Tourette syndrome and obsessive-compulsive disorder: A comprehensive review of structural alterations and neurological mechanisms

Impact of visual stimulus complexity on associative learning and associated reaction times in migraine patients

The semantic complexity and verbalizability of visual stimuli can influence associative learning. The Rutgers Acquired Equivalence Test (RAET) uses semantically rich stimuli (faces and colored fish) to assess associative learning and generalization, while a modified version, the Polygon test, employs simpler stimuli with reduced semantic content (grayscale circles and geometric shapes). Although cognitive alterations are well-documented in migraine patients during interictal periods, the impact of visual stimulus complexity on associative learning and reaction times has not been studied. Forty-one migraine patients without aura completed both the RAET and Polygon tests. Performance metrics included acquisition error ratios, retrieval and generalization error ratios, and reaction times. The two tests were compared using non-parametric statistical methods. Migraine patients demonstrated comparable acquisition performance on the RAET and Polygon test. However, reaction times were significantly longer in the Polygon test across both acquisition and test phases. Retrieval and generalization performance were also similar between tests, despite longer reaction times with semantically reduced stimuli. Migraine patients showed consistent learning performance across visual stimuli of varying semantic complexity. Prolonged reaction times with simpler stimuli suggest increased cognitive demands, potentially mitigated by cortical compensatory mechanisms that maintain learning ability under challenging conditions.

Brain Iron Alteration in Pediatric Tourette Syndrome: A Quantitative Susceptibility Mapping Study

BACKGROUND

The cortico-striato-thalamo-cortical circuits play a crucial role in the pathogenesis of Tourette syndrome (TS). While iron deficiency has been reported in adult TS, the iron content in pediatric TS remains poorly understood. This study aims to quantitatively assess whole-brain iron deposition in pediatric TS compared to typically developing (TD) children using quantitative susceptibility mapping (QSM).

METHODS

In this prospective study, we recruited 50 children with a clinical diagnosis of TS and 50 age- and gender-matched TD controls. Whole-brain images were acquired using 3D T1 and multi-echo gradient-recalled echo sequences. QSM maps were generated using the STISuite toolbox. After normalizing the QSM maps to Montreal Neurological Institute space, voxel-based analysis was applied to compare between-group differences in iron content. Additionally, we evaluated the relationship between iron content and tic severity in TS children using the Pearson's correlation test.

RESULTS

Compared to TD children, those with TS exhibited iron deficiency in the right anterior cingulum (pFDR < 0.001). Conversely, increased QSM values were observed in the bilateral putamen of TS children (pFDR < 0.001). Notably, QSM values in the left putamen showed a significant negative correlation with tic severity (p = 0.044).

CONCLUSIONS

Our findings suggest that disturbed brain iron homeostasis in specific regions is associated with pediatric TS. These results reinforce the importance of the cortico-striato-thalamo-cortical circuits in TS pathogenesis and highlight the potential role of iron dysregulation. Furthermore, our study demonstrates that QSM could serve as a valuable auxiliary biomarker for diagnosing and potentially monitoring pediatric TS.

Advances in Clustering and Classification of Tic Disorders: A Systematic Review

Purpose

Tic disorders (TD) are common neurodevelopmental disorders characterized by heterogeneous tic symptoms in children, making diagnostic classification difficult. This complexity requires accurate subtyping using data-driven computational methods to identify patterns within clinical data. This systematic review primarily summarizes the current evidence for the classification of TD using a data-driven approach.

Patients and Methods

We conducted a systematic literature search on PubMed and Web of Science up to December 2023 and identified 16 publications analyzing 14 unique samples, totaling approximately 6000 subjects.

Results

Nine studies classified different subtypes of TD based on symptoms and behavior. Seven studies identified novel factor structures based on TD and its complex comorbidity patterns. Seven studies highlighted associations between TD symptom patterns and genetics, reflecting the diversity of underlying genetic mechanisms underlying TD.

Conclusion

This systematic review reveals significant variability in research on the classification of TD, which limits the application of findings for accurate diagnosis and guiding treatment strategies in pediatric psychiatry. Further research incorporating multidimensional information (such as genetic, neuroimaging, and environmental and social factors) is essential to improve the understanding of TD subtypes.

