Combining tract- and atlas-based analysis reveals microstructural abnormalities in early Tourette syndrome children

White matter alterations predict outcomes of comprehensive behavioral intervention for tics in children with Tourette syndrome: A diffusion MRI study

AIM

Tourette syndrome (TS) is a neurodevelopmental disorder that cause sudden uncontrolled rapid and repeated vocal sounds or movements called tics. Herein, diffusion magnetic resonance imaging (dMRI) connectometry was implemented to evaluate the white matter connectivity differences among TS patients.

METHODS

A total of 63 TS and 77 typically developed (TD) individuals were enrolled in the present study. dMRI connectometry was utilized to identify differences in connectivity patterns of white matter tracts in TS patients based on quantitative anisotropy (QA). QA was compared between TS and TD patients and correlated with severity scores such as Yale Global Tic Severity Scale (YGTSS) and Premonitory Urge for Tics Scale (PUTS).

RESULTS

Higher white matter connectivity of corpus callosum and bilateral cingulum as well as lower connectivity of corticothalamic and corticostriatal pathways were evident in TS relative to TD. The baseline YGTSS motor, YGTSS total, and PUTS were negatively correlated with corticostriatal pathway, corticothalamic pathway, and bilateral cingulum integrity, respectively. The changes in tic severity scores were also positively correlated with alterations in the white matter integrity of these brain regions following behavioral therapy.

CONCLUSION

Patients with TS have several abnormalities in their white matter microstructure particularly in the cortico-striato-thalamo-cortical (CSTC) circuit, correlated with the severity of the disease. Besides, the post-behavioral therapy changes in the white matter integrity of these regions are demonstrated as response predictors.

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.

The microstructural change of the brain and its clinical severity association in pediatric Tourette syndrome patients

BACKGROUND

Gilles de la Tourette syndrome (GTS) is a prevalent pediatric neurological disorder. Most studies point to abnormalities in the cortico-striato-thalamocortical (CSTC) circuits. Neuroimaging studies have shown GTS's extensive impact on the entire brain. However, due to participant variability and potential drug and comorbidity impact, the results are inconsistent. To mitigate the potential impact of participant heterogeneity, we excluded individuals with comorbidities or those currently undergoing medication treatments. Based on the hypothesis of abnormality within the CSTC circuit, we investigated microstructural changes in white matter using diffusion spectrum imaging (DSI). This study offers the first examination of microstructural changes in treatment-naïve pediatric patients with pure GTS using diffusion spectrum imaging.

METHODS

This single-center prospective study involved 30 patients and 30 age- and gender-matched healthy volunteers who underwent sagittal T1-weighted MRI and DSI. We analyzed generalized fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity.

RESULTS

No significant differences were observed in mean diffusivity and axial diffusivity values between the two groups. However, the patient group exhibited significantly higher generalized fractional anisotropy values in the right frontostriatal tract of the dorsolateral prefrontal cortex, the right frontostriatal tract of the precentral gyrus, and bilateral thalamic radiation of the dorsolateral prefrontal cortex. Additionally, the generalized fractional anisotropy value of the right frontostriatal tract of the precentral gyrus is inversely correlated with the total tic severity scores at the most severe condition.

CONCLUSION

Treatment-naïve pediatric GTS patients demonstrated increased connectivity within the CSTC circuit as per diffusion spectrum imaging, indicating possible CSTC circuit dysregulation. This finding could also suggest a compensatory change. It thus underscores the necessity of further investigation into the fundamental pathological changes in GTS. Nevertheless, the observed altered connectivity in GTS patients might serve as a potential target for therapeutic intervention.

Characterisation of brain microstructural alterations in children with obstructive sleep apnea syndrome using diffusion kurtosis imaging

Obstructive sleep apnea (OSA) is a common chronic sleep-related breathing disorder in children. Previous studies showed widespread alterations in white matter (WM) in children with OSA mainly by using diffusion tensor imaging (DTI), while diffusional kurtosis imaging (DKI) extended DTI and exhibited improved sensitivity in detecting developmental and pathological changes in neural tissues. Therefore, we conducted whole-brain DTI and DKI analyses and compared the differences in kurtosis and diffusion parameters within the skeleton between 41 children with OSA and 32 healthy children. Between-group differences were evaluated by tract-based spatial statistics (TBSS) analysis (p < 0.05, TFCE corrected), and partial correlations between DKI metrics and sleep parameters were assessed considering age and gender as covariates. Compared with the controls, children with OSA showed significantly decreased kurtosis fractional anisotropy (KFA) mainly in white matter regions with a complex fibre arrangement including the posterior corona radiate (PCR), superior longitudinal fasciculus (SLF), and inferior fronto-occipital fasciculus (IFOF), while decreased FA in white matter regions with a coherent fibre arrangement including the posterior limb of internal capsule (PLIC), anterior thalamic radiation (ATR), and corpus callosum (CC). Notably, the receiver operating characteristic (ROC) curve analysis demonstrated the KFA value in complex tissue regions significantly (p < 0.001) differentiated children with OSA from the controls. In addition, the KFA value in the left PCR, SLF, and IFOF showed significant partial correlations to the sleep parameters for children with OSA. Combining DKI derived kurtosis and diffusion parameters can provide complementary neuroimaging biomarkers for assessing white matter alterations, and reveal pathological changes and monitor disease progression in paediatric OSA.

