From genes to brain: understanding brain development in neurogenetic disorders using neuroimaging techniques

Pharmacotherapy of Disruptive Behaviors in Children with Intellectual Disabilities

Disruptive behaviors are a class of predominantly externalizing behaviors that include physical aggression, property destruction, temper outbursts, verbal aggression, and some forms of self-injurious behaviors. Externalizing behaviors are also major components of disruptive, impulse-control and conduct disorders, disruptive mood dysregulation disorder, trauma-related and stressor-related disorders, intermittent explosive disorder, personality disorders, and other neuropsychiatric and neurodevelopmental disorders. Disruptive behaviors and associated disorders are among the most frequent reasons for child behavioral health referrals and are the most common reason for referrals among children with intellectual disabilities. The focus of this paper is on the adjunctive role of integrated psychopharmacological treatment in the management of children with disruptive behaviors and co-occurring intellectual disabilities. The decision-making process for adding pharmacotherapy to a comprehensive treatment plan incorporates not only a working knowledge of basic behavioral neurobiology of disruptive behaviors but also an understanding of the strengths and weaknesses of various pharmacotherapies. Importantly, there is little evidence to support the use of psychopharmacologic agents in managing difficult behaviors in children with intellectual disabilities, but with that said, risperidone has the strongest evidence base for its use.

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.

Basal ganglia involvement in ARX patients: The reason for ARX patients very specific grasping?

The ARX (Aristaless Related homeoboX) gene was identified in 2002 as responsible for XLAG syndrome, a lissencephaly characterized by an almost complete absence of cortical GABAergic interneurons, and for milder forms of X-linked Intellectual Disability (ID) without apparent brain abnormalities. The most frequent mutation found in the ARX gene, a duplication of 24 base pairs (c.429_452dup24) in exon 2, results in a recognizable syndrome in which patients present ID without primary motor impairment, but with a very specific upper limb distal motor apraxia associated with a pathognomonic hand-grip, described as developmental Limb Kinetic Apraxia (LKA).

In this study, we first present ARX expression during human fetal brain development showing that it is strongly expressed in GABAergic neuronal progenitors during the second and third trimester of pregnancy. We show that although ARX expression strongly decreases towards the end of gestation, it is still present after birth in some neurons of the basal ganglia, thalamus and cerebral cortex, suggesting that ARX also plays a role in more mature neuron functioning. Then, using morphometric brain MRI in 13 ARX patients carrying c.429_452dup24 mutation and in 13 sex- and age-matched healthy controls, we show that ARX patients have a significantly decreased volume of several brain structures including the striatum (and more specifically the caudate nucleus), hippocampus and thalamus as well as decreased precentral gyrus cortical thickness. We observe a significant correlation between caudate nucleus volume reduction and motor impairment severity quantified by kinematic parameter of precision grip.

As basal ganglia are known to regulate sensorimotor processing and are involved in the control of precision gripping, the combined decrease in cortical thickness of primary motor cortex and basal ganglia volume in ARX dup24 patients is very likely the anatomical substrate of this developmental form of LKA.

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c.429_452dup24 in ARX is responsible for ID with Limb Kinetic Apraxia.

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During human brain development, ARX is expressed in GABAergic neuronal progenitors.

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ARX patients have a significantly decreased caudate nucleus volume by MRI.

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This caudate nucleus volume reduction is correlated with motor impairment severity.

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These anatomic findings may explain this developmental form of Limb Kinetic Apraxia.

Apert and Crouzon syndromes-Cognitive development, brain abnormalities, and molecular aspects

Apert and Crouzon are the most common craniosynostosis syndromes associated with mutations in the fibroblast growth factor receptor 2 (FGFR2) gene. We conducted a study to examine the molecular biology, brain abnormalities, and cognitive development of individuals with these syndromes. A retrospective longitudinal review of 14 patients with Apert and Crouzon syndromes seen at the outpatient Craniofacial Surgery Hospital for Rehabilitation of Craniofacial Anomalies in Brazil from January 1999 through August 2010 was performed. Patients between 11 and 36 years of age (mean 18.29 ± 5.80), received cognitive evaluations, cerebral magnetic resonance imaging, and molecular DNA analyses. Eight patients with Apert syndrome (AS) had full scale intelligence quotients (FSIQs) that ranged from 47 to 108 (mean 76.9 ± 20.2), and structural brain abnormalities were identified in five of eight patients. Six patients presented with a gain-of-function mutation (p.Ser252Trp) in FGFR2 and FSIQs in those patients ranged from 47 to78 (mean 67.2 ± 10.7). One patient with a gain-of-function mutation (p.Pro253Arg) had a FSIQ of 108 and another patient with an atypical splice mutation (940-2A →G) had a FSIQ of 104. Six patients with Crouzon syndrome had with mutations in exons IIIa and IIIc of FGFR2 and their FSIQs ranged from 82 to 102 (mean 93.5 ± 6.7). These reveal that molecular aspects are another factor that can be considered in studies of global and cognitive development of patients with Apert and Crouzon syndrome (CS). © 2016 Wiley Periodicals, Inc.

