Enhanced cognitive control in Tourette Syndrome during task uncertainty

Tourette Syndrome (TS) is a developmental neurological condition that is characterised by the presence of multiple motor and one or more vocal tics. Tics are highly stereotyped repetitive behaviours that fluctuate in type, complexity and severity. TS has been linked to impaired cognitive control processes, however, a recent study (Mueller et al. in Curr Biol 16:570-573, 2006) demonstrated that young people with TS, although exhibiting chronic motor and vocal tics, nevertheless performed significantly better than a group of age-matched controls on a task that required extremely high levels of cognitive control (i.e., predictably shifting between executing pro-saccade and anti-saccade responses to a visual stimulus). As predictable task sequences allow task-related cognitive processes to commence prior to the presentation of target stimuli we examined whether the superior performance of the TS group could be replicated when task sequences were varied unpredictably. Our results confirmed that both the TS group and an age-matched control group benefited, by the same extent, when the saccade task (pro-saccade vs. anti-saccade) was pre-cued. In contrast, while the control group showed a significant decrease in performance on task switch trials relative to task repetition trials-the TS group exhibited no significant 'costs' of switching task. While task performance was modulated by response and target location shifts in the control group, these factors had less impact on the TS group's performance on task switch trials. These results confirm and extend the previous demonstration that individuals with TS exhibit paradoxically greater levels of cognitive control than healthy controls.

Neuroimaging of neuronal circuits involved in tic generation in patients with Tourette syndrome

OBJECTIVE

To identify brain regions generating tics in patients with Tourette syndrome using sleep as a baseline.

METHODS

We used [15O]H2O PET to study nine patients with Tourette syndrome and nine matched control subjects. For patients, conditions included tic release states and sleep stage 2; and for control subjects, rest states and sleep stage 2.

RESULTS

Our study showed robust activation of cerebellum, insula, thalamus, and putamen during tic release.

CONCLUSION

The network of structures involved in tics includes the activated regions and motor cortex. The prominent involvement of cerebellum and insula suggest their involvement in tic initiation and execution.

The role of abnormal neural oscillations in the pathophysiology of co-occurring Tourette syndrome and attention-deficit/hyperactivity disorder

OBJECTIVE

To examine the role of aberrant neural oscillatory activity in the pathophysiology of co-occurring Tourette Syndrome (TS) and Attention-Deficit/Hyperactivity Disorder (ADHD).

METHOD

Neural oscillations refer to periodic variations in the recording of neural activity. The temporal synchronization of oscillations represents a mechanism of neural communication implicated in normal brain functioning as well as psychopathology. We reviewed physiological, imaging, and neuropsychological evidence that tics and symptoms of ADHD may result from abnormal oscillatory activity in the brain.

RESULTS

Structural and functional abnormalities in the cortical-striatal-thalamo-cortical circuits may result in the disruption of oscillatory activity within the basal ganglia of individuals with TS and lead to transient hyperpolarization of selected thalamocortical regions. Extended to TS plus ADHD this or similar mechanisms, in turn, would lead to the dysrhythmia of particular vulnerable cortical regions and give rise to various deficits in motor control (TS + ADHD) as well as impulsivity and attention (ADHD). Compensatory systems within the prefrontal cortex could be activated and trained to modulate the misguided striatal and thalamocortical oscillations.

CONCLUSIONS

Although it is highly likely that abnormal neural oscillations have a prominent role in co-occurrence of TS + ADHD, its final relevance in this case deserves further differentiated research (i.e. oscillatory networks disentangled from other neuropsychiatric disorders).

A developmental fMRI study of self-regulatory control in Tourette's syndrome

OBJECTIVE

Disturbances in the maturation of neural systems that mediate self-regulatory processes may contribute to the development of Tourette's syndrome by releasing motor and vocal tics from regulatory control. The purpose of this study was to examine the age correlates of functional activity in neural circuits that subserve self-regulatory control in children and adults with Tourette's syndrome.

METHOD

The participants were 136 children and adults, which included 66 Tourette's syndrome patients and 70 healthy comparison subjects. During performance of the Stroop interference task, the authors compared the functional magnetic resonance imaging (fMRI) blood-oxygen-level dependent response in patients with Tourette's syndrome with that of healthy comparison subjects. General linear modeling of Stroop-related activations was used to compare the differential effects of age and behavioral performance on changes in self-regulatory control between the two diagnostic groups.

RESULTS

Although the correlations of age with behavioral performance on the Stroop task were similar between patients with Tourette's syndrome and healthy comparison subjects, the two groups differed significantly in their correlations of age with the magnitude of regional brain activation during the task. Interactions of age with diagnosis were detected in the ventral prefrontal (Brodmann's areas 10 and 24) and posterior cingulate cortices (Brodmann's area 31), and post hoc analyses indicated that subjects with Tourette's syndrome deactivated these regions less with advancing age. Greater activation of bilateral frontostriatal regions (Brodmann's areas 9/46, 45/46; lenticular nucleus; and thalamus) accompanied poorer performance in the patient group, which-in the presence of normal behavioral performance on the Stroop task-suggests that greater activation of the frontostriatal systems helps to maintain task performance in individuals with Tourette's syndrome.

CONCLUSIONS

Normative developmental correlates of activity in frontostriatal circuits that subserve self-regulatory control are disturbed in persons with Tourette's syndrome. These aberrant developmental correlates are likely a consequence of greater anatomical and functional disturbances in these circuits in adults with Tourette's syndrome, which leads to impaired regulation of tic behaviors. Reduced default-mode processing in ventral prefrontal and posterior cingulate cortices in adults with Tourette's syndrome suggests the presence of greater difficulty in engaging mental processes that become active when freed from the demands of more challenging cognitive tasks. However, individuals with Tourette's syndrome appear to co-opt normal developmental processes in circuits that subserve age-related improvement in self-regulatory control while presumably struggling to maintain adequate task performance.

Neuroimaging of tic disorders with co-existing attention-deficit/hyperactivity disorder

BACKGROUND

Tourette syndrome (TS) and Attention-Deficit/Hyperactivity Disorder (ADHD) are common and debilitating neuropsychiatric illnesses that typically onset in the preschool years. Recently, both conditions have been subject to neuroimaging studies, with the aim of understanding their underlying neurobiological correlates.

OBJECTIVE

The relation of TS and ADHD is discussed against the background of findings from previous Magnetic Resonance Imaging (MRI) studies.

METHODS

We review the designs and major findings of previous studies that have examined TS with comorbid ADHD, and we briefly contrast these findings with those in ADHD without comorbid tic disorders.

RESULTS

The frequent comorbidity of TS and ADHD may reflect a common underlying neurobiological substrate, and studies confirm the hypothesized involvement of fronto-striatal circuits in both TS and ADHD. However, poor inhibitory control and volumetric reductions in fronto-striatal circuits appear to be core features of ADHD, whereas reduced volumes of the caudate nucleus, together with activation and hypertrophy of prefrontal regions that likely help to suppress tics, seem to be core features of TS.

