Emerging treatments for Tourette's disorder

Selective Activation of D3 Dopamine Receptors Ameliorates DOI-Induced Head Twitching Accompanied by Changes in Corticostriatal Processing

D3 receptors, a key component of the dopamine system, have emerged as a potential target of therapies to improve motor symptoms across neurodegenerative and neuropsychiatric conditions. In the present work, we evaluated the effect of D3 receptor activation on the involuntary head twitches induced by 2,5-dimethoxy-4-iodoamphetamine (DOI) at behavioral and electrophysiological levels. Mice received an intraperitoneal injection of either a full D3 agonist, WC 44 [4-(2-fluoroethyl)-N-[4-[4-(2-methoxyphenyl)piperazin 1-yl]butyl]benzamide] or a partial D3 agonist, WW-III-55 [N-(4-(4-(4-methoxyphenyl)piperazin-1-yl)butyl)-4-(thiophen-3-yl)benzamide] five minutes before the intraperitoneal administration of DOI. Compared to the control group, both D3 agonists delayed the onset of the DOI-induced head-twitch response and reduced the total number and frequency of the head twitches. Moreover, the simultaneous recording of neuronal activity in the motor cortex (M1) and dorsal striatum (DS) indicated that D3 activation led to slight changes in a single unit activity, mainly in DS, and increased its correlated firing in DS or between presumed cortical pyramidal neurons (CPNs) and striatal medium spiny neurons (MSNs). Our results confirm the role of D3 receptor activation in controlling DOI-induced involuntary movements and suggest that this effect involves, at least in part, an increase in correlated corticostriatal activity. A further understanding of the underlying mechanisms may provide a suitable target for treating neuropathologies in which involuntary movements occur.

Pharmacotherapeutic Strategies and New Targets in OCD

Effective pharmacological and psychotherapeutic treatments are well established for obsessive-compulsive disorder (OCD). Serotonin reuptake inhibitors (SRIs) are first-line treatment and are of benefit to about half of patients. Augmentation of SRI treatment with low-dose neuroleptics is an evidence-based second-line strategy. Specialty psychotherapy is also used as both first-line and second-line treatment and can benefit many. However, a substantial number of patients do not respond to these treatments. New alternatives are urgently needed. This review summarizes evidence for these established pharmacotherapeutic strategies, and for others that have been investigated in refractory disease but are not supported by the same level of evidence. We focus on three neurotransmitter systems in the brain: serotonin, dopamine, and glutamate. We summarize evidence from genetic, neuroimaging, animal model, and other lines of investigation that probe these three systems in patients with OCD. We also review recent work on predictors of response to current treatments. While many studies suggest abnormalities that may provide insight into the pathophysiology of the disorder, most studies have been small, and non-replication of reported findings has been common. Nevertheless, the gradual accrual of evidence for neurotransmitter dysregulation may in time lead the way to new pharmacological strategies.

The association between tic medication therapy and psychiatric comorbidities among patients with Tourette syndrome: A national population-based study in Taiwan

BACKGROUND

Tourette syndrome (TS) is often comorbid with attention deficit hyperactivity disorder, obsessive-compulsive disorder, and depression. Medications are the main treatment for TS. Relationships between TS medication therapy and psychiatric comorbidities remain unclear. This study explored the impacts of TS medication on the risk of psychiatric comorbidities using a nationally representative sample of TS in Taiwan.

METHODS

Data from National Health Insurance Research Database in Taiwan was used to identify 997,213 children and adolescents aged 6-18 years who had received a diagnosis of TS based on ICD-9-CM codes in 2000-2010. Cox's proportional hazard regression analysis was conducted to estimate the risk of comorbidities among subjects with and without tic medication therapy.

RESULTS

We found that in TS patients, a lower risk of psychiatric comorbidities occurred in the tic medication therapy group (p = 0.012) and the crude hazard ratio (HR) was 0.6 (95% confidence interval (CI) = 0.4-0.8, p < 0.001). After adjusting for potential confounders of gender, age, income, level of care, department visited, brain injury, and the number of suicide attempts, the risk of comorbidities was still significantly lower in the tic medication therapy group (adjusted HR = 0.5, 95% CI = 0.3-0.6, p < 0.001).

DISCUSSION

One limitation was that we did not include all mediations used to treat psychiatric comorbidities among TS patients. This study found the effectiveness of TS medications on improving psychiatric comorbidities.

CONCLUSIONS

Compared to those without medication, medication therapy appears to have a benefit of decreasing the risk of psychiatric comorbidities. Strategies to improve medication regimens should be considered in clinical settings.

