Cerebellar abnormalities in infants and toddlers with Williams syndrome

Neuroimaging research in Williams syndrome: Beginning to bridge the gap with clinical care

Williams syndrome (WS) is a genetic disorder affecting multiple organ systems. Cardinal features include cardiovascular disease, distinct facies, and a unique cognitive profile characterized by intellectual disability, hypersociability, and visuospatial weaknesses. Here, we synthesize neuroimaging research in WS with a focus on how the current literature and future work may be leveraged to improve health and quality of life in WS. More than 80 neuroimaging studies in WS have been conducted, the vast majority of which have focused on identifying morphometric brain differences. Aside from decreased volume of the parieto-occipital region and increased cerebellar volume, morphometric findings have been variable across studies. fMRI studies investigating the visuospatial deficit have identified dorsal stream dysfunction and abnormal activation of the hippocampal formation. Minimal work has been done using PET or MRS. Future approaches that conduct neuroimaging in tandem with clinical phenotyping, utilize novel imaging techniques to visualize brain vasculature or provide biochemical and molecular information, and include more homogenous age groups across the lifespan, have significant potential to advance clinical care.

Gait characteristics of children with Williams syndrome with impaired visuospatial recognition: a three-dimensional gait analysis study

Williams syndrome (WS) is a genetically based neurodevelopmental disorder characterized by intellectual disability and impaired visuospatial recognition. The aim of this study was to analyze the gait characteristics of WS children with impaired visuospatial recognition using a three-dimensional gait analysis (3DGA) to clarify the gait adaptation needed to compensate for it. 3DGA was performed in 8 WS children with impaired visuospatial recognition (mean age, 11.8 years) and 9 age-, sex-, height-, and weight-matched controls. Clinical data, fundamental motor tests, and gait variables while walking on a flat surface and walking up a mat were compared between the two groups, and the correlations between variables were analyzed in the WS children. WS children showed impairment of balance function without muscle weakness. In walking on a flat surface, the WS group showed reduced walking speed, short step length, increased variability of step length, increased knee flexion throughout the stance phase, increased horizontal pelvic range of motion (ROM), and a low Gait Deviation Index and a high Gait Profile Score, which are indices of gait quality. In walking up a mat, the WS group showed further reduced walking speed and decreased sagittal hip flexion and ankle dorsiflexion ROM in the swing phase. Impaired balance function was significantly correlated with increased variability of step length and decreased sagittal ankle dorsiflexion ROM in the swing phase. The detailed gait pattern of WS children with impaired visuospatial recognition was presented. These findings show that impaired visuospatial recognition and balance function contribute to gait adaptation.

Macrocerebellum in Achondroplasia: A Further CNS Manifestation of FGFR3 Mutations?

Achondroplasia is the result of a mutation in the fibroblast growth factor receptor 3 gene (FGFR3). Appearances suggestive of macrocerebellum have not been described in this patient group. We retrospectively reviewed MR imaging studies of the brain in 23 children with achondroplasia. A constellation of imaging findings that are recognized in macrocerebellum was observed, including cerebellar hemisphere enlargement (inferior and superior extension, wrapping around the brainstem); an effaced retro- and infravermian cerebellar subarachnoid CSF space; a shortened midbrain; distortion of the tectal plate; and mass effect on the brainstem. All MR imaging studies exhibited some of these findings. Quantitative analysis confirmed an increased cerebellar volume compared with age- and sex-matched controls. We hypothesized that this may be due to direct effects of the FGFR3 mutation on cerebellar morphogenesis.

Cerebellar Contributions to Language in Typical and Atypical Development: A Review

In this review, we present the growing literature suggesting, from a variety of angles, that the cerebellum contributes to higher-order cognitive functions, rather than simply sensorimotor functions, and more specifically to language and its development. The cerebellum's association with language function is determined by the specific cortico-cerebellar connectivity to the right cerebellum from the left cortical hemisphere. The findings we review suggest that the cerebellum plays an important role as part of a broader language network, and also implies that the cerebellum may be a potential new therapeutic target to treat speech and language deficits, especially during development.