CONCLUSION

The etiological relationship between TS and ADHD must be clarified further with cross-sectional and, if possible, longitudinal imaging studies that examine samples of substantial size, including subgroups with pure TS and ADHD, as well as with comorbid conditions.

Antineuronal antibody status and phenotype analysis in Tourette's syndrome

The Gilles de la Tourette syndrome (GTS) spectrum includes psychiatric comorbidities, mainly obsessive-compulsive disorder (OCD) and attention-deficit-hyperactivity disorder (ADHD). The role of environmental factors, e.g., antineuronal antibodies (ANeA), remains unclear. We compared the clinical features of ANeA-positive and ANeA-negative patients in 53 children and 75 adults with GTS. All diagnoses were made according to DSM-IV-TR criteria. A positive ANeA Western immunoblot showed bands for at least 1 of 3 reported striatal antigens (40, 45, and 60 kDa). Twelve children (23%) and 18 adults (25%) with GTS were ANeA-positive. Disease duration, tic phenomenology and severity, frequency of echo/pali/coprophenomena, self-injurious and aggressive behavior, or frequency of OCD comorbidity did not significantly differ between ANeA-positive and negative patients. Similar findings were obtained analyzing separately the three different antibody reactivities. A comorbid diagnosis of ADHD was significantly less frequent in GTS patients positive for the anti-60 kDa antibody only. Using a multivariate logistic regression model, adjusting for age, gender, and age at disease onset, a comorbid diagnosis of ADHD remained inversely associated with anti-60 kDa antibodies (odds ratio = 0.14; P = 0.002; 95% confidence interval 0.04-0.49). ANeA status does not differentiate a specific phenotype of GTS.

A Measure of Functional Impairment in Youth with Tourette's Syndrome

OBJECTIVE

Tourette's Syndrome (TS) during childhood is linked to varied behavioral and psychological difficulties and functional impairment. The current study was undertaken to examine both tic-related impairment and impairment from other psychological problems in 59 youth (mean age 11.4 years, 69% male) with TS.

METHODS

Caretakers completed a checklist about the impact of tics and other psychological difficulties on family, school, and social functioning. In addition, a clinician administered a measure of tic severity to families.

RESULTS

Over half of the sample reported one significant problem area due to the presence of tics, with over a third reporting two or more problem areas. Problems were heterogeneous in nature, with no report of a particular problem area in more than 25% of the children. The rate of nontic-related impairment was very high, with 70% of parents reporting at least one problem area.

CONCLUSIONS

Treating both tic and nontic-related impairments concurrently may improve functioning more so than treating the symptoms separately.

Development and implementation of an MR-compatible whole body video system

In conventional fMRI, the possibilities for remote visual monitoring of a volunteer or patient during scanning are very limited. However, performance during motor paradigms, monitoring of ventilated patients, or patients with movement disorders is often of particular interest. In order to facilitate remote visual monitoring during MRI examinations, an MR-compatible video system was developed and implemented to allow monitoring of the face and the body, separately, with two cameras. The system reliably allows the recording of video data during MRI scanning without affecting MR image quality. The applicability of the system for the online recording of tics during an fMRI study with Tourette patients is demonstrated. Monitoring of a motor task in healthy controls and Tourette patients was possible with exact synchronisation to the fMRI paradigm. Details of system set up and example control measurements are presented. Further, electronic and mechanical components are described in detail enabling easy reproduction of the system.

Speeded processing of grammar and tool knowledge in Tourette's syndrome

Tourette's syndrome (TS) is a developmental disorder characterized by motor and verbal tics. The tics, which are fast and involuntary, result from frontal/basal-ganglia abnormalities that lead to unsuppressed behaviors. Language has not been carefully examined in TS. We tested the processing of two basic aspects of language: idiosyncratic and rule-governed linguistic knowledge. Evidence suggests that idiosyncratic knowledge (e.g., in irregular past tense formation; bring-brought) is stored in a mental lexicon that depends on the temporal-lobe-based declarative memory system that also underlies conceptual knowledge. In contrast, evidence suggests that rule-governed combination (e.g., in regular past tenses; walk+-ed) takes place in a mental grammar that relies on the frontal/basal-ganglia-based procedural memory system, which also underlies motor skills such as how to use a hammer. We found that TS children were significantly faster than typically developing control children in producing rule-governed past tenses (slip-slipped, plim-plimmed, bring-bringed) but not irregular and other unpredictable past tenses (bring-brought, splim-splam). They were also faster than controls in naming pictures of manipulated (hammer) but not non-manipulated (elephant) items. These data were not explained by a wide range of potentially confounding subject- and item-level factors. The results suggest that the processing of procedurally based knowledge, both of grammar and of manipulated objects, is particularly speeded in TS. The frontal/basal-ganglia abnormalities may thus lead not only to tics, but also to a wider range of rapid behaviors, including the cognitive processing of rule-governed forms in language and other types of procedural knowledge.

Case reports and review of Tourette syndrome

Tourette syndrome (TS) is characterized by at least one motor and one verbal tic with duration of more than one year with no 3-month period without tics. It is one of the most common childhood movement disorders and often causes significant morbidity in the children it affects. TS as well as its numerous comorbidities are often under-recognized if the clinical suspicion of the physician is not high. In this review, we describe two patients with TS that varied in their degree of symptoms and treatment. We would like to emphasize with this review that TS occurs more commonly than it is diagnosed and is often confused with other conditions, such as seasonal allergies, sinusitis, and seizures. Correct diagnosis is important in order to allow appropriate treatment and to improve the quality of life for these patients.

Postural control anomalies in children with Tourette syndrome

The goal of the present study was to determine whether postural control is affected in Gilles-de-la-Tourette syndrome (TS). Center of pressure (COP) displacements were recorded in children with TS and unaffected siblings in three conditions using a force platform: (1) Eyes-Open, (2) Eyes-Closed, (3) One-Leg standing with eyes open. The COP range and velocity were higher in children with TS than in unaffected siblings in all conditions. These differences could not be attributed to age, present tic severity, comorbidities (hyperactivity and compulsions) or medication. The data suggest that sub-clinical postural control anomalies are present in TS.

Memory and executive functions in adults with Gilles de la Tourette syndrome and chronic tic disorder

INTRODUCTION

The main aim of the current study was to assess whether adults with either Tourette syndrome (TS) or chronic tic disorder (CTD) show a similar neuropsychological profile. Neuropsychological investigations of tic disorders have been mostly focused on children, mainly because symptoms peak during that period. Little has been carried out on adults, even if a significant proportion of the tic population experience moderate or marked levels of tic frequency throughout adulthood. Still, it is not clear whether neuropsychological performances are affected to the same degree in adults with TS and CTD.