Mutations in ASH1L confer susceptibility to Tourette syndrome

Tourette syndrome (TS) is a childhood-onset neuropsychiatric disorder characterized by repetitive motor movements and vocal tics. The clinical manifestations of TS are complex and often overlap with other neuropsychiatric disorders. TS is highly heritable; however, the underlying genetic basis and molecular and neuronal mechanisms of TS remain largely unknown. We performed whole-exome sequencing of a hundred trios (probands and their parents) with detailed records of their clinical presentations and identified a risk gene, ASH1L, that was both de novo mutated and associated with TS based on a transmission disequilibrium test. As a replication, we performed follow-up targeted sequencing of ASH1L in additional 524 unrelated TS samples and replicated the association (P value = 0.001). The point mutations in ASH1L cause defects in its enzymatic activity. Therefore, we established a transgenic mouse line and performed an array of anatomical, behavioral, and functional assays to investigate ASH1L function. The Ash1l^+/- mice manifested tic-like behaviors and compulsive behaviors that could be rescued by the tic-relieving drug haloperidol. We also found that Ash1l disruption leads to hyper-activation and elevated dopamine-releasing events in the dorsal striatum, all of which could explain the neural mechanisms for the behavioral abnormalities in mice. Taken together, our results provide compelling evidence that ASH1L is a TS risk gene.

Comprehensive Behavioral Intervention for Tics reduces perception-action binding during inhibitory control in Gilles de la Tourette syndrome

Gilles de la Tourette Syndrome (GTS) is a developmental disorder. Empirical studies and an emerging cognitive framework on GTS suggest that GTS is a disorder of abnormally strong ‘perception-action binding’. Theoretical considerations imply that the effectiveness of long-established behavioral interventions might be related to a normalization of increased binding in GTS. This has not been tested yet. We examined the effect of a standardized Comprehensive Behavior Intervention for Tics (CBIT) in N = 21 adolescent GTS patients and N = 21 healthy controls on perception-action binding in an inhibitory control paradigm. Prior to CBIT, GTS patients showed compromised performance compared to controls, specifically when inhibitory control was triggered by uni-modal visual compared to bi-modal stimuli. After CBIT intervention, GTS patient’s performance was at the same level as healthy controls. This is supported by a Bayesian data analysis. CBIT specifically affected inhibitory control in a condition where reconfigurations of perception-action bindings are necessary to perform inhibitory control. A power of 95% was evident for these effects. CBIT reduces increased ‘binding’ between perception and action in GTS and thereby increases the ability to perform response inhibition. The results are the first to provide insights as to why CBIT is effective by relating elements of this intervention to overarching cognitive theoretical frameworks on perception-action bindings.

The histidine decarboxylase model of tic pathophysiology: a new focus on the histamine H3 receptor

Histamine dysregulation was implicated as a rare cause of Tourette syndrome and other tic disorders a decade ago by a landmark genetic study in a high density family pedigree, which implicated a hypomorphic mutation in the histidine decarboxylase (Hdc) gene as a rare but high penetrance genetic cause. Studies in Hdc knockout (KO) mice have confirmed that this mutation causes tic-relevant behavioural and neurochemical abnormalities that parallel what is seen in patients and thus validate the KO as a potentially informative model of tic pathophysiology. Recent studies have focused on the potential role of the histamine H₃ receptor in this model, and by association in tic disorders and related neuropsychiatric conditions. The H₃ receptor is up-regulated in the striatum in Hdc KO mice. As the H₃ receptor has constitutive activity in the absence of ligand, this receptor up-regulation may have significant cellular effects despite the absence of neurotransmitter histamine in these mice. Activation in vivo of H₃ receptors in wild type mice regulates signalling in striatal medium spiny neurons (MSNs) that interacts non-linearly with dopamine receptor signalling. Baseline signalling alterations in MSNs in Hdc KO mice resemble those seen after H₃ receptor agonist treatment in wild type animals. H₃ receptor agonist treatment in the KOs further accentuates most of these signalling abnormalities and produces behavioural stereotypy. Together, these data suggest the intriguing hypothesis that constitutive signalling by up-regulated H₃ receptors explains many of the molecular and behavioural abnormalities seen in these animals. LINKED ARTICLES: This article is part of a themed section on New Uses for 21st Century. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.3/issuetoc.

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.

Modeling tics in rodents: Conceptual challenges and paths forward

BACKGROUND

Recent advances in our understanding of the neurobiology of tics have led to the development of novel rodent models capturing different pathophysiological and phenotypic aspects of Tourette syndrome. The proliferation of these models, however, raises vexing questions on what standards should be adopted to assess their theoretical validity and empirical utility. Assessing the homology of a rodent motoric burst with a tic remains problematic, due to our incomplete knowledge of the underpinnings of tics, their high phenotypic complexity and variability, limitations in our ability test key aspects of tic phenomenology (such as premonitory sensory phenomena) in animals, and between-species differences in neuroanatomy and behavioral repertoire. These limitations underscore that any interpretation of behavioral output in an animal model cannot exclusively rely on the recognition of features that bear superficial resemblance with tics, but must be supported by other etiological and convergent phenomenological criteria.