Vitamin D3 improves iminodipropionitrile-induced tic-like behavior in rats through regulation of GDNF/c-Ret signaling activity

Children with chronic tic disorders (CTD), including Tourette syndrome (TS), have significantly reduced serum 25-hydroxyvitamin D [25(OH)D]. While vitamin D3 supplementation (VDS) may reduce tic symptoms in these children, its mechanism is unclear. The study aim was to investigate the effects and mechanisms of vitamin D deficiency (VDD) and VDS on TS model behavior. Forty 5-week-old male Sprague-Dawley rats were randomly divided into (n = 10 each): control, TS model, TS model with VDD (TS + VDD), or TS model with VDS (TS + VDS; two intramuscular injections of 20,000 IU/200 g) groups. The VDD model was diet-induced (0 IU vitamin D/kg); the TS model was iminodipropionitrile (IDPN)-induced. All groups were tested for behavior, serum and striatal 25(OH)D and dopamine (DA), mRNA expressions of vitamin D receptor (VDR), glial cell line-derived neurotrophic factor (GDNF), protooncogene tyrosine-protein kinase receptor Ret (c-Ret), and DA D1 (DRD1) and D2 (DRD2) receptor genes in the striatum. TS + VDD had higher behavior activity scores throughout, and higher total behavior score at day 21 compared with TS model. In contrast, day 21 TS + VDS stereotyped behavior scores and total scores were lower than TS model. The serum 25(OH)D in TS + VDD was < 20 ng/mL, and lower than control. Striatal DA of TS was lower than control. Compared with TS model, striatal DA of TS + VDD was lower, while in TS + VDS it was higher than TS model. Furthermore, mRNA expression of VDR, GDNF, and c-Ret genes decreased in TS model, and GDNF expression decreased more in TS + VDD, while TS + VDS had higher GDNF and c-Ret expressions. VDD aggravates, and VDS ameliorates tic-like behavior in an IDPN-induced model. VDS may upregulate GDNF/c-Ret signaling activity through VDR, reversing the striatal DA decrease and alleviating tic-like behavior.

Efficacy of cognitive-behavioral therapy combined with habit reversal training on anxiety disorders in children with Tourette's syndrome

BACKGROUND

Cognitive-behavioral therapy (CBT) and habit reversal training (HRT) have shown application potential in addressing tic symptoms and comorbid psychiatric conditions. Despite their theoretical potential, empirical evidence on their combined efficacy remains limited.

AIM

To evaluate the efficacy of CBT combined with HRT on anxiety disorders in children with Tourette's syndrome (TS).

METHODS

Clinical data of children with TS admitted to our hospital from January 2022 to June 2023 were collected, and the patients were grouped into the conventional therapy (control) group and the CBT combined with HRT group. Baseline characteristics, anxiety scores, tic severity scores, treatment adherence, and parental satisfaction were assessed. Statistical analysis was performed using t-tests, chi-square tests, and correlation analysis.

RESULTS

A total of 136 patients, including 65 patients in the control group and 71 patients in the CBT combined with HRT group, were included. The CBT combined with HRT group showed remarkable improvements compared with the control group. Post-intervention assessment revealed a decrease in anxiety scores from 63.52 ± 1.81 to 40.53 ± 1.64 (t = 2.022, P = 0.045), and the Yale Global Tic Severity Scale total score decreased from 22.14 ± 5.67 to 16.28 ± 4.91 (t = 2.288, P = 0.024). Treatment adherence was significantly higher in the CBT combined with HRT group (85.47 ± 7.62%) compared with the control group (82.32 ± 6.54%; t = 2.596, P = 0.010). Parental satisfaction scores were also higher in the CBT combined with HRT group (8.69 ± 1.77) compared with the control group (7.87 ± 1.92; t = 2.592, P = 0.011).

CONCLUSION

This study demonstrates that CBT combined with HRT significantly reduces anxiety symptoms and tic severity in children with TS, with higher treatment adherence and parental satisfaction. These findings support the potential application of this comprehensive therapeutic approach for TS treatment.

Neuroimaging assessment of basal ganglia volumes in Tourette Syndrome: a systematic review and meta-analysis

INTRODUCTION

An increasing number of studies indicate that anatomical, physiological, and histological differences in the basal ganglia(BG) lie in the etiology of Tourette Syndrome(TS). However, the fact that there are very few studies on the anatomy of the BG in TS, small sample sizes, and unclear information as a consequence of these studies' contradictory findings is a significant gap in the scientific literature. The current systematic review and meta-analysis were performed to examine the differences in BG volumes between TS and controls.