Multidimensional morphometric 3D MRI analyses for detecting brain abnormalities in children: impact of control population

Automated morphometric approaches are used to detect epileptogenic structural abnormalities in 3D MR images in adults, using the variance of a control population to obtain z-score maps in an individual patient. Due to the substantial changes the developing human brain undergoes, performing such analyses in children is challenging. This study investigated six features derived from high-resolution T1 datasets in four groups: normal children (1.5T or 3T data), normal clinical scans (3T data), and patients with structural brain lesions (3T data), with each n = 10. Normative control data were obtained from the NIH study on normal brain development (n = 401). We show that control group size substantially influences the captured variance, directly impacting the patient's z-scores. Interestingly, matching on gender does not seem to be beneficial, which was unexpected. Using data obtained at higher field scanners produces slightly different base rates of suprathreshold voxels, as does using clinically derived normal studies, suggesting a subtle but systematic effect of both factors. Two approaches for controlling suprathreshold voxels in a multidimensional approach (combining features and requiring a minimum cluster size) were shown to be substantial and effective in reducing this number. Finally, specific strengths and limitations of such an approach could be demonstrated in individual cases.

Knowledge and perceptions about fragile X syndrome: implications for diagnosis, intervention, and research

We surveyed 439 professionals in the field of autism to assess their knowledge and perceptions about fragile X syndrome (FXS) and related issues. Almost half had worked with at least one child diagnosed with FXS, yet most lacked basic knowledge about the condition, underestimated its significance in the etiology of autism spectrum disorders, and rarely accessed fragile X-specific resources. A majority perceived etiology to be an important variable in therapeutic response while three quarters felt that professionals in the field of autism should play an active role in referring children for etiological evaluation. Despite these opinions, most respondents either rarely or never inquired about etiology when working with a new client. The survey results underscore the need for training and education so that autism professionals can become effective partners in diagnostic genetic referral and in research and implementation of syndrome-specific interventions.

Primary immunodeficiency diseases associated with neurologic manifestations

Primary immunodeficiency diseases (PID) are a heterogeneous group of inherited disorders of the immune system, predisposing individuals to recurrent infections, allergy, autoimmunity, and malignancies. A considerable number of these conditions have been found to be also associated with neurologic signs and symptoms. These manifestations are considered core features of some immunodeficiency syndromes, such as ataxia-telangiectasia and purine nucleoside phosphorylase deficiency, or occur less prominently in some others. Diverse pathological mechanisms including defective responses to DNA damage, metabolic errors, and autoimmune phenomena have been associated with neurologic abnormalities; however, several issues remain to be elucidated. Greater awareness of these associated features and gaining a better understanding of the contributing mechanisms will lead to prompt diagnosis and treatment and possibly development of novel preventive and therapeutic strategies. In this review, we aim to provide a brief description of the clinical and genetic characteristics of PID associated with neurologic complications.

Brain tissue- and region-specific abnormalities on volumetric MRI scans in 21 patients with Bardet-Biedl syndrome (BBS)

Background

Bardet-Biedl syndrome (BBS) is a heterogeneous human disorder inherited in an autosomal recessive pattern, and characterized by the primary findings of obesity, polydactyly, hypogonadism, and learning and behavioural problems. BBS mouse models have a neuroanatomical phenotype consisting of third and lateral ventriculomegaly, thinning of the cerebral cortex, and reduction in the size of the corpus striatum and hippocampus. These abnormalities raise the question of whether humans with BBS have a characteristic morphologic brain phenotype. Further, although behavioral, developmental, neurological and motor defects have been noted in patients with BBS, to date, there are limited reports of brain findings in BBS. The present study represents the largest systematic evaluation for the presence of structural brain malformations and/or progressive changes, which may contribute to these functional problems.

