Specific EEG resting state biomarkers in FXS and ASD.

BACKGROUND: Fragile X syndrome (FXS) and autism spectrum disorder (ASD) are neurodevelopmental conditions that often have a substantial impact on daily functioning and quality of life. FXS is the most common cause of inherited intellectual disability (ID) and the most common monogenetic cause of ASD. Previous literature has shown that electrophysiological activity measured by electroencephalogram (EEG) during resting state is perturbated in FXS and ASD. However, whether electrophysiological profiles of participants with FXS and ASD are similar remains unclear. The aim of this study was to compare EEG alterations found in these two clinical populations presenting varying degrees of cognitive and behavioral impairments. METHODS: Resting state EEG signal complexity, alpha peak frequency (APF) and power spectral density (PSD) were compared between 47 participants with FXS (aged between 5-20), 49 participants with ASD (aged between 6-17), and 52 neurotypical (NT) controls with a similar age distribution using MANCOVAs with age as covariate when appropriate. MANCOVAs controlling for age, when appropriate, and nonverbal intelligence quotient (NVIQ) score were subsequently performed to determine the impact of cognitive functioning on EEG alterations. RESULTS: Our results showed that FXS participants manifested decreased signal complexity and APF compared to ASD participants and NT controls, as well as altered power in the theta, alpha and low gamma frequency bands. ASD participants showed exaggerated beta power compared to FXS participants and NT controls, as well as enhanced low and high gamma power compared to NT controls. However, ASD participants did not manifest altered signal complexity or APF. Furthermore, when controlling for NVIQ, results of decreased complexity in higher scales and lower APF in FXS participants compared to NT controls and ASD participants were not replicated. CONCLUSIONS: These findings suggest that signal complexity and APF might reflect cognitive functioning, while altered power in the low gamma frequency band might be associated with neurodevelopmental conditions, particularly FXS and ASD.

Reversible encephalitis-like episodes in fragile X-associated tremor/ataxia syndrome: a case report.

BACKGROUND: Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder caused by CGG repeat expansion of FMR1 gene. Both FXTAS and neuronal intranuclear inclusion disease (NIID) belong to polyglycine diseases and present similar clinical, radiological, and pathological features, making it difficult to distinguish these diseases. Reversible encephalitis-like attacks are often observed in NIID. It is unclear whether they are presented in FXTAS and can be used for differential diagnosis of NIID and FXTAS. CASE PRESENTATION: A 63-year-old Chinese male with late-onset gait disturbance, cognitive decline, and reversible attacks of fever, consciousness impairment, dizziness, vomiting, and urinary incontinence underwent neurological assessment and examinations, including laboratory tests, electroencephalogram test, imaging, skin biopsy, and genetic test. Brain MRI showed T2 hyperintensities in middle cerebellar peduncle and cerebrum, in addition to cerebellar atrophy and DWI hyperintensities along the corticomedullary junction. Lesions in the brainstem were observed. Skin biopsy showed p62-positive intranuclear inclusions. The possibilities of hypoglycemia, lactic acidosis, epileptic seizures, and cerebrovascular attacks were excluded. Genetic analysis revealed CGG repeat expansion in FMR1 gene, and the number of repeats was 111. The patient was finally diagnosed as FXTAS. He received supportive treatment as well as symptomatic treatment during hospitalization. His encephalitic symptoms were completely relieved within one week. CONCLUSIONS: This is a detailed report of a case of FXTAS with reversible encephalitis-like episodes. This report provides new information for the possible and rare features of FXTAS, highlighting that encephalitis-like episodes are common in polyglycine diseases and unable to be used for differential diagnosis.

Hypnotic treatment improves sleep architecture and EEG disruptions and rescues memory deficits in a mouse model of fragile X syndrome.

