The Cerebellum in Drug-naive Children with Tourette Syndrome and Obsessive–Compulsive Disorder

The Pathophysiology of Tics: An Anatomic Review

The underlying pathophysiology of tics in Tourette syndrome is a topic of major scientific interest. To date, there is an absence of consensus among researchers regarding the precise anatomic location responsible for tics. The goal of this article is to review the current understanding of these brain circuits and data supporting specific anatomic regions. In summary, current scientific evidence supports the likelihood of multiple areas of abnormality within cortico-basal ganglia-thalamocortical (CBGTC) circuitry or their connected brain regions. A reasonable anatomic hypothesis is that a disruption anywhere within specific circuitry can ultimately lead to the development of a tic disorder.

A coordinate-based meta-analysis of grey matter volume differences between adults with obsessive-compulsive disorder (OCD) and healthy controls

According to the cortico-striato-thalamo-cortical (CSTC) model of obsessive-compulsive disorder (OCD), the striatum plays a primary role in its neuropathophysiology. Hypothesising that volumetric alterations are more pronounced in subcortical areas of patients within the CSTC circuit compared to healthy controls (HCs), we conducted a coordinate-based meta-analysis of magnetic resonance imaging (MRI) studies. We included 26 whole-brain MRI studies, comprising 3,010 subjects: 1,508 patients (788 men, 720 women; mean age: 30.26 years, SD = 8.16) and 1,502 HCs (801 men, 701 women; mean age: 29.47 years, SD = 7.88). This meta-analysis demonstrated significant grey matter volume increases in the bilateral putamen, lateral globus pallidus, left parietal cortex, right pulvinar, and left cerebellum in adults with OCD, alongside decreases in the right hippocampus/caudate, bilateral medial frontal gyri, and other cortical regions. Volume increases were predominantly observed in subcortical areas, with the exception of the left parietal cortex and cerebellar dentate, while volume decreases were primarily cortical, aside from the right hippocampus/caudate. Further exploration of these neuropathophysiological correlates could inform specific prevention and treatment strategies, advancing precision mental health in clinical applications.

Tic-Related Obsessive-Compulsive and Eating Disorders in Dandy-Walker Variant: A Case Report and Systematic Reappraisal of Psychiatric Profiles

Dandy-Walker complex (DWC) consists of a continuum of brain malformations involving the posterior fossa, often leading to psychiatric manifestations during adulthood. We discussed the case of a young woman with Dandy-Walker variant (DWV) and a comorbid complex neuropsychiatric presentation, who was diagnosed with an eating disorder, obsessive-compulsive disorder, and a tic disorder. Afterwards, we conducted a Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020-compliant systematic review reappraising all evidence of psychiatric outcomes in adults with DWC. Overall, 34 studies were eligible for data extraction, comprising 36 patients. Psychiatric profiles were more common among young adult males, with DWC lesions, especially DWV subtype, being often discovered incidentally after admission to mental health inpatient facilities. Most patients were diagnosed with psychosis and bipolar disorder, often comorbid with cognitive impairment. Psychotropic polypharmacy was frequently prescribed, generally leading to complete recovery. Evidence from our case report and systematic review indicates the importance of monitoring long-term psychiatric sequelae among adult patients with DWC malformations.

Cerebellar Microstructural Abnormalities in Obsessive-Compulsive Disorder (OCD): a Systematic Review of Diffusion Tensor Imaging Studies

Previous neuroimaging studies have suggested that obsessive-compulsive disorder (OCD) is associated with altered resting-state functional connectivity of the cerebellum. In this study, we aimed to describe the most significant and reproducible microstructural abnormalities and cerebellar changes associated with obsessive-compulsive disorder (OCD) using diffusion tensor imaging (DTI) investigations. PubMed and EMBASE were searched for relevant studies using the PRISMA 2020 protocol. A total of 17 publications were chosen for data synthesis after screening titles and abstracts, full-text examination, and executing the inclusion criteria. The patterns of cerebellar white matter (WM) integrity loss, determined by fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD) metrics, varied across studies and symptoms. Changes in fractional anisotropy (FA) values were described in six publications, which were decreased in four and increased in two studies. An increase in diffusivity parameters of the cerebellum (i.e., MD, RD, and AD) in OCD patients was reported in four studies. Alterations of the cerebellar connectivity with other brain areas were also detected in three studies. Heterogenous results were found in studies that investigated cerebellar microstructural abnormalities in correlation with symptom dimension or severity. OCD's complex phenomenology may be characterized by changes in cerebellar WM connectivity across wide networks, as shown by DTI studies on OCD patients in both children and adults. Classification features in machine learning and clinical tools for diagnosing OCD and determining the prognosis of the disorder might both benefit from using cerebellar DTI data.