Characterization of white matter microstructural abnormalities associated with cognitive dysfunction in cerebral small vessel disease with cerebral microbleeds

BACKGROUND

Diffusion tensor imaging (DTI) is recommended as a sensitive method to explore white matter (WM) microstructural alterations. Cerebral small vessel disease (CSVD) may be accompanied by extensive WM microstructural deterioration, while cerebral microbleeds (CMBs) are an important factor affecting CSVD.

METHODS

Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) images from 49 CSVD patients with CMBs (CSVD-c), 114 CSVD patients without CMBs (CSVD-n), and 83 controls were analyzed using DTI-derived tract-based spatial statistics to detect WM diffusion changes among groups.

RESULTS

Compared with the CSVD-n and control groups, the CSVD-c group showed a significant FA decrease and AD, RD and MD increases mainly in the cognitive and sensorimotor-related WM tracts. There was no significant difference in any diffusion metric between the CSVD-n and control groups. Furthermore, the widespread regional diffusion alterations among groups were significantly correlated with cognitive parameters in both the CSVD-c and CSVD-n groups. Notably, we applied the multiple kernel learning technique in multivariate pattern analysis to combine multiregion and multiparameter diffusion features, yielding an average accuracy >77 % for three binary classifications, which showed a considerable improvement over the single modality approach.

LIMITATIONS

We only grouped the study according to the presence or absence of CMBs.

CONCLUSIONS

CSVD patients with CMBs have extensive WM microstructural deterioration. Combining DTI-derived diffusivity and anisotropy metrics can provide complementary information for assessing WM alterations associated with cognitive dysfunction and serve as a potential discriminative pattern to detect CSVD at the individual level.

Theta Activity Dynamics during Embedded Response Plan Processing in Tourette Syndrome

Gilles de la Tourette syndrome (GTS) is a neuropsychiatric disorder. Because motor signs are the defining feature of GTS, addressing the neurophysiology of motor processes is central to understanding GTS. The integration of voluntary motor processes is subject to so-called "binding problems", i.e., how different aspects of an action are integrated. This was conceptualized in the theory of event coding, in which 'action files' accomplish the integration of motor features. We examined the functional neuroanatomical architecture of EEG theta band activity related to action file processing in GTS patients and healthy controls. Whereas, in keeping with previous data, behavioral performance during action file processing did not differ between GTS and controls, underlying patterns of neural activity were profoundly different. Superior parietal regions (BA7) were predominantly engaged in healthy controls, but superior frontal regions (BA9, BA10) in GTS indicated that the processing of different motor feature codes was central for action file processing in healthy controls, whereas episodic processing was more relevant in GTS. The data suggests a cascade of cognitive branching in fronto-polar areas followed by episodic processing in superior frontal regions in GTS. Patients with GTS accomplish the integration of motor plans via qualitatively different neurophysiological processes.

Identify aberrant white matter microstructure in ASD, ADHD and other neurodevelopmental disorders: A meta-analysis of diffusion tensor imaging studies

BACKGROUND

Neurodevelopmental disorders (NDDs) usually present overlapping symptoms. Abnormal white matter (WM) microstructure has been found in these disorders. Identification of common and unique neural abnormalities across NDDs could provide further insight into the underlying pathophysiological mechanisms.

METHODS

We performed a voxel-based meta-analysis of whole-brain diffusion tensor imaging (DTI) studies in autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD) and other NDDs. A systematic literature search was conducted through March 2020 to identify studies that compared measures of WM microstructure between patients with NDDs and neurotypical controls. Peak voxel coordinates were meta-analyzed via anisotropic effect size-signed differential mapping (AES-SDM) as well as activation likelihood estimation (ALE).

RESULTS

Our final sample included a total of 4137 subjects from 66 studies across five NDDs. Fractional anisotropy (FA) reductions were found in the splenium of the CC in ADHD, and the genu and splenium of CC in ASD. And mean diffusivity (MD) increases were shown in posterior thalamic radiation in ASD. No consistent abnormalities were detected in specific learning disorder, motor disorder or communication disorder. Significant differences between child/adolescent and adult patients were found within the CC across NDDs, reflective of aberrant neurodevelopmental processes in NDDs.