Methods

A case-control study of 21 patients, most aged 13-35 years, except for 2 patients aged 4 and 8 years, who were diagnosed with BBS by clinical criteria and genetic analysis of known BBS genes, and were evaluated by qualitative and volumetric brain MRI scans. Healthy controls were matched 3:1 by age, sex and race. Statistical analysis was performed using SAS language with SAS STAT procedures.

Results

All 21 patients with BBS were found to have statistically significant region- and tissue-specific patterns of brain abnormalities. There was 1) normal intracranial volume; 2) reduced white matter in all regions of the brain, but most in the occipital region; 3) preserved gray matter volume, with increased cerebral cortex volume in only the occipital lobe; 4) reduced gray matter in the subcortical regions of the brain, including the caudate, putamen and thalamus, but not in the cerebellum; and 5) increased cerebrospinal fluid volume.

Conclusions

There are distinct and characteristic abnormalities in tissue- and region- specific volumes of the brain in patients with BBS, which parallel the findings, described in BBS mutant mouse models. Some of these brain abnormalities may be progressive and associated with the reported neurological and behavioral problems. Further future correlation of these MRI scan findings with detailed neurologic and neuropsychological exams together with genotype data will provide better understanding of the pathophysiology of BBS.

Is the good-imitator-poor-talker profile syndrome-specific in Down syndrome?: evidence from standardised imitation and language measures

The emergence of the Down syndrome (DS) behavioural phenotype during early development may be of great importance for early intervention. The main goal of this study was to investigate the good-imitator-poor-talker developmental profile in DS at preschool age. Twenty children with Down syndrome (DS; mean nonverbal mental age NMA 1 y10 m) and 15 children with non-specific mental retardation (NS-MR; mean NMA 1 y11 m) participated in this study. The Preschool Imitation and Praxis Scale (PIPS) and the Dutch version of the MacArthur-Bates Communicative Development Inventories (N-CDI) were used to determine absolute and relative (contrasted to a nonverbal mental age reference) imitation and language abilities. Results revealed that there was clear evidence for a good-imitator-poor-talker profile in preschoolers with DS. However, only the advanced bodily imitation ability seems to be syndrome-specific. Clinical implications of these findings are considered.

Regional cortical volumes and congenital heart disease: a MRI study in 22q11.2 deletion syndrome

Children with congenital heart disease (CHD) who survive surgery often present impaired neurodevelopment and qualitative brain anomalies. However, the impact of CHD on total or regional brain volumes only received little attention. We address this question in a sample of patients with 22q11.2 deletion syndrome (22q11DS), a neurogenetic condition frequently associated with CHD. Sixty-one children, adolescents, and young adults with confirmed 22q11.2 deletion were included, as well as 80 healthy participants matched for age and gender. Subsequent subdivision of the patients group according to CHD yielded a subgroup of 27 patients with normal cardiac status and a subgroup of 26 patients who underwent cardiac surgery during their first years of life (eight patients with unclear status were excluded). Regional cortical volumes were extracted using an automated method and the association between regional cortical volumes, and CHD was examined within a three-condition fixed factor. Robust protection against type I error used Bonferroni correction. Smaller total cerebral volumes were observed in patients with CHD compared to both patients without CHD and controls. The pattern of bilateral regional reductions associated with CHD encompassed the superior parietal region, the precuneus, the fusiform gyrus, and the anterior cingulate cortex. Within patients, a significant reduction in the left parahippocampal, the right middle temporal, and the left superior frontal gyri was associated with CHD. The present results of global and regional volumetric reductions suggest a role for disturbed hemodynamic in the pathophysiology of brain alterations in patients with neurodevelopmental disease and cardiac malformations.

Molecular and cellular mechanisms elucidating neurocognitive basis of functional impairments associated with intellectual disability in Down syndrome

Down syndrome, the most common genetic cause of intellectual disability, is associated with brain disorders due to chromosome 21 gene overdosage. Molecular and cellular mechanisms involved in the neuromorphological alterations and cognitive impairments are reported herein in a global model. Recent advances in Down syndrome research have lead to the identification of altered molecular pathways involved in intellectual disability, such as Calcineurin/NFATs pathways, that are of crucial importance in understanding the molecular basis of intellectual disability pathogenesis in this syndrome. Potential treatments in mouse models of Down syndrome, including antagonists of NMDA or GABA(A) receptors, and microRNAs provide new avenues to develop treatments of intellectual disability. Nevertheless, understanding the links between molecular pathways and treatment strategies in human beings requires further research.