Fragile X syndrome (FXS) is associated with disrupted cognition and sleep abnormalities. Sleep loss negatively impacts cognitive function, and one untested possibility is that disrupted cognition in FXS is exacerbated by abnormal sleep. We tested whether ML297, a hypnotic acting on G-protein-activated inward-rectifying potassium (GIRK) channels, could reverse sleep phenotypes and disrupted memory in Fmr1-/y mice. Fmr1-/y mice exhibit reduced non-rapid eye movement (NREM) sleep and fragmented NREM architecture, altered sleep electroencephalogram (EEG) oscillations, and reduced EEG coherence between cortical areas; these are partially reversed following ML297 administration. Treatment following contextual fear or spatial learning restores disrupted memory consolidation in Fmr1-/y mice. During memory recall, Fmr1-/y mice show an altered balance of activity among hippocampal principal neurons vs. parvalbumin-expressing interneurons; this is partially reversed by ML297. Because sleep disruption could impact neurophysiological phenotypes in FXS, augmenting sleep may improve disrupted cognition in this disorder.

Unmethylated Mosaic Full Mutation Males without Fragile X Syndrome.

Fragile X syndrome (FXS) is the leading inherited cause of intellectual disability (ID) and single gene cause of autism. Although most patients with FXS and the full mutation (FM) have complete methylation of the fragile X messenger ribonucleoprotein 1 (FMR1) gene, some have mosaicism in methylation and/or CGG repeat size, and few have completely unmethylated FM alleles. Those with a complete lack of methylation are rare, with little literature about the cognitive and behavioral phenotypes of these individuals. A review of past literature was conducted regarding individuals with unmethylated and mosaic FMR1 FM. We report three patients with an unmethylated FM FMR1 alleles without any behavioral or cognitive deficits. This is an unusual presentation for men with FM as most patients with an unmethylated FM and no behavioral phenotypes do not receive fragile X DNA testing or a diagnosis of FXS. Our cases showed that mosaic males with unmethylated FMR1 FM alleles may lack behavioral phenotypes due to the presence of smaller alleles producing the FMR1 protein (FMRP). However, these individuals could be at a higher risk of developing fragile X-associated tremor/ataxia syndrome (FXTAS) due to the increased expression of mRNA, similar to those who only have a premutation.

Differential cognitive and behavioral development from 6 to 24 months in autism and fragile X syndrome.

BACKGROUND: Specifying early developmental differences among neurodevelopmental disorders with distinct etiologies is critical to improving early identification and tailored intervention during the first years of life. Recent studies have uncovered important differences between infants with fragile X syndrome (FXS) and infants with familial history of autism spectrum disorder who go on to develop autism themselves (FH-ASD), including differences in brain development and behavior. Thus far, there have been no studies longitudinally investigating differential developmental skill profiles in FXS and FH-ASD infants. METHODS: The current study contrasted longitudinal trajectories of verbal (expressive and receptive language) and nonverbal (gross and fine motor, visual reception) skills in FXS and FH-ASD infants, compared to FH infants who did not develop ASD (FH-nonASD) and typically developing controls. RESULTS: Infants with FXS showed delays on a nonverbal composite compared to FH-ASD (as well as FH-nonASD and control) infants as early as 6 months of age. By 12 months an ordinal pattern of scores was established between groups on all domains tested, such that controls > FH-nonASD > FH-ASD > FXS. This pattern persisted through 24 months. Cognitive level differentially influenced developmental trajectories for FXS and FH-ASD. CONCLUSIONS: Our results demonstrate detectable group differences by 6 months between FXS and FH-ASD as well as differential trajectories on each domain throughout infancy. This work further highlights an earlier onset of global cognitive delays in FXS and, conversely, a protracted period of more slowly emerging delays in FH-ASD. Divergent neural and cognitive development in infancy between FXS and FH-ASD contributes to our understanding of important distinctions in the development and behavioral phenotype of these two groups.