CONCLUSIONS

The current study demonstrated atypical WM patterns in ASD, ADHD and other NDDs. Microstructural abnormalities in the splenium of the CC were possibly shared among ASD and ADHD.

Brain volumes and white matter microstructure in 8- to 10-year-old children born with fetal growth restriction

BACKGROUND

Fetal growth restriction caused by placental insufficiency is associated with increased risk of poor neurodevelopment, even in the absence of specific perinatal brain injury. Placental insufficiency leads to chronic hypoxaemia that may alter cerebral tissue organisation and maturation.

OBJECTIVE

The aim of this study was to assess the effects fetal growth restriction and fetal haemodynamic abnormalities have on brain volumes and white matter microstructure at early school age.

MATERIALS AND METHODS

This study examined 32 children born with fetal growth restriction at 24 to 40 gestational weeks, and 27 gestational age-matched children, who were appropriate for gestational age. All children underwent magnetic resonance imaging (MRI) at the age of 8-10 years. Cerebral volumes were analysed, and tract-based spatial statistics and atlas-based analysis of white matter were performed on 17 children born with fetal growth restriction and 14 children with birth weight appropriate for gestational age.

RESULTS

Children born with fetal growth restriction demonstrated smaller total intracranial volumes compared to children with normal fetal growth, whereas no significant differences in grey or white matter volumes were detected. On atlas-based analysis of white matter, children born with fetal growth restriction demonstrated higher mean and radial diffusivity values in large white matter tracts when compared to children with normal fetal growth.

CONCLUSION

Children ages 8-10 years old born with fetal growth restriction demonstrated significant changes in white matter microstructure compared to children who were appropriate for gestational age, even though no differences in grey and white matter volumes were detected. Poor fetal growth may impact white matter maturation and lead to neurodevelopmental impairment later in life.

Microstructural Abnormalities of White Matter Across Tourette Syndrome: A Voxel-Based Meta-Analysis of Fractional Anisotropy

Introduction: Tourette syndrome (TS) is a neuropsychiatric disorder with multiple motor and vocal tics whose neural basis remains unclear. Diffusion tensor imaging (DTI) studies have demonstrated white matter microstructural alternations in TS, but the findings are inconclusive. In this study, we aimed to elucidate the most consistent white matter deficits in patients with TS.

Method: By systematically searching online databases up to December 2020 for all DTI studies comparing fractional anisotropy (FA) between patients with TS and healthy controls (HCs), we conducted anisotropic effect size-signed differential mapping (AES-SDM) meta-analysis to investigate FA differences in TS, as well as performed meta-regression analysis to explore the effects of demographics and clinical characteristics on white matter abnormalities among TS.

Results: A total of eight datasets including 168 patients with TS and 163 HCs were identified. We found that TS patients showed robustly decreased FA in the corpus callosum (CC) and right inferior longitudinal fasciculus (ILF) compared with HCs. These two regions preserved significance in the sensitivity analysis. No regions of increased FA were reported. Meta-regression analysis revealed that age, sex, tic severity, or illness duration of patients with TS were not linearly correlated with decreased FA.

Conclusion: Patients with TS display deficits of white matter microstructure in the CC and right ILF known to be important for interhemispheric connections as well as long association fiber bundles within one hemisphere. Because the results reported in the primary literature were highly variable, future investigations with large samples would be required to support the identified white matter changes in TS.

Characterization of Brain Microstructural Abnormalities in High Myopia Patients: A Preliminary Diffusion Kurtosis Imaging Study

Objective

To evaluate microstructural damage in high myopia (HM) patients using 3T diffusion kurtosis imaging (DKI).

Materials and Methods

This prospective study included 30 HM patients and 33 age- and sex-matched healthy controls (HCs) with DKI. Kurtosis parameters including kurtosis fractional anisotropy (FA), mean kurtosis (MK), axial kurtosis (AK), and radial kurtosis (RK) as well as diffusion metrics including FA, mean diffusivity, axial diffusivity (AD), and radial diffusivity derived from DKI were obtained. Group differences in these metrics were compared using tract-based spatial statistics. Partial correlation analysis was used to evaluate correlations between microstructural changes and disease duration.

