Recent advances in Tourette syndrome

Gastrodin - A potential drug used for the treatment of Tourette Syndrome

Gastrodin (Gas) represents the major active component of Gastrodia elata, a Chinese herb. Clinically, Gas is widely used for its sedative, anticonvulsive and neuroprotective properties. This work aimed to assess Gas for its efficacy in Tourette Syndrome (TS) treatment. Twenty-four rats were randomized to the blank control (n = 6) and experimental (n = 18) groups. The experimental group was administered continuous injection of 3, 3'-iminodipropionitrile (IDPN) intraperitoneally for 7 days, and subdivided into the IDPN + NS, IDPN + Hal, and IDPN + Gas groups (n = 6). The control and IDPN + NS groups received saline intragastrically, while the IDPN + Hal and IDPN + Gas groups were administered Gas and Haloperidol, respectively, for 8 weeks. Then, micro-positron emission tomography (PET) was performed for measuring the density and brain distribution of dopamine D2 receptors (D2Rs), dopamine transporters (DATs), 5-HT2A receptors (5-HT2ARs) and 5-HT transporters (SERTs). According to stereotypical behavior experiments, IDPN significantly induced abnormal stereotypical behaviors in rats in comparison with control animals. In addition, micro-PET revealed that by reducing the amounts of D2Rs and increasing those of DATs, Gas could significantly reduce stereotypical TS-like behaviors in this rat model system. Furthermore, Gas treatment reduced the density of SERTs, which could indirectly decrease DA release. The current study demonstrated that Gas could be effective in treating TS.

Impaired automatic but intact volitional inhibition in primary tic disorders

The defining character of tics is that they can be transiently suppressed by volitional effort of will, and at a behavioural level this has led to the concept that tics result from a failure of inhibition. However, this logic conflates the mechanism responsible for the production of tics with that used in suppressing them. Volitional inhibition of motor output could be increased to prevent the tic from reaching the threshold for expression, although this has been extensively investigated with conflicting results. Alternatively, automatic inhibition could prevent the initial excitation of the striatal tic focus-a hypothesis we have previously introduced. To reconcile these competing hypotheses, we examined different types of motor inhibition in a group of 19 patients with primary tic disorders and 15 healthy volunteers. We probed proactive and reactive inhibition using the conditional stop-signal task, and applied transcranial magnetic stimulation to the motor cortex, to assess movement preparation and execution. We assessed automatic motor inhibition with the masked priming task. We found that volitional movement preparation, execution and inhibition (proactive and reactive) were not impaired in tic disorders. We speculate that these mechanisms are recruited during volitional tic suppression, and that they prevent expression of the tic by inhibiting the nascent excitation released by the tic generator. In contrast, automatic inhibition was abnormal/impaired in patients with tic disorders. In the masked priming task, positive and negative compatibility effects were found for healthy controls, whereas patients with tics exhibited strong positive compatibility effects, but no negative compatibility effect indicative of impaired automatic inhibition. Patients also made more errors on the masked priming task than healthy control subjects and the types of errors were consistent with impaired automatic inhibition. Errors associated with impaired automatic inhibition were positively correlated with tic severity. We conclude that voluntary movement preparation/generation and volitional inhibition are normal in tic disorders, whereas automatic inhibition is impaired-a deficit that correlated with tic severity and thus may constitute a potential mechanism by which tics are generated.

Treatment options for tic disorders

Introduction: Gilles de la Tourette syndrome (GTS) is a neurodevelopmental disorder, characterized by the presence of multiple motor and, at least one, phonic tics, for more than one year, beginning before 18 years of age; its treatment is often a challenge for the clinicianAreas covered: GTS treatment requires a multidisciplinary management to treat each patient's symptom. Although individuals with GTS often have comorbid psychiatric disorders, the focus of this review will only be on the management of tics.Expert opinion: The authors summarized the steps that clinicians should follow treating GTS patient; the impact of the tics on a patients' life should be the first step; different patients could present different levels of tolerance to the symptoms. Second, comorbidities should be considered before starting a treatment for tic. Finally, clinicians must focus the attention of the patient and family, on the length of the treatment and the duration of time after which the effects of the drug will occur. Before the treatment, the potential side effects must be mentioned to the parents, and the choice of treatment must be made in the light of the patient's tolerance to these.

Predictors of the Clinical Course of Tourette Syndrome: A Longitudinal Study

OBJECTIVE

Tourette syndrome (TS) is a chronic childhood neurodevelopmental disorder characterized by motor and vocal tics and frequent comorbidities. The clinical presentation of Tourette syndrome is heterogeneous and the prognosis for each individual child is difficult to define. This large prospective longitudinal study explores predictors in childhood of the clinical course of tics and comorbidities in early adulthood.

METHODS

The cohort was recruited at the Danish National Tourette Clinic. Data were collected at baseline (N = 314; ages, 5-19 years) and follow-up 6 years later (n = 227; ages, 11-26 years) to examine changes in the expression of tics and comorbidities. Childhood clinical factors, represented by 4 binary clinical outcomes, were selected as possible predictors of the clinical course of tics and comorbidities in early adulthood; these were tic severity and diagnoses of obsessive compulsive disorder (OCD), attention-deficit hyperactivity disorder (ADHD), and emotional disorders.

RESULTS

The strongest predictors of high tic scores, OCD, or ADHD diagnoses in early adulthood were the corresponding tic (odds ratio [OR]: 1.09), OCD (OR: 1.08), and ADHD (OR: 1.13) severity scores (per scale point) in childhood. Being female (OR: 3.94) and childhood ADHD severity (OR: 1.11) predicted future emotional disorders. Special education, genetic factors, and psychosocial factors were also predictive for the clinical course of Tourette syndrome.

CONCLUSION

We identified strong clinical predictors of Tourette syndrome-associated outcomes in early adulthood that are directly applicable to clinical Tourette syndrome populations and may help to guide new patients, plan early interventions, and implement preventive measures.

Gastrodin alleviates Tourette syndrome via Nrf-2/HO-1/HMGB1/NF-кB pathway

The aim is to study the effects of gastrodin (GA) on striatal inflammation and oxidative stress in rats with Tourette syndrome (TS). The rat model of TS was induced by 3,3'-iminodipropionitrile. Behavioral tests were carried out by stereotype experiment. The concentrations of amino acid transmitters glutamic acid (Glu) and γ-aminobutyric acid (GABA) in striatum were determined by high-performance liquid chromatography. Superoxide dismutase (SOD) and malondialdehyde (MDA) in serum and striatum were detected by commercial kits. Cytokines in serum and striatum were detected by enzyme-linked immunosorbent assay kits. Western blot analysis was used to detect striatum nuclear erythroid factor 2-related factor 2 (Nrf-2)/heme oxygenase-1 (HO-1)/high mobility group box 1 protein (HMGB1)/nuclear factor-кB (NF-кB) pathway-related proteins. The expressions of Nrf-2 and P-NF-кBp65 in striatum were detected by immunohistochemistry. Compared with the control group, the stereotype scores of rats in the model group significantly increased, and the contents of Glu and GABA in striatum obviously increased. GA significantly reduced the stereotype scores and decreased the contents of Glu and GABA. The levels of SOD in serum and striatum were decreased and the content of MDA in serum and striatum were increased compared with the control group, while GA significantly restored the changes. GA significantly adjusted Nrf-2/HO-1/HMGB1/NF-кB pathway-related proteins changes consistent with immunohistochemical changes. GA may protect striatum of rats with TS by regulating Nrf-2/HO-1/HMGB1/NF-кB pathway protein changes in striatum.

