Compulsive behavior in Prader-Willi syndrome: examining severity in early childhood

Specificity of Early Childhood Hyperphagia Profiles in Neurogenetic Conditions

Hyperphagia is highly penetrant in Prader-Willi syndrome (PWS) and has increasingly been reported in other neurogenetic conditions (NGC). The Hyperphagia Questionnaire (HQ) was completed by caregivers of 4-8-year-olds with PWS (n = 17), Angelman syndrome (AS; n = 22), Williams syndrome (WS; n = 25), or low-risk controls (LRC; n = 35). All NGC groups were significantly elevated in HQ Total and Behavior scores compared to LRC. Only AS and WS were significantly elevated in the Drive domain, and only PWS in the Severity domain. After controlling for externalizing behavior, HQ Total scores were higher for PWS relative to other groups. Hyperphagic symptoms may not differentiate PWS from other NGCs in early childhood. However, hyperphagic phenotypes may be most severe in PWS. Further investigation of these profiles may inform etiology and syndrome-specific treatments.

Endocrine features of Prader-Willi syndrome: a narrative review focusing on genotype-phenotype correlation

Prader-Willi syndrome (PWS) is a complex genetic disorder caused by three different types of molecular genetic abnormalities. The most common defect is a deletion on the paternal 15q11-q13 chromosome, which is seen in about 60% of individuals. The next most common abnormality is maternal disomy 15, found in around 35% of cases, and a defect in the imprinting center that controls the activity of certain genes on chromosome 15, seen in 1-3% of cases. Individuals with PWS typically experience issues with the hypothalamic-pituitary axis, leading to excessive hunger (hyperphagia), severe obesity, various endocrine disorders, and intellectual disability. Differences in physical and behavioral characteristics between patients with PWS due to deletion versus those with maternal disomy are discussed in literature. Patients with maternal disomy tend to have more frequent neurodevelopmental problems, such as autistic traits and behavioral issues, and generally have higher IQ levels compared to those with deletion of the critical PWS region. This has led us to review the pertinent literature to investigate the possibility of establishing connections between the genetic abnormalities and the endocrine disorders experienced by PWS patients, in order to develop more targeted diagnostic and treatment protocols. In this review, we will review the current state of clinical studies focusing on endocrine disorders in individuals with PWS patients, with a specific focus on the various genetic causes. We will look at topics such as neonatal anthropometry, thyroid issues, adrenal problems, hypogonadism, bone metabolism abnormalities, metabolic syndrome resulting from severe obesity caused by hyperphagia, deficiencies in the GH/IGF-1 axis, and the corresponding responses to treatment.

The Prader-Willi syndrome Profile: validation of a new measure of behavioral and emotional problems in Prader-Willi syndrome

BACKGROUND

Prader-Willi syndrome (PWS) is a rare, neurodevelopmental disorder caused by the lack of expression of paternally imprinted genes on chromosome 15q11-13. PWS features a complex behavioral phenotype, including hyperphagia, anxiety, compulsivity, rigidity, repetitive speech, temper outbursts, aggressivity, and skin-picking. Questionnaires exist for measuring hyperphagia, but not for the aggregation of other problems that are distinctive to PWS. A PWS-specific tool is needed for phenotypic research, and to help evaluate treatment efficacy in future clinical trials aimed at attenuating PWS's hyperphagia and related problems. In this 4-phase study, we leveraged our expertise in PWS with feedback from families and specialists to validate the PWS Profile, a novel, informant-based measure of behavioral and emotional problems in this syndrome.