Results

Compared to HCs, HM patients showed significantly reduced AK, RK, MK, and FA and significantly increased AD, predominately in the bilateral corticospinal tract, right inferior longitudinal fasciculus, superior longitudinal fasciculus, inferior fronto-occipital fasciculus, and left thalamus (all p < 0.05, threshold-free cluster enhancement corrected). In addition, DKI-derived kurtosis parameters (AK, RK, and MK) had negative correlations (r = −0.448 to −0.376, all p < 0.05) and diffusion parameter (AD) had positive correlations (r = 0.372 to 0.409, all p < 0.05) with disease duration.

Conclusion

HM patients showed microstructural alterations in the brain regions responsible for motor conduction and vision-related functions. DKI is useful for detecting white matter abnormalities in HM patients, which might be helpful for exploring and monitoring the pathogenesis of the disease.

Inhibitory control in children with tic disorder: aberrant fronto-parietal network activity and connectivity

Chronic tic disorders, including Tourette syndrome, are typically thought to have deficits in cognitive inhibition and top down cognitive control due to the frequent and repetitive occurrence of tics, yet studies reporting task performance results have been equivocal. Despite similar behavioural performance, individuals with chronic tic disorder have exhibited aberrant patterns of neural activation in multiple frontal and parietal regions relative to healthy controls during inhibitory control paradigms. In addition to these top down attentional control regions, widespread alterations in brain activity across multiple neural networks have been reported. There is a dearth, however, of studies examining event-related connectivity during cognitive inhibitory paradigms among affected individuals. The goal of this study was to characterize neural oscillatory activity and effective connectivity, using a case–control design, among children with and without chronic tic disorder during performance of a cognitive inhibition task. Electroencephalogram data were recorded in a cohort of children aged 8–12 years old (60 with chronic tic disorder, 35 typically developing controls) while they performed a flanker task. While task accuracy did not differ by diagnosis, children with chronic tic disorder displayed significant cortical source-level, event-related spectral power differences during incongruent flanker trials, which required inhibitory control. Specifically, attenuated broad band oscillatory power modulation within the anterior cingulate cortex was observed relative to controls. Whole brain effective connectivity analyses indicated that children with chronic tic disorder exhibit greater information flow between the anterior cingulate and other fronto-parietal network hubs (midcingulate cortex and precuneus) relative to controls, who instead showed stronger connectivity between central and posterior nodes. Spectral power within the anterior cingulate was not significantly correlated with any connectivity edges, suggesting lower power and higher connectivity are independent (versus resultant) neural mechanisms. Significant correlations between clinical features, task performance and anterior cingulate spectral power and connectivity suggest this region is associated with tic impairment (r = −0.31, P = 0.03) and flanker task incongruent trial accuracy (r’s = −0.27 to −0.42, P’s = 0.0008–0.04). Attenuated activation of the anterior cingulate along with dysregulated information flow between and among nodes within the fronto-parietal attention network may be neural adaptations that result from frequent engagement of neural pathways needed for inhibitory control in chronic tic disorder.

Altered frontal-mediated inhibition and white matter connectivity in pediatric chronic tic disorders

Tics are unique from most movement disorders, in that they are partially suppressible. As part of the inhibitory motor network, the pre-supplementary motor area is engaged in motor control and may be involved in tic physiology. We used dual-site transcranial magnetic stimulation to assess inhibitory connectivity between right pre-supplementary motor area and left primary motor cortex, which has previously been demonstrated in healthy adults. We also used diffusion tensor imaging to investigate white matter connectivity in children with chronic tics. Twelve children with chronic tic disorder and fourteen typically developing controls underwent MRI with diffusion tensor imaging indices analysis followed by single and paired-pulse transcranial magnetic stimulation with conditioning pulse over the right pre-supplementary motor area followed by left motor cortex test pulse. Neurophysiologic and imaging data relationships to measures of tic severity and suppressibility were also evaluated in tic patients. Pre-supplementary motor area-mediated inhibition of left motor cortex was present in healthy control children but not in chronic tic disorder participants. Less inhibition correlated with worse tic suppressibility (ρ = - 0.73, p = 0.047). Imaging analysis showed increased fractional anisotropy in the right superior longitudinal fasciculus, corpus callosum, corona radiata and posterior limb of the internal capsule (p < 0.05) in tic participants, which correlated with lower self-reported tic suppressibility (ρ = - 0.70, p = 0.05). Physiologic data revealed impaired frontal-mediated motor cortex inhibition in chronic tic participants, and imaging analysis showed abnormalities in motor pathways. Collectively, the neurophysiologic and neuroanatomic data correlate with tic suppressibility, supporting the relevancy to tic pathophysiology.