Cannabidiol (Epidyolex®) for severe behavioral manifestations in patients with tuberous sclerosis complex, mucopolysaccharidosis type III and fragile X syndrome: protocol for a series of randomized, placebo-controlled N-of-1 trials.

BACKGROUND: Many rare genetic neurodevelopmental disorders (RGNDs) are characterized by intellectual disability (ID), severe cognitive and behavioral impairments, potentially diagnosed as a comorbid autism spectrum disorder or attention-deficit hyperactivity disorder. Quality of life is often impaired due to irritability, aggression and self-injurious behavior, generally refractory to standard therapies. There are indications from previous (case) studies and patient reporting that cannabidiol (CBD) may be an effective treatment for severe behavioral manifestations in RGNDs. However, clear evidence is lacking and interventional research is challenging due to the rarity as well as the heterogeneity within and between disease groups and interindividual differences in treatment response. Our objective is to examine the effectiveness of CBD on severe behavioral manifestations in three RGNDs, including Tuberous Sclerosis Complex (TSC), mucopolysaccharidosis type III (MPS III), and Fragile X syndrome (FXS), using an innovative trial design. METHODS: We aim to conduct placebo-controlled, double-blind, block-randomized, multiple crossover N-of-1 studies with oral CBD (twice daily) in 30 patients (aged ≥ 6 years) with confirmed TSC, MPS III or FXS and severe behavioral manifestations. The treatment is oral CBD up to a maximum of 25 mg/kg/day, twice daily. The primary outcome measure is the subscale irritability of the Aberrant Behavior Checklist. Secondary outcome measures include (personalized) patient-reported outcome measures with regard to behavioral and psychiatric outcomes, disease-specific outcome measures, parental stress, seizure frequency, and adverse effects of CBD. Questionnaires will be completed and study medication will be taken at the participants' natural setting. Individual treatment effects will be determined based on summary statistics. A mixed model analysis will be applied for analyzing the effectiveness of the intervention per disorder and across disorders combining data from the individual N-of-1 trials. DISCUSSION: These N-of-1 trials address an unmet medical need and will provide information on the effectiveness of CBD for severe behavioral manifestations in RGNDs, potentially generating generalizable knowledge at an individual-, disorder- and RGND population level. TRIAL REGISTRATION: EudraCT: 2021-003250-23, registered 25 August 2022, https://www.clinicaltrialsregister.eu/ctr-search/trial/2021-003250-23/NL .

Characterising the social interaction style of autism in young adult males with fragile X syndrome.

BACKGROUND: The characterisation of autism in fragile X syndrome (FXS) has been a source of controversy due to the complexity of disentangling autism traits from common features of the FXS phenotype. Autism in FXS is significantly underdiagnosed in the community, which may be partly due to insufficient clinical description of the social interaction profile of autism within the FXS phenotype. In this study, we applied a classic framework for characterising social interaction styles in autism to a sample of young adult males with FXS and co-occurring autism to enhance understanding of how the social challenges associated with autism manifest within FXS. METHODS: Participants were 41 males (M age = 18 years) with FXS and co-occurring autism. Interaction samples were coded for expression of predominately 'active' (characterised by a desire to make social approaches) or 'passive' (characterised by lack of initiation of social approach towards others) interaction profiles. Differences in the expression of phenotypic features of FXS, including anxiety, attention-deficit/hyperactivity disorder, cognitive, adaptive and language impairments and autism symptom severity, were examined across those with passive and active interaction styles. RESULTS: Approximately half of the sample was classified as active and half as passive, demonstrating diversity in the social phenotype of autism associated with FXS. The two subtypes did not differ in autism severity, anxiety or attention-deficit/hyperactivity disorder symptoms or in cognitive, adaptive or language abilities. CONCLUSIONS: This study enhances understanding of FXS-associated autism by documenting phenotypic variability in the social interaction profile in this group, with active and passive social interaction styles represented. The two social interaction styles were not associated with differential expression of common phenotypic features of FXS, suggesting similar support needs.