Isolated macrocerebellum: description of six cases and literature review

BACKGROUND

Macrocerebellum is a rare entity described as an isolated and abnormal increase of the cerebellum (CB) size without morphological or signal abnormalities. There have been only eleven patients with macrocerebellum reported in the literature so far.

METHODS

From December 2011 to March 2014, among 950 paediatric patients that underwent a magnetic resonance scan of the brain in our department, in six subjects an abnormal increase of the cerebellar volume was suspected. A volumetric analysis was performed in all patients on T1- weighted 3D imaging to confirm the diagnosis of macrocerebellum. The ratios between (I) volume of the CB and volume of the supratentorial structures (STB) and (II) volume of the CB and the sum of CB and STB (WB) were calculated in order to normalize the absolute values obtained and compared with the normal values present in literature.

RESULTS AND DISCUSSION

Quantitative analysis confirmed an increased cerebellar volume relatively to the STB volume ("t": 6.9518; P<0.001) and to the WB ("t": 7.1415; P<0.001) volume in comparison to the normal controls available in literature. Clinical characteristics and other neuroradiological findings of the patients are described. We also describe the differential features between isolated macrocerebellum and other pathological conditions that are characterized by cerebellar enlargement such as Lhermitte-Duclos, Sotos syndrome, Costello syndrome, Williams syndrome, Alexander disease and fucosidosis. Furthermore a detailed literature review is provided. Macrocerebellum is always associated with an abnormal mental and motor development.

CONCLUSION

Macrocerebellum is a neuroradiological entity that can be identified qualitatively and confirmed quantitatively through volumetric analysis. This is the largest cohort of patients with macrocerebellum described so far. The data available in literature on this entity show that macrocerebellum is not a specific disease but an epiphenomenon found in heterogeneous brain disorders.

The utility of rodent models of autism spectrum disorders

PURPOSE OF REVIEW

This review discusses the ways that rodent models of autism spectrum disorders (ASDs) have been used to gain critical information about convergent molecular pathways, the mechanisms underlying altered microcircuit structure and function, and as a screen for potential cutting edge-treatments for ASDs.

RECENT FINDINGS

There is convergent evidence that impaired developmental pruning of connections may be a common finding among several mouse models of ASDs. Recent studies have uncovered impaired autophagy by pathological mTOR activation as a potential contributor to microcircuit dysfunction and behavior. ASD-related disinhibition and exaggerated synaptic plasticity in multiple distinct circuits in cortex and reward circuits in striatum also contribute to social dysfunction and repetitive behaviors. New exciting molecular therapeutic techniques have reversed cognitive deficits in models of ASD, indicating that mouse models could be used for preclinical translational studies of new treatments.

SUMMARY

Rodent models of ASDs coupled to new emerging technologies for genome editing, cell-specific functional and structural imaging, and neuronal activity manipulation will yield critical insights into ASD pathogenesis and fuel the emergence of new treatments.

7q11.23 Duplication syndrome: Physical characteristics and natural history

In order to describe the physical characteristics, medical complications, and natural history of classic 7q11.23 duplication syndrome [hereafter Dup7 (MIM 609757)], reciprocal duplication of the region deleted in Williams syndrome [hereafter WS (MIM 194050)], we systematically evaluated 53 individuals aged 1.25-21.25 years and 11 affected adult relatives identified in cascade testing. In this series, 27% of probands with Dup7 had an affected parent. Seven of the 26 de novo duplications that were examined for inversions were inverted; in all seven cases one of the parents had the common inversion polymorphism of the WS region. We documented the craniofacial features of Dup7: brachycephaly, broad forehead, straight eyebrows, broad nasal tip, low insertion of the columella, short philtrum, thin upper lip, minor ear anomalies, and facial asymmetry. Approximately 30% of newborns and 50% of older children and adults had macrocephaly. Abnormalities were noted on neurological examination in 88.7% of children, while 81.6% of MRI studies showed structural abnormalities such as decreased cerebral white matter volume, cerebellar vermis hypoplasia, and ventriculomegaly. Signs of cerebellar dysfunction were found in 62.3%, hypotonia in 58.5%, Developmental Coordination Disorder in 74.2%, and Speech Sound Disorder in 82.6%. Behavior problems included anxiety disorders, ADHD, and oppositional disorders. Medical problems included seizures, 19%; growth hormone deficiency, 9.4%; patent ductus arteriosus, 15%; aortic dilation, 46.2%; chronic constipation, 66%; and structural renal anomalies, 18%. We compare these results to the WS phenotype and offer initial recommendations for medical evaluation and surveillance of individuals who have Dup7.