RESULTS

The authors developed a bank of 73 items that tapped both common and less frequent but clinically significant problems in PWS (Phase 1). An iterative feedback process with families and stakeholders was used to ensure content and construct validity (Phase 2). After adding, omitting, or revising items, in Phase 3, we pilot tested the measure in 112 participants. Results were reviewed by an international team of PWS specialists and revised again (Phase 3). The final, 57-item Profile was then administered to 761 participants (Phase 4). Principal component factor analyses (n = 873) revealed eight conceptually meaningful factors, accounting for 60.52% of test variance, and were readily interpretated as: Rigidity, Insistence; Aggressive Behaviors; Repetitive Questioning, Speech; Compulsive Behaviors; Depression, Anxiety; Hoarding; Negative Distorted Thinking; and Magical Distorted Thinking. Factors were internally consistent and showed good test-retest reliability and convergent validity with existent measures of behavioral problems. Profile factors were not related to IQ, BMI, or parental SES. Three Profile factors differed across PWS genetic subtypes. Age and gender differences were found in only one Profile factor, Hoarding.

CONCLUSIONS

The PWS Profile is a valid, psychometrically-sound questionnaire that already has shown responsivity to treatment in a previous clinical trial. The Profile can extend the reach of future clinical trials by evaluating the impact of novel agents not only on hyperphagia, but also on the emotional and behavioral problems that characterize PWS.

Behavioral features in Prader-Willi syndrome (PWS): consensus paper from the International PWS Clinical Trial Consortium

Prader-Willi syndrome (PWS) is a rare neurodevelopmental genetic disorder associated with a characteristic behavioral phenotype that includes severe hyperphagia and a variety of other behavioral challenges such as temper outbursts and anxiety. These behaviors have a significant and dramatic impact on the daily functioning and quality of life for the person with PWS and their families. To date, effective therapies addressing these behavioral challenges have proven elusive, but several potential treatments are on the horizon. However, a limiting factor for treatment studies in PWS is the lack of consensus in the field regarding how to best define and measure the complex and interrelated behavioral features of this syndrome. The International PWS Clinical Trials Consortium (PWS-CTC, www.pwsctc.org) includes expert PWS scientists, clinicians, and patient advocacy organization representatives focused on facilitating clinical trials in this rare disease. To address the above gap in the field, members of the PWS-CTC “Behavior Outcomes Working Group” sought to develop a unified understanding of the key behavioral features in PWS and build a consensus regarding their definition and description. The primary focus of this paper is to present consensus definitions and descriptions of key phenotypic PWS behaviors including hyperphagia, temper outbursts, anxiety, obsessive–compulsive behaviors, rigidity, and social cognition deficits. Patient vignettes are provided to illustrate the interrelatedness and impact of these behaviors. We also review some available assessment tools as well as new instruments in development which may be useful in measuring these behavioral features in PWS.

Food and Non-Food-Related Behavior across Settings in Children with Prader-Willi Syndrome

This study sought to describe food- and non-food-related behaviors of children aged 3 to 18 years with Prader–Willi syndrome (PWS) in home and school settings, as assessed by 86 parents and 63 teachers using 7 subscales of the Global Assessment of Individual’s Behavior (GAIB). General Behavior Problem, Non-Food-Related Behavior Problem, and Non-Food-Related Obsessive Speech and Compulsive Behavior (OS/CB) scores did not differ significantly between parent and teacher reports. Food-Related Behavior Problem scores were higher in parent versus teacher reports when the mother had less than a college education (difference of 13.6 points, 95% Confidence Interval (CI) 5.1 to 22). Parents assigned higher Food-Related OS/CB scores than teachers (difference of 5.7 points, 95% CI 2.4 to 9.0). Although teachers reported fewer Food-Related OS/CB, they scored overall OS/CB higher for interfering with daily activities compared with parents (difference of 0.9 points, 95% CI 0.4 to 1.4). Understanding how behaviors manifest in home and school settings, and how they vary with socio-demographic and patient characteristics can help inform strategies to reduce behavior problems and improve outcomes.