Adaptive behaviour deficits in individuals with 3q29 deletion syndrome.

BACKGROUND: 3q29 deletion syndrome (3q29del) is associated with a significantly increased risk for neurodevelopmental and neuropsychiatric phenotypes. Mild to moderate intellectual disability (ID) is common in this population, and previous work by our team identified substantial deficits in adaptive behaviour. However, the full profile of adaptive function in 3q29del has not been described nor has it been compared with other genomic syndromes associated with elevated risk for neurodevelopmental and neuropsychiatric phenotypes. METHODS: Individuals with 3q29del (n = 32, 62.5% male) were evaluated using the Vineland Adaptive Behaviour Scales, Third Edition, Comprehensive Parent/Caregiver Form (Vineland-3). We explored the relationship between adaptive behaviour and cognitive function, executive function, and neurodevelopmental and neuropsychiatric comorbidities in our 3q29del study sample, and we compared subjects with 3q29del with published data on fragile X syndrome, 22q11.2 deletion syndrome and 16p11.2 deletion and duplication syndromes. RESULTS: Individuals with 3q29del had global deficits in adaptive behaviour that were not driven by specific weaknesses in any given domain. Individual neurodevelopmental and neuropsychiatric diagnoses had a small effect on adaptive behaviour, and the cumulative number of comorbid diagnoses was significantly negatively associated with Vineland-3 performance. Both cognitive ability and executive function were significantly associated with adaptive behaviour, and executive function was a better predictor of Vineland-3 performance than cognitive ability. Finally, the severity of adaptive behaviour deficits in 3q29del was distinct from previously published data on comparable genomic disorders. CONCLUSIONS: Individuals with 3q29del have significant deficits in adaptive behaviour, affecting all domains assessed by the Vineland-3. Executive function is a better predictor of adaptive behaviour than cognitive ability in this population and suggests that interventions targeting executive function may be an effective therapeutic strategy.

Neural correlates of face processing among preschoolers with fragile X syndrome, autism spectrum disorder, autism siblings, and typical development.

The current study examined patterns of event-related potential (ERP) responses during a face processing task in groups of preschoolers uniquely impacted by autism spectrum disorder (ASD), including (1) children with ASD; (2) children with fragile X syndrome (FXS); (3) children with familial risk for ASD, but without a diagnosis (i.e., ASIBs); and (4) a low-risk control (LRC) group. Children with FXS have a high incidence of ASD diagnoses, but there have been no studies of the ERP response to faces in children with FXS and little work focused on children with ASD who have cognitive impairment. The current study examined children's ERP responses to faces and houses in four groups: LRC (N = 28, age = 5.2 years), ASIB (N = 23, age = 5.5 years), FXS (N = 19, age = 5.82 years), and ASD (N = 23, age = 5.5 years). The FXS and ASD groups were characterized by the presence of cognitive impairment. Pictures of upright and inverted faces and houses were presented while recording EEG with a 128-channel system. The N170 occurred at about 200 ms post stimulus onset, was largest on the posterior-lateral electrodes, and was larger for faces than houses. The P1 and N170 ERP components were larger for the FXS group than for the other three groups. The N170 ERP amplitude for the ASD and ASIB groups was smaller than both the LRC and FXS groups, and the LRC and FXS groups had the largest N170 responses on the right side. No difference was found in N170 latency between groups. The similarity of the ASD and ASIB responses suggest a common genetic or environmental origin of the reduced response. Although children with FXS have a high incidence of ASD outcomes, they differed from ASD and ASIB children in this study. Specifically, the children with FXS were hyperresponsive to all stimulus types while the ASD and ASIB groups showed attenuated responses for specific stimuli.

FMR1 Carriers Report Executive Function Changes Prior to Fragile X-Associated Tremor/Ataxia Syndrome: A Longitudinal Study.