Putamen gray matter volumes in neuropsychiatric and neurodegenerative disorders

Putamen is enriched with dopamine and associated with dopamine-related phenotypes including many neuropsychiatric and neurodegenerative disorders that manifest with motor impairment, impulsive behavior, and cognitive deficits. The gray matter volume of the putamen is age-dependent and genetically controlled. In most neuropsychiatric and neurodegenerative disorders, including Parkinson's spectrum disorders, Huntington's disease, dementia with Lewy bodies, Alzheimer's disease, multiple sclerosis, attention deficit hyperactivity disorder, developmental dyslexia, and major depression, the putamen volume is significantly reduced. On the other hand, in individuals with bipolar disorder, schizophrenia spectrum disorders, especially neuroleptics-medicated patients with schizophrenia, autism spectrum disorders, obsessive-compulsive spectrum disorders, and cocaine/amphetamine dependence, the putamen volume is significantly enlarged. Therefore, the putamen volume may serve as a structural neural marker for many neuropsychiatric and neurodegenerative disorders and a predictor of treatment outcomes in individuals afflicted with these conditions. We provided an overview of the genetic bases of putamen volume and explored potential mechanisms whereby altered putamen volume manifests in these neuropsychiatric and neurodegenerative conditions, with a specific focus on dopaminergic processes.

Rhynchophylline Attenuates Neurotoxicity in Tourette Syndrome Rats

Tourette syndrome (TS) is a chronic neuropsychiatric disorder with clinical manifestations of involuntary and repeated muscle twitching and vocal twitching. The drugs used to treat TS are relatively limited. The aim of this study was to investigate the effects of rhynchophylline (RH) and the underlying mechanism in 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI)-induced neurotoxicity in a TS rat model. A TS model was induced with DOI. The rats were divided into control, TS, TS + tiapride (25 mg/kg), and TS + RH (20 and 40 mg/kg) groups. Behavioral tests were performed 24 h after the last administration by nodding and stereotype experiments. Interleukin-6 (IL-6), IL-1β, and tumor necrosis factor-α (TNF-α) levels in striatum and serum were detected with an enzyme-linked immunosorbent assay (ELISA). Western blot analysis was used to detect the expression levels of Toll-like receptor (TLR)/nucleotide-binding domain (NOD)-like receptor protein 3 (NLRP3)/nuclear factor kappa B (NF-κB) signal proteins in the striatum. The expression of TLR2 and NF-κB p65 subunit was detected with immunohistochemical analysis. RH may significantly improve behavioral changes in rats with DOI-induced TS and reduce the levels of inflammatory factors in serum and striatum. RH inhibited the activation of TLR/NLRP3/NF-κB signaling proteins in the striatum of TS rats. In BV2 cells, DOI-induced inflammation mediated through TLR/NLRP3/NF-κB was significantly inhibited following RH administration. The therapeutic effect of RH in TS was studied and its mechanism of action mediated via the TLR/NLRP3/NF-κB pathway was clarified in vitro and in vivo.

The Potential of Cannabinoid-Based Treatments in Tourette Syndrome

Novel pharmacological treatments are needed for Tourette syndrome. Our goal was to examine the current evidence base and biological rationale for the use of cannabis-derived medications or medications that act on the cannabinoid system in Tourette syndrome. We conducted a comprehensive literature search of PubMed for randomized controlled trials or clinical trials of cannabis-derived medications in Tourette syndrome. Data regarding the population, intervention, safety profile, and outcomes for each trial were extracted and reported and the evidence supporting use of individual cannabis-derived medications was critiqued. There is a strong biological rationale regarding how cannabis-derived medications could affect tic severity. Anecdotal case reports and series have noted that many patients report that their tics improve after using cannabis. However, only two small randomized, placebo-controlled trials of Δ⁹-tetrahydrocannabinol have been published; these suggested possible benefits of cannabis-derived agents for the treatment of tics. Trials examining other agents active on the cannabinoid system for tic disorders are currently ongoing. Cannabinoid-based treatments are a promising avenue of new research for medications that may help the Tourette syndrome population. However, given the limited research available, the overall efficacy and safety of cannabinoid-based treatments is largely unknown. Further trials are needed to examine dosing, active ingredients, and optimal mode of administration of cannabis-derived compounds, assuming initial trials suggest efficacy. Clinical use for refractory patients should at the very least be restricted to adult populations, given the uncertain efficacy and risk of developmental adverse effects that cannabinoids may have in children. Even in adult populations, cannabis-derived medications are associated with significant issues such as the effects they have on driving safety and the fact that they cause positive urine drug screens that can affect employment.

Histamine H3 receptor antagonists/inverse agonists: Where do they go?

Since the discovery of the histamine H₃ receptor in 1983, tremendous advances in the pharmacological aspects of H₃ receptor antagonists/inverse agonists have been accomplished in preclinical studies. At present, there are several drug candidates that reached clinical trial studies for various indications. However, entrance of these candidates to the pharmaceutical market is not free from challenges, and a variety of difficulties is engaged with their developmental process. In this review, the potential role of H₃ receptors in the pathophysiology of various central nervous system, metabolic and allergic diseases is discussed. Thereafter, the current status for H₃ receptor antagonists/inverse agonists in ongoing clinical trial studies is reviewed and obstacles in developing these agents are emphasized.

Executive control development in Tourette syndrome and its role in tic reduction

Tourette syndrome (TS) is a childhood-onset disorder characterized by motor and vocal tics. Recent findings point to a possible role of executive functions system development in the tic reduction observed with age. The goal of the present work was to track the development of executive functions system measured by well-established cognitive tasks and its correlation with diminished tic severity over time in order to understand the role of executive functions in the remission process observed in most adults. The first study followed 25 young TS patients, measuring their executive functions and clinical condition at three time- points. In the second study we compared executive functions performance of 19 adult TS patients with 19 healthy controls and 12 remitted TS patients. The first study showed that tic reduction is related to the development of the executive functions components associated with response inhibition. The second study similarly showed impaired inhibition ability in TS patients but not in controls or the remitted TS patients. The remitted group performed at normal or even higher levels on certain measures. We conclude that inhibition, an important executive function, is impaired in subjects suffering from TS and that intact executive function development is related to remission processes.

Tourette disorder and other tic disorders

Tourette disorder is a developmental neuropsychiatric condition characterized by vocal and motor tics that can range in severity from mild to disabling. It represents one end of a spectrum of tic disorders and is estimated to affect 0.5-0.7% of the population. Accumulated evidence supports a substantial genetic contribution to disease risk, but the identification of genetic variants that confer risk has been challenging. Positive findings in candidate gene association studies have not replicated, and genomewide association studies have not generated signals of genomewide significance, in large part because of inadequate sample sizes. Rare mutations in several genes have been identified, but their causality is difficult to establish. As in other complex neuropsychiatric disorders, it is likely that Tourette disorder risk involves a combination of common, low-effect and rare, larger-effect variants in multiple genes acting together with environmental factors. With the ongoing collection of larger patient cohorts and the emergence of affordable high-throughput genomewide sequencing, progress is expected to accelerate in coming years.

Lipopolysaccharide aggravated DOI-induced Tourette syndrome: elaboration for recurrence of Tourette syndrome

Tourette syndrome (TS) is a neurological disorder characterized by highest familial recurrence rate among neuropsychiatric diseases with complicated inheritance. Recurrence of Tourette syndrome was frequently observed in clinical. Unexpectedly, the mechanism of recurrence of Tourette syndrome was failure to elucidate. Here, we first shown that lipopolysaccharide(LPS) may played an important role in the recurrence of Tourette syndrome. The TS model in rats was induced by DOI (the selective 5-HT2A/2C agonist 1-(2, 5-dimethoxy-4-iodophenyl) -2- aminopropane). The rats were randomly divided into 4 groups:(1)Control;(2) Control + LPS; (2)TS; (3)TS + LPS. The results demonstrated that the LPS treatment significantly increased stereotypic score and autonomic activity. LPS treatment also significantly increased inflammatory cytokines such as interleukin-6 (IL-6), interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in serum and striatum. Also, highly expressed TLR4, MyD88, P-NF-κBp65, P-IκBα in TS rats were increased respectively by LPS treatment as indicted in western blot analysis and immunohistochemistry analysis. Thus, it was supposed that lipopolysaccharide(LPS) may played an important role in the recurrence of Tourette syndrome and its mechanism was related to TLR/NF-κB pathway.