Brief Report: Challenging Behaviors in Toddlers and Preschoolers with Angelman, Prader-Willi, and Williams Syndromes

Children with neurogenetic syndromes (NGS) experience comorbid challenging behaviors and psychopathology. We examined challenging behaviors in 86 toddlers and preschoolers across three NGS [Angelman syndrome (AS), Prader-Willi syndrome (PWS), and Williams syndrome (WS)] and 43 low-risk controls (LRC), using the Child Behavior Checklist for Ages 1½-5. Challenging behavior profiles differed across NGS, with generally elevated behaviors in AS and WS, but not PWS, relative to LRC. Withdrawn and autism spectrum symptoms were particularly elevated in AS. Although several profiles were similar to those previously reported in older children and adults, we also observed inconsistencies that suggest non-linear developmental patterns of challenging behaviors. These findings underscore the importance of characterizing early challenging behaviors to inform atypical phenotypic development and targeted intervention.

Brain structural alterations in obese children with and without Prader-Willi Syndrome

Prader-Willi syndrome (PWS) is a genetic imprinting disorder that is mainly characterized by hyperphagia and childhood obesity. Previous neuroimaging studies revealed that there is a significant difference in brain activation patterns between obese children with and without PWS. However, whether there are differences in the brain structure of obese children with and without PWS remains elusive. In the current study, we used T1-weighted and diffusion tensor magnetic resonance imaging to investigate alterations in the brain structure, such as the cortical volume and white matter integrity, in relation to this eating disorder in 12 children with PWS, 18 obese children without PWS (OB) and 18 healthy controls. Compared with the controls, both the PWS and OB groups exhibited alterations in cortical volume, with similar deficit patterns in 10 co-varying brain regions in the bilateral dorsolateral and medial prefrontal cortices, right anterior cingulate cortex, and bilateral temporal lobe. The white matter integrities of the above regions were then examined with an analysis method based on probabilistic tractography. The PWS group exhibited distinct changes in the reduced fractional anisotropy of white matter fibers connected to the co-varying regions, whereas the OB group did not. Our findings indicated that PWS and OB share similar gray matter alterations that are responsible for the development of eating disorders. Additionally, the distinct white matter alterations might explain the symptoms associated with food intake in PWS, including excessive hyperphagia and constant hunger. Hum Brain Mapp 38:4228-4238, 2017. © 2017 Wiley Periodicals, Inc.

Deficits in voice and multisensory processing in patients with Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a rare neurodevelopmental and genetic disorder that is characterized by various expression of endocrine, cognitive and behavioral problems, among which a true obsession for food and a deficit of satiety that leads to hyperphagia and severe obesity. Neuropsychological studies have reported that PWS display altered social interactions with a specific weakness in interpreting social information and in responding to them, a symptom closed to that observed in autism spectrum disorders (ASD). Based on the hypothesis that atypical multisensory integration such as face and voice interactions would contribute in PWS to social impairment we investigate the abilities of PWS to process communication signals including the human voice. Patients with PWS recruited from the national reference center for PWS performed a simple detection task of stimuli presented in an uni-o or bimodal condition, as well as a voice discrimination task. Compared to control typically developing (TD) individuals, PWS present a specific deficit in discriminating human voices from environmental sounds. Further, PWS present a much lower multisensory benefits with an absence of violation of the race model indicating that multisensory information do not converge and interact prior to the initiation of the behavioral response. All the deficits observed in PWS were stronger for the subgroup of patients suffering from Uniparental Disomy, a population known to be more sensitive to ASD. Altogether, our study suggests that the deficits in social behavior observed in PWS derive at least partly from an impairment in deciphering the social information carried by voice signals, face signals, and the combination of both. In addition, our work is in agreement with the brain imaging studies revealing an alteration in PWS of the "social brain network" including the STS region involved in processing human voices.