The multimodality neuroimage findings in individuals with Tourette syndrome

Chronic tic disorder and Gilles de la Tourette syndrome are very common childhood-onset diseases. However, the pathophysiology underlying these disorders is not yet clear and most studies focus on the disinhibition of the cortico-striatal-thalamo-cortical circuit. Although dysfunction of this circuit is possible, routine clinical neuroimaging studies such as T1-weighted or T2-weighted MRI usually reveal normal results. Therefore, special neuroimaging techniques may be needed to investigate the possible microstructural or functional changes in the brain. Previous structural studies, such as those using diffusion tensor imaging, and volumetric MRI studies, revealed the main abnormalities to be located in the cortico-striatal-thalamo-cortical circuit and to be related to brain regions such as basal ganglion, thalamus, frontal cortex, and motor cortex. Some other potential regions, such as the amygdala, hippocampus or cerebellum, are also occasionally reported. Perfusion studies, such as those using positron emission tomography or functional MRI, also suggest hemodynamic changes over those brain regions related to the cortico-striatal-thalamo-cortical circuit. However, the results can be different in adult and pediatric groups, and neuroimaging findings are also inconsistent between different studies, which may reflect the high diversity of this disease or differences in enrolled patient groups with different comorbidities. Therefore, in this review article, we will focus on the neuroimaging findings relating to Tourette syndrome in different age groups using different imaging techniques.

Altered structural cerebral cortex in children with Tourette syndrome

PURPOSE

In this study, we used magnetic resonance imaging (MRI) to investigate the anatomical alterations of cerebral cortex in children with Tourette syndrome (TS) and explore whether such deficits were related with their clinical symptoms.

METHODS

All subjects were scanned in a 3.0T MRI scanner with three-dimensional T1-weighted images (3DT1WI). Then, some surface-based features were extracted by using the FreeSurfer software. After that, the between-group differences of those features were assessed.

RESULTS

Sixty TS patients and 52 age- and gender-matched healthy control were included in this study. Surface-based analyses revealed altered cortical thickness, cortical sulcus, cortical curvature and local gyrification index (LGI) in TS group compared with healthy controls. The brain regions with significant-group differences in cortical thickness included postcentral gyrus, superiorparietal gyrus, rostral anterior cingulate cortex in the left hemisphere and frontal pole, lateral occipital gyrus, inferior temporal gyrus in the right hemisphere. In addition, the superior temporal gyrus, medial orbitofrontal gyrus, supramarginal gyrus, medial orbitofrontal gyrus, superiorparietal gyrus and lateral occipital gyrus showed significant between-group differences for cortical sulcus. Moreover, the brain regions with significant between-group differences in cortical curvature were located in caudal anterior cingulate cortex, supramarginal gyrus, inferior parietal gyrus and lateral occipital gyrus. The alteration of LGI were most prominent in the inferior temporal gyrus and insula. Additionally, there was no statistical difference in brain surface area for TS children compared with controls.

CONCLUSION

The results of this study revealed that cortical thickness, sulcus, cortical curvature and LGI were changed in multiple brain regions for children with TS.

Characteristics of diffusion tensor imaging of central nervous system in children with tourette's disease

To investigate the characteristics of diffusion tensor imaging (DTI) of the central nervous system in children with Tourette syndrome (TS).Fifteen children with TS (TS group) and 15 normal children (control group) were studied, and all of them underwent DTI. The apparent diffusion coefficient (ADC) and fractional anisotropy (FA) parameters were calculated using the DTIStudio software. The region of interest was delineated manually. The ADC and FA values of the bilateral caudate nucleus, bilateral globus pallidus, bilateral putamen, bilateral thalamus, and bilateral frontal lobe white matter were measured using the region of interest editor software. The differences of FA values and ADC values between the same brain areas were compared. The associations between ADC, FA values and Yale Global Tic Severity Scale (YGTSS) scores were evaluated by Pearson correlation analyses.The FA values of left globus pallidus and left thalamus were significantly lower in the TS group than in the control group (P < .05), while the ADC values of the right caudate nucleus and bilateral thalamus were significantly higher in the TS group than in the control group (P < .05). The decrease in FA in the left thalamus significantly correlated with the YGTSS score (r = 0.692; P < .05). No correlation was found between FA and ADC values in other brain regions and the YGTSS score (P > .05).After the DTI analyses, abnormalities were found in the left globus pallidus, right caudate nucleus, and bilateral thalamus in children with TS. Especially the changes in the left thalamus structure was crucial in the pathophysiological clock of TS.