Phenotype Development in Adolescents With Tourette Syndrome: A Large Clinical Longitudinal Study

Tourette syndrome (TS) is a neurodevelopmental disorder characterized by frequent comorbidities and a wide spectrum of phenotype presentations. This study aimed to describe the development of phenotypes in TS and tic-related impairment in a large longitudinal study of 226 children and adolescents followed up after 6 years. The participants were clinically examined to assess tic severity and impairment, obsessive compulsive disorder (OCD), and attention-deficit/hyperactivity disorder (ADHD). The development in phenotypes changed toward less comorbidity with 40% TS-only (no OCD or ADHD) (TS without OCD or ADHD) at baseline and 55% at follow-up.Tic-related impairment was expected to improve with an age-related tic decline, but surprisingly the impairment score did not reflect the tic decline. Sex, vocal and motor tics, and OCD and ADHD severity were highly significantly correlated to the impairment score. Knowledge of TS phenotype development is used in clinical settings to guide patients and for genetic, etiological, and clinical research purposes.

LY294002, a PI3K inhibitor, attenuates Tourette syndrome in rats

The present study was designed to investigate the effects of LY294002 on Tourette syndrome (TS) in rats. TS model was induced in rats by DOI (the selective 5-HT2A/2C agonist 1- (2, 5- dimethoxy -4 - iodophenyl) -2- aminopropane). Behavior was assessed by stereotypic score and autonomic activity. Inflammatory cytokines such as interleukin-6 (IL-6), interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in serum and striatum were detected. The protein levels of PI3K/Akt/NF-B in striatum were detected by Western Blot. LY294002 treatment significantly reduced IL-6, IL-1β and TNF-α in serum and striatum of TS rats, Also, highly expressed P-PI3K, P-Akt, P-NF-κBp65, P-IκBα in TS rats were restored respectively by LY294002 treatment as indicted in western blot analysis and immunohistochemistry analysis. Thus, it was supposed that the protective effect of LY294002 against TS in rat might be associated with the regulation of PI3K/Akt/NF-B pathway.

Dysfunctions of the basal ganglia-cerebellar-thalamo-cortical system produce motor tics in Tourette syndrome

Motor tics are a cardinal feature of Tourette syndrome and are traditionally associated with an excess of striatal dopamine in the basal ganglia. Recent evidence increasingly supports a more articulated view where cerebellum and cortex, working closely in concert with basal ganglia, are also involved in tic production. Building on such evidence, this article proposes a computational model of the basal ganglia-cerebellar-thalamo-cortical system to study how motor tics are generated in Tourette syndrome. In particular, the model: (i) reproduces the main results of recent experiments about the involvement of the basal ganglia-cerebellar-thalamo-cortical system in tic generation; (ii) suggests an explanation of the system-level mechanisms underlying motor tic production: in this respect, the model predicts that the interplay between dopaminergic signal and cortical activity contributes to triggering the tic event and that the recently discovered basal ganglia-cerebellar anatomical pathway may support the involvement of the cerebellum in tic production; (iii) furnishes predictions on the amount of tics generated when striatal dopamine increases and when the cortex is externally stimulated. These predictions could be important in identifying new brain target areas for future therapies. Finally, the model represents the first computational attempt to study the role of the recently discovered basal ganglia-cerebellar anatomical links. Studying this non-cortex-mediated basal ganglia-cerebellar interaction could radically change our perspective about how these areas interact with each other and with the cortex. Overall, the model also shows the utility of casting Tourette syndrome within a system-level perspective rather than viewing it as related to the dysfunction of a single brain area.

Tourette syndrome is a neuropsychiatric disorder characterized by vocal and motor tics. Tics represent a cardinal symptom traditionally associated with a dysfunction of the basal ganglia leading to an excess of the dopamine neurotransmitter. This view gives a restricted clinical picture and limits therapeutic approaches because it ignores the influence of altered interactions between the basal ganglia and other brain areas. In this respect, recent evidence supports a more articulated framework where cerebellum and cortex are also involved in tic production. Building on these data, we propose a computational model of the basal ganglia-cerebellar-thalamo-cortical network to investigate the specific mechanisms underlying motor tic production. The model reproduces the results of recent experiments and suggests an explanation of the system-level processes underlying tic production. Moreover, it furnishes predictions related to the amount of tics generated when there are dysfunctions in the basal ganglia-cerebellar-thalamo-cortical circuits. These predictions could be important in identifying new brain target areas for future therapies based on a system-level view of Tourette syndrome.

Specific executive control impairments in Tourette syndrome: The role of response inhibition

BACKGROUND

Tourette syndrome (TS) is a childhood-onset disorder characterized by motor and vocal tics. While cognitive features of common comorbid conditions such as attention deficit hyperactive disorder and obsessive compulsive disorder have been widely investigated, the cognitive profile of TS patients remains to be precisely defined. In this regard, the executive functions system (EF) is of especial interest.

AIMS

The aim of the study was to delineate the various components of executive processes in adult TS patients.

METHODS

A sample of 19 adults diagnosed with TS and 19 age-matched control subjects underwent computerized battery of executive tasks, as well as block design and memory tests. All patients received a thorough clinical assessment with an emphasis on illness severity.

RESULTS

There was a marked impairment in response inhibition ability regardless of comorbid conditions, In addition, there was decreased accuracy in set shifting, but not in response time. These results imply that impaired response inhibition in the EF system is the primary cognitive impairment in TS and that many of the previously reported impaired executive functions in TS are secondary to this impairment.

CONCLUSIONS

This finding of impaired response inhibition in TS may imply that rehabilitation of this inhibition component could prove to be an important therapeutic strategy in adults with TS.

Tourette syndrome in the context of evolution and behavioral ecology

Tourette syndrome, and the closely related spectrum of tic disorders, are inherited neuropsychiatric conditions characterized by the presence of repetitive and stereotyped movements. Tics are elicited by either environmental experiences or internal signals that instruct the basal ganglia to initiate automatic or procedural movements. In most vertebrates the basal ganglia encode instructions for habitually used sequences of motor movements that are essential to survival. Tic disorders may represent evolved phenotypes with a lower threshold for basal ganglia-directed actions. This may have produced a susceptibility to extraneous tics, but also produced fast-acting tactical solutions to immediate physical problems. During periods of nonstop movement, continual foraging, and sustained vigilance, it may have been advantageous to allow subcortical motor commands to intrude into ongoing motor activities. It is clear that the engrams for individual motor responses held in the basal ganglia are selected by converging cortical and subcortical inputs. This form of convergent action selection results in the selection of the most contextually reinforced actions. Today people with Tourette's have tics that seem arbitrary and inappropriate; however, this may be due to the vast discrepancies in reinforcement between the ancestral environment and the modern one. In prehistoric environments, the motor behaviors of individuals with tic disorders may have been appropriate in environmental context, and had ecological relevance in survival and self-promotion.