The neurobiological drive for overeating implicated in Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a genetic imprinting disorder characterized mainly by hyperphagia and early childhood obesity. Previous fMRI studies examined the activation of eating-related neural circuits in PWS patients with or without exposures to food cues and found an excessive eating motivation and a reduced inhibitory control of cognitive processing of food. However, the effective connectivity between various brain areas or neural circuitry critically implicated in both the biological and behavioral control of overeating in PWS is largely unexplored. The current study combined resting-state fMRI and Granger causality analysis (GCA) techniques to investigate interactive causal influences among key neural pathways underlying overeating in PWS. We first defined the regions of interest (ROIs) that demonstrated significant alterations of the baseline brain activity levels in children with PWS (n = 21) as compared to that of their normal siblings controls (n = 18), and then carried out GCA to characterize the region-to-region interactions among these ROIs. Our data revealed significantly enhanced causal influences from the amygdala to the hypothalamus and from both the medial prefrontal cortex and anterior cingulate cortex to the amygdala in patients with PWS (P < 0.001). These alterations offer new explanations for hypothalamic regulation of homeostatic energy intake and impairment in inhibitory control circuit. The deficits in these dual aspects may jointly contribute to the extreme hyperphagia in PWS. This study provides both a new methodological and a neurobiological perspective to aid in a better understanding of neural mechanisms underlying obesity in the general public. This article is part of a Special Issue entitled 1618.

Explorative function in Prader-Willi syndrome analyzed through an ecological spatial task

This study was aimed at evaluating the spatial abilities in individuals with Prader-Willi syndrome (PWS) by using an ecological large-scale task with multiple rewards. To evaluate the extent of spatial deficit in PWS individuals, we compare their performances with those of individuals with Williams Syndrome (WS) in which the spatial deficits have been widely described. Participants had to explore an open space to search nine rewards placed in buckets arranged according to three spatial configurations: a Cross, a 3×3 Matrix and a Cluster composed by three groups of three buckets each. PWS individuals exhibited an explorative deficit in Cluster and Cross configurations, while WS participants in Matrix and Cross configurations. The findings indicate that the structural affordances of the environment influence the explorative strategies and can be related to how spatial information is processed.

Learning by observation and learning by doing in Prader-Willi syndrome

BACKGROUND

New competencies may be learned through active experience (learning by doing) or observation of others' experience (learning by observation). Observing another person performing a complex action accelerates the observer's acquisition of the same action, limiting the time-consuming process of learning by doing. Here, we compared learning by observation and learning by doing in individuals with Prader-Willi syndrome (PWS). It is hypothesized that PWS individuals could show more difficulties with learning by observation than learning by doing because of their specific difficulty in interpreting and using social information.

METHODS

The performance of 24 PWS individuals was compared with that of 28 mental age (MA)- and gender-matched typically developing (TD) children in tasks of learning a visuo-motor sequence by observation or by doing. To determine whether the performance pattern exhibited by PWS participants was specific to this population or whether it was a nonspecific intellectual disability effect, we compared the PWS performances with those of a third MA- and gender-matched group of individuals with Williams syndrome (WS).

RESULTS

PWS individuals were severely impaired in detecting a sequence by observation, were able to detect a sequence by doing, and became as efficient as TD children in reproducing an observed sequence after a task of learning by doing. The learning pattern of PWS children was reversed compared with that of WS individuals.

CONCLUSIONS

The observational learning deficit in PWS individuals may be rooted, at least partially, in their incapacity to understand and/or use social information.

Psychiatric disorders in children with Prader-Willi syndrome-Results of a 2-year longitudinal study