BACKGROUND: Men with fragile X-associated tremor/ataxia syndrome (FXTAS) often develop executive dysfunction, characterized by disinhibition, frontal dyscontrol of movement, and working memory and attention changes. Although cross-sectional studies have suggested that earlier executive function changes may precede FXTAS, the lack of longitudinal studies has made it difficult to address this hypothesis. OBJECTIVE: To determine whether executive function deterioration experienced by premutation carriers (PC) in daily life precedes and predicts FXTAS. METHODS: This study included 66 FMR1 PC ranging from 40 to 78 years (mean, 59.5) and 31 well-matched healthy controls (HC) ages 40 to 75 (mean, 57.7) at baseline. Eighty-four participants returned for 2 to 5 follow up visits over a duration of 1 to 9 years (mean, 4.6); 28 of the PC developed FXTAS. The Behavior Rating Inventory of Executive Function-Adult Version (BRIEF-A) was completed by participants and their spouses/partners at each visit. RESULTS: Longitudinal mixed model regression analyses showed a greater decline with age in PC compared to HC on the Metacognition Index (MI; self-initiation, working memory, organization, task monitoring). Conversion to FXTAS was associated with worsening MI and Behavioral Regulation Index (BRI; inhibition, flexibility, emotion modulation). For spouse/partner report, FXTAS conversion was associated with worsening MI. Finally, increased self-report executive function problems at baseline significantly predicted later development of FXTAS. CONCLUSIONS: Executive function changes experienced by male PC represent a prodrome of the later movement disorder. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Language Skills Influence Transition Planning in Adolescents With Fragile X Syndrome.

Individuals with fragile X syndrome (FXS) and their parents have a range of experiences navigating the crucial transition period between adolescence and adulthood. Semistructured interviews of 47 mothers of adolescents with FXS (mean child age = 15.89 years) were analyzed to identify mothers' changing expectations during the adolescent period and parent goals related to work and postsecondary education. Mothers' work and education goals were explored in relation to child factors such as language skills and autism characteristics. Lower language skills were associated with lower likelihood of reporting vocational goals. Results suggest that adolescents with FXS with lower language ability are less likely to have vocational plans for adulthood during this critical period and may need greater transition planning assistance.

Cholesterol alterations in fragile X syndrome, autism spectrum disorders and other neurodevelopmental disorders.

Neurodevelopmental disorders (NDDs) are a group of etiologically diverse diseases primarily associated with abnormal brain development, impaired cognition, and various behavioral problems. The majority of NDDs present a wide range of clinical phenotypes while sharing distinct cellular and biochemical alterations. Low plasma cholesterol levels have been reported in a subset of NNDs including, autism spectrum disorder (ASD) and fragile X syndrome (FXS). The present review focuses on cholesterol metabolism and discusses the current evidence of lipid disruption in ASD, FXS, and other genetically related NDDs. The characterization of these common deficits might provide valuable insights into their underlying physiopathology and help identify potential therapeutic targets.

An Exploratory Study of Pragmatic Language Use Across Contexts With the Pragmatic Rating Scale-School Age Among Autistic Boys and Boys With Fragile X Syndrome Plus Autism.

PURPOSE: Autistic boys and boys with co-occurring fragile X syndrome and autism spectrum disorder (FXS + ASD) demonstrate similar pragmatic language difficulties. The Pragmatic Rating Scale-School Age (PRS-SA) captures ecologically valid metrics of pragmatic language impairments in these populations. It is traditionally scored based on the Autism Diagnostic Observation Schedule (ADOS), which may limit the use of the PRS-SA more broadly in research and clinical contexts. METHOD: This study evaluated the feasibility of the PRS-SA based on a shorter, semistructured conversational context compared to the ADOS in school-age autistic boys (n = 16) and boys with FXS + ASD (n = 16), matched on ASD traits. Differences across ADOS and conversational contexts and associations with ASD-related social difficulties were evaluated. RESULTS: Findings revealed differences in PRS-SA scores between ADOS and conversational contexts, but only for the FXS + ASD group. Limited associations were observed between PRS-SA scores and ASD traits. CONCLUSIONS: Results from this study indicate the feasibility of using the PRS-SA in a shorter conversational context than the ADOS to assess pragmatic language among autistic boys. For boys with FXS + ASD, contextual differences warrant careful consideration in future work.