Histamine H3R receptor activation in the dorsal striatum triggers stereotypies in a mouse model of tic disorders

Tic disorders affect ~5% of the population and are frequently comorbid with obsessive-compulsive disorder, autism, and attention deficit disorder. Histamine dysregulation has been identified as a rare genetic cause of tic disorders; mice with a knockout of the histidine decarboxylase (Hdc) gene represent a promising pathophysiologically grounded model. How alterations in the histamine system lead to tics and other neuropsychiatric pathology, however, remains unclear. We found elevated expression of the histamine H3 receptor in the striatum of Hdc knockout mice. The H3 receptor has significant basal activity even in the absence of ligand and thus may modulate striatal function in this knockout model. We probed H3R function using specific agonists. The H3 agonists R-aminomethylhistamine (RAMH) and immepip produced behavioral stereotypies in KO mice, but not in controls. H3 agonist treatment elevated intra-striatal dopamine in KO mice, but not in controls. This was associated with elevations in phosphorylation of rpS6, a sensitive marker of neural activity, in the dorsal striatum. We used a novel chemogenetic strategy to demonstrate that this dorsal striatal activity is necessary and sufficient for the development of stereotypy: when RAMH-activated cells in the dorsal striatum were chemogenetically activated (in the absence of RAMH), stereotypy was recapitulated in KO animals, and when they were silenced the ability of RAMH to produce stereotypy was blocked. These results identify the H3 receptor in the dorsal striatum as a contributor to repetitive behavioral pathology.

Histidine Decarboxylase Knockout Mice as a Model of the Pathophysiology of Tourette Syndrome and Related Conditions

While the normal functions of histamine (HA) in the central nervous system have gradually come into focus over the past 30 years, the relationship of abnormalities in neurotransmitter HA to human disease has been slower to emerge. New insight came with the 2010 description of a rare nonsense mutation in the biosynthetic enzyme histidine decarboxylase (Hdc) that was associated with Tourette syndrome (TS) and related conditions in a single family pedigree. Subsequent genetic work has provided further support for abnormalities of HA signaling in sporadic TS. As a result of this genetic work, Hdc knockout mice, which were generated more than 15 years ago, have been reexamined as a model of the pathophysiology of TS and related conditions. Parallel work in these KO mice and in human carriers of the Hdc mutation has revealed abnormalities in the basal ganglia system and its modulation by dopamine (DA) and has confirmed the etiologic, face, and predictive validity of the model. The Hdc-KO model thus serves as a unique platform to probe the pathophysiology of TS and related conditions, and to generate specific hypotheses for subsequent testing in humans. This chapter summarizes the development and validation of this model and recent and ongoing work using it to further investigate pathophysiological changes that may contribute to these disorders.

Brain histamine depletion enhances the behavioural sequences complexity of mice tested in the open-field: Partial reversal effect of the dopamine D2/D3 antagonist sulpiride

Markers of histaminergic dysregulation were found in several neuropsychiatric disorders characterized by repetitive behaviours, thoughts and stereotypies. We analysed the effect of acute histamine depletion by means of i. c.v. injections of alpha-fluoromethylhistidine, a blocker of histidine decarboxylase, on the temporal organization of motor sequences of CD1 mice behaviour in the open-field test. An ethogram encompassing 9 behavioural components was employed. Durations and frequencies were only slightly affected by treatments. However, as revealed by multivariate t-pattern analysis, histamine depletion was associated with a striking increase in the number of behavioural patterns. We found 42 patterns of different composition occurring, on average, 520.90 ± 50.23 times per mouse in the histamine depleted (HD) group, whereas controls showed 12 different patterns occurring on average 223.30 ± 20.64 times. Exploratory and grooming behaviours clustered separately, and the increased pattern complexity involved exclusively exploratory patterns. To test the hypothesis of a histamine-dopamine interplay on behavioural pattern phenotype, non-sedative doses of the D2/D3 antagonist sulpiride (12.5-25-50 mg/kg) were additionally administered to different groups of HD mice. Sulpiride counterbalanced the enhancement of exploratory patterns of different composition, but it did not affect the mean number of patterns at none of the doses used. Our results provide new insights on the role of histamine on repetitive behavioural sequences of freely moving mice. Histamine deficiency is correlated with a general enhancement of pattern complexity. This study supports a putative involvement of histamine in the pathophysiology of tics and related disorders.

Deep TMS add-on treatment for intractable Tourette syndrome: A feasibility study

OBJECTIVES

In a considerable minority of patients who suffer from Tourette syndrome (TS) the disorder persists into adulthood and is associated with severe symptoms and limited therapeutic options. Repetitive transcranial magnetic stimulation (rTMS) to the supplementary motor area (SMA) has shown promising therapeutic results. Deep rTMS is a novel technology that enables deeper non-invasive cortical stimulation. This open-label pilot study is the first to examine the possible role of deep rTMS as add-on treatment for intractable TS.

METHODS

Twelve patients were recruited in order to examine bilateral SMA inhibition via deep TMS using the HBDL coil, as a possible treatment for adult TS treatment-resistant patients. Two patients did not complete the 20-day study protocol.

RESULTS

There were no significant side effects. While tics did not improve among the group as a whole, the subgroup of six patients with combined TS and OCD (obsessive compulsive syndrome) showed significant improvement in tic severity (P = 0.037).

CONCLUSIONS

These findings support the safety of deep rTMS for treating TS. The results also highlight the importance of studying the different TS syndromes separately (e.g., with or without OCD comorbidity) when evaluating deep rTMS protocols for TS patients.

Histamine regulation of microglia: Gene-environment interaction in the regulation of central nervous system inflammation

Microglia mediate neuroinflammation and regulate brain development and homeostasis. Microglial abnormalities are implicated in a range of neuropsychiatric pathology, including Tourette syndrome (TS) and autism. Histamine (HA) is both a neurotransmitter and an immune modulator. HA deficiency has been implicated as a rare cause of TS and may contribute to other neuropsychiatric conditions. In vitro studies suggest that HA can regulate microglia, but this has never been explored in vivo. We used immunohistochemistry to examine the effects of HA deficiency in histidine decarboxylase (Hdc) knockout mice and of HA receptor stimulation in wild-type animals. We find HA to regulate microglia in vivo, via the H4 receptor. Chronic HA deficiency in Hdc knockout mice reduces ramifications of microglia in the striatum and (at trend level) in the hypothalamus, but not elsewhere in the brain. Depletion of histaminergic neurons in the hypothalamus has a similar effect. Microglia expressing IGF-1 are particularly reduced, However, the microglial response to challenge with lipopolysacchariade (LPS) is potentiated in Hdc knockout mice. Genetic abnormalities in histaminergic signaling may produce a vulnerability to inflammatory challenge, setting the state for pathogenically dysregulated neuroimmune responses.

Investigation of a Possible Role for the Histidine Decarboxylase Gene in Tourette Syndrome in the Chinese Han Population: A Family-Based Study

Tourette syndrome (TS) is a polygenic neuropsychiatric disease. Previous studies have indicated that dysregulation in the histaminergic system may play a crucial role in disease onset. In this study, we investigated the role of the histidine decarboxylase gene (HDC) in TS susceptibility in the Chinese Han population. After genotyping 241 TS nuclear families trios, we analyzed three tag HDC single nucleotide polymorphisms (rs854150, rs854151, and rs854157) in a family-based study using the transmission disequilibrium test (TDT) and haplotype relative risk (HRR). TDT showed no over-transmission in these SNPs across the HDC region (for rs854150: χ² = 0.472, P = 0.537, OR = 1.097, 95%CI = 0.738–1.630; for rs854151: χ² = 0.043, P = 0.889, OR = 1.145, 95%CI = 0.767–1.709; for rs854157:χ² = 0.984, P = 0.367, OR = 1.020, 95%CI = 0.508–2.049). HRR also showed the same tendency (for rs854150: χ² = 0.211, P = 0.646, OR = 1.088, 95%CI = 0.759–1.559; for rs854151: χ² = 0.134, P = 0.714, OR = 0.935, 95%CI = 0.653–1.339; for rs854157:χ² = 0.841, P = 0.359, OR = 1.206, 95%CI = 0.808–1.799). Additionally, the haplotype-based haplotype relative risk showed a negative association. Although these findings indicate an unlikely association between HDC and TS in the Chinese Han population, a potential role for HDC cannot be ruled out in TS etiology. Future research should investigate this more thoroughly using different populations and larger samples.