Comorbidities and Disease Duration in Tourette Syndrome: Impact on Cognition and Quality of Life of Children

BACKGROUND

Cognitive functions represent foundational factors for mental health and quality of life (QoL). In Tourette syndrome (TS), psychiatric comorbidities are common and have been inconsistently reported to affect the cognition and QoL of patients, while the role of tic disorder duration has not been yet explored.

METHODS

To examine how comorbidities and TS duration may influence cognition and QoL, N = 80 children with TS (6-16 years) were evaluated using the Wechsler Intelligence Scale for Children (WISC-IV). Standardized questionnaires were used to assess the presence and severity of TS main comorbidities and QoL. Data were interpreted using linear correlations, regression, and mediation analysis.

RESULTS

Depression and attention-deficit/hyperactivity disorder (ADHD) symptoms accounted for poorer cognitive performance. Anxiety oppositely predicted better cognitive performance, while no significant role for obsessive compulsive disorder (OCD) was observed. Disease duration was associated with lower total IQ, verbal reasoning, and working memory abilities. Depression, anxiety, and TS duration also deeply influenced QoL measures.

CONCLUSIONS

TS common comorbidities have a differential impact on the cognitive abilities of children and adolescents, which translates into a complex influence on their perceived QoL. A longer clinical history of tics was related to worse cognitive outcomes, which prompts further consideration of disease duration in both clinical and research settings involving children and adolescents.

Temperament Traits in Pediatric Obsessive-Compulsive Disorder in Relation to Tourette Syndrome and Attention-Deficit Hyperactivity Disorder

INTRODUCTION

Pediatric obsessive-compulsive disorder (OCD), attention-deficit hyperactivity disorder (ADHD), and Tourette syndrome (TS) are often concurrent. This study explores the temperament profile of complex OCD phenotypes.

METHODS

A clinical registry recorded demographic data, psychiatric diagnoses, and temperament traits, including novelty seeking (exploratory behaviors), harm avoidance (fear of uncertainty), reward dependence (sentimentality), and persistence (perseverance). Temperament data were accrued from the Junior Temperament and Character Inventory (JTCI). Participants were divided into (1) OCD only; (2) OCD+ADHD or TS; and (3) OCD+ADHD+TS to compare temperament.

RESULTS

Participants include 126 youths with OCD (61.9% male, 88.9% white) between the ages 6 and 18 years (12.7 ± 3.1). Among the three groups, the complex neurodevelopmental disorder group OCD+ADHD+TS expresses the highest novelty seeking and lowest persistence. Harm avoidance is increased in all groups compared to reference controls, irrespective of concurrent ADHD or TS. For the OCD+ADHD+TS group, contamination and washing symptoms have higher novelty seeking (p < 0.01), while counting and ordering have lower novelty seeking (p < 0.05). Harm avoidance is increased with aggressive, somatic, and checking symptoms in OCD only (p < 0.01), while persistence is increased with repeating and counting symptoms in the comorbid groups (OCD+ADHD or TS, OCD+ADHD+TS).

DISCUSSION/CONCLUSION

The complex subtype, OCD+ADHD+TS, is associated with high novelty seeking and low persistence, while high harm avoidance is linked to pediatric OCD irrespective of ADHD or TS co-occurrence. In sum, pediatric OCD with ADHD and TS confers a unique temperament profile, further refining complex phenotypes of pediatric OCD for future research.

Altered dynamic functional and effective connectivity in drug-naive children with Tourette syndrome

Tourette syndrome (TS) is a developmental neuropsychiatric disorder characterized by repetitive, stereotyped, involuntary tics, the neurological basis of which remains unclear. Although traditional resting-state MRI (rfMRI) studies have identified abnormal static functional connectivity (FC) in patients with TS, dynamic FC (dFC) remains relatively unexplored. The rfMRI data of 54 children with TS and 46 typically developing children (TDC) were analyzed using group independent component analysis to obtain independent components (ICs), and a sliding-window approach to generate dFC matrices. All dFC matrices were clustered into two reoccurring states, the state transition metrics were obtained. We conducted Granger causality and nodal topological analyses to further investigate the brain regions that may play the most important roles in driving whole-brain switching between different states. We found that children with TS spent more time in state 2 (PFDR < 0.001), a state characterized by strong connectivity between ICs, and switched more quickly between states (PFDR = 0.025) than TDC. The default mode network (DMN) may play an important role in abnormal state transitions because the FC that changed the most between the two states was between the DMN and other networks. Additionally, the DMN had increased degree centrality, efficiency and altered causal influence on other networks. Certain alterations related to executive function (r = -0.309, P < 0.05) and tic symptom ratings (r = 0.282; 0.413, P < 0.05) may represent important aspects of the pathophysiology of TS. These findings facilitate our understanding of the neural basis for the clinical presentation of TS.