METHOD

Patients diagnosed with TS were compared with a CTD group and a control group free of psychiatric or neurological diagnosis, comparable in terms of age, gender, and intelligence. All participants completed two tests of memory (Rey-Osterreich Complex Figure, California Verbal Learning Test), one test of motor dexterity (Purdue pegboard), and four tasks of executive function (Stroop, Color Trail Test, Tower of London, Wisconsin Card Sorting Test).

RESULTS

TS and CTD patients showed nonverbal memory impairments while verbal memory and executive functioning remained intact. Results also indicated that nonverbal memory performances decrease as a function of tic severity.

CONCLUSION

Both TS and CTD patients present a specific nonverbal deficit whilst the executive and motor functions are relatively intact. The two tic disorder subgroups might be part of a spectrum implicating mainly nonverbal memory.

Role of atypical opiates in OCD. Experimental approach through the study of 5-HT(2A/C) receptor-mediated behavior

RATIONALE

The selective serotonin (5-HT) reuptake inhibitors (SSRIs) represent the first-line pharmacotherapy for obsessive-compulsive disorder (OCD), and atypical antipsychotic drugs, which block 5-HT2A receptors, are used in augmentation strategies. Opiate drugs are also effective in treatment-refractory OCD and Tourette syndrome. The 5-HT2A-related behavior (i.e., head twitch) has been related with tics, stereotypes, and compulsive symptoms observed in Tourette syndrome and OCD.

OBJECTIVES

The aim of this study was to explore whether 5-HT2A-related behavior is affected by atypical opiate drugs.

MATERIALS AND METHODS

Head-twitch response was induced in mice by administration of either 5-hydroxytryptophan (5-HTP) or the 5-HT2A/C agonist (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI). Dose-effect curves of atypical opiate drugs [(+/-)-tramadol, (-)-methadone and levorphanol], morphine, and other psychoactive drugs (fluvoxamine, desipramine, nefazodone, and clozapine) were performed. Opioid mechanisms were investigated by administration of naloxone.

RESULTS

All the opiates tested reduced both 5-HTP and DOI-induced behavior in a naloxone-reversible fashion, atypical opiates being more effective. The effects of the other drugs depended on the protocol, clozapine being the most effective.

CONCLUSIONS

Combined 5-HT and opioid properties result in a greater efficacy in antagonizing 5-HT2A-related behavior. These results provide behavioral evidence to support convergent effects of the 5-HT and opioid systems in discrete brain areas, offering the potential for therapeutic advances in the management of refractory stereotypes and compulsive behaviors.

Effect of vagal nerve stimulation in a case of Tourette's syndrome and complex partial epilepsy

We report on a 30-year-old man with Tourette's syndrome (TS) and medication-refractory epilepsy whose tics improved after implantation of a vagal nerve stimulator (VNS). To verify the patient's observation, we performed a blinded video assessment using the modified Rush video-based tic rating scale. The patient underwent two separate video recordings (VNS on and VNS off). A rater, blinded to patient's VNS status, evaluated the videos with the modified Rush video-based tic rating scale. There were improvements in total tic score and motor and phonic tic frequency. If verified by controlled clinical trials, this observation may provide insights into the pathophysiology of tics and may lead to a novel therapy for patients with severe TS.

Tourette's syndrome: clinical features, pathophysiology, and therapeutic approaches

Tourette's syndrome (TS) is a disorder characterized by simple and complex motor tics, vocal tics, and frequently obsessive-compulsive symptoms. Its onset occurs before the age of 21. Typically, TS shows a waxing and waning course, but a chronification of the tics, even during later life, is often observed. TS mainly occurs in boys, and shows genetic heritability with differing penetrance. The pathological mechanism is still unclear Neuroanatomical and neuroimaging studies, as well as effective treatment using antipsychotics, suggest that a disturbance of the dopaminergic system in the basal ganglia plays an important role in the pathogenesis of TS. Several possibly causative mechanisms of the disturbed dopaminergic neurotransmission are discussed, with the main emphasis on the-infection-triggered-inflammatory immune process. Extrapyramidal movement disorders are known to occur as a symptom of poststreptococcal disease, such as in Sydenham's chorea. Cases of childhood TS are proposed to be caused by such a poststreptococcal mechanism, being part of a spectrum of childhood neurobehavioral disorders termed pediatric autoimmune neuropsychiatric disorder associated with streptococcal infection (PANDAS). The overlap between TS and PANDAS is discussed, and a critical view of the PANDAS concept is presented. The therapeutic implications of the different pathological mechanisms are described, taking into consideration not only the acute or chronic natures of different infections, but also an autoimmune process. Moreover, therapeutic strategies using typical and atypical antipsychotics, and also experimental therapies such as repetitive transcranial magnetic stimulation and deep brain stimulation, are critically discussed.

Attitude and knowledge of high school pupils towards adolescents with special needs (Tourette's syndrome)

OBJECTIVE

To determine high school pupils' attitudes towards adolescents with special needs (for example: TS); to learn what they know about the symptomatology and the exceptional behavior of TS; and what they think about their social future.

METHODS

Ninety-nine pupils participated in the study. Their mean age was 16.7 +/- 0.8 years. Forty-eight point five percent were boys, and the rest girls. They completed a questionnaire concerning knowledge and attitudes towards adolescents with special needs (diagnosed as TS). They had participated in lessons and class talks about handicapped children with psycho- behavioral symptoms.

RESULTS

The scores for their knowledge were at a level of 68.9%. Half of the pupils knew and responded correctly that TS was of genetic origin; but the most important: they expressed a comprehensive and tolerant attitude towards impaired behavior in TS at a level of 55.3%. The tolerant attitude increased with advancing age and with school grades. The attitudes were more comprehensive in families suffering form their own emotional or other psychiatric difficulties. Forty-three point four percent of pupils understand and consider TS to be an emotional, behavioral and psychiatric entity. Sixty-two point six percent of pupils understand as well and believe that the disruptive behavior and outbursts in TS are involuntary and not under the adolescent's control. On the other hand, a quarter of the pupils see justification for repeated punishment of TS adolescents for their impaired behavior. Fifty-six point six percent of regular pupils were ready to develop friendship with TS classmates in spite of their unexpected and unruly behaviour. Eight-three point eight percent of pupils believe it is better to inform teachers and classmates about the impaired behavior of these TS adolescents. Concerning the future of these disabled adolescents, pupils scored a level of 44% for their optimistic beliefs about success in future life; 52% believe that in spite of all difficulties TS adolescents would be able to live an ordinary life, to raise a family and to work.

CONCLUSIONS

It is crucial to improve pupils' attitudes in schools (as well as their teachers') towards adolescents with special needs (including TS). The authors recommend that TS be considered as a neuro-behavioral and psychiatric disorder; it should be considered as a disability, which calls for comprehension, (not punishment). It would also be of value to speak in classes about the handicaps and neurobehavioral limitations for example of these TS adolescents, as well as about other pupils in school with special needs, in order to behave socially correctly towards them. The final aim will be that pupils in school will learn to accept the different child and adolescent as they are.

