Sensory Gating in Neurodevelopmental Disorders: A Scoping Review

This review aimed to explore the current understanding of sensory gating in neurodevelopmental disorders as a possible transdiagnostic mechanism. We applied methods according to the Joanna Briggs Institute Manual for Evidence Synthesis, following the population, concept, and context scoping review eligibility criteria. Using a comprehensive search strategy in five relevant research databases (Medline, EMBASE, CINAHL, PsychInfo, and Scopus), we searched for relevant peer-reviewed, primary research articles and unpublished data. Two independent reviewers screened the titles and abstracts, full-texts, and completed data extraction. We identified a total of 81 relevant articles and used descriptive analyses to summarize the characteristics and outcomes of all identified studies. Literature regarding sensory gating was most common in autistic populations with relatively fewer studies examining attention-deficit/hyperactivity disorder, tic disorders, and childhood-onset fluency disorder (COFD). The methods to assess sensory gating varied widely both within and between groups and included measures such as habituation, prepulse inhibition, affect-modulated inhibition, medication and other intervention trials. Most consistently, when participants complete questionnaires about their sensory experiences, those who have neurodevelopmental disorders report differences in their sensory gating. Affect-modulated inhibition appears to be discrepant between samples with and without neurodevelopmental disorder diagnoses. Habituation was the most commonly reported phenomenon and many differences in habituation have been found in autistic individuals and individuals with tic disorders whereas concerns with inhibition seemed more common in COFD. Overall, the evidence is inconsistent within and between disorders suggesting there is still much to learn about sensory gating in neurodevelopmental disorders.

Cross-sectional Exploration of the Relationship Between Glutamate Abnormalities and Tic Disorder Severity Using Proton Magnetic Resonance Spectroscopy

Glutamate (Glu) has been reported to be closely related to the pathophysiology of Tic Disorders (TD). By using proton magnetic resonance spectroscopy (1H-MRS), we aimed to investigate the relationship between in vivo Glu levels and the severity of TD. We performed a cross-sectional study in medication-free patients with TD and healthy controls aged between 5 and 13 years using 1H-MRS at 3 T. First, we measured the Glu levels in both patients and controls and observed the difference in subgroups, including mild TD patients and moderate TD patients. We then examined the correlations between the Glu levels and clinical features of the patients. Finally, we assessed the diagnostic value of 1H-MRS and the influencing factors. Our results show that the Glu levels in the striatum of all patients with TD were not significantly different from those of the healthy controls. Subgroup analysis revealed that the Glu levels in the moderate TD group were higher than those in the mild TD group and healthy controls. The correlation analysis showed that Glu levels are strongly positive correlated with TD severity. The optimal cutoff value of Glu levels to differentiate mild tics from moderate tics was 1.244, with a sensitivity of 88.2% and a specificity of 94.7%. Multiple linear regression models revealed that the severity of TD is one of the important factors that affect Glu levels. We conclude that Glu levels are mainly associated with the severity of tics, thus it could serve as a key biomarker for TD classification.

Treatment use among children with Tourette syndrome living in the United States, 2014

Treatment of Tourette syndrome (TS) can be complicated by changes over time in tic expression, severity, and co-occurring disorders. Using the 2014 National Survey of the Diagnosis and Treatment of ADHD and Tourette Syndrome, this study provides descriptive estimates of the use of behavioral interventions and medication among children living with TS. Parent-reported data on 115 children aged 5-17 years ever diagnosed with TS were analyzed to provide descriptive, unweighted results. Overall, 77.4% of children had current or past use of any TS treatment; 59.1% ever used behavioral interventions and 56.1% had ever taken TS medication. Children with "moderate" or "severe" versus "mild" TS, ≥1 co-occurring disorders, and tics that interfered with functioning were significantly more likely to have used one or more TS treatments. Side effects were reported for 84.4% of children who took TS medication. Most parents of children with current TS (87.2%) were satisfied with the management of their child's TS. However, parents of children with "moderate" or "severe" current TS were significantly more dissatisfied compared to parents of children with "mild" TS. Findings from this study could be used to inform efforts to support children living with TS and their families.

Interrogating the Genetic Determinants of Tourette's Syndrome and Other Tic Disorders Through Genome-Wide Association Studies

OBJECTIVE

Tourette's syndrome is polygenic and highly heritable. Genome-wide association study (GWAS) approaches are useful for interrogating the genetic architecture and determinants of Tourette's syndrome and other tic disorders. The authors conducted a GWAS meta-analysis and probed aggregated Tourette's syndrome polygenic risk to test whether Tourette's and related tic disorders have an underlying shared genetic etiology and whether Tourette's polygenic risk scores correlate with worst-ever tic severity and may represent a potential predictor of disease severity.

METHODS

GWAS meta-analysis, gene-based association, and genetic enrichment analyses were conducted in 4,819 Tourette's syndrome case subjects and 9,488 control subjects. Replication of top loci was conducted in an independent population-based sample (706 case subjects, 6,068 control subjects). Relationships between Tourette's polygenic risk scores (PRSs), other tic disorders, ascertainment, and tic severity were examined.

RESULTS

GWAS and gene-based analyses identified one genome-wide significant locus within FLT3 on chromosome 13, rs2504235, although this association was not replicated in the population-based sample. Genetic variants spanning evolutionarily conserved regions significantly explained 92.4% of Tourette's syndrome heritability. Tourette's-associated genes were significantly preferentially expressed in dorsolateral prefrontal cortex. Tourette's PRS significantly predicted both Tourette's syndrome and tic spectrum disorders status in the population-based sample. Tourette's PRS also significantly correlated with worst-ever tic severity and was higher in case subjects with a family history of tics than in simplex case subjects.

CONCLUSIONS

Modulation of gene expression through noncoding variants, particularly within cortico-striatal circuits, is implicated as a fundamental mechanism in Tourette's syndrome pathogenesis. At a genetic level, tic disorders represent a continuous spectrum of disease, supporting the unification of Tourette's syndrome and other tic disorders in future diagnostic schemata. Tourette's PRSs derived from sufficiently large samples may be useful in the future for predicting conversion of transient tics to chronic tic disorders, as well as tic persistence and lifetime tic severity.

Neuroimaging in Tourette Syndrome: Research Highlights From 2014-2015

Tourette Syndrome (ts) is a developmental neuropsychiatric disorder of the central nervous system defined by the presence of chronic tics. While investigations of the underlying brain mechanisms have provided valuable information, a complete understanding of the pathophysiology of ts remains elusive. Neuroimaging methods provide remarkable tools for examining the human brain, and have been used to study brain structure and function in ts. In this article, we review ts neuroimaging studies published in 2014-2015. We highlight a number of noteworthy studies due to their innovative methods and interesting findings. Yet, we note that many of the recent studies share common concerns, specifically susceptibility to motion artifacts and modest sample sizes. Thus, we encourage future work to carefully address potential methodological confounds and to study larger samples to increase the potential for replicable results.