Dystonic tics induced by deep brain stimulation of the posterior subthalamic area for essential tremor

OBJECTIVE The posterior subthalamic area (PSA) is a promising target of deep brain stimulation (DBS) for medication-refractory essential tremor (ET). This case series describes a novel adverse effect manifesting as dystonic tics in patients with ET undergoing DBS of the PSA. METHODS Six patients with ET received electrode implants for DBS of the dorsal and caudal zona incerta subregions of the PSA. RESULTS Five of the 6 patients developed dystonic tics soon after clinical programming. These tics were of varying severity and required reduction of the electrical stimulation amplitude. This reduction resolved tic occurrence without significantly affecting ET control. Dystonic tics were not observed in 39 additional patients who underwent DBS of the same brain regions for controlling non-ET movement disorders. CONCLUSIONS The pathophysiology of tic disorders is poorly understood and may involve the basal ganglia and related cortico-striato-thalamo-cortical circuits. This series is the first report of DBS-induced tics after stimulation of any brain target. Although the PSA has not previously been implicated in tic pathophysiology, it may be a candidate region for future studies.

Functional Evaluations of Genes Disrupted in Patients with Tourette's Disorder

Tourette's disorder (TD) is a highly heritable neurodevelopmental disorder with complex genetic architecture and unclear neuropathology. Disruptions of particular genes have been identified in subsets of TD patients. However, none of the findings have been replicated, probably due to the complex and heterogeneous genetic architecture of TD that involves both common and rare variants. To understand the etiology of TD, functional analyses are required to characterize the molecular and cellular consequences caused by mutations in candidate genes. Such molecular and cellular alterations may converge into common biological pathways underlying the heterogeneous genetic etiology of TD patients. Herein, we review specific genes implicated in TD etiology, discuss the functions of these genes in the mammalian central nervous system and the corresponding behavioral anomalies exhibited in animal models, and importantly, review functional analyses that can be performed to evaluate the role(s) that the genetic disruptions might play in TD. Specifically, the functional assays include novel cell culture systems, genome editing techniques, bioinformatics approaches, transcriptomic analyses, and genetically modified animal models applied or developed to study genes associated with TD or with other neurodevelopmental and neuropsychiatric disorders. By describing methods used to study diseases with genetic architecture similar to TD, we hope to develop a systematic framework for investigating the etiology of TD and related disorders.

Streptococcal infection and immune response in children with Tourette's syndrome

BACKGROUND

Streptococcal infection and basal ganglia inflammation are hypothesized to be involved in Tourette's syndrome (TS). There is a need for effective therapies for managing TS. We studied streptococcal infection and immunity in TS following immunomodulator (pidotimod) therapy.

METHODS

Blood samples from 58 patients with TS and 128 age-matched healthy controls enabled measurement of antistreptolysin O (ASO), T cells, natural killer (NK) cells, interleukin-6 (IL-6) and interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α). Forty-four patients with abnormal T cell numbers were divided into two groups and treated with pidotimod granules (pidotimod group, n = 20) or pidotimod plus dopaminergic receptor antagonists (combination group, n = 24). Yale Global Tic Severity Scale (YGTSS) scores and immunologic indices were assessed after treatment.

RESULTS

An ASO >1:200 was found in 22.4% of children with TS, 7.5% of controls, and 38.9% of children with both TS and attention deficit hyperactivity disorder (ADHD) compared to 15.0% of children with TS alone (P < 0.05). Children with TS showed decreased CD3(+) and CD4(+) T cells, CD4(+)/CD8(+) ratio, IL-6 and IL-8, increased NKC and TNF-α (P < 0.05) as compared to controls. ASO-positive children with TS had lower CD4(+) T cells as compared to ASO-negative children with TS, and lower IL-6 and IL-8 levels as compared to controls (P < 0.05). After 8 weeks of pidotimod treatment, IL-8 was increased compared to either tiapride hydrochloride or haloperidol and pidotimod (P < 0.05).

CONCLUSIONS

Streptococcal infection in TS patients is associated with immune and cytokine dysfunction, which can be potentially managed with immunomodulator therapy.

The role of atypical antipsychotics for treatment of Tourette's syndrome: an overview

Tourette's syndrome (TS) is a neuropsychiatric disorder of childhood onset characterized by multiple motor and phonic tics that fluctuate over time. Tic symptoms often improve by late adolescence, but some children and adults with TS may experience significant tic-related morbidity, including social and family problems, academic difficulties, and pain. When more conservative interventions are not successful, and when certain psychiatric co-morbidities further complicate the clinical profile, treating TS with an atypical antipsychotic medication may be a reasonable second-tier approach. However, the evidence supporting efficacy and safety of the atypical antipsychotics for treatment of tics is still very limited. The objective of this paper is to provide an updated overview of the role of atypical antipsychotics for treatment of TS, with evidence-based guidance on their use. Evidence for efficacy of different typical and atypical antipsychotics for treatment of tics was examined by conducting a systematic, keyword-related search of 'atypical antipsychotics' and 'Tourette's syndrome' in PubMed (National Library of Medicine, Washington, DC, USA). Four recent treatment consensus publications were also reviewed. This review focused on literature published from 2000 to 2013 and on available randomized controlled trials in TS. Evidence supporting the use of atypical antipsychotics for treatment of TS is limited. There are few randomized medication treatment trials in TS (i.e. risperidone, aripiprazole, ziprasidone), which employed varying methodologies, thereby restricting meaningful comparisons among studies. Future collaborations among clinical sites with TS expertise employing high-quality study design may better elucidate the role of atypical antipsychotics for treatment of TS.

Timing recalibration in childhood Tourette syndrome associated with persistent pimozide treatment

In this study, we have tested the effects of the dopamine D2 receptor blocker pimozide on timing performance in patients with Tourette syndrome (TS). Nine children with TS were tested off-medication and following 3 months of daily treatment with pimozide. Subjects completed a time reproduction and a time production task using supra-second temporal intervals. We show that pimozide improves motor timing performance by reducing the patients' variability in reproducing the duration of visual stimuli. On the other hand, this medication has no effect on the reproduction accuracy and on both variability and accuracy of the performance on the time production task. Our results suggest that pimozide might have improved motor timing variability as a result of its beneficial side effect on endogenous dopamine levels (i.e., normalization).

Prenatal and Perinatal Morbidity in Children with Tic Disorders: A Mainstream School-based Population Study in Central Spain

Background

While current research suggests that genetic factors confer the greatest risk for the development of tic disorders, studies of environmental factors are relatively few, with a lack of consistent risk factors across studies. Our aim is to analyze the association of tic disorders with exposure to prenatal and perinatal morbidity.

Methods

This was a nested case–control study design. Cases and controls were selected and identified from a mainstream, school-based sample. The diagnosis of tic disorders was assigned by a movement disorder neurologist using ‘Diagnostic and statistical manual of mental disorders, 4th edition, text revision’ criteria, and neuropsychiatric comorbidities were screened using the Spanish computerized version of the Diagnostic Interview Schedule for Children Predictive Scale. Information regarding the exposure to pre-perinatal risk factors was collected by a retrospective review of the birth certificates. Logistic regression analyses were then performed to test the association of tic disorders with pre-perinatal risk factors.

Results

Out of 407 participants, complete pre-perinatal data were available in 153 children (64 with tics and 89 without tics). After adjusting for family history of tics, neonatal respiratory distress syndrome, body mass index, prenatal infection, and coexisting comorbid neuropsychiatric disturbances, tic disorders were associated with prenatal exposure to tobacco (odds ratio [OR] = 3.07, 95% confidence interval [CI] 1.24–7.60, p = 0.007), and cesarean section (OR = 5.78, 95% CI 1.60–20.91, p = 0.01).