NEW METHOD

Here, we discuss two complementary approaches for the study and validation of tic-like manifestations in rodents, based respectively on the use of contextual modulators and accompanying features of repetitive motor manifestations and on the reproduction of pathogenic factors.

RESULTS

Neither strategy can by itself provide convincing evidence that a model informatively recapitulates tic pathophysiology. Their combination holds promise to enhance the rigorous evaluation and translational relevance of rodent models of tic disorders.

CONCLUSIONS

This systematic consideration of different approaches to the validation and study of animal models of tic pathophysiology provides a framework for future work in this area.

Extended-Release Guanfacine Does Not Show a Large Effect on Tic Severity in Children with Chronic Tic Disorders

OBJECTIVE

To evaluate the tolerability, safety, and preliminary efficacy of extended-release guanfacine in children with chronic tic disorders, including Tourette's disorder (collectively referred to as CTD).

METHODS

This was a multisite, 8-week, randomized, double-blind, placebo-controlled trial. The primary outcome measure was the Yale Global Tic Severity Scale (YGTSS) total score. Key secondary outcomes included the Improvement item of Clinical Global Impressions-Improvement (CGI-I) scale and the Tic Symptom Self-report (TSSR). Adverse events were monitored at each visit.

RESULTS

Thirty-four subjects (23 boys and 11 girls) of ages 6 to 17 years (mean = 11.1 ± 3.1) with CTD were randomly assigned to extended-release guanfacine (n = 16) or placebo (n = 18). At baseline, the mean YGTSS total score was 26.3 ± 6.6 for the guanfacine group versus 27.7 ± 8.7 for the placebo group. Within the guanfacine group (mean final daily dose of 2.6 ± 1.1 mg, n = 14), the mean YGTSS total score declined to 23.6 ± 6.42 [t(15) = 1.84, p = 0.08; effect size = 0.35]. The results were similar in the placebo group with a score of 24.7 ± 10.54 at week 8 [t(17) = 1.83, p = 0.08; effect size = 0.38]. There was no significant difference in the rate of positive response on the CGI-I between the guanfacine group and placebo (19% [3/16] vs. 22% [4/18], p = 1.0). The most common adverse events were fatigue, drowsiness, dry mouth, headache, and irritability. Two subjects in the guanfacine group discontinued early-one because of an adverse event (depressed mood) and one because of lack of efficacy; two subjects in the placebo group discontinued because of lack of efficacy.

CONCLUSIONS

This pilot study did not confirm a clinically meaningful effect size within the guanfacine group. These results do not support the launch of a larger efficacy trial for tics in children and adolescents with CTD.

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.

Clinical effectiveness and patient perspectives of different treatment strategies for tics in children and adolescents with Tourette syndrome: a systematic review and qualitative analysis

BACKGROUND

Tourette syndrome (TS) is a neurodevelopmental condition characterised by chronic motor and vocal tics affecting up to 1% of school-age children and young people and is associated with significant distress and psychosocial impairment.

OBJECTIVE

To conduct a systematic review of the benefits and risks of pharmacological, behavioural and physical interventions for tics in children and young people with TS (part 1) and to explore the experience of treatment and services from the perspective of young people with TS and their parents (part 2).

DATA SOURCES

For the systematic reviews (parts 1 and 2), mainstream bibliographic databases, The Cochrane Library, education, social care and grey literature databases were searched using subject headings and text words for tic* and Tourette* from database inception to January 2013.

REVIEW/RESEARCH METHODS

For part 1, randomised controlled trials and controlled before-and-after studies of pharmacological, behavioural or physical interventions in children or young people (aged < 18 years) with TS or chronic tic disorder were included. Mixed studies and studies in adults were considered as supporting evidence. Risk of bias associated with each study was evaluated using the Cochrane tool. When there was sufficient data, random-effects meta-analysis was used to synthesize the evidence and the quality of evidence for each outcome was assessed using the Grading of Recommendations Assessment, Development and Evaluation approach. For part 2, qualitative studies and survey literature conducted in populations of children/young people with TS or their carers or in health professionals with experience of treating TS were included in the qualitative review. Results were synthesized narratively. In addition, a national parent/carer survey was conducted via the Tourettes Action website. Participants included parents of children and young people with TS aged under 18 years. Participants (young people with TS aged 10-17 years) for the in-depth interviews were recruited via a national survey and specialist Tourettes clinics in the UK.