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.

Macrocerebellum, epilepsy, intellectual disability, and gut malrotation in a child with a 16q24.1-q24.2 contiguous gene deletion

Macrocerebellum is a rare condition characterized by enlargement of the cerebellum with conservation of the overall shape and cytoarchitecture. Here, we report on a child with a distinctive constellation of clinical features including macrocerebellum, epilepsy, apparent intellectual disability, dysautonomia, gut malrotation, and poor gut motility. Oligonucleotide chromosome microarray analysis identified a 16q24.1-q24.2 deletion that included four OMIM genes (FBXO31, MAP1LC3B, JPH3, and SLC7A5). Review of prior studies describing individuals with similar or overlapping16q24.1-q24.2 deletions identified no other reports of macrocerebellum. These observations highlight a potential genetic cause of this rare disorder and raise the possibility that one or more gene(s) in the 16q24.1-q24.2 interval regulate cerebellar development.

Learning by observation: insights from Williams syndrome

Observing another person performing a complex action accelerates the observer’s acquisition of the same action and limits the time-consuming process of learning by trial and error. Observational learning makes an interesting and potentially important topic in the developmental domain, especially when disorders are considered. The implications of studies aimed at clarifying whether and how this form of learning is spared by pathology are manifold. We focused on a specific population with learning and intellectual disabilities, the individuals with Williams syndrome. The performance of twenty-eight individuals with Williams syndrome was compared with that of mental age- and gender-matched thirty-two typically developing children on tasks of learning of a visuo-motor sequence by observation or by trial and error. Regardless of the learning modality, acquiring the correct sequence involved three main phases: a detection phase, in which participants discovered the correct sequence and learned how to perform the task; an exercise phase, in which they reproduced the sequence until performance was error-free; an automatization phase, in which by repeating the error-free sequence they became accurate and speedy. Participants with Williams syndrome beneficiated of observational training (in which they observed an actor detecting the visuo-motor sequence) in the detection phase, while they performed worse than typically developing children in the exercise and automatization phases. Thus, by exploiting competencies learned by observation, individuals with Williams syndrome detected the visuo-motor sequence, putting into action the appropriate procedural strategies. Conversely, their impaired performances in the exercise phases appeared linked to impaired spatial working memory, while their deficits in automatization phases to deficits in processes increasing efficiency and speed of the response. Overall, observational experience was advantageous for acquiring competencies, since it primed subjects’ interest in the actions to be performed and functioned as a catalyst for executed action.

The cerebellum in children with spina bifida and Chiari II malformation: Quantitative volumetrics by region

Few volumetric MRI studies of the entire cerebellum have been published; even less quantitative information is available in patients with hindbrain malformations, including the Chiari II malformation which is ubiquitous in patients with spina bifida meningomyelocele (SBM). In the present study, regional volumetric analyses of the cerebellum were conducted in children with SBM/Chiari II and typically developing (TD) children. Total cerebellar volume was significantly reduced in the SBM group relative to the TD group. After correcting for total cerebellum volume, and relative to the TD group, the posterior lobe was significantly reduced in SBM, the corpus medullare was not different, and the anterior lobe was significantly enlarged. Children with thoracic level lesions had smaller cerebellar volumes relative to those with lumbar/sacral lesions, who had smaller volumes compared to TD children. The reduction in cerebellar volume in the group with SBM represents not a change in linear scaling but rather a reconfiguration involving anterior lobe enlargement and posterior lobe reduction.