Deviant trajectories of cortical maturation in 22q11.2 deletion syndrome (22q11DS): a cross-sectional and longitudinal study

22q11.2 deletion syndrome (22q11DS) is associated with an increased susceptibility to develop schizophrenia. Despite a large body of literature documenting abnormal brain structure in 22q11DS, cerebral changes associated with brain maturation in 22q11DS remained largely unexplored. To map cortical maturation from childhood to adulthood in 22q11.2 deletion syndrome, we used cerebral MRI from 59 patients with 22q11DS, aged 6 to 40, and 80 typically developing controls; three year follow-up assessments were also available for 32 patients and 31 matched controls. Cross-sectional cortical thickness trajectories during childhood and adolescence were approximated in age bins. Repeated-measures were also conducted with the longitudinal data. Within the group of patients with 22q11DS, exploratory measures of cortical thickness differences related to COMT polymorphism, IQ, and schizophrenia were also conducted. We observed deviant trajectories of cortical thickness changes with age in patients with 22q11DS. In affected preadolescents, larger prefrontal thickness was observed compared to age-matched controls. Afterward, we observed greater cortical loss in 22q11DS with a convergence of cortical thickness values by the end of adolescence. No compelling evidence for an effect of COMT polymorphism on cortical maturation was observed. Within 22q11DS, significant differences in cortical thickness were related to cognitive level in children and adolescents, and to schizophrenia in adults. Deviant trajectories of cortical thickness from childhood to adulthood provide strong in vivo cues for a defect in the programmed synaptic elimination, which in turn may explain the susceptibility of patients with 22q11DS to develop psychosis.

Psychosis in children with velocardiofacial syndrome (22q11.2 deletion syndrome)

Velocardiofacial syndrome, now known as 22q11.2 deletion syndrome (22qDS), is estimated to affect more than 700 children born in the United States each year. Some clinical studies have found increased rates of schizophrenia in adults with 22qDS. However, these studies have been limited by small sample size and possible ascertainment bias. The psychiatric disorders most commonly reported in children and adolescents with 22qDS have been attention-deficit/hyperactivity disorder, oppositional defiant disorder, anxiety disorders, and major depression. Psychotic symptoms have been observed in 14% to 28% of children with 22qDS, but their clinical significance remains uncertain. A 5-year follow-up study of 22qDS children who reported psychotic symptoms at baseline found they had an increased risk for a subsequent psychotic disorder. Thus, a broad differential diagnosis should be considered when 22qDS children present with psychotic symptoms. Longitudinal studies are needed to better understand the full extent of the psychopathology associated with 22qDS.

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.

Template-O-Matic: a toolbox for creating customized pediatric templates

Processing pediatric neuroimaging data is a challenge due to pervasive morphological changes that occur in the human brain during normal development. This is of special relevance when reference data is used as part of the processing approach, as in spatial normalization and tissue segmentation. Current approaches construct reference data (templates) by averaging brain images from a control group of subjects, or by creating custom templates from the group under study. In this technical note, we describe a new, and generalized method of constructing such appropriate reference data by statistically analyzing a large sample (n=404) of healthy children, as acquired during the NIH MRI study of normal brain development. After eliminating non-contributing demographic variables, we modeled the effects of age (first, second, and third-order terms) and gender, for each voxel in gray matter and white matter. By appropriate weighting with the parameter estimates from these analyses, complete tissue maps can be generated automatically from this database to match a pediatric population selected for study. The algorithm is implemented in the form of a toolbox for the SPM5 image data processing suite, which we term Template-O-Matic. We compare the performance of this approach with the current method of template generation and discuss the implications of our approach.

Neural phenotypes of common and rare genetic variants

Neuroimaging methods offer a powerful way to bridge the gaps between genes, neurobiology and behavior. Such investigations may be further empowered by complementary strategies involving chromosomal abnormalities associated with particular neurobehavioral phenotypes, which can help to localize causative genes and better understand the genetics of complex traits in the general population. Here we review the evidence from studies using these convergent approaches to investigate genetic influences on brain structure: (1) studies of common genetic variations associated with particular neuroanatomic phenotypes, and (2) studies of possible 'genetic subtypes' of neuropsychiatric disorders with very high penetrance, with a focus on neuroimaging studies using novel computational brain mapping algorithms. Finally, we discuss the contribution of behavioral neurogenetics research to our understanding of the genetic basis of neuropsychiatric disorders in the broader population.