Psychiatric disorders such as psychosis are highly prevalent in adults with Prader-Willi syndrome (PWS). However, knowledge about the presence and progression of psychiatric disorders in children with PWS is very limited. Sixty-one children with PWS aged 7-17 years were tested using the Diagnostic Interview Schedule for Children (DISC) and Compulsive Behaviour Checklist (CBC), and 38/61 were retested after 2 years. Prevalence of psychiatric disorders and the association with age, gender, genetic subtype, and total IQ were assessed. In addition, occurrence and characteristics of compulsions were determined. Prior to the study, two boys were known with psychotic symptoms and treated with antipsychotics. At baseline, none scored positive for psychotic disorder. During the follow-up, only one boy with known psychotic symptoms required a dose adjustment of his antipsychotic medication. After 2 years, none of the children had a psychotic disorder according to the DISC. Oppositional defiant disorder (ODD) was the most common diagnosis and present in 20% of children with PWS, and this was not associated with age (β = -0.081, P = 0.546), gender (β = 0.013, P = 0.923), genetic subtype (β = -0.073, P = 0.584), or total IQ (β = -0.150, P = 0.267). The most common compulsions were hoarding and fixed hygiene sequences. In our large group of 61 children with PWS, the majority had no psychotic disorder and no progression was found during 2-year follow-up. ODD was present in 20% of children. No changes in the prevalence of psychiatric disorders were found during the 2-year follow-up study and genetic subtype was not related to psychosis, depression, or ODD.

Ontogenesis of oxytocin pathways in the mammalian brain: late maturation and psychosocial disorders

Oxytocin (OT), the main neuropeptide of sociality, is expressed in neurons exclusively localized in the hypothalamus. During the last decade, a plethora of neuroendocrine, metabolic, autonomic and behavioral effects of OT has been reported. In the urgency to find treatments to syndromes as invalidating as autism, many clinical trials have been launched in which OT is administered to patients, including adolescents and children. However, the impact of OT on the developing brain and in particular on the embryonic and early postnatal maturation of OT neurons, has been only poorly investigated. In the present review we summarize available (although limited) literature on general features of ontogenetic transformation of the OT system, including determination, migration and differentiation of OT neurons. Next, we discuss trajectories of OT receptors (OTR) in the perinatal period. Furthermore, we provide evidence that early alterations, from birth, in the central OT system lead to severe neurodevelopmental diseases such as feeding deficit in infancy and severe defects in social behavior in adulthood, as described in Prader-Willi syndrome (PWS). Our review intends to propose a hypothesis about developmental dynamics of central OT pathways, which are essential for survival right after birth and for the acquisition of social skills later on. A better understanding of the embryonic and early postnatal maturation of the OT system may lead to better OT-based treatments in PWS or autism.

Obesity: pathophysiology and intervention

Obesity presents a major health hazard of the 21st century. It promotes co-morbid diseases such as heart disease, type 2 diabetes, obstructive sleep apnea, certain types of cancer, and osteoarthritis. Excessive energy intake, physical inactivity, and genetic susceptibility are main causal factors for obesity, while gene mutations, endocrine disorders, medication, or psychiatric illnesses may be underlying causes in some cases. The development and maintenance of obesity may involve central pathophysiological mechanisms such as impaired brain circuit regulation and neuroendocrine hormone dysfunction. Dieting and physical exercise offer the mainstays of obesity treatment, and anti-obesity drugs may be taken in conjunction to reduce appetite or fat absorption. Bariatric surgeries may be performed in overtly obese patients to lessen stomach volume and nutrient absorption, and induce faster satiety. This review provides a summary of literature on the pathophysiological studies of obesity and discusses relevant therapeutic strategies for managing obesity.

Altered functional brain networks in Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a genetic imprinting disorder characterized mainly by hyperphagia and early childhood obesity. Previous functional neuroimaging studies used visual stimuli to examine abnormal activities in the eating-related neural circuitry of patients with PWS. It was found that patients with PWS exhibited both excessive hunger and hyperphagia consistently, even in situations without any food stimulation. In the present study, we employed resting-state functional MRI techniques to investigate abnormal brain networks related to eating disorders in children with PWS. First, we applied amplitude of low-frequency fluctuation analysis to define the regions of interest that showed significant alterations in resting-state brain activity levels in patients compared with their sibling control group. We then applied a functional connectivity (FC) analysis to these regions of interest in order to characterize interactions among the brain regions. Our results demonstrated that patients with PWS showed decreased FC strength in the medial prefrontal cortex (MPFC)/inferior parietal lobe (IPL), MPFC/precuneus, IPL/precuneus and IPL/hippocampus in the default mode network; decreased FC strength in the pre-/postcentral gyri and dorsolateral prefrontal cortex (DLPFC)/orbitofrontal cortex (OFC) in the motor sensory network and prefrontal cortex network, respectively; and increased FC strength in the anterior cingulate cortex/insula, ventrolateral prefrontal cortex (VLPFC)/OFC and DLPFC/VLPFC in the core network and prefrontal cortex network, respectively. These findings indicate that there are FC alterations among the brain regions implicated in eating as well as rewarding, even during the resting state, which may provide further evidence supporting the use of PWS as a model to study obesity and to provide information on potential neural targets for the medical treatment of overeating.

