonological awareness and its relationship with basic reading in boys with FXS. Individual differences in genetic, social-behavioral and environmental factors were also investigated as predictors of phonological awareness.

METHODS

Participants included 54 boys with FXS and 53 typically developing (TD) mental age-matched peers who completed assessments of phonological awareness, nonverbal intelligence, and reading annually for up to 4 years. FMRP level and autism symptomatology were also measured within the FXS group. Hierarchical linear modeling was used to examine change in phonological awareness over time and its predictors. Linear regression was used to examine phonological awareness as a predictor of word reading.

RESULTS

Boys with FXS exhibited slower growth than TD peers in phonological awareness only when nonverbal cognitive abilities were not controlled. The rate of change in phonological awareness decreased significantly after age 10 in boys with FXS. Phonological awareness accounted for 18% unique variance in basic reading ability after controlling for nonverbal cognition, with similar relationships across groups.

CONCLUSION

Phonological awareness skills in the boys with FXS were commensurate with their nonverbal cognitive abilities, with similar relationships between phonological awareness and reading as observed in the TD mental age-matched peers. More research is needed to examine potential causal relationships between phonological awareness, other language skills, and reading abilities in individuals with FXS and other neurodevelopmental disorders.

Fragile X syndrome: an aging perspective

Cognitive and behavioral correlates of molecular variations related to the FMR1 gene have been studied rather extensively, but research about the long-term outcome in individuals with fragile X spectrum disorders remains sparse. In this review, we present an overview of aging research and recent findings in regard to cellular and clinical manifestations of aging in fragile X syndrome, and the FMR1 premutation.

Cognitive, environmental, and linguistic predictors of syntax in fragile X syndrome and Down syndrome

PURPOSE

To examine which cognitive, environmental, and speech-language variables predict expressive syntax in boys with fragile X syndrome (FXS), boys with Down syndrome (DS), and typically developing (TD) boys, and whether predictive relationships differed by group.

METHOD

We obtained Index of Productive Syntax ( Scarborough, 1990) scores for 18 boys with FXS only, 20 boys with both FXS and an autism spectrum disorder, 27 boys with DS, and 25 younger TD boys of similar nonverbal mental age. Predictors included group (diagnosis), nonverbal cognition, phonological working memory (PWM), maternal education, speech intelligibility, and expressive vocabulary. The research questions were addressed via hierarchical linear regression.

RESULTS

Diagnostic group, nonverbal cognition, and PWM predicted 56% of the variance in syntactic ability, with approximately three-fourths of the predicted variance explained by group membership alone. The other factors did not contribute any additional significant variance in this final model. There was no evidence that predictor effects differed by group.

CONCLUSIONS

Nonverbal cognition and PWM have an effect on expressive syntax beyond that of diagnostic group. These effects are estimated to be the same in boys with FXS, boys with DS, and TD boys. Explanations for residual variance and the relative role of different predictors are discussed.

Motor deficits on a ladder rung task in male and female adolescent and adult CGG knock-in mice

The fragile X premutation is a tandem CGG trinucleotide repeat expansion on the FMR1 gene between 55 and 200 repeats in length. A CGG knock-in (CGG KI) mouse with CGG trinucleotide repeat lengths between 70 and 350 has been developed and used to model the histopathology and cognitive deficits reported in carriers of the fragile X premutation. Previous studies have shown that CGG KI mice show progressive deficits in processing spatial and temporal information. To characterize the motor deficits associated with the fragile X premutation, male and female CGG KI mice ranging from 2 to 16 months of age with trinucleotide repeats ranging from 72 to 240 CGG in length were tested for their ability to perform a skilled ladder rung walking test. The results demonstrate that both male and female CGG KI mice showed a greater number of foot slips as a function of increased CGG repeat length, independent of the age of the animal or general activity level.

Narrative Skill in Boys with Fragile X Syndrome with and without Autism Spectrum Disorder

We examined recalled narratives of boys with fragile X syndrome with autism spectrum disorder (FXS-ASD; N=28) and without ASD (FXS-O; N=29), and compared them to those of boys with Down syndrome (DS; N=33) and typically developing boys (TD; N=39). Narratives were scored for mentions of macrostructural Story Grammar elements (Introduction, Relationship, Initiating Events, Internal Response, Attempts/Actions, and Ending). We found that narrative recall is predicted by short-term memory and nonverbal mental age levels in almost all groups (except TD), but not by expressive syntax or caregiver education. After adjusting for these covariates, there were no differences between the three groups with intellectual disability (ID). The FXS-ASD group, however, had significantly poorer performance than the TD group on the overall Story Grammar score, and both the FXS-O and FXS-ASD groups had lower Attempts/Actions scores than the TD group. We conclude that some form of narrative impairment may be associated with FXS, that this impairment may be shared by other forms of ID, and that the presence of ASD has a significantly detrimental effect on narrative recall.

A review of mathematical learning disabilities in children with fragile X syndrome

The prevalence rate of mathematical learning disabilities (MLD) among children with fragile X syndrome who do not meet criteria for intellectual and developmental disabilities (approximately 50% of female children) exceeds the rate reported in the general population. The purpose of this article is two-fold: (1) to review the findings on MLD in persons with fragile X syndrome; and (2) to discuss fragile X syndrome as a possible model for understanding pathways to MLD.