Social cognition in hyperkinetic movement disorders: a systematic review

Numerous lines of research indicate that our social brain involves a network of cortical and subcortical brain regions that are responsible for sensing and controlling body movements. However, it remains unclear whether movement disorders have a systematic impact on social cognition. To address this question, we conducted a systematic review examining the influence of hyperkinetic movement disorders (including Huntington disease, Tourette syndrome, dystonia, and essential tremor) on social cognition. Following the PRISMA guidelines and registering the protocol in the PROSPERO database (CRD42022327459), we analyzed 50 published studies focusing on theory of mind (ToM), social perception, and empathy. The results from these studies provide evidence of impairments in ToM and social perception in all hyperkinetic movement disorders, particularly during the recognition of negative emotions. Additionally, individuals with Huntington's Disease and Tourette syndrome exhibit empathy disorders. These findings support the functional role of subcortical structures (such as the basal ganglia and cerebellum), which are primarily responsible for movement disorders, in deficits related to social cognition.

Resting-state functional connectivity-based parcellation of the human dentate nucleus: new findings and clinical relevance

For years, the cerebellum was left out of functional magnetic resonance imaging (fMRI) studies due to technological limitations. The advent of novel data acquisition and reconstruction strategies (e.g., whole-brain simultaneous multi-slice imaging) employing multi-channel array coils has overcome such limitations, ushering unprecedented improvements in temporal signal-to-noise ratio and spatiotemporal resolution. Here, we aim to provide a brief report on the deep cerebellar nuclei, specifically focusing on the dentate nuclei, the primary output nuclei, situated within both cognitive and motor cerebello-cerebral circuits. We highlight the importance of functional parcellation in refining our understanding of broad resting-state functional connectivity (RSFC) in both health and disease. First, we review work relevant to the functional topography of the dentate nuclei, including recent advances in functional parcellation. Next, we review RSFC studies using the dentate nuclei as seed regions of interest in neurological and psychiatric populations and discuss the potential benefits of applying functionally defined subdivisions. Finally, we discuss recent technological advances and underscore ultrahigh-field neuroimaging as a tool to potentiate functionally parcellated RSFC analyses in clinical populations.

Abnormal cerebellum connectivity patterns related to motor subtypes of Parkinson's disease

Cerebellar dysfunction may substantially contribute to the clinical symptoms of Parkinson's disease (PD). The role of cerebellar subregions in tremors and gait disturbances in PD remains unknown. To investigate alterations in cerebellar subregion volumes and functional connectivity (FC), as well as FC between the dentate nucleus (DN) and ventral lateral posterior nucleus (VLp) of the thalamus, which are potentially involved in different PD motor subtypes. We conducted morphometric and resting-state functional connectivity analyses in various cerebellar subregions in 22 tremor-dominant (TD)-PD and 35 postural instability gait difficulty dominant (PIGD)-PD patients and 38 sex- and age-matched healthy controls (HCs). The volume and FC alterations in various cerebellar subregions and the neural correlates of these changes with the clinical severity scores were investigated. The PIGD-PD group showed greater FC between the right motor cerebellum (CBMm) and left postcentral gyrus than the HC group, and a higher FC was associated with less severe PIGD symptoms. In contrast, the TD-PD group had decreased FC between the right DN and left VLp compared with the PIGD-PD and HC groups, and lower FC was associated with worse TD symptoms. Furthermore, the PIGD-PD group had higher FC between the left DN and left inferior temporal gyrus than the TD-PD group. Morphometric analysis revealed that the TD-PD group showed a significantly higher volume of left CBMm than the HC group. Our findings point to differential alteration patterns in cerebellar subregions and offer a new perspective on the pathophysiology of motor subtypes of PD.

Cerebellar gamma-aminobutyric acid: Investigation of group effects in neurodevelopmental disorders

Neurodevelopmental disorders (NDDs) including autism spectrum disorder (ASD), attention-deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD) are thought to arise in part from the disruption in the excitatory/inhibitory balance of gamma-aminobutyric acid (GABA) and glutamate in the brain. Recent evidence has shown the involvement of the cerebellum in cognition and affect regulation, and cerebellar atypical function or damage is reported frequently in NDDs. Magnetic resonance spectroscopy studies have reported decreases in GABA in cortical brain areas in the NDDs, however, GABA levels in the cerebellum have not been examined. To determine possible group effects, we used a MEGA-PRESS acquisition to investigate GABA+ levels in a cerebellar voxel in 343 individuals (aged 2.5-22 years) with ASD, ADHD, OCD and controls. Using a mixed effects model, we found no significant differences between groups in GABA+ concentration. Our findings suggest that cerebellar GABA+ levels do not differentiate NDD groups.