[Behavioral characteristics of children with Prader-Willi syndrome in preschool and school age: an exploratory study on ritualistic behavior]

Parents of 64 children and youths with Prader-Willi syndrome (PWS) describe their children's behaviour on the "Temperament and Atypical Behavior Scale" (TABS) and the German version of the "Developmental Behavior Checklist" (VFE). In the younger age group, there are no specific behavioural abnormalities which characterize a behavioral phenotype. In the older age group the data reveal elevated levels of abnormal behaviors (communication disturbance, social relations and disruptive behaviors). Parents stress ritualistic behaviors as especially challenging. The results concerning form and age-dependency of abnormal behaviors are discussed in the context of prevention and treatment options.

PET scan perfusion imaging in the Prader-Willi syndrome: new insights into the psychiatric and social disturbances

The Prader-Willi syndrome (PWS), a rare multisystem genetic disease, leads to severe disabilities, such as morbid obesity, endocrine dysfunctions, psychiatric disorders, and social disturbances. We explored the whole brain of patients with PWS to detect abnormalities that might explain the behavioral and social disturbances, as well as the psychiatric disorders of these patients. Nine patients with PWS (six males, three females; mean age 16.4 years) underwent a positron emission tomography (PET) scan with H(2)(15)O as a tracer to measure regional cerebral blood flow (rCBF). The images were compared with those acquired from nine controls (six males, three females; mean age 21.2 years). A morphologic magnetic resonance imaging (MRI) was also performed in PWS patients, and their cognitive and behavioral skills were assessed with Wechsler Intelligence Scale for Children III and the Child Behavior Check List (CBCL). The MRI images showed no evident anatomic abnormalities, whereas PET scans revealed hypoperfused brain regions in PWS patients compared with controls, particularly in the anterior cingulum and superior temporal regions. We observed a significant relationship (P<0.05) between rCBF in the hypoperfused regions and CBCL scores. The functional consequences of these perfusion abnormalities in specific brain regions might explain the behavioral and social problems observed in these individuals.

A preliminary analysis of the phenomenology of skin-picking in Prader-Willi syndrome

To examine the nature and psychosocial correlates of skin-picking behavior in youth with Prader-Willi Syndrome (PWS). Parents of 67 youth (aged 5-19 years) with PWS were recruited to complete an internet-based survey that included measures of: skin-picking behaviors, the automatic and/or focused nature of skin-picking, severity of skin-picking symptoms, anxiety symptoms, developmental functioning, symptoms of inattention, impulsivity, and oppositionality, and quality of life. Results indicated that skin-picking was endorsed in 95.5% of youth. Direct associations of moderate strength were found between skin-picking severity and symptoms of anxiety, inattention, oppositionality, developmental functioning, and quality of life. Other descriptive data, such as areas picked, cutaneous factors, antecedents, and consequences related to skin-picking are reported. The prevalence and consequences associated with skin-picking in PWS indicate a greater need for clinician awareness of the behavior and interventions tailored to meet the needs of this population.