Cerebellar disorders in childhood: cognitive problems

Over the last decade, increasing evidence of cognitive functions of the cerebellum during development and learning processes could be ascertained. Posterior fossa malformations such as cerebellar hypoplasia or Joubert syndrome are known to be related to developmental problems in a marked to moderate extent. More detailed analyses reveal special deficits in attention, processing speed, visuospatial functions, and language. A study about Dandy Walker syndrome states a relationship of abnormalities in vermis lobulation with developmental problems. Further lobulation or volume abnormalities of the cerebellum and/or vermis can be detected in disorders as fragile X syndrome, Downs's syndrome, William's syndrome, and autism. Neuropsychological studies reveal a relation of dyslexia and attention deficit disorder with cerebellar functions. These functional studies are supported by structural abnormalities in neuroimaging in these disorders. Acquired cerebellar or vermis atrophy was found in groups of children with developmental problems such as prenatal alcohol exposure or extreme prematurity. Also, focal lesions during childhood or adolescence such as cerebellar tumor or stroke are related with neuropsychological abnormalities, which are most pronounced in visuospatial, language, and memory functions. In addition, cerebellar atrophy was shown to be a bad prognostic factor considering cognitive outcome in children after brain trauma and leukemia. In ataxia teleangiectasia, a neurodegenerative disorder affecting primarily the cerebellar cortex, a reduced verbal intelligence quotient and problems of judgment of duration are a hint of the importance of the cerebellum in cognition. In conclusion, the cerebellum seems to play an important role in many higher cognitive functions, especially in learning. There is a suggestion that the earlier the incorrect influence, the more pronounced the problems.

Gait function in adults with Williams syndrome

Despite early neurological reports of gait abnormalities in Williams syndrome (WS), a rare genetically based neurodevelopmental disorder, there has not yet been any systematic investigation of gait dysfunction in this disorder. The current study examined the gait characteristics in adults with WS and a neurologically normal control group as they walked at self-selected slow, preferred and fast speeds using the GAITRite walkway. The WS group showed hypokinetic gait, which manifested as reduced gait speed and stride length, but with a disproportionate increase in cadence (stepping frequency) as speed was increased. The WS group also showed increased variability of stride length and a broad based stepping pattern implicating a compensatory strategy for postural instability. Performance IQ correlated significantly with stride length in the WS group. While these results should be considered preliminary due to the small sample size, these findings have implications for our understanding of the neural basis of gait dysfunction in WS.

Defining the social phenotype in Williams syndrome: a model for linking gene, the brain, and behavior

Research into phenotype-genotype correlations in neurodevelopmental disorders has greatly elucidated the contribution of genetic and neurobiological factors to variations in typical and atypical development. Etiologically relatively homogeneous disorders, such as Williams syndrome (WS), provide unique opportunities for elucidating gene-brain-behavior relationships. WS is a neurogenetic disorder caused by a hemizygous deletion of approximately 25 genes on chromosome 7q11.23. This results in a cascade of physical, cognitive-behavioral, affective, and neurobiological aberrations. WS is associated with a markedly uneven neurocognitive profile, and the mature state cognitive profile of WS is relatively well developed. Although anecdotally, individuals with WS have been frequently described as unusually friendly and sociable, personality remains a considerably less well studied area. This paper investigates genetic influences, cognitive-behavioral characteristics, aberrations in brain structure and function, and environmental and biological variables that influence the social outcomes of individuals with WS. We bring together a series of findings across multiple levels of scientific enquiry to examine the social phenotype in WS, reflecting the journey from gene to the brain to behavior. Understanding the complex multilevel scientific perspective in WS has implications for understanding typical social development by identifying important developmental events and markers, as well as helping to define the boundaries of psychopathology.