RESULTS

For part 1, 70 studies were included in the quantitative systematic review. The evidence suggested that for treating tics in children and young people with TS, antipsychotic drugs [standardised mean difference (SMD) -0.74, 95% confidence interval (CI) -1.08 to -0.41; n = 75] and noradrenergic agents [clonidine (Dixarit(®), Boehringer Ingelheim) and guanfacine: SMD -0.72, 95% CI -1.03 to -0.40; n = 164] are effective in the short term. There was little difference among antipsychotics in terms of benefits, but adverse effect profiles do differ. Habit reversal training (HRT)/comprehensive behavioural intervention for tics (CBIT) was also shown to be effective (SMD -0.64, 95% CI -0.99 to -0.29; n = 133). For part 2, 295 parents/carers of children and young people with TS contributed useable survey data. Forty young people with TS participated in in-depth interviews. Four studies were in the qualitative review. Key themes were difficulties in accessing specialist care and behavioural interventions, delay in diagnosis, importance of anxiety and emotional symptoms, lack of provision of information to schools and inadequate information regarding medication and adverse effects.

LIMITATIONS

The number and quality of clinical trials is low and this downgrades the strength of the evidence and conclusions.

CONCLUSIONS

Antipsychotics, noradrenergic agents and HRT/CBIT are effective in reducing tics in children and young people with TS. The balance of benefits and harms favours the most commonly used medications: risperidone (Risperdal(®), Janssen), clonidine and aripiprazole (Abilify(®), Otsuka). Larger and better-conducted trials addressing important clinical uncertainties are required. Further research is needed into widening access to behavioural interventions through use of technology including mobile applications ('apps') and video consultation.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42012002059.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Investigating young people’s experiences of successful or helpful psychological interventions for tic disorders: An Interpretative Phenomenological Analysis study

There is emerging evidence for talking therapies in the treatment of tic disorders. This study explored experiences of young people who self-identified as having had a successful or helpful talking therapy, in order to understand the phenomenology, value and meaning of outcomes. The experiences of seven participants aged 10–17 years were described in semi-structured interviews and analysed using Interpretative Phenomenological Analysis. Themes included the challenging battle with tics and process of re-defining self-identity, making sense of and managing experiences, the value of control, and spectrum of positive change. The results highlighted valued outcomes that could be incorporated into clinical practice and future evaluation.

Ablation of fast-spiking interneurons in the dorsal striatum, recapitulating abnormalities seen post-mortem in Tourette syndrome, produces anxiety and elevated grooming

Tic disorders, including Tourette syndrome (TS), are thought to involve pathology of cortico-basal ganglia loops, but their pathology is not well understood. Post-mortem studies have shown a reduced number of several populations of striatal interneurons, including the parvalbumin-expressing fast-spiking interneurons (FSIs), in individuals with severe, refractory TS. We tested the causal role of this interneuronal deficit by recapitulating it in an otherwise normal adult mouse using a combination transgenic-viral cell ablation approach. FSIs were reduced bilaterally by ∼40%, paralleling the deficit found post-mortem. This did not produce spontaneous stereotypies or tic-like movements, but there was increased stereotypic grooming after acute stress in two validated paradigms. Stereotypy after amphetamine, in contrast, was not elevated. FSI ablation also led to increased anxiety-like behavior in the elevated plus maze, but not to alterations in motor learning on the rotorod or to alterations in prepulse inhibition, a measure of sensorimotor gating. These findings indicate that a striatal FSI deficit can produce stress-triggered repetitive movements and anxiety. These repetitive movements may recapitulate aspects of the pathophysiology of tic disorders.

Histamine and histamine receptors in Tourette syndrome and other neuropsychiatric conditions

The potential contributions of dysregulation of the brain's histaminergic modulatory system to neuropsychiatric disease, and the potential of histamine-targeting medications as therapeutic agents, are gradually coming into focus. The H3R receptor, which is expressed primarily in the central nervous system, is a promising pharmacotherapeutic target. Recent evidence for a contribution of histamine dysregulation to Tourette syndrome and tic disorders is particularly strong; although specific mutations in histamine-associated genes are rare, they have led to informative studies in animal models that may pave the way for therapeutic advances. A controlled study of an H3R antagonist in Tourette syndrome is ongoing. Preclinical studies of H3R antagonists in schizophrenia, attention deficit disorder, and narcolepsy have all shown promise. Recently reported controlled studies have been disappointing in schizophrenia and attention deficit disorder, but the H3R antagonist pitolisant shows promise in the treatment of narcolepsy and excessive daytime sleepiness and is currently under regulatory review for these conditions. This article is part of the Special Issue entitled 'Histamine Receptors'.

