Recent progress on Tourette syndrome

A systematic review exploring perceptions of Tourette syndrome and tic disorders using the common-sense model of illness representations

OBJECTIVE

Tic disorders (TDs) are neurodevelopmental conditions characterised by tics and typically appear during childhood. The Common Sense Model of Self-Regulation (CSM) provides a useful theoretical framework for understanding health beliefs in people with TDs - and parents' beliefs given 'shared' illness experiences between child and parent. Exploring health beliefs in adults can also provide insight as to how TD-related beliefs may evolve over time. This systematic review aimed to use the CSM to synthesise findings from published studies exploring illness perceptions in people with TDs and parents.

METHODS

Six databases were searched for studies reporting findings assessing perceptions and beliefs of TDs that aligned with ≥1 CSM illness representation dimension. Forty-four studies were eligible and narratively synthesised.

RESULTS

The evidence particularly highlights the negative consequences of TDs upon employment opportunities, schooling and education, social lives and relationships - with experiences of stigma and discrimination weaving throughout these consequences. Findings from several studies reflecting emotional responses report feelings of self-consciousness, abnormality, and anxiety arising from TDs.

CONCLUSION

Findings have identified potential implications for research and practice, including identifying TD-related knowledge and beliefs that could be addressed through psychoeducation, and physiological and psychological outcomes which could be addressed through appropriate interventions.

PROTOCOL REGISTRATION

PROSPERO CRD42023446800.

Genetic architecture of tic disorders: A systematic review of 125 observational studies

BACKGROUND

To summarize and evaluate recent advances in the genetics of tic disorders (TDs) and to understand the possible pathogenic mechanisms behind this disorder.

METHODS

PubMed, EMBASE, the Cochrane Library, and four Chinese databases were searched from inception to September 2022. Observational original studies that explored genetic or chromosomal variations associated with the etiology, diagnosis, treatment, or prognosis of TDs were included. The Strengthening the Reporting of Genetic Association Studies (STREGA) statement was used to evaluate the quality of the included studies.

RESULTS

125 studies were finally included with 119 of moderate quality and 6 of low quality. A total of 32,439 cases with different types of TDs and 81,923 controls were included. The results involved 98 genes, 16 chromosomes, and multiple gene sets. Genome-wide studies were also included. The top three systems were the dopamine system, nervous system development, and the serotonin system. 96 loci in 56 genes and 20 regions in 14 chromosomes were reported to be relevant to TDs, with SLC6A4 (serotonin system) and NTN4 genes being relatively strongly correlated with the occurrence of TS, and ACP1 (serotonin system) and DBH (dopamine system) being relatively strongly correlated with TS comorbid with attention deficit hyperactivity disorder (ADHD).

CONCLUSION

Polygenic loci were found to play a key role in the occurrence and development of TDs. However, the applicability of the findings may be limited due to the small sample size, single-center design and the limited study quality of included studies. Future research with more comprehensive study designs and improved reporting transparency is needed to confirm the findings.

Immp2l knockdown in male mice increases stimulus-driven instrumental behaviour but does not alter goal-directed learning or neuron density in cortico-striatal circuits in a model of Tourette syndrome and autism spectrum disorder

Cortico-striatal neurocircuits mediate goal-directed and habitual actions which are necessary for adaptive behaviour. It has recently been proposed that some of the core symptoms of autism spectrum disorder (ASD) and Gilles de la Tourette syndrome (GTS), such as tics and other repetitive behaviours, may emerge because of imbalances in these neurocircuits. We have recently developed a model of ASD and GTS by knocking down Immp2l, a mitochondrial gene frequently associated with these disorders. The current study sought to determine whether Immp2l knockdown (KD) in male mice alters flexible, goal- or cue- driven behaviour using procedures specifically designed to examine response-outcome and stimulus-response associations, which underlie goal-directed and habitual behaviour, respectively. Whether Immp2l KD alters neuron density in cortico-striatal neurocircuits known to regulate these behaviours was also examined. Immp2l KD mice and wild type-like mice (WT) were trained on Pavlovian and instrumental learning procedures where auditory cues predicted food delivery and lever-press responses earned a food outcome. It was demonstrated that goal-directed learning was not changed for Immp2l KD mice compared to WT mice, as lever-press responses were sensitive to changes in the value of the food outcome, and to contingency reversal and degradation. There was also no difference in the capacity of KD mice to form habitual behaviours compared to WT mice following extending training of the instrumental action. However, Immp2l KD mice were more responsive to auditory stimuli paired with food as indicated by a non-specific increase in lever response rates during Pavlovian-to-instrumental transfer. Finally, there were no alterations to neuron density in striatum or any prefrontal cortex or limbic brain structures examined. Thus, the current study suggests that Immp2l is not necessary for learned maladaptive goal or stimulus driven behaviours in ASD or GTS, but that it may contribute to increased capacity for external stimuli to drive behaviour. Alterations to stimulus-driven behaviour could potentially influence the expression of tics and repetitive behaviours, suggesting that genetic alterations to Immp2l may contribute to these core symptoms in ASD and GTS. Given that this is the first application of this battery of instrumental learning procedures to a mouse model of ASD or GTS, it is an important initial step in determining the contribution of known risk-genes to goal-directed versus habitual behaviours, which should be more broadly applied to other rodent models of ASD and GTS in the future.