METHOD

The protocol was registered with PROSPERO(CRD42023445845). Pertaining studies were ascertained via a search of the published literature in academic databases. The software Comprehensive Meta-Analysis was utilised for statistical analysis.

RESULTS

527 articles were reached, and after the exclusion stages, 8 articles remained for the current systematic review and 7 articles for the quantitative meta-analysis. After evaluating each component of the BG individually, no difference was found between the BG volumes of controls and TS.

CONCLUSION

The failure to discover the predicted volume difference can be explained by either the severity of the tic or the exclusion of comorbidity. The difference in BG volume is likely related to TS cases with more severe tics and severe comorbidities.

Relationship between transcranial magnetic stimulation markers of motor control and clinical recovery in obsessive compulsive disorder/Gilles de la Tourette syndrome: a proof of concept case study

Background

Obsessive compulsive disorder (OCD) and Gilles de la Tourette syndrome (GTS) are neurodevelopmental disorders characterized by difficulties in controlling intrusive thoughts (obsessions) and undesired actions (tics), respectively. Both conditions have been associated with abnormal inhibition but a tangible deficit of inhibitory control abilities is controversial in GTS.

Methods

Here, we examined a 25 years-old male patient with severe OCD symptoms and a mild form of GTS, where impairments in motor control were central. Transcranial magnetic stimulation (TMS) was applied over the primary motor cortex (M1) to elicit motor-evoked potentials (MEPs) during four experimental sessions, allowing us to assess the excitability of motor intracortical circuitry at rest as well as the degree of MEP suppression during action preparation, a phenomenon thought to regulate movement initiation.

Results

When tested for the first time, the patient presented a decent level of MEP suppression during action preparation, but he exhibited a lack of intracortical inhibition at rest, as evidenced by reduced short-interval intracortical inhibition (SICI) and long-interval intracortical inhibition (LICI). Interestingly, the patient's symptomatology drastically improved over the course of the sessions (reduced obsessions and tics), coinciding with feedback given on his good motor control abilities. These changes were reflected in the TMS measurements, with a significant strengthening of intracortical inhibition (SICI and LICI more pronounced than previously) and a more selective tuning of MEPs during action preparation; MEPs became even more suppressed, or selectively facilitated depending on the behavioral condition in which they we probed.

Conclusion

This study highlights the importance of better understanding motor inhibitory mechanisms in neurodevelopmental disorders and suggests a biofeedback approach as a potential novel treatment.

Can Red Blood Cell and Platelet Parameters Be Associated With Inflammation in Children With Tic Disorder?

OBJECTIVE

Tic disorder (TD) is one of the neurodevelopmental disorders and its etiology has not been fully elucidated. Complete blood count (CBC) values have been used as indicators of a systemic inflammatory response. In our study, we aimed to assess hemogram parameters in drug-naive, comorbidity-free children with TD compared with controls.

METHODS

This retrospective study included 62 drug-naive children with TD who had undergone CBC within one month prior to the study. A control group of 48 healthy children, matched for age and gender, without any organic or psychiatric disorders, was included. Statistical analysis was performed by using IBM SPSS Statistics for Windows, Version 22.0 (Released 2013; IBM Corp., Armonk, New York, United States).  Results: Hematocrit (p = 0.044), mean corpuscular volume (p = 0.002), platelet count (p = 0.011), and plateletcrit (p = 0.031) values were significantly higher in the TD group, whereas mean corpuscular hemoglobin concentration (p = 0.00) was significantly lower in the TD group. Additionally, a significant negative correlation was observed between the duration of illness and platelet (p = 0.05, r=-0.282), plateletcrit (p = 0.038, r = -0.295), and neutrophil count (p = 0.006, r = -0.391), while a positive correlation was found between the duration of illness and eosinophil count (p = 0.018, r = 0.336).

CONCLUSION

The results revealed several significant differences in hemogram parameters between TD patients and the control group. These may suggest the role of inflammation and/or other underlying mechanisms in TD and may inspire new studies. Future studies with larger and more homogeneous samples, including comprehensive inflammatory markers, may contribute to a deeper understanding of the relationship between inflammation and TD.