Histidine decarboxylase knockout mice, a genetic model of Tourette syndrome, show repetitive grooming after induced fear

Tics, such as are seen in Tourette syndrome (TS), are common and can cause profound morbidity, but they are poorly understood. Tics are potentiated by psychostimulants, stress, and sleep deprivation. Mutations in the gene histidine decarboxylase (Hdc) have been implicated as a rare genetic cause of TS, and Hdc knockout mice have been validated as a genetic model that recapitulates phenomenological and pathophysiological aspects of the disorder. Tic-like stereotypies in this model have not been observed at baseline but emerge after acute challenge with the psychostimulant d-amphetamine. We tested the ability of an acute stressor to stimulate stereotypies in this model, using tone fear conditioning. Hdc knockout mice acquired conditioned fear normally, as manifested by freezing during the presentation of a tone 48h after it had been paired with a shock. During the 30min following tone presentation, knockout mice showed increased grooming. Heterozygotes exhibited normal freezing and intermediate grooming. These data validate a new paradigm for the examination of tic-like stereotypies in animals without pharmacological challenge and enhance the face validity of the Hdc knockout mouse as a pathophysiologically grounded model of tic disorders.

Corticostriatal interactions in the generation of tic-like behaviors after local striatal disinhibition

The pathophysiology of the tics that define Gilles de la Tourette syndrome (TS) is not well understood. Local disinhibition within the striatum has been hypothesized to play a pathogenic role. In support of this, experimental disinhibition by local antagonism of GABA-A receptors within the striatum produces tic-like phenomenology in monkey and rat. We replicated this effect in mice via local picrotoxin infusion into the dorsal striatum. Infusion of picrotoxin into sensorimotor cortex produced similar movements, accompanied by signs of behavioral activation; higher-dose picrotoxin in the cortex produced seizures. Striatal inhibition with local muscimol completely abolished tic-like movements after either striatal or cortical picrotoxin, confirming their dependence on the striatal circuitry; in contrast, cortical muscimol attenuated but did not abolish movements produced by striatal picrotoxin. Striatal glutamate blockade eliminated tic-like movements after striatal picrotoxin, indicating that glutamatergic afferents are critical for their generation. These studies replicate and extend previous work in monkey and rat, providing additional validation for the local disinhibition model of tic generation. Our results reveal a key role for corticostriatal glutamatergic afferents in the generation of tic-like movements in this model.

Targeted ablation of cholinergic interneurons in the dorsolateral striatum produces behavioral manifestations of Tourette syndrome

Gilles de la Tourette syndrome (TS) is characterized by tics, which are transiently worsened by stress, acute administration of dopaminergic drugs, and by subtle deficits in motor coordination and sensorimotor gating. It represents the most severe end of a spectrum of tic disorders that, in aggregate, affect ∼ 5% of the population. Available treatments are frequently inadequate, and the pathophysiology is poorly understood. Postmortem studies have revealed a reduction in specific striatal interneurons, including the large cholinergic interneurons, in severe disease. We tested the hypothesis that this deficit is sufficient to produce aspects of the phenomenology of TS, using a strategy for targeted, specific cell ablation in mice. We achieved ∼ 50% ablation of the cholinergic interneurons of the striatum, recapitulating the deficit observed in patients postmortem, without any effect on GABAergic markers or on parvalbumin-expressing fast-spiking interneurons. Interneuron ablation in the dorsolateral striatum (DLS), corresponding roughly to the human putamen, led to tic-like stereotypies after either acute stress or d-amphetamine challenge; ablation in the dorsomedial striatum, in contrast, did not. DLS interneuron ablation also led to a deficit in coordination on the rotorod, but not to any abnormalities in prepulse inhibition, a measure of sensorimotor gating. These results support the causal sufficiency of cholinergic interneuron deficits in the DLS to produce some, but not all, of the characteristic symptoms of TS.

Dysregulated intracellular signaling in the striatum in a pathophysiologically grounded model of Tourette syndrome

Tic disorders produce substantial morbidity, but their pathophysiology remains poorly understood. Convergent evidence suggests that dysregulation of the cortico-basal ganglia circuitry is central to the pathogenesis of tics. Tourette syndrome (TS), the most severe end of the continuum of tic disorders, is substantially genetic, but causative mutations have been elusive. We recently described a mouse model, the histidine decarboxylase (Hdc) knockout mouse, that recapitulates a rare, highly penetrant mutation found in a single family; these mice exhibit TS-like phenomenology. These animals have a global deficit in brain histamine and a consequent dysregulation of DA in the basal ganglia. Histamine modulation of DA effects is increasingly appreciated, but the mechanisms underlying this modulation remain unclear; the consequences of modest DA elevation in the context of profound HA deficiency are difficult to predict, but understanding them in the Hdc knockout mouse may provide generalizable insights into the pathophysiology of TS. Here we characterized signaling pathways in striatal cells in this model system, at baseline and after amphetamine challenge. In vivo microdialysis confirms elevated DA in Hdc-KO mice. We find dephosphorylation of Akt and its target GSK3β and activation of the MAPK signaling cascade and its target rpS6; these are characteristic of the effects of DA on D2- and D1-expressing striatal neurons, respectively. Strikingly, there is no alteration in mTOR signaling, which can be regulated by DA in both cell types. These cellular effects help elucidate striatal signaling abnormalities in a uniquely validated mouse model of TS and move towards the identification of new potential therapeutic targets for tic disorders.