Discussion

This nested case–control study of children with tic disorders demonstrates higher adjusted odds for tics in children with exposure to cesarean delivery and maternal smoking. Longitudinal, population-based samples are required to confirm these results.

Case report on Tourette syndrome treated successfully with aripiprazole

SUMMARY

Tourette syndrome is a childhood-onset neuropsychiatric disorder characterized by multiple motor and vocal tics of at least one year in duration. This case report describes the history of a 16-year-old boy with a 6-year history of Tourette syndrome who was seriously disabled by his symptoms. Treatment with aripiprazole 10mg/d completely resolved his symptoms in about a month allowing him to return to the life that he had been missing because of his illness. In such cases the potential long-term negative effects of using antipsychotic medications need to weighed against the disruptive effects persistent Tourette symptoms can have on patient's lives.

Tourette syndrome and procedures related to dental treatment: a systematic review

PURPOSE

Dental treatment of patients with Tourette syndrome (TS) may present special challenges to the dentist. The aim was to systematically review the literature regarding perioperative procedures including sedation and general anaesthesia (GA) of patients with TS.

MATERIALS AND METHODS

Literature searches were performed in PubMed and Embase to identify papers concerning TS in combination with dental treatment, sedation, and/or GA in order to study outcomes regarding co-morbidity, perioperative complications, and drug interactions.

RESULTS

The literature search identified six publications (case reports or series) which addressed the topic. No unexpected adverse effects or drug interactions in relation to sedation or GA in TS patients and no perioperative complications were reported.

CONCLUSIONS

The literature on TS is scarce and the evidence level is low. Therefore, guidelines regarding the dental treatment of patients with TS cannot be formulated at the present time.

Animal models of tic disorders: a translational perspective

Tics are repetitive, sudden movements and/or vocalizations, typically enacted as maladaptive responses to intrusive premonitory urges. The most severe tic disorder, Tourette syndrome (TS), is a childhood-onset condition featuring multiple motor and at least one phonic tic for a duration longer than 1 year. The pharmacological treatment of TS is mainly based on antipsychotic agents; while these drugs are often effective in reducing tic severity and frequency, their therapeutic compliance is limited by serious motor and cognitive side effects. The identification of novel therapeutic targets and development of better treatments for tic disorders is conditional on the development of animal models with high translational validity. In addition, these experimental tools can prove extremely useful to test hypotheses on the etiology and neurobiological bases of TS and related conditions. In recent years, the translational value of these animal models has been enhanced, thanks to a significant re-organization of our conceptual framework of neuropsychiatric disorders, with a greater focus on endophenotypes and quantitative indices, rather than qualitative descriptors. Given the complex and multifactorial nature of TS and other tic disorders, the selection of animal models that can appropriately capture specific symptomatic aspects of these conditions can pose significant theoretical and methodological challenges. In this article, we will review the state of the art on the available animal models of tic disorders, based on genetic mutations, environmental interventions as well as pharmacological manipulations. Furthermore, we will outline emerging lines of translational research showing how some of these experimental preparations have led to significant progress in the identification of novel therapeutic targets for tic disorders.

Response inhibition and interference control in obsessive-compulsive spectrum disorders

Over the past 20 years, motor response inhibition and interference control have received considerable scientific effort and attention, due to their important role in behavior and the development of neuropsychiatric disorders. Results of neuroimaging studies indicate that motor response inhibition and interference control are dependent on cortical–striatal–thalamic–cortical (CSTC) circuits. Structural and functional abnormalities within the CSTC circuits have been reported for many neuropsychiatric disorders, including obsessive–compulsive disorder (OCD) and related disorders, such as attention-deficit hyperactivity disorder, Tourette’s syndrome, and trichotillomania. These disorders also share impairments in motor response inhibition and interference control, which may underlie some of their behavioral and cognitive symptoms. Results of task-related neuroimaging studies on inhibitory functions in these disorders show that impaired task performance is related to altered recruitment of the CSTC circuits. Previous research has shown that inhibitory performance is dependent upon dopamine, noradrenaline, and serotonin signaling, neurotransmitters that have been implicated in the pathophysiology of these disorders. In this narrative review, we discuss the common and disorder-specific pathophysiological mechanisms of inhibition-related dysfunction in OCD and related disorders.

Histidine decarboxylase deficiency causes tourette syndrome: parallel findings in humans and mice

Tourette syndrome (TS) is characterized by tics, sensorimotor gating deficiencies, and abnormalities of cortico-basal ganglia circuits. A mutation in histidine decarboxylase (Hdc), the key enzyme for the biosynthesis of histamine (HA), has been implicated as a rare genetic cause. Hdc knockout mice exhibited potentiated tic-like stereotypies, recapitulating core phenomenology of TS; these were mitigated by the dopamine (DA) D2 antagonist haloperidol, a proven pharmacotherapy, and by HA infusion into the brain. Prepulse inhibition was impaired in both mice and humans carrying Hdc mutations. HA infusion reduced striatal DA levels; in Hdc knockout mice, striatal DA was increased and the DA-regulated immediate early gene Fos was upregulated. DA D2/D3 receptor binding was altered both in mice and in humans carrying the Hdc mutation. These data confirm histidine decarboxylase deficiency as a rare cause of TS and identify HA-DA interactions in the basal ganglia as an important locus of pathology.

Tourette syndrome and chronic tic disorder are associated with lower socio-economic status: findings from the Avon Longitudinal Study of Parents and Children cohort

AIM

Only a few studies have examined the relationship between Tourette syndrome or chronic tic disorder and socio-economic status (SES). Existing studies are primarily cross-sectional, arise from specialty clinics, and use single measures of SES. In this study we examine this relationship in a longitudinal, population-based sample.

METHOD

Data are from 7152 children born during 1991 and 1992 in the county of Avon, UK, from the Avon Longitudinal Study of Parents and Children, who were followed up to age 13. After exclusions for intellectual disability* and autism, 6768 participants (3351 males [49.5%]) and 3417 females [50.5%]) remained. Parental SES was assessed using multiple measures during pregnancy and at 33 months of age. Presence of Tourette syndrome or chronic tics was determined from repeated maternal questionnaires up to when the child was 13 years of age.

RESULTS

Multiple SES measures were associated with an approximately twofold increased risk of Tourette syndrome and chronic tics. A postnatal composite factor score (lowest vs highest tertile odds ratio 2.09, 95% confidence interval 1.38-3.47) provided the best fit to the data.

INTERPRETATIONS

As is seen in several childhood conditions, such as cerebral palsy and autism, lower SES is a risk factor for Tourette syndrome/chronic tics. Potential explanations include differential exposure to environmental risk factors or parental psychopathology as a measure of an increased genetic risk leading to decreased parental SES.

Prenatal risk factors for Tourette Syndrome: a systematic review

BACKGROUND

Tourette Syndrome (TS) appears to be an inherited disorder, although genetic abnormalities have been identified in less than 1% of patients, and the mode of inheritance is uncertain. Many studies have investigated environmental factors that might contribute to the onset and severity of tics and associated comorbidities such as obsessive compulsive disorder (OCD) and attention deficit hyperactive disorder (ADHD). A systematic review and qualitative analysis were performed to provide a broad view of the association between pre- and perinatal factors and TS.

METHODS

The Medline, Embase and PsycINFO databases were searched using terms specific to Tourette's syndrome and keywords such as "pregnancy", "prenatal", "perinatal", "birth" and "neonatal". Studies were limited to studies on human subjects published in English or French through October 2012.

RESULTS

22 studies were included. Studies were of limited methodological quality, with most samples derived from specialty clinics, and most exposures ascertained retrospectively. The majority of the results for demographic factors of parents, including age, education, socioeconomic status, and marital status, revealed no significant association with the onset of TS, or the presence of comorbidity. Many factors were reported to be significantly associated with the onset of TS, the presence of comorbidity and symptom severity, but the most consistently reported factors were maternal smoking and low birth weight.