Clinical management of behavioral characteristics of Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a complex neurodevelopmental disorder caused by an abnormality on the long arm of chromosome 15 (q11-q13) that results in a host of phenotypic characteristics, dominated primarily by hyperphagia and insatiable appetite. Characteristic behavioral disturbances in PWS include excessive interest in food, skin picking, difficulty with a change in routine, temper tantrums, obsessive and compulsive behaviors, and mood fluctuations. Individuals with PWS typically have intellectual disabilities (borderline to mild/moderate mental retardation) and exhibit a higher overall behavior disturbance compared to individuals with similar intellectual disability. Due to its multisystem disorder, family members, caregivers, physicians, dieticians, and speech-language pathologists all play an important role in the management and treatment of symptoms in an individual with PWS. This article reviews current research on behavior and cognition in PWS and discusses management guidelines for this disorder.

Cognitive profile in a large French cohort of adults with Prader-Willi syndrome: differences between genotypes

BACKGROUND

Prader-Willi syndrome (PWS) is a rare genetic disorder characterised by developmental abnormalities leading to somatic and psychological symptoms. These include dysmorphic features, impaired growth and sexual maturation, hyperphagia, intellectual delay, learning disabilities and maladaptive behaviours. PWS is caused by a lack of expression of maternally imprinted genes situated in the 15q11-13 chromosome region. The origin is a 'de novo' deletion in the paternal chromosome in 70% of the cases and a maternal uniparental disomy in 25%. The two main genotypes show differences, notably regarding cognitive and behavioural features, but the mechanisms are not clear. This study assessed cognitive impairment in a cohort of adults with genetically confirmed PWS, analysed their profiles of cognitive strengths and weaknesses, and compared the profiles in terms of genotype.

METHODS

Ninety-nine male and female adults participated, all inpatients on a specialised unit for the multidisciplinary care of PWS. The Wechsler Adult Intelligence Scale (WAIS-III) was administered to all patients in identical conditions by the same psychologist. Eighty-five patients were able to cope with the test situation. Their scores were analysed with non-parametric statistical tools. The correlations with sex, age and body mass index were explored. Two genotype groups were compared: deletion (n = 57) and non-deletion (n = 27).

RESULTS

The distribution of intelligence quotients in the total cohort was non-normal, with the following values (medians): Full Scale Intelligence Quotient (FSIQ): 52.0 (Q1:46.0; Q3:60.0), Verbal Intellectual Quotient (VIQ): 53.0 (Q1:48; Q3:62) and Performance Intellectual Quotient (PIQ): 52.5 (Q1:48; Q3:61). No correlation was found with sex, age or body mass index. Comparison between groups showed no significant difference in FSIQ or VIQ. PIQ scores were significantly better in the deletion group. The total cohort and the deletion group showed the VIQ = PIQ profile, whereas VIQ > PIQ was observed in the non-deletion group. The subtest scores in the two groups showed significant differences, with the deletion group scoring better in three subtests: object assembly, picture arrangement and digit symbol coding. Some relative strengths and weaknesses concerned the total cohort, but others concerned only one genotype.

DISCUSSION

We documented a global impairment in the intellectual abilities of a large sample of French PWS patients. The scores were slightly lower than those reported in most other studies. Our data confirmed the previously published differences in the cognitive profiles of the two main PWS genotypes and offer new evidence to support this hypothesis. These results could guide future neuropsychological studies to determine the cognitive processing in PWS. This knowledge is essential to improve our understanding of gene-brain-behaviour relationships and to open new perspectives on therapeutic and educational programmes.

Associations between repetitive questioning, resistance to change, temper outbursts and anxiety in Prader-Willi and Fragile-X syndromes

BACKGROUND

The behavioural phenotypes of Prader-Willi (PWS) and Fragile-X (FraX) syndromes both comprise repetitive behaviours with differences between the profiles. In this study we investigated the context and antecedents to the repetitive behaviours and the association with other behavioural phenotypic characteristics in order to generate testable hypotheses regarding the cause of the behaviours.