Clinical pharmacology of nondopaminergic drugs in Tourette syndrome

Treatment of tics and Gilles de la Tourette syndrome (GTS) by nondopaminergic drugs was initiated more than three decades ago. These approaches were driven by the wish to circumvent antipsychotic-related side effects (metabolic disturbances, parkinsonian syndromes, tardive dyskinesia) or to use these treatments as a valuable add-on therapy in patients at least partially refractory to antipsychotics. In this review, we will therefore discuss the potential value of treating tics with alpha2 receptor agonists, nicotine, tetrabenazine, GABA agonists, botulinum toxin, cannabinoids, and immune modulators (plasmapheresis, intravenous immunoglobulins, antibiotic prophylaxis). Future directions for clinical trials based on our expanding understanding of the pathophysiology of GTS with regard to cholinergic, glutamatergic, and histaminergic neurotransmission will also be briefly outlined.

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.

Tic modulation using sensory tricks

Background

A sensory trick, or geste antagoniste, is defined as a physical gesture (such as a touch on a particular body part) that mitigates the production of an involuntary movement. This phenomenon is most commonly described as a feature of dystonia. Here we present a case of successful modulation of tics using sensory tricks.

Case Report

A case report and video are presented. The case and video demonstrate a 19-year-old male who successfully controlled his tics with various sensory tricks.

Discussion

It is underappreciated by movement disorder physicians that sensory tricks can play a role in tics. Introducing this concept to patients could potentially help in tic control. In addition, understanding the pathophysiological underpinnings of sensory tricks could help in the understanding of the pathophysiology of tics.

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.

Transcranial magnetic stimulation at 1 Hertz improves clinical symptoms in children with Tourette syndrome for at least 6 months

Tourette syndrome (TS) is characterized by multiple motor and phonic tics. Repetitive transcranial magnetic stimulation (rTMS) targeting the supplemental motor area (SMA) can reduce tic severity. Here, we investigated whether 1 Hz rTMS targeted to the SMA could improve symptoms in children with TS. Twenty-five children with TS (aged under 16 years) received 20 daily sessions of rTMS to the SMA at a frequency of 1 Hz, 110% of resting motor threshold (RMT). Clinical assessment and physiological measures of the left and right RMT were conducted at different times during treatment and follow-up. After four weeks of treatment we observed statistically significant reductions on the Yale Global Tic Severity Scale, Clinical Global Impression Scale, Swanson, Nolan and Pelham Rating Scale, version IV for attention-deficit hyperactivity disorder, Children's Depression Inventory, Spence Children's Anxiety Scale and a novel Attention Test. In addition, symptom improvement correlated with an increase of both right and left RMT and was stable at six months follow-up. Therefore, we found that 1 Hz rTMS to the SMA can improve clinical symptoms in children with TS for at least six months.

Systematic review: pharmacological treatment of tic disorders--efficacy of antipsychotic and alpha-2 adrenergic agonist agents

We conducted a meta-analysis of randomized, placebo-controlled trials to determine the efficacy of antipsychotic and alpha-2 agonists in the treatment of chronic tic disorders and examine moderators of treatment effect. Meta-analysis demonstrated a significant benefit of antipsychotics compared to placebo (standardized mean difference (SMD)=0.58 (95% confidence interval (CI): 0.36-0.80). Stratified subgroup analysis found no significant difference in the efficacy of the 4 antipsychotic agents tested (risperidone, pimozide, haloperidol and ziprasidone). Meta-analysis also demonstrated a benefit of alpha-2 agonists compared to placebo (SMD=0.31 (95% confidence interval CI: 0.15-0.48). Stratified subgroup analysis and meta-regression demonstrated a significant moderating effect of co-occurring ADHD. Trials which enrolled subjects with tics and ADHD demonstrated a medium-to-large effect (SMD=0.68 (95%CI: 0.36-1.01) whereas trials that excluded subjects with ADHD demonstrated a small, non-significant benefit (SMD=0.15 (95%CI: -0.06 to 0.36). Our findings demonstrated significant benefit of both antipsychotics and alpha-2 agonists in treating tics but suggest alpha-2 agonists may have minimal benefit in tic patients without ADHD.

Treatment practices in Tourette syndrome: the European perspective

AIMS

National differences in licensing laws suggest that the use of medications for the treatment of Tourette syndrome differs between European countries. However, variability in prescribing practices has never been investigated. This study aims to systematically examine European prescribing practices in Tourette syndrome.