P300 differences exist between Tourette's syndrome with and without attention deficiency and hyperactivity disorder in children

OBJECTIVE

To study the characteristics of P300 in Tourette's syndrome (TS) with and without attention deficiency and hyperactivity disorder (ADHD).

METHOD

Auditory evoked P300 were recorded in 19 TS only (TS-ADHD) children, 15 TS with ADHD (TS + ADHD) children and 20 unaffected control subjects, and their waveforms, amplitudes, latencies and topographies were compared at Fz, Cz, C3, C4 and Pz.

RESULTS

The TS + ADHD group showed shorter latencies than control subjects at all electrode sites (P<0.05 or 0.01), and the TS-ADHD group at CZ and PZ (P<0.05); however, there was no significant difference between control subjects and the TS-ADHD group. The TS-ADHD group showed smaller amplitudes than the control group at all electrode sites (P<0.05), and the TS + ADHD group at Cz (P<0.05); however, there were no significant differences between control subjects and the TS + ADHD group. There was no significant difference in the prevalence of abnormal waveforms between the control, TS, TS-ADHD and TS + ADHD groups, but there were significant differences in the variability of localization of P300 between the control and the TS group (P=0.003), control and TS + ADHD groups (P=0.000), and the TS-ADHD and TS + ADHD groups (P=0.039). P300 in the TS + ADHD group tended to spread out to the left and that of the TS-ADHD group tended to spread out to the right.

CONCLUSIONS

P300 differences exist between TS-ADHD and TS + ADHD in children. These suggested that establishment different development defects or delay of communications between different structures rather than a delay in maturation of the structures themselves may be involved in TS + ADHD and TS-ADHD children and ADHD symptoms in TS patients are likely a trait rather than adventitious or acquired within the TS syndrome.

A controlled family study of attention-deficit/hyperactivity disorder and Tourette's disorder

OBJECTIVE

Although attention-deficit/hyperactivity disorder (ADHD) is frequently comorbid with Tourette's disorder (TD), it is unclear whether they have a common genetic etiology. Familial relationships between DSM-IV ADHD and TD are studied in TD+ADHD, TD-only (TD-ADHD), ADHD-only (ADHD-TD), and control groups.

METHOD

Case-control, direct-interview family study of 692 relatives of 75 TD+ADHD, 74 TD-only, 41 ADHD-only, and 49 control probands collected between 1999 and 2004. Age-corrected prevalence rates, odds ratios, and predictors of TD, ADHD, and OCD among relatives are estimated from blinded best-estimate diagnoses using survival Kaplan-Meier and generalized estimating equation regression analyses.

RESULTS

In relatives of the TD-only group, although ADHD exceeded control rates (p=.03), ADHD-TD (p=.51) rates were not increased. In the ADHD-only group, TD was increased (p=.004) but TD-ADHD rates were not increased (p=.18). Comorbid ADHD+TD diagnoses in relatives were elevated in all case groups (p<or=.03). TD in relatives predicted comorbid ADHD (p<.001), and ADHD in relatives predicted comorbid TD (p<.001). OCD in relatives predicted both ADHD (p=.002) and TD (p<.001) in relatives.

CONCLUSIONS

TD and ADHD are not alternate phenotypes of a single underlying genetic cause. There is an increased risk of comorbid ADHD and TD in affected families, possibly reflecting some overlapping neurobiology or pathophysiology.

Botulinum toxin in the management of laryngeal tics

SUMMARY

The objective of the study was to demonstrate the utility of botulinum toxin (BTX; Botox: Allergan Pharmaceuticals, Irvine, CA) type A injections for symptom reduction in laryngeal tics. The study consisted of case studies and literature review. Case histories of two patients with laryngeal tics are presented. Treatment was administered using BTX type A injected into the thyroarytenoid muscles using electromyographic guidance or via direct laryngoscopy. Treatment outcomes were measured using clinical rating scales with a range from 0 (no response) to 4 (maximal response). A subjective assessment of reduction in premonitory sensations was recorded. Subject 1 was a 49-year-old female with onset of laryngeal tic (throat clearing) at 46 years. She received six injections over 24 months. The lowest effective dose was 1.25 units bilaterally, producing complete resolution of the tic behavior (peak effect of 4/4) and reduction of the premonitory sensations. The median duration of benefit was 13 weeks. Subject 2 was a 14-year-old male with Gilles de la Tourette syndrome with laryngeal symptoms including throat clearing, barking, and crowing. He received three injections, with the lowest effective dose of 0.625 units bilaterally. He achieved marked reduction (peak effect of 3/4) of the throat clearing, barking, and crowing behaviors. There was also substantial reduction of the premonitory sensations. The median duration of benefit was 10 weeks. The cases presented herein are examples of successful treatment with low-dose BTX type A to reduce the symptoms of laryngeal tics, leading to improved quality of life. These cases add to the relatively small number of similar patients reported in the literature, and support the use of chemical neuromuscular blockade for treatment of laryngeal tic symptoms.

Functional brain asymmetry, attentional modulation, and interhemispheric transfer in boys with Tourette syndrome

We tested the hypothesis that children with Tourette syndrome (TS) would exhibit aberrant brain lateralization compared to a healthy control (HC) group in an attention-modulation version of a verbal dichotic listening task using consonant-vowel syllables. The modulation of attention to focus on the right ear stimulus in the dichotic listening situation is thought to involve the same prefrontal attentional and executive functions that are involved in the suppression of tics, whereas, performance when focusing attention on the left ear stimulus additionally involves a callosal transfer of information. In light of presumed disturbances in transfer of information across the corpus callosum, we hypothesized that children with TS would, however, have difficulty modulating the functional lateralization that ensues through a shift of attention to the left side. This hypothesis was tested by exploring the correlations between CC size and left ear score in the forced-left condition. Twenty boys with TS were compared with 20 age- and handedness-matched healthy boys. Results indicated similar performance in the TS and HC groups for lateralization of hemispheric function. TS subjects were also able to shift attention normally when instructed to focus on the right ear stimulus. When instructed to focus attention on the left ear stimulus, however, performance deteriorated in the TS group. Correlations with CC area further supported the hypothesized presence of deviant callosal functioning in the TS group.

Reduced white matter connectivity in the corpus callosum of children with Tourette syndrome

BACKGROUND

Brain imaging studies have revealed anatomical anomalies in the brains of individuals with Tourette syndrome (TS). Prefrontal regions have been found to be larger and the corpus callosum (CC) area smaller in children and young adults with TS compared with healthy control subjects, and these anatomical features have been understood to reflect neural plasticity that helps to attenuate the severity of tics.

METHOD

CC white matter connectivity, as measured by the Fractional Anisotropy (FA) index from diffusion tensor images, was assessed in 20 clinically well-defined boys with Tourette syndrome and 20 age- and gender-matched controls.