Adaptive, behavioral, and cognitive outcomes in individuals with fragile X syndrome with varying autism severity.

This study aimed to determine the association between severity of autism spectrum disorder (ASD) and cognitive, behavioral, and molecular measures in individuals with fragile X syndrome (FXS). Study inclusion criteria included individuals with FXS and (1) age 6-40 years, (2) full-scale IQ < 84, and (3) language ≥3-word phrases. ASD symptom severity was determined by Autism Diagnostic Observation Schedule-2 (ADOS-2). Other measures identified non-verbal IQ, adaptive skills, and aberrant behaviors. Molecular measures included blood FMR1 and CYFIP1 mRNA levels, FMRP and MMP9 levels. Analysis of variance (ANOVA) and Spearman's correlations were used to compare ASD severity groups. Data from 54 individuals was included with no/mild (N = 7), moderate (N = 18), and severe (N = 29) ASD. Individuals with high ASD severity had lower adaptive behavior scores (47.48 ± 17.49) than the no/mild group (69.00 ± 20.45, p = 0.0366); they also had more challenging behaviors, lethargy, and stereotypic behaviors. CYFIP1 mRNA expression levels positively correlated with the ADOS-2 comparison score(r2  = 0.33, p = 0.0349), with no significant correlations with other molecular markers. In conclusion, autism symptom severity is associated with more adverse cognitive and adaptive skills and specific behaviors in FXS, whereas CYFIP1 mRNA expression levels may be a potential biomarker for severity of ASD in FXS.

Fragile X Syndrome and Fetal Alcohol Syndrome: Occurrence of Dual Diagnosis in a Set of Triplets.

BACKGROUND: Fragile X syndrome (FXS) and fetal alcohol syndrome disorders are both common causes of intellectual disability in children. When both conditions are present in the same individual, the resultant phenotype may make identification of clinical issues and management challenging. CASE PRESENTATION: In this case report, we present a case of triplets who had significant in utero alcohol exposure; 2 of whom also have FXS and the other not having the fragile X mutation. The siblings with FXS have subtle differences in the physical phenotype compared with the other one, who has prominent features of partial fetal alcohol syndrome instead. However, all 3 siblings have intellectual impairment (although this is more severe in the 2 with FXS), meet diagnostic criteria for autism spectrum disorder, and present with severe behavioral challenges. The clinical presentation of the 2 siblings with FXS is much more severe as compared to a child with FXS alone, and this is likely due to the additive effect of in utero alcohol exposure and environmental factors. We discuss the combination of these 2 pathologies and how this can affect the overall clinical presentation. CONCLUSION: In the management of children with FXS, evaluation for other risk factors that can have neurobehavioral sequelae is important, and these can affect clinical presentation and prognosis.

Developmental delays in cortical auditory temporal processing in a mouse model of Fragile X syndrome.