METHODS

All members of the European Society for the Study of Tourette syndrome actively prescribing for paediatric and/or adult Tourette syndrome populations were invited to complete an online questionnaire covering pharmacological treatment of the five main symptom domains of Tourette syndrome: tics, attention-deficit hyperactivity symptoms, obsessive-compulsive symptoms, anxiety and depression.

RESULTS

Response rates were good, with 44/57 (77%) members returning the questionnaire. Risperidone (n=13), methylphenidate (n=21) and sertraline (n=17) were the most commonly prescribed medications for the treatment of tics, attention-deficit hyperactivity symptoms and obsessive-compulsive symptoms, respectively. However, there was a large variability in both the medication choices and the dosages used for each of these symptom domains.

CONCLUSIONS

This is the first large-scale survey on prescribing habits for the pharmacological management of Tourette syndrome in Europe. In general, dopamine blockers were widely used for tics, selective serotonin reuptake inhibitors for depression, obsessive-compulsive symptoms and anxiety, and stimulants for attention-deficit hyperactivity symptoms, but there was high variation within these choices. Future studies need to target specific patient groups.

Clinical features of tic-related obsessive-compulsive disorder: results from a large multicenter study

OBJECTIVE

To evaluate the clinical features of obsessive-compulsive disorder (OCD) patients with comorbid tic disorders (TD) in a large, multicenter, clinical sample.

METHOD

A cross-sectional study was conducted that included 813 consecutive OCD outpatients from the Brazilian OCD Research Consortium and used several instruments of assessment, including the Yale-Brown Obsessive-Compulsive Scale, the Dimensional Yale-Brown Obsessive-Compulsive Scale, the Yale Global Tic Severity Scale (YGTSS), the USP Sensory Phenomena Scale, and the Structured Clinical Interview for DSM-IV Axis I Disorders.

RESULTS

The sample mean current age was 34.9 years old (SE 0.54), and the mean age at obsessive-compulsive symptoms (OCS) onset was 12.8 years old (SE 0.27). Sensory phenomena were reported by 585 individuals (72% of the sample). The general lifetime prevalence of TD was 29.0% (n = 236), with 8.9% (n = 72) presenting Tourette syndrome, 17.3% (n = 141) chronic motor tic disorder, and 2.8% (n = 23) chronic vocal tic disorder. The mean tic severity score, according to the YGTSS, was 27.2 (SE 1.4) in the OCD + TD group. Compared to OCD patients without comorbid TD, those with TD (OCD + TD group, n = 236) were more likely to be males (49.2% vs. 38.5%, p < .005) and to present sensory phenomena and comorbidity with anxiety disorders in general: separation anxiety disorder, social phobia, specific phobia, generalized anxiety disorder, post-traumatic stress disorder, attention-deficit hyperactivity disorder, impulse control disorders in general, and skin picking. Also, the "aggressive," "sexual/religious," and "hoarding" symptom dimensions were more severe in the OCD + TD group.

CONCLUSION

Tic-related OCD may constitute a particular subgroup of the disorder with specific phenotypical characteristics, but its neurobiological underpinnings remain to be fully disentangled.

European clinical guidelines for Tourette syndrome and other tic disorders. Part II: pharmacological treatment

To develop a European guideline on pharmacologic treatment of Tourette syndrome (TS) the available literature was thoroughly screened and extensively discussed by a working group of the European Society for the Study of Tourette syndrome (ESSTS). Although there are many more studies on pharmacotherapy of TS than on behavioral treatment options, only a limited number of studies meets rigorous quality criteria. Therefore, we have devised a two-stage approach. First, we present the highest level of evidence by reporting the findings of existing Cochrane reviews in this field. Subsequently, we provide the first comprehensive overview of all reports on pharmacological treatment options for TS through a MEDLINE, PubMed, and EMBASE search for all studies that document the effect of pharmacological treatment of TS and other tic disorders between 1970 and November 2010. We present a summary of the current consensus on pharmacological treatment options for TS in Europe to guide the clinician in daily practice. This summary is, however, rather a status quo of a clinically helpful but merely low evidence guideline, mainly driven by expert experience and opinion, since rigorous experimental studies are scarce.

Treatment strategies for tics in Tourette syndrome

TOURETTE SYNDROME (TS) IS A CHRONIC NEURODEVELOPMENTAL DISORDER CHARACTERIZED BY TICS: repetitive, involuntary movements and vocalizations. These symptoms can have a significant impact on patients' daily functioning across many domains. Tics tend to be most severe in child and adolescent sufferers, so their presence has the potential to impact a period of life that is both critical for learning and is often associated with the experience of greater social tension and self-consciousness than adulthood. Furthermore, control over tics that lead to physical impairment or self-injurious behaviour is of vital importance in maintaining health and quality of life. There are numerous complicating factors in the prescription of treatment for tics, due to both the side effects associated with alleviating agents and patient characteristics, such as age and comorbid conditions. This review summarizes literature pertaining to the efficacy and safety of both traditionally prescribed and more modern medications. We also discuss the merits of behavioural and surgical techniques and highlight newer emerging treatments. Although treatment response is to some extent variable, there are a number of agents that are clearly useful as first-line treatments for TS. Other interventions may be of most benefit to patients exhibiting refractory tics or more specific symptom profiles.