RESULTS

The hypothesis that children with TS would show reduced measures of connectivity in CC fibers was confirmed for all subregions of the CC. There was no significant interaction of TS and region. Reductions in FA in CC regions may reflect either fewer interhemispheric fibers or reduced axonal myelination. FA values did not correlate significantly with the severity of tic symptoms. Group differences in measures of connectivity did not seem to be attributable to the presence of comorbid ADHD or OCD, to medication exposure, or group differences in IQ.

CONCLUSION

Our findings of a reduced interhemispheral white matter connectivity add to the understanding of neural connectivity and plasticity in the brains of children who have TS.

Tourette syndrome: the self under siege

Tourette syndrome is a neurodevelopmental disorder characterized by motor and vocal tics--rapid, repetitive, stereotyped movements or vocalizations. Tourette syndrome typically has a prepubertal onset, and boys are more commonly affected than girls. Symptoms usually begin with transient bouts of simple motor tics. By age 10 years, most children are aware of nearly irresistible somatosensory urges that precede the tics. These urges likely reflect a defect in sensorimotor gating because they intrude into the child's conscious awareness and become a source of distraction and distress. A momentary sense of relief typically follows the completion of a tic. Over the course of hours, tics occur in bouts, with a regular intertic interval. Tics increase during periods of emotional excitement and fatigue. Tics can become "complex" in nature and appear to be purposeful. Tics can be willfully suppressed for brief intervals and can be evoked by the mere mention of them. Tics typically diminish during periods of goal-directed behavior, especially those that involve both heightened attention and fine motor or vocal control, as occur in musical and athletic performances. Over the course of months, tics wax and wane. New tics appear, often in response to new sources of somatosensory irritation, such as the appearance of a persistent vocal tic (a cough) following a cold. Over the course of years, tic severity typically peaks between 8 and 12 years of age. By the end of the second decade of life, many individuals are virtually tic free. Less than 20% of cases continue to experience clinically impairing tics as adults. Tics rarely occur in isolation, and other coexisting conditions--such as behavioral disinhibition, hypersensitivity to a broad range of sensory stimuli, problems with visual motor integration, procedural learning difficulties, attention-deficit hyperactivity disorder (ADHD), obsessive-compulsive disorder, depression, anxiety, and emotional instability--are often a greater source of impairment than the tics themselves. Emerging behavioral treatments of Tourette syndrome are based in part on an understanding of the moment-to-moment experience of somatosensory urges and motor response. With identification of specific genes of major effect and advances in our understanding of the neural circuitry of sensorimotor gating, habit formation, and procedural memory--together with insights from postmortem brain studies, in vivo brain imaging, and electrophysiologic recordings--we might be on the threshold of a deeper understanding of the phenomenology and natural history of Tourette syndrome.

Brief review of habit reversal training for Tourette syndrome

It is well established that Tourette syndrome has a neurobiologic origin. Although pharmacotherapy is the most commonly prescribed intervention, there is considerable evidence to support the use of behavior therapy, specifically habit reversal training, as an alternative or adjunct treatment for some individuals with Tourette syndrome. Unfortunately, many professionals are unfamiliar with habit reversal training. The purpose of this review is to provide readers with a brief review of empiric studies on habit reversal training, update readers on the current state and future of behavior therapy for Tourette syndrome, and provide resources for those readers interested in additional information.

Increased event-related theta activity as a psychophysiological marker of comorbidity in children with tics and attention-deficit/hyperactivity disorders

OBJECTIVE

The question as to whether coexisting tic disorder (TD) and attention-deficit/hyperactivity disorder (ADHD) in children represent a combination of two independent pathologies, a separate nosologic entity manifested by both tics and hyperactivity or a phenotype subgroup of one of the two major clinical forms has received increasing attention. The aim of the present study was to classify the TD+ADHD comorbidity in the neurocognitive domain and to elucidate the neurophysiological background of TD+ADHD coexistence by analyzing event-related electroencephalographic (EEG) oscillations in the theta (3-7.5 Hz) frequency band.

METHODS

Event-related potentials were recorded at 10 electrodes in 53 children (9-13 years old) from four groups (healthy controls, TD-only, ADHD-only, and combined TD+ADHD patients), while they performed an auditory selective attention task requiring a button press to a predefined target. Event-related theta oscillations were analyzed by means of time-frequency decomposition (wavelet analysis) in two latency ranges-early (0-200 ms) and late (200-450 ms). The effects of psychopathology factors (TD and ADHD) and task variables (attended channel and stimulus task relevance) on early (ETR) and late (LTR) theta responses were evaluated statistically. Theta response measures were further correlated with psychopathology scores and spontaneous theta EEG activity.

RESULTS

(1) The ETR was enhanced only in comorbid children and did not differ between the control, TD-only, and ADHD-only groups. (2) The LTR was larger in children with ADHD (ADHD-only and comorbid), but this effect was mediated by the spontaneous theta EEG activity. (3) The ETR was larger to attended stimuli at frontal-central electrodes contralateral to the side of attention, to the target stimulus type at frontal locations, and at the hemisphere contralateral to the side of the response. The functional reactivity and scalp distribution of ETRs were modulated by psychopathological factors.

CONCLUSIONS

In the neurocognitive domain, the TD+ADHD comorbidity can be identified as a unique nosologic entity. Both the spontaneous theta activity and late event-related theta oscillations appear as neurophysiological markers of the ADHD condition. In children, the early event-related theta oscillations may be associated with representations of relevant target features in working memory.

SIGNIFICANCE

(1) A new model is proposed according to which TD+ADHD comorbidity can be classified at different levels (from neurobiological to cognitive). (2) The functional significance of stimulus-synchronized theta oscillations in children is described for the first time.

Blink reflex abnormalities in children with Tourette syndrome

Tourette syndrome (TS) is a common disorder which typically occurs during childhood or early adolescence. There is no definitive diagnostic test for TS. The objective of this study was to demonstrate whether neurophysiological abnormalities of the blink reflex can be observed in children with TS. We enrolled 15 children with TS, diagnosed according to DSM IV Diagnostic Criteria, and 15 controls. The blink reflex was elicited by stimulating the supraorbital nerve in order to measure the early response (R1), homolateral and contralateral R2 (late) responses, amplitude of R1 and duration of R2. The mean duration of R2 was significantly longer in TS patients than in the controls (P < 0.001, Student's t-test). An abnormal pattern of the blink reflex can be, even in childhood, an early neurophysiologic marker of TS, which is not related to the duration of TS or to the age of onset.

Enhanced cognitive control in young people with Tourette's syndrome

Tourette's syndrome (TS) is a neurodevelopmental disorder characterized by the presence of chronic vocal and motor tics. Tics are sudden, highly stereotyped, movements that can be simple or complex in appearance. Since patients with TS have difficulties preventing unwanted movements, one might expect that their ability to voluntarily control goal-directed movements would be similarly poor. Indeed, it has been suggested that TS sufferers are impaired at inhibiting reflexively triggered movements and in rapidly selecting or switching between different motor sets. This idea is consistent with current views on the neurological basis of TS that posit a dysfunction of the neural circuits linking the frontal lobes and the striatum. These circuits are known to be involved in the voluntary control of action. By using an oculomotor switching task, we show for the first time that young people with TS exhibit paradoxically greater levels of cognitive control over their movements than their age-matched controls. This finding is consistent with an increased need to monitor and control movements and may indicate a subcortical locus for the triggering of tics. It also suggests that the constant need to suppress tics could have resulted in an enhancement of the executive processes involved in inhibitory control.