BACKGROUND: Autism spectrum disorders (ASD) encompass a wide array of debilitating symptoms, including sensory dysfunction and delayed language development. Auditory temporal processing is crucial for speech perception and language development. Abnormal development of temporal processing may account for the language impairments associated with ASD. Very little is known about the development of temporal processing in any animal model of ASD. METHODS: In the current study, we quantify auditory temporal processing throughout development in the Fmr1 knock-out (KO) mouse model of Fragile X Syndrome (FXS), a leading genetic cause of intellectual disability and ASD-associated behaviors. Using epidural electrodes in awake and freely moving wildtype (WT) and KO mice, we recorded auditory event related potentials (ERP) and auditory temporal processing with a gap-in-noise auditory steady state response (gap-ASSR) paradigm. Mice were recorded at three different ages in a cross sectional design: postnatal (p)21, p30 and p60. Recordings were obtained from both auditory and frontal cortices. The gap-ASSR requires underlying neural generators to synchronize responses to gaps of different widths embedded in noise, providing an objective measure of temporal processing across genotypes and age groups. RESULTS: We present evidence that the frontal, but not auditory, cortex shows significant temporal processing deficits at p21 and p30, with poor ability to phase lock to rapid gaps in noise. Temporal processing was similar in both genotypes in adult mice. ERP amplitudes were larger in Fmr1 KO mice in both auditory and frontal cortex, consistent with ERP data in humans with FXS. CONCLUSIONS: These data indicate cortical region-specific delays in temporal processing development in Fmr1 KO mice. Developmental delays in the ability of frontal cortex to follow rapid changes in sounds may shape language delays in FXS, and more broadly in ASD.

Behavioural and physiological indicators of anxiety reflect shared and distinct profiles across individuals with neurogenetic syndromes.

Anxiety is heightened in individuals with intellectual disability, particularly in those with specific neurogenetic syndromes. Assessment of anxiety for these individuals is hampered by a lack of appropriate measures that cater for communication impairment, differences in presentation, and overlapping features with co-occurring conditions. Here, we adopt a multi-method approach to identify fine-grained behavioural and physiological (via salivary cortisol) responses to anxiety presses in people with fragile X (FXS; n = 27; Mage = 20.11 years; range 6.32 - 47.04 years) and Cornelia de Lange syndromes (CdLS; n = 27; Mage = 18.42 years; range 4.28 - 41.08 years), two neurogenetic groups at high risk for anxiety, compared to neurotypical children (NT; n = 21; Mage = 5.97 years; range 4.34 - 7.30 years). Results indicate that physical avoidance of feared stimuli and proximity seeking to a familiar adult are prominent behavioural indicators of anxiety/stress in FXS and CdLS. Heightened pervasive physiological arousal was identified in these groups via salivary cortisol. An association between autistic characteristics and anxiety was evident in the FXS group but not in the CdLS group pointing to syndrome-specific nuances in the association between anxiety and autism. This study furthers understanding of the behavioural and physiological presentation of anxiety in individuals with intellectual disability and progresses theoretical developments regarding the development and maintenance of anxiety at the intersection of autism.

Electroencephalographic (EEG) Biomarkers in Genetic Neurodevelopmental Disorders.

Collectively, neurodevelopmental disorders are highly prevalent, but more than a third of neurodevelopmental disorders have an identifiable genetic etiology, each of which is individually rare. The genes associated with neurodevelopmental disorders are often involved in early brain development, neuronal signaling, or synaptic plasticity. Novel treatments for many genetic neurodevelopmental disorders are being developed, but disease-relevant clinical outcome assessments and biomarkers are limited. Electroencephalography (EEG) is a promising noninvasive potential biomarker of brain function. It has been used extensively in epileptic disorders, but its application in neurodevelopmental disorders needs further investigation. In this review, we explore the use of EEG in 3 of the most prevalent genetic neurodevelopmental disorders-Angelman syndrome, Rett syndrome, and fragile X syndrome. Quantitative analyses of EEGs, such as power spectral analysis or measures of connectivity, can quantify EEG signatures seen on qualitative review and potentially correlate with phenotypes. In both Angelman syndrome and Rett syndrome, increased delta power on spectral analysis has correlated with clinical markers of disease severity including developmental disability and seizure burden, whereas spectral power analysis on EEG in fragile X syndrome tends to demonstrate abnormalities in gamma power. Further studies are needed to establish reliable relationships between quantitative EEG biomarkers and clinical phenotypes in rare genetic neurodevelopmental disorders.