Early developmental pathways to autism spectrum disorder in tuberous sclerosis complex

Heterogeneity of Autism Characteristics in Genetic Syndromes: Key Considerations for Assessment and Support

Purpose of Review

Elevated prevalence of autism characteristics is reported in genetic syndromes associated with intellectual disability. This review summarises recent evidence on the behavioural heterogeneity of autism in the following syndromes: Fragile X, Cornelia de Lange, Williams, Prader-Willi, Angelman, Down, Smith-Magenis, and tuberous sclerosis complex. Key considerations for assessment and support are discussed.

Recent Findings

The profile and developmental trajectory of autism-related behaviour in these syndromes indicate some degree of syndrome specificity which may interact with broader behavioural phenotypes (e.g. hypersociability), intellectual disability, and mental health (e.g. anxiety). Genetic subtype and co-occurring epilepsy within syndromes contribute to increased significance of autism characteristics. Autism-related strengths and challenges are likely to be overlooked or misunderstood using existing screening/diagnostic tools and criteria, which lack sensitivity and specificity within these populations.

Summary

Autism characteristics are highly heterogeneous across genetic syndromes and often distinguishable from non-syndromic autism. Autism diagnostic assessment practices in this population should be tailored to specific syndromes. Service provisions must begin to prioritise needs-led support.

Resting-State fMRI Networks in Children with Tuberous Sclerosis Complex

BACKGROUND AND PURPOSE

There are no published studies examining resting state networks (RSNs) and their relationship with neurodevelopmental metrics in tuberous sclerosis complex (TSC). We aimed to identify major resting-state functional magnetic resonance imaging (rs-fMRI) networks in infants with TSC and correlate network analyses with neurodevelopmental assessments, autism diagnosis, and seizure history.

METHODS

Rs-fMRI data from 34 infants with TSC, sedated with propofol during the scan, were analyzed to identify auditory, motor, and visual RSNs. We examined the correlations between auditory, motor, and visual RSNs at approximately 11.5 months, neurodevelopmental outcome at approximately 18.5 months, and diagnosis of autism spectrum disorders at approximately 36 months of age.

RESULTS

RSNs were obtained in 76.5% (26/34) of infants. We observed significant negative correlations between auditory RSN and auditory comprehension test scores (p = .038; r = -.435), as well as significant positive correlations between motor RSN and gross motor skills test scores (p = .023; r = .564). Significant positive correlations between motor RSNs and gross motor skills (p = .012; r = .754) were observed in TSC infants without autism, but not in TSC infants with autism, which could suggest altered motor processing. There were no significant differences in RSNs according to seizure history.

CONCLUSIONS

Negative correlation between auditory RSN, as well as positive correlation between motor RSN and developmental outcome measures might reflect different brain mechanisms and, when identified, may be helpful in predicting later function. A larger study of TSC patients with a healthy control group is needed before auditory and motor RSNs could be considered as neurodevelopmental outcome biomarkers.

Characterizing the Interplay Between Autism Spectrum Disorder and Comorbid Medical Conditions: An Integrative Review

Co-occurring medical disorders and associated physiological abnormalities in individuals with autism spectrum disorder (ASD) may provide insight into causal pathways or underlying biological mechanisms. Here, we review medical conditions that have been repeatedly highlighted as sharing the strongest associations with ASD-epilepsy, sleep, as well as gastrointestinal and immune functioning. We describe within each condition their prevalence, associations with behavior, and evidence for successful treatment. We additionally discuss research aiming to uncover potential aetiological mechanisms. We then consider the potential interaction between each group of conditions and ASD and, based on the available evidence, propose a model that integrates these medical comorbidities in relation to potential shared aetiological mechanisms. Future research should aim to systematically examine the interactions between these physiological systems, rather than considering these in isolation, using robust and sensitive biomarkers across an individual's development. A consideration of the overlap between medical conditions and ASD may aid in defining biological subtypes within ASD and in the development of specific targeted interventions.

Early autism symptoms in infants with tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is a rare, autosomal dominant genetic syndrome that confers significantly increased risk for autism spectrum disorder (ASD), with 50-60% of infants with TSC meeting criteria for ASD by 3 years of age. In a previous study of the current longitudinal cohort, we found that infants with TSC who develop ASD (TSC/ASD) evidence decreased cognitive abilities that diverge from infants with TSC and no ASD (TSC/no ASD). We extended this work by asking whether TSC/ASD infants (n = 13) differed from TSC/no ASD infants (n = 10) and infants with low developmental risk and no ASD (LR; n = 21) in their social communication functioning during the first year of life. We measured early ASD symptoms with the Autism Observation Scale for Infants (AOSI) at 9 and 12 months of age. At both ages, infants in the TSC/ASD group had significantly higher AOSI total scores than infants in the TSC/no ASD and LR groups, which were not fully explained by differences in cognitive abilities. Several items on the AOSI at both ages were predictive of ASD outcome, particularly those representing core social communication deficits (e.g., social referencing). Our findings signal the need for further study of this population within the first year and provide strong justification for early identification and early intervention targeting social communication skills in infants with TSC. Autism Res 2017, 10: 1981-1990. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

LAY SUMMARY

We examined early signs of autism spectrum disorder (ASD) in infants with tuberous sclerosis complex (TSC), approximately 50% of whom will meet criteria for ASD by age 3. Infants with TSC and ASD showed deficits in social communication behaviors by 9 months of age that were clearly distinguishable from behaviors in infants with TSC who do not develop ASD and low risk infants. Results support the importance of early ASD screening and intervention for infants with TSC.