Neural correlates of tic generation in Tourette syndrome: an event-related functional MRI study

Little is known about the neural correlates of tics and associated urges. In the present study, we aimed to explore the neural basis of tics in patients with Tourette syndrome by using event-related functional MRI (fMRI). Ten patients (6 women, 4 men; age: mean +/- SD = 31 +/- 11.2) were studied while spontaneously exhibiting a variety of motor and vocal tics. On the basis of synchronized video/audio recordings, fMRI activities were analysed 2 s before and at tic onset irrespective of the clinical phenomenology. We identified a brain network of paralimbic areas such as anterior cingulate and insular cortex, supplementary motor area (SMA) and parietal operculum (PO) predominantly activated before tic onset (P < 0.05, corrected for multiple comparisons). In contrast, at the beginning of tic action, significant fMRI activities were found in sensorimotor areas including superior parietal lobule bilaterally and cerebellum. The results of this study indicate that paralimbic and sensory association areas are critically implicated in tic generation, similar to movements triggered internally by unpleasant sensations, as has been shown for pain or itching.

Dopamine transporter genotype influences the physiological response to medication in ADHD

Attention deficit hyperactivity disorder (ADHD) is a complex, multifactorial disorder characterized by physical hyperactivity and behavioural disinhibition. Short interval cortical inhibition (SICI), measured in motor cortex with transcranial magnetic stimulation, is reduced in ADHD and correlates with symptom severity. However, ADHD medication-induced changes in SICI vary widely among normal individuals and have not been well studied in children with ADHD. Therefore, we undertook this study to measure and compare effects of two ADHD medications, methylphenidate (MPH), a psychostimulant, and atomoxetine (ATX), a selective norepinephrine reuptake inhibitor, on SICI in children with ADHD. In addition, we wished to determine whether a genetic variation in the dopamine transporter (DAT1), a site of action of MPH, could influence the effects of MPH or ATX on SICI. We performed a randomized, double-blind, single-dose, crossover study comparing 0.5 mg/kg MPH with 1.0 mg/kg ATX in 16 children with ADHD, aged 8-17. Seven were homozygotes and 9 heterozygotes for the DAT1 variable number of tandem repeats 10-repeat allele. Medication and genotype effects on SICI were estimated with repeated measures, mixed model regression. We found that MPH and ATX had similar effects on SICI. However, medication effects differed significantly by DAT1 genotype [F(2,13) = 13.04, P = 0.0008]. Both MPH and ATX increased SICI in heterozygotes but not in 10-repeat homozygotes. In conclusion, MPH and ATX have similar effects on SICI in children with ADHD. A genetic variation in DAT1, previously linked to ADHD risk and MPH behavioural responses, influences the neurophysiological effects of both MPH and ATX.

Deep brain stimulation of the anterior internal capsule for the treatment of Tourette syndrome: technical case report

OBJECTIVE AND IMPORTANCE

Medical treatment of Tourette syndrome is often ineffective or is accompanied by debilitating side effects, therefore prompting the need to evaluate surgical therapies.

CLINICAL PRESENTATION

We present the case of a 37-year-old woman with severe Tourette syndrome since the age of 10 years. Her symptoms included frequent vocalizations and severe head and arm jerks that resulted in unilateral blindness. Trials of more than 40 medications and other therapies had failed to relieve the tics.

INTERVENTION

We implanted bilateral electrodes in the anterior limb of the internal capsule, terminating in the vicinity of the nucleus accumbens. At 18-month follow-up, optimal stimulation continued to lower her tic frequency and severity significantly.

CONCLUSION

Our findings suggest that stimulation of the anterior internal capsule may be a safe and effective procedure for the treatment of Tourette syndrome.

Annotation: Tourette syndrome: a relentless drumbeat--driven by misguided brain oscillations

OBJECTIVE

This annotation reviews recent evidence that points to the likely role of aberrant neural oscillations in the pathogenesis of Tourette syndrome (TS).

METHODS

The available anatomic and electrophysiological findings in TS are reviewed in the context of an emerging picture of the crucial role that neural oscillations play in maintaining normal central nervous system (CNS) function.

RESULTS

Neurons form behavior-dependent oscillating networks of various sizes and frequencies that bias input selection and facilitate synaptic plasticity, mechanisms that cooperatively support temporal representation as well as the transfer and long-term consolidation of information. Coherent network activity is likely to modulate sensorimotor gating as well as focused motor actions. When these networks are dysrhythmic, there may be a loss of control of sensory information and motor action. The known electrophysiological effects of medications and surgical interventions used to treat TS likely have an ameliorative effect on these aberrant oscillations. Similarly, a strong case can be made that successful behavioral treatments involve the willful training regions of the prefrontal cortex to engage in tic suppression and the performance of competing motor responses to unwanted sensory urges such that these prefrontal regions become effective modulators of aberrant thalamocortical rhythms.

CONCLUSIONS

A deeper understanding of neural oscillations may illuminate the complex, challenging, enigmatic, internal world that is TS.

Fine-motor skill deficits in childhood predict adulthood tic severity and global psychosocial functioning in Tourette's syndrome

BACKGROUND

Most children with Tourette's syndrome (TS) experience a significant decline in tic symptoms during adolescence. Currently no clinical measures have been identified that can predict whose tic symptoms will persist into adulthood. Patients with TS have deficits on neuropsychological tests involving fine-motor coordination and visual-motor integration. We seek to determine if these neuropsychological tests are useful in predicting future symptom severity.

METHODS

Thirty-two children, aged 8-14, with TS underwent clinical evaluation and a focused neuropsychological testing battery consisting of the Purdue Pegboard, Beery Visual-Motor Integration (VMI) Test and the Rey-Osterreith Complex Figure Task (RCFT). A follow-up clinical assessment was performed on these children an average of 7.5 years later. Ordinal logistic regression analysis was used to correlate neuropsychological testing at Time 1 with tic severity, OCD severity and global psychosocial functioning at Time 2.

RESULTS

Poor performance with the dominant hand on the Purdue Pegboard test predicted worse adulthood tic severity and correlated with tic severity at the time of childhood assessment. Poor performance on the VMI and Purdue Pegboard tests (both dominant and non-dominant hand) also predicted worse adulthood global psychosocial functioning. None of the neuropsychological tests were useful in predicting the future course of OCD symptoms in TS patients.

CONCLUSION

Fine motor skill deficits may be a predictor of future tic severity and global psychosocial function in children with TS. We hypothesize that performance on the Purdue Pegboard test may serve as a useful endophenotype in the study of TS and provide a rough measure of the degree of basal ganglia dysfunction present in TS patients.