CONCLUSIONS

There are few studies evaluating the relationship between pre and perinatal events and TS, and existing studies have major limitations, including the use of clinic rather than epidemiologically derived samples, retrospective data collection on pre and perinatal events and multiple hypothesis testing without appropriate statistical correction. The mechanism by which prenatal and perinatal adversities could lead to TS onset or symptom severity is unknown, but may be related to changes in the dopaminergic system as a result of early brain injury.

Slitrk gene duplication and expression in the developing zebrafish nervous system

BACKGROUND

The Slitrk family of leucine-rich repeat (LRR) transmembrane proteins bears structural similarity to the Slits and the Trk receptor families, which exert well-established roles in directing nervous system development. Slitrks are less well understood, although they are highly expressed in the developing vertebrate nervous system. Moreover, slitrk variants are associated with several sensory and neuropsychiatric disorders, including myopia, deafness, obsessive-compulsive disorder (OCD), schizophrenia, and Tourette syndrome. Loss-of-function studies in mice show that Slitrks modulate neurite outgrowth and inhibitory synapse formation, although the molecular mechanisms of Slitrk function remain poorly characterized.

RESULTS

As a prelude to examining the functional roles of Slitrks, we identified eight slitrk orthologs in zebrafish and observed that seven of the eight orthologs were actively transcribed in the nervous system at embryonic, larval, and adult stages. Similar to previous findings in mice and humans, zebrafish slitrks exhibited unique but overlapping spatial and temporal expression patterns in the developing brain, retina, and spinal cord.

CONCLUSIONS

Zebrafish express Slitrks in the developing central nervous system at times and locations important to neuronal morphogenesis and synaptogenesis. Future studies will use zebrafish as a convenient, cost-effective model organism to characterize the functional roles of Slitrks in nervous system development.

Common and rare alleles of the serotonin transporter gene, SLC6A4, associated with Tourette's disorder

To evaluate the hypothesis that functionally over-expressing alleles of the serotonin transporter (SERT) gene (solute carrier family 6, member 4, SLC6A4) are present in Tourette's disorder (TD), just as we previously observed in obsessive compulsive disorder (OCD), we evaluated TD probands (N = 151) and controls (N = 858). We genotyped the refined SERT-linked polymorphic region 5-HTTLPR/rs25531 and the associated rs25532 variant in the SLC6A4 promoter plus the rare coding variant SERT isoleucine-to-valine at position 425 (I425V). The higher expressing 5-HTTLPR/rs25531 LA allele was more prevalent in TD probands than in controls (χ(2)  = 5.75; P = 0.017; odds ratio [OR], 1.35); and, in a secondary analysis, surprisingly, it was significantly more frequent in probands who had TD alone than in those who had TD plus OCD (Fisher's exact test; P = 0.0006; OR, 2.29). Likewise, the higher expressing LAC haplotype (5-HTTLPR/rs25531/rs25532) was more frequent in TD probands than in controls (P = 0.024; OR, 1.33) and also in the TD alone group versus the TD plus OCD group (P = 0.0013; OR, 2.14). Furthermore, the rare gain-of-function SERT I425V variant was observed in 3 male siblings with TD and/or OCD and in their father. Thus, the cumulative count of SERT I425V becomes 1.57% in OCD/TD spectrum conditions versus 0.15% in controls, with a recalculated, family-adjusted significance of χ(2) = 15.03 (P < 0.0001; OR, 9.0; total worldwide genotyped, 2914). This report provides a unique combination of common and rare variants in one gene in TD, all of which are associated with SERT gain of function. Thus, altered SERT activity represents a potential contributor to serotonergic abnormalities in TD. The present results call for replication in a similarly intensively evaluated sample. © 2013 Movement Disorder Society.

Antipsychotic augmentation of serotonin reuptake inhibitors in treatment-resistant obsessive-compulsive disorder: a meta-analysis of double-blind, randomized, placebo-controlled trials

Because of the high number of patients with obsessive-compulsive disorder (OCD) not responding satisfactorily to initial monotherapy with serotonin reuptake inhibitors (SRIs), the evaluation of additional treatment options is highly relevant. To examine efficacy of add-on pharmacotherapy with antipsychotics, a systematic literature search was applied to identify all double-blind, randomized, placebo-controlled trials (DB-PC-RCTs) determining the efficacy of antipsychotic augmentation of SRIs in treatment-resistant OCD. The primary outcome of the pooled meta-analytic data analysis was response to the adjunctive antipsychotic treatment measured by both the rates of participants achieving response [defined as ≥ 35% reduction in Yale-Brown Obsessive-Compulsive Scale (YBOCS)] and mean changes in YBOCS total score. Twelve DB-PC-RCTs investigating quetiapine (N = 5), risperidone (N = 3), olanzapine (N = 2), aripiprazole (N = 1) and haloperidol (N = 1) with a total of 394 subjects were included. Significantly more patients responded to augmentation with antipsychotics than with placebo [relative risk = 2.10, 95% confidence intervals (CI) 1.16-3.80]. Additionally, the mean reduction of the YBOCS total score revealed an efficacy in favour of the antipsychotic medication [standardized mean difference (SMD) = 0.54, 95% CI 0.15-0.93]. Significant efficacy was identifiable only for risperidone, but not for quetiapine and olanzapine. The results regarding aripiprazole and haloperidol were inconsistent. Overall, about one-third of SRI-resistant OCD patients benefited from an augmentation strategy with antipsychotics. Based on the favourable risk:benefit ratio, risperidone can be considered as the agent of first choice and should be preferred to quetiapine and olanzapine. Further trials, mainly with higher antipsychotic doses, are required to optimize pharmacological treatment recommendations for SRI-refractory OCD.

Involvement of tryptophan hydroxylase 2 gene polymorphisms in susceptibility to tic disorder in Chinese Han population

Background

Tryptophan hydroxylase-2 (TPH2) is a potential candidate gene for screening tic disorder (TD).

Methods

A case–control study was performed to examine the association between the TPH2 gene and TD. The Sequenom® Mass ARRAY iPLEX GOLD System was used to genotype two single nucleotide polymorphisms (SNPs) of the TPH2 gene in 149 TD children and in 125 normal controls.

Results

For rs4565946, individuals with the TT genotype showed a significantly higher risk of TD than those with TC plus CC genotypes [odds ratio (OR) =3.077, 95% confidence interval (CI): 1.273–7.437; P = 0.009], as did male TD children with the TT genotype (OR = 3.228, 95% CI: 1.153–9.040; P = 0.020). The G allele of rs4570625 was significantly more frequent in TD children with higher levels of tic symptoms (Yale Global Tic Severity Scale, YGTSS) than those in controls among the male children (OR = 1.684, 95%: 1.097–2.583; P = 0.017]. TD children with severe tic symptoms had significantly higher frequencies of rs4546946 TT genotype than did normal controls in boys (OR = 3.292, 95% CI: 1.139–9.513; P = 0.022). We also found that genotype distributions of both SNPs were different between the Asian and European populations.

Conclusions

Our results indicated that the TT genotype of rs4565946 is a potential genetic risk factor for TD, and the allele G of rs4570625 might be associated with the severity of tic symptoms in boys. These polymorphisms might be susceptibility loci for TD in the Chinese Han population. Because of the confounding of co-existing attention deficit hyperactivity disorder (ADHD),these findings need to be confirmed by studies in much larger samples.