The cerebellum in cognitive processes: supporting studies in children

Over the last decade, increasing evidence of cognitive functions of the cerebellum during development and learning processes could be ascertained. Posterior fossa malformations such as cerebellar hypoplasia or Joubert syndrome are known to be related to developmental problems in a marked to moderate extent. More detailed analyses reveal special deficits in attention, processing speed, visuospatial functions and language. A study about Dandy Walker syndrome states a relationship of abnormalities in vermis lobulation with developmental problems. Further lobulation or volume abnormalities of the cerebellum and/or vermis can be detected in disorders as fragile X syndrome, Downs's syndrome or William's syndrome. Neuropsychological studies reveal a relation of dyslexia and attention deficit disorder with cerebellar functions. These functional studies are supported by structural abnormalities in neuroimaging in these disorders. Acquired cerebellar or vermis atrophy was found in groups of children with developmental problems such as prenatal alcohol exposure or extreme prematurity. Also focal lesions during childhood or adolescence such as cerebellar tumour or stroke are related with neuropsychological abnormalities, which are most pronounced in visuo-spatial, language and memory functions. In addition, cerebellar atrophy was shown to be a bad prognostic factor considering cognitive outcome in children after brain trauma and leukaemia. In ataxia teleangiectasia, a neurodegenerative disorder affecting primarily the cerebellar cortex, a reduced verbal IQ and problems of judgment of duration are a hint of the importance of the cerebellum in cognition. In conclusion, the cerebellum seems to play an important role in many higher cognitive functions especially in learning. There is a suggestion that the earlier the incorrect influence the more pronounced the problems.

Language abilities in Williams syndrome: a critical review

Williams syndrome is a rare genetic disorder in which, it is claimed, language abilities are relatively strong despite mild to moderate mental retardation. Such claims have, in turn, been interpreted as evidence either for modular preservation of language or for atypical constraints on cognitive development. However, this review demonstrates that there is, in fact, little evidence that syntax, morphology, phonology, or pragmatics are any better than predicted by nonverbal ability, although performance on receptive vocabulary tests is relatively good. Similarly, claims of an imbalance between good phonology and impaired or atypical lexical semantics are without strong support. There is, nevertheless, consistent evidence for specific deficits in spatial language that mirror difficulties in nonverbal spatial cognition, as well as some tentative evidence that early language acquisition proceeds atypically. Implications for modular and neuroconstructivist accounts of language development are discussed.

Nomograms of the axial fetal cerebellar hemisphere circumference and area throughout gestation

OBJECTIVE

The widely applied transcerebellar diameter (TCD) obtained at axial cranial imaging, measures the distance between the lateral aspects of the cerebellum and incorporates the width of the cerebellar vermis. Our objective was to create reference ranges of axial fetal cerebellar hemisphere circumference (CHC) and area (CHA), independent of the cerebellar vermis, throughout gestation.

METHODS

This cross-sectional study involved pregnant patients between 14 and 41 weeks of gestation. Inclusion criteria consisted of well-established dates (confirmed by early ultrasound), non-anomalous singleton fetuses and intact amniotic membranes. Sonographic measurements included biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL), humerus length (HL), TCD, and estimated fetal weight (EFW). Values of axial fetal CHC and CHA were each calculated as the mean of three separate measurements. The 5th, 50th and 95th centiles were estimated at each week of gestational age (GA) by least-squares regression for the mean and standard deviation (SD) of the CHC and CHA as functions of GA. r2 and associated P-values for the relationships of CHC and CHA with other sonographic biometric measurements were calculated.

RESULTS

The study included 651 consecutive patients. All attempts at obtaining axial fetal CHC and CHA were successful. Mean maternal age was 27.3+/-6.7 years, median gravidity was 1 (range 1-16), and median parity was 1 (range 0-6). Mean CHC (cm) throughout gestation was modeled as -2.091+0.2563xGA (weeks) (SD=-0.075+0.0164xGA), and mean CHA (cm2) was modeled as 0.245-0.0765xGA+0.00506xGA2 (SD=1.167-0.1565xGA+0.006785xGA(2)-0.00008028xGA3). Fetal axial CHC and CHA correlated significantly and strongly with BPD, HC, AC, HL, FL, TCD and EFW (all R2 values were >or=0.95, and all P-values were <0.001).