Tourette syndrome in children: an updated review

Tourette syndrome (TS) is a common neuropsychiatric disorder in children characterized by multiple motor and vocal tics that fluctuate in severity and lasting for at least 1 year. Boys are more commonly affected than girls. Symptoms usually begin with simple motor or vocal tics which then evolve into more complex motor and vocal tics over time. Premonitory sensory urges are common in children over the age of 8 years, and these urges help distinguish tics from symptoms of other movement disorders. Common comorbidities of TS include attention deficit hyperactivity disorder, obsessive-compulsive disorder and learning difficulties. Several genes have been assessed as candidate genes for TS; environmental factors such as stress and streptococcal infections might also contribute to its etiology. The pathophysiology of TS mainly involves dysfunction of basal ganglia-related circuits and hyperactive dopaminergic innervations. A thorough history assessment and neurological examination are important for the correct diagnosis and differentiation from other movement disorders. Treatment for TS should focus on improving the patient's social functioning, minimizing the impairment from cormobid disorders, and controlling tics, if they are severe. Commonly used medications for TS include a2-adrenergic agonists and atypical neuroleptics. Habit reversal therapy is an effective option for TS, and repetitive transcranial magnetic stimulation may be a promising approach for severe cases.

Levetiracetam as an alternative therapy for Tourette syndrome

Tourette syndrome is a common childhood-onset neuropsychiatric disorder characterized by chronic tics and frequent comorbid conditions such as attention deficit disorder. Most currently used tic-suppressing drugs are frequently associated with serious adverse events. Thus, alternative therapeutic agents with more favorable side-effect profiles are being evaluated. New hypotheses and recent studies involving GABAergic system in the pathophysiology of Tourette syndrome suppose a reason for the evaluation of GABAergic drugs. Levetiracetam is a drug with an atypical GABAergic mechanism of action that might be expected to improve tics. Although trials performed to evaluate the efficacy of levetiracetam in the treatment of Tourette syndrome have provided conflicting results, it may be useful in some patients. The established safe profile of levetiracetam makes this drug an alternative for treatment if intolerance to currently used drugs appears, but additional evaluation with larger and longer duration controlled studies are necessary to assess the real efficacy in patients with Tourette syndrome.

Should an obsessive-compulsive spectrum grouping of disorders be included in DSM-V?

The obsessive-compulsive (OC) spectrum has been discussed in the literature for two decades. Proponents of this concept propose that certain disorders characterized by repetitive thoughts and/or behaviors are related to obsessive-compulsive disorder (OCD), and suggest that such disorders be grouped together in the same category (i.e. grouping, or "chapter") in DSM. This article addresses this topic and presents options and preliminary recommendations to be considered for DSM-V. The article builds upon and extends prior reviews of this topic that were prepared for and discussed at a DSM-V Research Planning Conference on Obsessive-Compulsive Spectrum Disorders held in 2006. Our preliminary recommendation is that an OC-spectrum grouping of disorders be included in DSM-V. Furthermore, we preliminarily recommend that consideration be given to including this group of disorders within a larger supraordinate category of "Anxiety and Obsessive-Compulsive Spectrum Disorders." These preliminary recommendations must be evaluated in light of recommendations for, and constraints upon, the overall structure of DSM-V.

Clinical course of Tourette syndrome

OBJECTIVE

Tourette syndrome (TS) is a childhood-onset neuropsychiatric disorder characterized by multiple motor and vocal tics lasting at least a year in duration. Children with TS often experience comorbid conditions such as obsessive-compulsive disorder (OCD) and attention-deficit disorder. The goal of this article was to review the long-term clinical course of tics and comorbid conditions in children with TS.

METHOD

We conducted a traditional literature search to locate relevant articles regarding long-term outcome and prognosis in TS and tic disorders.

RESULTS

Tics typically have an onset between the ages of 4 and 6 years and reach their worst-ever severity between the ages of 10 and 12 years. On average, tic severity declines during adolescence. By early adulthood, roughly three-quarters of children with TS will have greatly diminished tic symptoms and over one-third will be tic free. Comorbid conditions, such as OCD and other anxiety and depressive disorders, are more common during the adolescence and early adulthood of individuals with TS than in the general population.

CONCLUSION

Although tics are the sine qua non of TS, they are often not the most enduring or impairing symptoms in children with TS. Measures used to enhance self-esteem, such as encouraging strong friendships and the exploration of interests, are crucial to ensuring positive adulthood outcome in TS.