[Clinical observation on acupuncture for treatment of Tourette's syndrome]

OBJECTIVE

To explore an ideal program for acupuncture treatment of Tourette's syndrome (TS).

METHODS

One hundred and two cases of TS were randomly divided into a treatment group of 68 cases and a control group of 34 cases. The treatment group were treated with acupuncture at Taichong (LR 3) and Hegu (LI 4) as main, and the control group with oral administration of heloperidol. Their therapeutic effects were compared, and changes of somatosensory evoked potentials (SEP) before and after treatment were investigated in the treatment group.

RESULTS

After treatment for 3 courses, 56 cases were cured, 10 improved and 2 ineffective with an effective rate of 97.1% in the treatment group; and 15 cases were cured, 11 improved and 8 ineffective with an effective rate of 76.5% in the control group, with a very significant difference in the effective rate between the two groups (P < 0.001); after treatment, the abnormal rate of SEP decreased by 41.1% in the treatment group (P < 0.001).

CONCLUSION

Acupuncture is a very effective therapy for TS and has a certain restoring action on mild abnormal change of SEP.

PET imaging of the basal ganglia

The present chapter reviews PET imaging in basal ganglia disorders; Parkinson's disease is used as a model of these disorders because the neurochemical pathobiology of this disease is well known and great advances in the imaging area have been achieved. Other basal ganglia disorders including Tourette's syndrome, dystonia, Huntington's chorea and Wilson's disease are also dealt with. With PET and SPECT techniques, the whole integrative dopaminergic network of neurons can be studied, which plays an important role in differential diagnostics. Furthermore, pharmacological effects of medication can be visualized and the role of stereotaxic neurosurgery can be evaluated. Finally, functional imaging gives clues about the prognosis and rehabilitation aspects of the basal ganglia disorders.

Dopamine and the diseased brain

Dysfunction of central dopaminergic neurotransmission has been implicated in a series of neuropsychiatric disorders, including Tourette's syndrome, schizophrenia, and drug and alcohol dependence. The behavioral and psychopathological manifestations of central dopaminergic dysfunction differ depending on the site of their neurobiological correlate. These sites may be found in the dorsal or ventral striatum, but also in cortical regions such as the limbic and prefrontal cortex, among other locations. A low basic dopamine turnover and an increase in the availability of dopamine D2 receptors in the caudate body have been associated with the severity of motor tics in Tourette's syndrome. In the ventral striatum and particularly in the nucleus accumbens, different drugs of abuse stimulate dopamine release and thus reinforce drug consumption. The downregulation of dopamine D2 receptors in this area of the brain has been associated with alcohol craving and an increase in the processing of alcohol-related stimuli in the medial prefrontal cortex. Brain imaging studies in which intrasynaptic dopamine release is manipulated in vivo have shown that increased subcortical dopamine release is associated with the pathogenesis of positive symptoms in schizophrenia. This review discusses a broad range of brain imaging and neuroendocrinological studies on dopaminergic dysfunction in neuropsychiatric disorders, including relevant findings on the basis of primate studies. In addition, the hypothesis is examined that phasic dopamine release is associated with salience attribution to external stimuli, insofar as it mediates reward anticipation in the ventral striatum and limbic cortex, habit formation in the dorsal striatum, and working memory function in the prefrontal cortex.

Interhemispheric connectivity and executive functioning in adults with Tourette syndrome

The prefrontal cortex (PFC) is relatively smaller, and the corpus callosum (CC) larger, in adults with Tourette syndrome (TS). The authors explored the possible roles of the PFC and the CC in mediating interhemispheric interference and coordination in TS adults. They measured performance on M. Kinsbourne and J. Cook's (1971) verbal-manual interference task and on the bimanual Purdue Pegboard in 38 adults with TS and 34 healthy adults. Compared with controls, TS subjects were impaired on the bimanual Purdue Pegboard. On the dual task, right-hand performance did not differ between groups, but the normally expected left-hand advantage (opposite hemisphere condition) was absent in TS subjects. In the control group only, better left-hand performance accompanied larger PFC volumes but not CC cross-sectional area. PFC dysfunction might have precluded executive control of interference in the TS group.

[Tourette syndrome: from a neurological clinic to a multidisciplinary approach]

Tourette Syndrome (TS) is a chronic, familial disorder, characterized by involuntary motor and phonic tics that wax and wane in severity. TS is frequently accompanied by behavioral, emotional and cognitive problems that are often more incapacitating than the tic disorder itself. After a review of the disorder, in which the multidisciplinary aspects are emphasized, the article describes the clinical features of 60 children with TS, 49 boys and 11 girls, aged 13 +/- 3.6 years (mean SD), treated in the Neuropediatric Unit at Shaare Zedek Medical Center. The children described had both motor and vocal tics, but also had ADHD (n = 44), obsessive-compulsive disorder (n = 32), learning disabilities (with 12 children learning in special education frameworks) and behavioral disorders (n = 36). The clinical profile of this group of children with TS is similar to that reported on referred patients regardless of cultural background. Since children with TS manifest multiple comorbidities, optimal therapy mandates the cooperation of a multidisciplinary team including a pediatric neurologist, a child psychiatrist, a psychologist and a family therapist. Working in concert, these specialists can implement a multimodal approach, addressing the neurological and psychiatric aspects of TS as well as enhancing the child's coping skills with the disorder itself and its consequences.

Atypical movement disorders in antiphospholipid syndrome

Movement disorders have only rarely been reported in association with antiphospholipid syndrome (APS). In such cases, chorea is the most common disorder observed, with occasional reports of hemidystonia, Parkinsonism, and hemiballism. We report here on 3 cases of APS (3 women ages 16, 46, and 56 years) who presented with movement disorders, including tics, tremor, myoclonus, and a corticobasal syndrome, never or rarely reported in association with this disease. Mild executive dysfunction was observed in all 3 patients. We also report the successful treatment of two of these patients with mild oral anticoagulation (INR 2-3). Movement disorders in APS seem more clinically heterogeneous than previously thought. Oral anticoagulation should be considered in the treatment of movement disorders associated with APS.

Recent advances in Tourette syndrome research

Tourette syndrome (TS) is a developmentally regulated neurobehavioral disorder characterized by involuntary, stereotyped, repetitive movements. Recent anatomical and neuroimaging studies have provided evidence for abnormal basal ganglia and dopaminergic function in TS. Basic research on striatal inhibitory mechanisms and dopaminergic function complements the recent neuroimaging and anatomical data. Parallel studies of basal ganglia participation in the normal performance and learning of stereotyped repetitive behaviors or habits has provided additional insight. These lines of research have provided new pieces to the TS puzzle, and their increasing convergence is showing how those pieces can be put together.