Cognitive and Neural Mechanisms of Behavior Therapy for Tics: A Perception-Action Integration Approach

European clinical guidelines recommend the use of Exposure and Response Prevention (ERP) and Comprehensive Behavioral Intervention for Tics (CBIT) as first-line treatments for tic disorders. Although ongoing efforts in research are being made to understand the mechanisms underlying these behavioral approaches, as of yet, the neurophysiological mechanisms behind behavioral interventions are poorly understood. However, this is essential to tailor interventions to individual patients in order to increase compliance and efficacy. The Theory of Event Coding (TEC) and its derivative BRAC (Binding and Retrieval in Action Control) provide a theoretical framework to investigate cognitive and neural processes in the context of tic disorders. In this context, tics are conceptualized as a phenomenon of enhanced perception-action binding, with premonitory urges constituting the perceptual and the motor or vocal expression constituting the action part of an event file. Based on this, CBIT is assumed to strongly affect stimulus-response binding in the context of response selection, whereas the effects of ERP presumably unfold during stimulus-response binding in the response inhibition context. Further studies are needed to clarify the neurophysiological processes underlying behavioral interventions to enable the individualization and further development of therapeutic approaches for tic disorders.

Teacher Knowledge of Tourette Syndrome and Associated Factors

BACKGROUND

TS is associated with learning disabilities and educational impairment. Teacher knowledge about TS may have a positive impact on students with TS, but factors associated with teacher knowledge of TS are not known.

METHODS

In this cross-sectional study, teachers of youth with TS and of a community control group completed a Teacher Understanding of Tourette Syndrome Survey (TUTS), a pilot questionnaire enquiring about self-perceived understanding, teacher knowledge, and sources of information. We compared TUTS scores between TS and control groups and between those who did and did not use specific sources of information about TS using Wilcoxon rank-sum tests. Bivariate correlation analyses were used to evaluate associations between teacher knowledge and potential contributing factors.

RESULTS

Data from 114 teachers of children with TS and 78 teachers of control subjects were included. Teachers of youth with TS had significantly more knowledge, had higher self-perceived understanding, and used more sources of information than teachers of the control group. Teachers who knew of the Tourette Association of America and who gathered information themselves had higher knowledge about TS than those who did not.

CONCLUSION

Teachers of children with TS know more about TS and use more sources to learn about TS than teachers of children without TS.

Successful Treatment of Tourette Syndrome With a Combination of Guanfacine and Aripiprazole: A Case Series

Tourette syndrome (TS) is a disorder of the nervous system that causes motor and vocal tics. Tics occur as sudden onset, rapid stereotyped purposeless movements or sounds. Combination therapies can be utilized for adequate control of motor and vocal tics. Patients diagnosed with TS and treated with aripiprazole and guanfacine from 2011-2022 at Saint Louis University Hospital were retrospectively surveyed. Three patients with TS treated with aripiprazole and guanfacine experienced significant improvement or complete resolution of their motor and vocal tics. In our cohort of three patients, the combination of guanfacine and aripiprazole significantly improved or resolved motor and vocal tics that were previously poorly controlled on other traditional medications.

Current and emerging pharmacotherapeutic strategies for Tourette syndrome

INTRODUCTION

Tourette syndrome (TS) is a chronic tic disorder characterized by both motor and vocal tics. The vast majority of patients present with co-morbid behavioral problems, especially tic-related obsessive-compulsive behaviors and attention-deficit and hyperactivity disorder. Evidence-based guidelines on the pharmacotherapy of TS have become available in recent years.

AREAS COVERED

The main purpose of this paper is to provide an overview of the current and emerging pharmacotherapeutic strategies for TS. A comprehensive search for the literature on the pharmacotherapy of tics was conducted using multiple databases (MEDLINE, Scopus, Web of Science, and Google Scholar), without date limits.

EXPERT OPINION

In consideration of the heterogeneity of the TS phenotypes, pharmacotherapy should be tailored to the individual patient. The choice of the pharmacological agent should take into account both the efficacy-to-tolerability ratio and the presence of co-morbid conditions. Evidence-based pharmacotherapy should aim at improving health-related quality life within a dynamic framework that typically requires active monitoring of the clinical presentation and reevaluation of the treatment intervention over time.

A 2-year longitudinal follow-up of quantitative assessment neck tics in Tourette's syndrome

Background

Neck motor tics in Tourette’s syndrome can cause severe neck complications. Although addressed in a few longitudinal studies, the clinical course of Tourette’s syndrome has not been quantitatively assessed. We had previously developed a method for quantifying the angular movements of neck tics using a compact gyroscope. Here, we present a follow-up study aimed at elucidating the clinical course of neck tics at both the group and individual levels.

Methods

Eleven patients with Tourette’s syndrome from our previous study participated in the present study, and their neck tics were recorded during a 5-min observation period. The severity of neck symptoms was assessed using the Yale Global Tic Severity Scale. The peak angular velocities and accelerations, tic counts, and severity scores in our previous study (baseline) and the present study (2-year follow-up) were compared at the group and individual levels. The individual level consistency between baseline and follow-up were calculated using intra-class correlation coefficients (ICCs, one-way random, single measure).

Results

At the group level, no significant change was observed between baseline and follow-up. At the individual level, angular velocity (ICC 0.73) and YGTSS scores (ICC 0.75) had substantial consistency over the two time points, and angular acceleration (ICC 0.59) and tic counts (ICC 0.69) had moderate consistency.

Conclusions

The intensity and frequency of neck tics did not change over time. Therefore, quantification of angular neck motor tics will aid in identifying patients with neck tics at high risk for severe neck complications.