Genetic susceptibility and neurotransmitters in Tourette syndrome

Family studies have consistently shown that Tourette syndrome (TS) is a familial disorder and twin studies have clearly indicated a genetic contribution in the etiology of TS. Whereas early segregation studies of TS suggested a single-gene autosomal dominant disorder, later studies have pointed to more complex models including additive and multifactorial inheritance and likely interaction with genetic factors. While the exact cellular and molecular base of TS is as yet elusive, neuroanatomical and neurophysiological studies have pointed to the involvement of cortico-striato-thalamocortical circuits and abnormalities in dopamine, glutamate, gamma-aminobutyric acid, and serotonin neurotransmitter systems, with the most consistent evidence being available for involvement of dopamine-related abnormalities, that is, a reduction in tonic extracellular dopamine levels along with hyperresponsive spike-dependent dopamine release, following stimulation. Genetic and gene expression findings are very much supportive of involvement of these neurotransmitter systems. Moreover, intriguingly, genetic work on a two-generation pedigree has opened new research pointing to a role for histamine, a so far rather neglected neurotransmitter, with the potential of the development of new treatment options. Future studies should be aimed at directly linking neurotransmitter-related genetic and gene expression findings to imaging studies (imaging genetics), which enables a better understanding of the pathways and mechanisms through which the dynamic interplay of genes, brain, and environment shapes the TS phenotype.

Emerging treatment strategies in Tourette syndrome: what's in the pipeline?

Tourette syndrome (TS) is a neurodevelopmental disorder characterized by multiple motor/phonic tics and a wide spectrum of behavioral problems (e.g., complex tic-like symptoms, attention deficit hyperactivity disorder, and obsessive-compulsive disorder). TS can be a challenging condition even for the specialists, because of the complexity of the clinical picture and the potential adverse effects of the most commonly prescribed medications. Expert opinions and consensus guidelines on the assessment and treatment of tic disorders have recently been published in Europe and Canada. All pharmacological treatment options are mere symptomatic treatments that alleviate, but do not cure, the tics. We still lack evidence of their effects on the natural long-term course and on the prognosis of TS and how these treatments may influence the natural course of brain development. The most commonly prescribed drugs are dopamine antagonists, such as typical (e.g., haloperidol, pimozide) and atypical neuroleptics (e.g., risperidone, aripiprazole), and α-2-adrenoreceptor agonists (e.g., clonidine). However, several studies have investigated the efficacy and tolerability of alternative pharmacological agents that may be efficacious, including the newest atypical antipsychotic agents (e.g., paliperidone, sertindole), tetrabenazine, drugs that modulate acetylcholine (e.g., nicotine) and GABA (e.g., baclofen, levetiracetam), tetrahydrocannabinol, botulinum toxin injections, anticonvulsant drugs (e.g., topiramate, carbamazepine), naloxone, lithium, norepinephrine, steroid 5α reductase, and other neuroactive agents (buspirone, metoclopramide, phytostigmine, and spiradoline mesylate). As regards nonpharmacological interventions, some of the more recent treatments that have been studied include electroconvulsive therapy and repetitive transcranial magnetic stimulation. This review focuses primarily on the efficacy and safety of these emerging treatment strategies in TS.

The psychopathological spectrum of Gilles de la Tourette syndrome

Gilles de la Tourette syndrome (GTS) holds a unique status as quintessentially neuropsychiatric condition at the interface between neurology (movement disorder) and psychiatry (behavioural condition). This is a reflection of the common observation that the vast majority of patients present with behavioural problems in association with the motor and vocal tics which define GTS. The present article focuses on the relationship between GTS and obsessive-compulsive disorder (OCD), attention-deficit and hyperactivity disorder (ADHD), affective disorders (both major depression and bipolar affective disorder), and personality disorders. Over the last decade, converging lines of research have pointed towards the concept of a 'GTS spectrum', encompassing motor phenomena and behavioural symptoms, with important implications for the clinical management of patients.

Long term clinical course of Tourette syndrome

BACKGROUND

Recent studies using cluster analysis and factor analysis have suggested that Tourette Syndrome (TS) should no longer be considered a unitary condition.

MATERIAL AND METHODS

We retrospectively studied the long term clinical course of 100 TS patients. The patients were assessed at the onset and after 10 years follow-up to evaluate the severity of tic, the Obsessive Compulsive Disorder (OCD), the Attention Deficit Hyperactivity Disorder (ADHD) and the presence of anxiety and depression, rage attacks, self injuries behavior. Moreover at the follow-up they completed an evaluation scale on quality of life to assess the impairment in everyday life after 10 years of illness.

RESULTS

The "pure TS" clinical group (38 subjects) showed after 10 years follow-up that 58% carried on with the same clinical phenotype, whereas 42% changed in "TS+OCD" phenotype. Fifty-five percentage required pharmacological treatment. All the "TS+ADHD" clinical group (48 subjects) showed after 10 years follow-up a different clinical phenotype: 62% "TS pure" phenotype, 35% "TS+OCD" phenotype, 2% "TS+ADHD+OCD" phenotype. Sixty-five percentage of the subject required pharmacological treatment. The "TS+ADHD+OCD" clinical group (14 subjects) after 10 years follow-up showed that 14% carried on with the same clinical phenotype, whereas 8.3% presented "TS pure" phenotype and 92% presented "TS+OCD" phenotype. Seventy-one percentage were in need of therapy. With regards to quality of life, patients presented widespread impairment correlated to the presence of comorbid conditions.

CONCLUSION

Our findings suggest that pure TS has quite a good long-term clinical course. By contrast, those who presented comorbid condition at the onset showed a more severe prognosis.

Pathogenetic model for Tourette syndrome delineates overlap with related neurodevelopmental disorders including Autism

Tourette syndrome (TS) is a highly heritable neuropsychiatric disorder characterised by motor and vocal tics. Despite decades of research, the aetiology of TS has remained elusive. Recent successes in gene discovery backed by rapidly advancing genomic technologies have given us new insights into the genetic basis of the disorder, but the growing collection of rare and disparate findings have added confusion and complexity to the attempts to translate these findings into neurobiological mechanisms resulting in symptom genesis. In this review, we explore a previously unrecognised genetic link between TS and a competing series of trans-synaptic complexes (neurexins (NRXNs), neuroligins (NLGNs), leucine-rich repeat transmembrane proteins (LRRTMs), leucine rich repeat neuronals (LRRNs) and cerebellin precursor 2 (CBLN2)) that links it with autism spectrum disorder through neurodevelopmental pathways. The emergent neuropathogenetic model integrates all five genes so far found to be uniquely disrupted in TS into a single pathogenetic chain of events described in context with clinical and research implications.

Pharmacological treatment of tic disorders and Tourette Syndrome

The present review gives an overview of current pharmacological treatment options of tic disorders and Tourette Syndrome (TS). After a short summary on phenomenology, clinical course and comorbid conditions we review indications for pharmacological treatment in detail. Unfortunately, standardized and large enough drug trials in TS patients fulfilling evidence based medicine standards are still scarce. Treatment decisions are often guided by individual needs and personal experience of treating clinicians. The present recommendations for pharmacological tic treatment are therefore based on both scientific evidence and expert opinion. As first-line treatment of tics risperidone (best evidence level for atypical antipsychotics) or tiapride (largest clinical experience in Europe and low rate of adverse reactions) are recommended. Aripiprazole (still limited but promising data with low risk for adverse reactions) and pimozide (best evidence of the typical antipsychotics) are agents of second choice. In TS patients with comorbid attention deficit hyperactivity disorder (ADHD) atomoxetine, stimulants or clonidine should be considered, or, if tics are severe, a combination of stimulants and risperidone. When mild to moderate tics are associated with obsessive-compulsive symptoms, depression or anxiety sulpiride monotherapy can be helpful. In more severe cases the combination of risperidone and a selective serotonin reuptake inhibitor should be given. In summary, further studies, particularly randomized, double-blind, placebo-controlled trials including larger and/or more homogenous patient groups over longer periods are urgently needed to enhance the scientific basis for drug treatment in tic disorders. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.