[Genetic linkage analysis of Gilles de la Tourette Syndrome in a Colombian family]

INTRODUCTION

Gilles de la Tourette Syndrome (GTS) is a chronic neuropsychiatric disorder characterized by phonic and motor tics. Although its physiopathologic bases are unknown, the cortical-striatal-thalamic-cortical circuit has been studied. The association of GTS with attention deficit hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), motors tics (MT) or phonics tics (PT), the high family aggregation, and the concordance studies in twins, support the genetics bases of this disorder. Currently, GTS is accepted as a complex disorder and the associated disorders could be alternative expressions of the same syndrome.

AIM

To evaluate genetic linkage to 2p11, 6p24, 11q23, 20q13 and 21q22 regions in an Antioquian family with enough power to detect linkage.

PATIENTS AND METHODS

With the Linkage program and using autosomic dominant, recessive and additive inheritance models, the genetic linkage was calculated; two phenotypic spectra was considered: one broad spectrum including affected individuals with GTS, ADHD, OCD, MT, and PT, and a narrow spectrum with only GTS.

RESULTS

The most probable inheritance pattern for a susceptibility locus in GTS and its associated disorders in this family is autosomic additive. The presence of a locus involved in GTS in the 2p11 region has been rejected.

CONCLUSION

The linkage values for D20S1085 and D6S477 markers are suggestive and therefore it is not possible reject that these markers will be in linkage disequilibrium with genes involved in the GTS, ADHD, OCD, MT, and PT etiology.

Repetitive transcranial magnetic stimulation (rTMS) in the treatment of obsessive-compulsive disorder (OCD) and Tourette's syndrome (TS)

There is evidence that motor and premotor cortex are hyperexcitable in obsessive-compulsive disorder (OCD) and Tourette's syndrome (TS). We tested whether low-frequency repetitive transcranial magnetic stimulation (rTMS) could normalize overactive motor cortical regions and thereby improve symptoms. Subjects with OCD or TS were treated with active rTMS to the supplementary motor area (SMA) for 10 daily sessions at 1 Hz, 100% of motor threshold, 1200 stimuli/day. Suggestions of clinical improvement were apparent as early as the first week of rTMS. At the second week of treatment, statistically significant reductions were seen in the YBOCS, YGTSS, CGI, HARS, HDRS, SAD, BDI, SCL-90, and SASS. Symptoms improvement was correlated with a significant increase of the right resting motor threshold and was stable at 3 months follow-up. Slow rTMS to SMA resulted in a significant clinical improvement and a normalization of the right hemisphere hyperexcitability, thereby restoring hemispheric symmetry in motor threshold.

Local-global processing in obsessive-compulsive disorder and comorbid Tourette's syndrome

Neuropsychological and neuroimaging studies implicate attentional difficulties in obsessive-compulsive disorder (OCD), but results are inconsistent due possibly to sample heterogeneity and lack of control of comorbid disorders, such as Tourette's syndrome (TS). Nevertheless, it has been suggested that OCD symptomatology may be a result of over-focused attention at a local level. Therefore, this study aimed to examine the ability of OCD patients (pure and comorbid OCD + TS) to process local and global stimuli. Using a local-global paradigm, participants were required to respond to the directed level (local or global) of various stimuli. Results indicate that pure OCD participants were impaired on the global task, whereas comorbid OCD + TS participants had difficulty processing local information. Results are consistent with previously reported lateralisation anomalies and suggest that OCD negatively affects the ability to process hierarchically presented stimuli.

The relationship of working memory, inhibition, and response variability in child psychopathology

INTRODUCTION

The aim of this study was to investigate the relationship between working memory and inhibition in children with attention deficit hyperactivity disorder (ADHD), high-functioning autism (HFA), and Tourette syndrome (TS), compared to normally developing children. Furthermore, the contribution of variation in processing speed on working memory and inhibition was investigated in these childhood psychopathologies.

METHOD

Four groups of children are reported in this study: 65 children with ADHD, 66 children with HFA, 24 children with TS, and 82 normal control children. All children were in the age range of 6-13 years.

RESULTS

The relationship between working memory and inhibition was similar in children with ADHD, HFA, TS, and normally developing children. The relationship between both domains did not alter significantly for any of the groups, when variation in processing speed was taken into account. More symptoms of hyperactivity/impulsivity are related to a poorer inhibitory process and greater response variability. More symptoms of autism are related to a poorer working memory process.

CONCLUSION

The current study showed that working memory, inhibition, and response variability, are distinct, but related cognitive domains in children with developmental psychopathologies. Research with experimental manipulations is needed to tackle the exact relationship between these cognitive domains.

Patient selection and assessment recommendations for deep brain stimulation in Tourette syndrome

In response to recent publicity regarding the potential use of deep brain stimulation (DBS) for reducing tic severity in Tourette's syndrome (TS), the Tourette Syndrome Association convened a group of TS and DBS experts to develop recommendations to guide the early use and potential clinical trials of DBS for TS and other tic disorders. The goals of these recommendations are to ensure that all surgical candidates are (1) fully informed about the risks, benefits, and alternative treatments available; (2) receive a comprehensive evaluation before surgery to ensure that DBS is clearly the appropriate clinical treatment choice; and (3) that early clinical experience will be documented publicly to facilitate rational decision-making for both clinical care and future clinical trials.

Preclinical models relevant to Tourette syndrome

Preclinical models, if used appropriately, can greatly accelerate the understanding of neuropsychiatric disorders. A number of animal models have predictive validity for antidopaminergic compounds that have traditionally been used to suppress motor and vocal tics in TS. Other models have been proposed that may have construct validity for specific hypotheses of infectious/immune and neural circuit etiologies of TS. A more comprehensive set of models is described, based on the hypothesis that primary symptoms of TS, including sensory tics and premonitory urges, result from dysfunction in brain mechanisms that regulate sensorimotor gating. These models utilize operational measures of central gating mechanisms, including PPI of the startle reflex, to achieve predictive validity across a number of different chemical classes of drugs, and to achieve construct validity across broad domains of neurodevelopmental, immune and genetic etiologies of TS. PPI-based animal models offer a number of strong advantages for predictive and mechanistic studies of TS. Ultimately, the utility of these "deficient gating" models will be judged by their ability to bring us closer to identifying the causes and effective treatments of this disorder.

Abnormal thalamic volume in treatment-naïve boys with Tourette syndrome

OBJECTIVE

Thalamic abnormality has been implicated in the pathophysiology of Tourette's syndrome (TS). We examined the presence of aberrant thalamic volume from the treatment-naïve boys with TS using magnetic resonance imaging (MRI).

METHOD

Volumetric MRI was performed on 18 treatment-naïve boys with TS, aged 7-14 years, and 16 healthy comparison subjects. The anatomical boundaries were then manually parcellated to measure the thalamic volume.

RESULTS

Tourette's syndrome subjects had a significantly larger left thalamus in comparison with those of healthy subjects. On the contrary, no group difference was observed from the right thalamic volume. TS subjects also showed a significant reduction in rightward asymmetry in thalamic volume compared with the healthy subjects.

CONCLUSION

Our findings provide new evidence of abnormal thalamic volume in pediatric TS.