A Rare Novel CLCN2 Variation and Risk of Gilles de la Tourette Syndrome: Whole-Exome Sequencing in a Multiplex Family and a Follow-Up Study in a Chinese Population

Rare inherited variations in multiplex families with Gilles de la Tourette syndrome (GTS) are suggested to play an important role in the genetic etiology of GTS. In order to explore the rare inherited variations with the risk of GTS, whole-exome sequencing (WES) was performed in a family with three affected patients with GTS. Among the five novel rare variations identified by WES, CLCN2 G161S was presented in three patients, but not in four unaffected individuals, and thus co-segregated with GTS. A validation study was also performed in a cohort of Chinses Han population to further examine the identified rare variants. CLCN2 G161S was genotyped in 207 sporadic patients with tic disorder including 111 patients with GTS and 489 healthy controls. Compared with that in controls [allele frequency (AF) = 0], CLCN2 G161S had higher variant AF in patients with tic (AF = 0.00483) and in patients with GTS (0.00900), respectively. However, this variant was absent from the current 1000 Genome databases, and the variant AF is very low in the current public databases including ExAC (AF = 0.00001) and gnomAD (AF = 0.00003). Our results suggest that CLCN2 G161S might play a major role in the genetic etiology of GTS, at least in a Chinese Han population.

Neural activation and connectivity during cued eye blinks in Chronic Tic Disorders

Objective

The pathophysiology of Chronic Tic Disorders (CTDs), including Tourette Syndrome, remains poorly understood. The goal of this study was to compare neural activity and connectivity during a voluntary movement (VM) paradigm that involved cued eye blinks among children with and without CTDs. Using the precise temporal resolution of electroencephalography (EEG), we used the timing and location of cortical source resolved spectral power activation and connectivity to map component processes such as visual attention, cue detection, blink regulation and response monitoring. We hypothesized that neural activation and connectivity during the cued eye blink paradigm would be significantly different in regions typically associated with effortful control of eye blinks, such as frontal, premotor, parietal, and occipital cortices between children with and without CTD.

Method

Participants were 40 children (23 with CTD, 17 age-matched Healthy Control [HC]), between the ages of 8–12 (mean age = 9.5) years old. All participants underwent phenotypic assessment including diagnostic interviews, behavior rating scales and 128-channel EEG recording. Upon presentation of a cue every 3 s, children were instructed to make an exaggerated blink.

Results

Behaviorally, the groups did not differ in blink number, latency, or ERP amplitude. Within source resolved clusters located in left dorsolateral prefrontal cortex, posterior cingulate, and supplemental motor area, children with CTD exhibited higher gamma band spectral power relative to controls. In addition, significant diagnostic group differences in theta, alpha, and beta band power in inferior parietal cortex emerged. Spectral power differences were significantly associated with clinical characteristics such as tic severity and premonitory urge strength. After calculating dipole density for 76 anatomical regions, the CTD and HC groups had 70% overlap of top regions with the highest dipole density, suggesting that similar cortical networks were used across groups to carry out the VM. The CTD group exhibited significant information flow increase and dysregulation relative to the HC group, particularly from occipital to frontal regions.

Conclusion

Children with CTD exhibit abnormally high levels of neural activation and dysregulated connectivity among networks used for regulation and effortful control of voluntary eye blinks.

•

First cortical source level EEG study on brain activity and connectivity in CTD.

•

Children with CTD exhibit aberrant levels of neural activation and connectivity.

•

Neural activation was significantly associated with tic severity and premonitory urge.

Age and gender interactions in white matter of schizophrenia and obsessive compulsive disorder compared to non-psychiatric controls: commonalities across disorders

Schizophrenia (SCZ) and obsessive-compulsive disorder (OCD) are psychiatric disorders with abnormalities in white matter structure. These disorders share high comorbidity and family history of OCD is a risk factor for SCZ which suggests some shared neurobiology. White matter was examined using diffusion tensor imaging in relativity large samples of SCZ (N = 48), OCD (N = 38) and non-psychiatric controls (N = 45). Fractional anisotropy (FA) was calculated and tract based spatial statistics were used to compare groups. In a whole brain analysis, SCZ and OCD both showed small FA reductions relative to controls in the corpus callosum. Both SCZ and OCD showed accelerated reductions in FA with age; specifically in the left superior longitudinal fasciculus in OCD, while the SCZ group demonstrated a more widespread pattern of FA reduction. Patient groups did not differ from each other in total FA or age effects in any regions. A general linear model using 13 a-priori regions of interest showed marginal group, group*gender, and group*age interactions. When OCD and SCZ groups were analyzed together, these marginal effects became significant (p < 0.05), suggesting commonalities exist between these patient groups. Overall, our results demonstrate a similar pattern of accelerated white matter decline with age and greater white matter deficit in females in OCD and SCZ, with overlap in the spatial pattern of deficits. There was no evidence for statistical differences in overall white matter between OCD and SCZ. Taken together, the results support the notion of shared neurobiology in SCZ and OCD.