METHOD

The parents or carers of 46 children with PWS (mean age 14.1 years; 20 girls), and 33 boys with FraX (mean age 13.11 years) were interviewed about their children's repetitive behaviour in a semi-structured format.

RESULTS

Children showed negative emotional behaviour (PWS: 87.0%; FraX: 79.4%) and repetitive questions (PWS: 78.3%; FraX: 73.5%) following changes in routine or expectations. Significantly more temper outbursts were reported to follow changes in children with PWS (89.1%) compared with boys with FraX (41.2%) (chi(2) = 20.93; P < 0.001). Anxiety that was frequently associated with repetitive and self-injurious behaviours in boys with FraX, followed changes in significantly more boys with FraX (76.5%) compared with children with PWS (6.5%) (chi(2) = 43.19, P < 0.001).

DISCUSSION

On the basis of these reports and existing literature, we hypothesise that decreases in predictability are aversive to children with PWS and FraX. We also hypothesise that these children have a propensity to show a syndrome-related pattern of behaviour (temper outbursts in PWS and displays of anxiety in FraX) when an event in the environment has this aversive property. We hypothesise that questions may be reinforcing to children in their own right by increasing the predictability of the environment. We outline how a specific cognitive deficit in the endophenotypes associated with both PWS and FraX could be investigated as a potential explanation for the hypothesised aversive properties of decreased predictability.

The relationship between compulsive behaviour and academic achievement across the three genetic subtypes of Prader-Willi syndrome

BACKGROUND

Prader-Willi syndrome (PWS) is a genetic syndrome associated with several physical, cognitive and behavioural characteristics. For many individuals with this syndrome, compulsive behaviour is often noted in both food and non-food situations. The focus of this paper is on the non-food-related compulsions in individuals with PWS and comparing differences across the three genetic subtypes of the syndrome.

METHODS

Compulsive behaviours in 73 people with PWS were assessed using the Yale-Brown Obsessive Compulsive Scale and the Compulsive Behavior Checklist. Compulsive behaviour and its relation to IQ and academic achievement also were evaluated. Phenotypic differences were characterized for the three most common genetic subtypes of the disorder: 16 individuals with the long Type I (TI) 15q deletion, 26 individuals with the short Type II (TII) 15q deletion and 31 individuals with maternal disomy 15.

RESULTS

There appeared to be important differences between the two deletion subtypes. Specifically, individuals with the TI deletion had more compulsions regarding personal cleanliness (i.e. excessive bathing/grooming), and their compulsions were more difficult to interrupt and interfered with social activities more than the other subtypes. Individuals with the TII deletion were more likely to have compulsions related to specific academic areas (i.e. rereading, erasing answers and counting objects or numbers).

CONCLUSIONS

These findings may help clinicians and researchers identify possible intervention strategies and supports based on the behavioural phenotype associated with genetic subtype in individuals with PWS.

Autistic-like symptomatology in Prader-Willi syndrome: a review of recent findings

Prader-Willi syndrome (PWS) is caused by either the structural loss of material or the absence of gene expression from the paternally inherited copy of chromosome 15 in the q11-q13 region. In addition to a well-described behavioral phenotype that includes hyperphagia, obsessive-compulsive symptoms, disruptive behavior, and an increased risk for mood disorders, recent evidence also suggests that some individuals with PWS have repetitive behavior and social deficits reminiscent of autism spectrum disorders. In particular, it appears as if those with maternal uniparental disomy (UPD) as the cause of PWS are at greater risk for autistic symptomatology than those with paternal deletions of 15q11-q13. These findings are particularly intriguing in light of data implicating maternal duplications and triplications of the same chromosomal interval in idiopathic autism, as well as evidence that functional alterations of genes in this region are associated with social deficits found in a variety of neurodevelopmental disorders. This paper will review the recent evidence for phenotypic similarities between autism and PWS and the risk of symptomatology for the UPD subtype.