Intellectual disabilities and child psychiatry: looking to the future

We begin this article by examining the role of intellectual disabilities within child psychiatry, highlighting the relatively steady role of disabilities and the recent movement to examine behavior in specific genetic syndromes. We next propose five questions for future work. Questions relate to (1) specifying the nature of gene-brain-behavior connections; (2) delineating environmental effects and gene-environment interactions; (3) understanding behaviors, physical characteristics, health issues, and other personal characteristics by which children with intellectual disabilities influence others; (4) clarifying the roles of gender and aging in behavioral functioning; and (5) working to improve pharmacological, educational, and other interventions and supports for children and their families. Although great advances have occurred over the past 50 years, intellectual disability research lags behind other areas of child psychiatry; much remains to be discovered that might help these children.

Working memory in individuals with fragile X syndrome

The present research tests the hypothesis that fragile X syndrome (FXS) is associated with a deficit in working memory (WM) and the deficit is more pronounced the higher the control requirements of the task. To this purpose, 15 boys with FXS and 15 typically developing children, matched for mental age, assessed with Logical Operation Test, were tested with batteries of 4 verbal and 4 visuospatial WM tasks requiring different levels of control. Children with FXS showed a performance equal to controls, in WM tasks requiring low and medium-low control but significant impairment in correspondence with greater control requirements. Results show that boys with FXS present a WM deficit only when high control is required by the task, supporting the hypothesis that control can be a critical variable distinguishing WM functions and explaining intellectual differences. On the contrary the hypothesis that the FXS is associated with a visuospatial deficit was not supported.

Three steps toward improving the measurement of behavior in behavioral phenotype research

As the numbers of syndrome-specific behavioral articles continue to grow, it seems a good time to pause and take stock of patterns that are emerging across these many studies. This article takes note of these patterns and summarizes the authors' reading of the behavioral phenotype waters. The authors propose that there are (at least) three overarching themes that relate to individual differences within syndromes. These include the roles of (1) development across the lifespan, (2) gender differences, and (3) other subject and environmental factors. The authors end with a cautionary note about measures and the need to supplement (alongside weaknesses and psychiatric vulnerabilities) the strengths and positive affect and attributes of individuals who have genetic syndromes.

Theory of mind deficits in children with fragile X syndrome

BACKGROUND

Given the consistent findings of theory of mind deficits in children with autism, it would be extremely beneficial to examine the profile of theory of mind abilities in other clinical groups such as fragile X syndrome (FXS) and Down syndrome (DS). Aim The aim of the present study was to assess whether boys with FXS are impaired in simple social situations that require them to understand their own and others' mental states - in essence: do they have a 'theory of mind'?

METHOD

Well-standardized tasks of theory of mind, the location change false belief task and the appearance-reality tasks were employed to examine whether any impairment might be specific to the FXS or part of a more generalized developmental deficit.

RESULTS

The results suggest that children with FXS do have impairment in theory of mind that is comparable to the deficit reported in other groups with learning disabilities such as DS. However, closer inspection of the impairment between these groups revealed qualitative differences in error types (realist vs. phenomenist), suggestive of atypical development that goes beyond general cognitive delay.

CONCLUSION

The findings are discussed in terms of the teasing apart of different components of social cognition in order to identify syndrome-specific deficiencies and proficiencies.

Measuring behavior in genetic disorders of mental retardation

As researchers have examined the so-called "behavioral phenotypes" of different genetic mental retardation conditions, the measurement of behavior becomes increasingly important. From earlier, more global examinations of noteworthy behaviors or profiles, recent researchers have moved from reliance on a single, all-encompassing questionnaire to more multimethod, multireporter approaches. This paper summarizes strengths and weaknesses in utilizing parent-report questionnaires and checklists; psychiatric nosology and specific psychiatric questionnaires; observational studies; reports from individuals with mental retardation themselves; profile analyses of psychometric test and subtest scores; and "grouping" analyses of items (factor analysis) and people (cluster analysis). Although we advocate a mixture of approaches to behavioral assessment, in future work researchers will require more theoretically driven methods for studying behavior, greater acknowledgment that the child's behavior is simply one event in ongoing interactions-transactions with other people, and more attention to age-related changes in behavioral phenotypes.

Trajectory of adaptive behavior in males with fragile X syndrome

Adaptive behavior in males with fragile X syndrome was longitudinally examined in 17 subjects, ages 1 to 17. Subjects received adaptive behavior evaluations on two occasions within one of three age periods. All domains of the Vineland Adaptive Behavior Scales increased from youngest to oldest age groups, yet older subjects (ages 10 to 17) showed significant declines in their adaptive behavior scores from first to second testing. A relative strength in Daily Living Skills and weakness in Socialization emerged only among older subjects. There was a significant relationship between adaptive behavior and mental age scores in all subjects. Discussion emphasized the parallels between declines in IQ and adaptive behavior as well as the need for further research on adaptive skills in young adults with fragile X syndrome.