Tics and Tourette: a clinical, pathophysiological and etiological review

PURPOSE OF REVIEW

Describe developments in the etiological understanding of Tourette syndrome.

RECENT FINDINGS

Tourette syndrome is a complex heterogenous clinical syndrome, which is not a unitary entity. Pathophysiological models describe gamma-aminobutyric acid-ergic-associated disinhibition of cortico-basal ganglia motor, sensory and limbic loops. MRI studies support basal ganglia volume loss, with additional white matter and cerebellar changes. Tourette syndrome cause likely involves multiple vulnerability genes and environmental factors. Only recently have some vulnerability gene findings been replicated, including histidine decarboxylase and neurexin 1, yet these rare variants only explain a small proportion of patients. Planned large genetic studies will improve genetic understanding. The role of inflammation as a contributor to disease expression is now supported by large epidemiological studies showing an association with maternal autoimmunity and childhood infection. Investigation of blood cytokines, blood mRNA and brain mRNA expression support the role of a persistent immune activation, and there are similarities with the immune literature of autistic spectrum disorder. Current treatment is symptomatic, although there is a better appreciation of factors that influence treatment response.

SUMMARY

At present, therapeutics is focused on symptom-based treatments, yet with improved etiological understanding, we will move toward disease-modifying therapies in the future.

Short-range connections in the developmental connectome during typical and atypical brain maturation

The human brain is remarkably complex with connectivity constituting its basic organizing principle. Although long-range connectivity has been focused on in most research, short-range connectivity is characterized by unique and spatiotemporally heterogeneous dynamics from infancy to adulthood. Alterations in the maturational dynamics of short-range connectivity has been associated with neuropsychiatric disorders, such as autism and schizophrenia. Recent advances in neuroimaging techniques, especially diffusion magnetic resonance imaging (dMRI), resting-state functional MRI (rs-fMRI), electroencephalography (EEG) and magnetoencephalography (MEG), have made quantification of short-range connectivity possible in pediatric populations. This review summarizes findings on the development of short-range functional and structural connections at the macroscale. These findings suggest an inverted U-shaped pattern of maturation from primary to higher-order brain regions, and possible "hyper-" and "hypo-" short-range connections in autism and schizophrenia, respectively. The precisely balanced short- and long-range connections contribute to the integration and segregation of the connectome during development. The mechanistic relationship among short-range connectivity maturation, the developmental connectome and emerging brain functions needs further investigation, including the refinement of methodological approaches.

Premonitory urges and tics in Tourette syndrome: computational mechanisms and neural correlates

Tourette syndrome is characterized by open motor behaviors - tics - but another crucial aspect of the disorder is the presence of premonitory urges: uncomfortable sensations that typically precede tics and are temporarily alleviated by tics. We review the evidence implicating the somatosensory cortices and the insula in premonitory urges and the motor cortico-basal ganglia-thalamo-cortical loop in tics. We consider how these regions interact during tic execution, suggesting that the insula plays an important role as a nexus linking the sensory and emotional character of premonitory urges with their translation into tics. We also consider how these regions interact during tic learning, integrating the neural evidence with a computational perspective on how premonitory-urge alleviation reinforces tics.

Altered topology of structural brain networks in patients with Gilles de la Tourette syndrome

Gilles de la Tourette syndrome is a neurodevelopmental disorder characterized by tics. Abnormal neuronal circuits in a wide-spread structural and functional network involved in planning, execution and control of motor functions are thought to represent the underlying pathology. We therefore studied changes of structural brain networks in 13 adult GTS patients reconstructed by diffusion tensor imaging and probabilistic tractography. Structural connectivity and network topology were characterized by graph theoretical measures and compared to 13 age-matched controls. In GTS patients, significantly reduced connectivity was detected in right hemispheric networks. These were furthermore characterized by significantly reduced local graph parameters (local clustering, efficiency and strength) indicating decreased structural segregation of local subnetworks. Contrasting these results, whole brain and right hemispheric networks of GTS patients showed significantly increased normalized global efficiency indicating an overall increase of structural integration among distributed areas. Higher global efficiency was associated with tic severity (R = 0.63, p = 0.022) suggesting the clinical relevance of altered network topology. Our findings reflect an imbalance between structural integration and segregation in right hemispheric structural connectome of patients with GTS. These changes might be related to an underlying pathology of impaired neuronal development, but could also indicate potential adaptive plasticity.

Tourette syndrome research highlights from 2016

This article presents highlights chosen from research that appeared during 2016 on Tourette syndrome and other tic disorders. Selected articles felt to represent meaningful advances in the field are briefly summarized.