CONCLUSION

Nomograms of axial fetal cerebellar hemisphere circumference and area throughout gestation, independent of the cerebellar vermis, have been provided.

Laterality in Persons with Intellectual Disability. I—Do Patients with Trisomy 21 and Williams–Beuren Syndrome Differ from Typically Developing Persons?

Persons with trisomy 21 (T21) and Williams-Beuren syndrome (WBS) have different brain abnormalities which may affect manual laterality. We assessed 45 persons with T21 and 34 with WBS (mean age 13) and 81 typically developing children (TD). Manual laterality was assessed with a fifteen-item task administered two times, and Bishop's card-reaching task. We found more left-handers in the T21 group compared to the other two groups. Inconsistent laterality was higher in the two groups with genetic diseases than in the TD group. For Bishop's test, both T21 and WBS participants were less right-oriented than the TD group. They displayed different response patterns in midline crossing when reaching for the cards, but did not display more midline crossing inhibition than the TD group. Is atypical handedness linked to specific genetic syndromes and, more specifically for persons with T21, to the trisomy of some of the genes?

Cloning and expression of a brain-specific putative UDP-GalNAc: polypeptide N-acetylgalactosaminyltransferase gene

We isolated a rat cDNA clone and its human orthologue, which are most homologous to UDP-GalNAc: polypeptide N-acetylgalactosaminyltransferase 9, by homology-based PCR from brain. Nucleotide sequence analysis of these putative GalNAc-transferases (designated pt-GalNAc-T) showed that they contained structural features characteristic of the GalNAc-transferase family. It was also found that human pt-GalNAc-T was identical to the gene WBSCR17, which is reported to be in the critical region of patients with Williams-Beuren Syndrome, a neurodevelopmental disorder, and to be predominantly expressed in brain and heart. In order to investigate the expression of pt-GalNAc-T in brain in more detail, we first examined that of human pt-GalNAc-T by Northern blot analysis and found the expression of the 5.0-kb mRNA to be most abundant in cerebral cortex with somewhat less abundant in cellebellum. The expression of rat pt-GalNAc-T was investigated more extensively. The brain-specific expression of 2.0-kb and 5.0-kb transcripts was demonstrated by Northern blot analysis. In situ hybridization in the adult brain revealed high levels of expression in cerebellum, hippocampus, thalamus, and cerebral cortex. Moreover, observation at high magnification revealed the expression to be associated with neurons, but not with glial cells. Analysis of the rat embryos also demonstrated that rat pt-GalNAc-T was expressed in the nervous system, including in the diencephalons, cerebellar primordium, and dorsal root ganglion. However, recombinant human pt-GalNAc-T, which was expressed in insect cells, did not glycosylate several peptides derived from mammalian mucins, suggesting that it may have a strict substrate specificity. The brain-specific expression of pt-GalNAc-T suggested its involvement in brain development, through O-glycosylation of proteins in the neurons.

Williams-Beuren syndrome: a challenge for genotype-phenotype correlations

Many human chromosomal abnormality syndromes include specific cognitive and behavioural components. Children with Prader-Willi syndrome lack a paternally derived copy of the proximal long arm of chromosome 15, and eat uncontrollably; in Angelman syndrome lack of a maternal contribution of 15q11-q13 results in absence of speech, frequent smiling and episodes of paroxysmal laughter; deletions on 22q11 can be associated with obsessive behaviour and schizophrenia. The neurodevelopmental disorder Williams-Beuren syndrome (WBS), is caused by a microdeletion at 7q11.23 and provides us with one of the most convincing models of a relationship that links genes with human cognition and behaviour. The hypothesis is that deletion of one or a series of genes causes neurodevelopmental abnormalities that manifest as the fractionation of mental abilities typical of WBS. Detailed molecular characterization of the deletion alongside well-defined cognitive profiling in WBS provides a unique opportunity to investigate the neuromolecular basis of complex cognitive behaviour, and develop integrated approaches to study gene function and genotype-phenotype correlations.