Tourette syndrome research highlights from 2016

This article presents highlights chosen from research that appeared during 2016 on Tourette syndrome and other tic disorders. Selected articles felt to represent meaningful advances in the field are briefly summarized.

Disrupted topological organization of structural networks revealed by probabilistic diffusion tractography in Tourette syndrome children

Tourette syndrome (TS) is a childhood-onset neurobehavioral disorder. Although previous TS studies revealed structural abnormalities in distinct corticobasal ganglia circuits, the topological alterations of the whole-brain white matter (WM) structural networks remain poorly understood. Here, we used diffusion MRI probabilistic tractography and graph theoretical analysis to investigate the topological organization of WM networks in 44 drug-naive TS children and 41 age- and gender-matched healthy children. The WM networks were constructed by estimating inter-regional connectivity probability and the topological properties were characterized using graph theory. We found that both TS and control groups showed an efficient small-world organization in WM networks. However, compared to controls, TS children exhibited decreased global and local efficiency, increased shortest path length and small worldness, indicating a disrupted balance between local specialization and global integration in structural networks. Although both TS and control groups showed highly similar hub distributions, TS children exhibited significant decreased nodal efficiency, mainly distributed in the default mode, language, visual, and sensorimotor systems. Furthermore, two separate networks showing significantly decreased connectivity in TS group were identified using network-based statistical (NBS) analysis, primarily composed of the parieto-occipital cortex, precuneus, and paracentral lobule. Importantly, we combined support vector machine and multiple kernel learning frameworks to fuse multiple levels of network topological features for classification of individuals, achieving high accuracy of 86.47%. Together, our study revealed the disrupted topological organization of structural networks related to pathophysiology of TS, and the discriminative topological features for classification are potential quantitative neuroimaging biomarkers for clinical TS diagnosis. Hum Brain Mapp 38:3988-4008, 2017. © 2017 Wiley Periodicals, Inc.

Altered Spontaneous Brain Activity in Children with Early Tourette Syndrome: a Resting-state fMRI Study

Tourette syndrome (TS) is a childhood-onset chronic disorder characterized by the presence of multiple motor and vocal tics. This study investigated the alterations of spontaneous brain activities in children with TS by resting-state functional magnetic resonance imaging (rs-fMRI). We obtained rs-fMRI scans from 21 drug-naïve and pure TS children and 29 demographically matched healthy children. The amplitude of low-frequency fluctuation (ALFF), fractional ALFF (fALFF) and regional homogeneity (ReHo) of rs-fMRI data were calculated to measure spontaneous brain activity. We found significant alterations of ALFF or fALFF in vision-related structures including the calcarine sulcus, the cuneus, the fusiform gyrus, and the left insula in TS children. Decreased ReHo was found in the right cerebellum. Further analysis showed that the ReHo value of the right cerebellum was positively correlated with TS duration. Our study provides empirical evidence for abnormal spontaneous neuronal activity in TS patients, which may implicate the neurophysiological mechanism in TS children. Moreover, the right cerebellum can be potentially used as a biomarker for the pathophysiology of early TS in children.

Combining Disrupted and Discriminative Topological Properties of Functional Connectivity Networks as Neuroimaging Biomarkers for Accurate Diagnosis of Early Tourette Syndrome Children

Tourette syndrome (TS) is a childhood-onset neurological disorder. To date, accurate TS diagnosis remains challenging due to its varied clinical expressions and dependency on qualitative description of symptoms. Therefore, identifying accurate and objective neuroimaging biomarkers may help improve early TS diagnosis. As resting-state functional MRI (rs-fMRI) has been demonstrated as a promising neuroimaging tool for TS diagnosis, previous rs-fMRI studies on TS revealed functional connectivity (FC) changes in a few local brain networks or circuits. However, no study explored the disrupted topological organization of whole-brain FC networks in TS children. Meanwhile, very few studies have examined brain functional networks using machine-learning methods for diagnostics. In this study, we construct individual whole-brain, ROI-level FC networks for 29 drug-naive TS children and 37 healthy children. Then, we use graph theory analysis to investigate the topological disruptions between groups. The identified disrupted regions in FC networks not only involved the sensorimotor association regions but also the visual, default-mode and language areas, all highly related to TS. Furthermore, we propose a novel classification framework based on similarity network fusion (SNF) algorithm, to both diagnose an individual subject and explore the discriminative power of FC network topological properties in distinguishing between TS children and controls. We achieved a high accuracy of 88.79%, and the involved discriminative regions for classification were also highly related to TS. Together, both the disrupted topological properties between groups and the discriminative topological features for classification may be considered as comprehensive and helpful neuroimaging biomarkers for assisting the clinical TS diagnosis.