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

Electrophysiological manifestations of stimulus evaluation, response inhibition and motor processing in Tourette syndrome patients

Gilles de la Tourette syndrome (GTS) is a neuropsychiatric disorder with childhood onset presenting with multiple fluctuating motor tics and one or more phonic tics. A significant proportion of people suffering from GTS are still symptomatic in adulthood and present other emotional and cognitive difficulties, along with motor problems that often accompany these comorbid conditions. The nature of these difficulties is still poorly understood and multiple comorbidities are often inadequately controlled. The current study investigates both stimulus evaluation and motor processing in GTS while controlling for comorbidity. Fifteen adults with GTS and 20 control participants were matched on gender, laterality and intelligence. The P300 component, the no-go anteriorization (NGA) as well as the stimulus and response-locked lateralized-readiness potentials (S-LRP, R-LRP) were elicited during a stimulus-response compatibility (SRC) paradigm. The standard version of the Stroop Color-Word Test (SCWT) was also administered. Reaction times showed that participants with GTS processed both the SRC and the SCWT more rapidly than the control group, while producing a delayed P300 peak latency. The GTS group also showed faster S-LRP onset in response to the incompatible and faster processing of interference in the SCWT. There was also a tendency toward a greater frontal shift of the NGA in the GTS group. The P300 latency showed that with GTS patients, stimulus evaluation occurs later whereas the overlapping pre-motor response selection processes occur faster. Our findings are congruent with a probable cortical motor over-activation hypothesis of GTS involving faster motor program selection in processing conflicting SR configuration.

Randomized trial of anger control training for adolescents with Tourette's syndrome and disruptive behavior

OBJECTIVE

To evaluate the efficacy of a 10-session individually administered anger control training (ACT) for adolescents with Tourette's syndrome (TS) and disruptive behavior.

METHOD

Twenty-six subjects (24 boys and 2 girls; mean age 12.7 years, SD 0.88) with TS and high levels of disruptive behavior were randomly assigned to ACT or treatment-as-usual (TAU). The parent-rated Disruptive Behavior Rating Scale and the Clinical Global Impression-Improvement Scale rated by the independent evaluator were used as primary outcome measures.

RESULTS

All randomized subjects completed end-point evaluation, and all subjects in the ACT group completed 3-month follow-up evaluation. The Disruptive Behavior Rating Scale score decreased by 52% in the ACT group compared with a decrease of 11% in the TAU control group (p <.001). On the Clinical Global Impression-Improvement Scale, the independent evaluator rated 9 (69%) of 13 subjects in the ACT condition as much improved or very much improved compared with 2 (15%) of 13 in the TAU condition (p <.01). This reduction of disruptive behavior in the ACT group was well maintained at 3-month follow-up.

CONCLUSIONS

Anger control training seems to reduce disruptive behavior in adolescents with TS. Larger trials are needed to confirm these results.Clinical trial registration information-Anger Control Training for Youth With Tourette's Syndrome. URL: http://www.clinicaltrials.gov. Unique identifier: NCT00486551.

Brain areas coactivating with motor cortex during chronic motor tics and intentional movements

BACKGROUND

Chronic tic disorders are characterized by motor tics that are often preceded by premonitory urges to tic. Functional neuroimaging studies have documented brain activity patterns prior to and during tics, but these studies have not examined whether the activation patterns differ from those seen in normal control subjects performing similar acts.

METHODS

A novel method was used to compare brain patterns during tics and intentional movements. First, the part of motor cortex specific to each patient's tic movement was identified. The brain areas activating prior to, during, and after that part of motor cortex during tics were then identified by temporally cross-correlating the time course of the localized motor region with activity in other brain areas. Given that motor cortex was active during tic execution, this yielded information regarding the brain areas active prior to, during, and after the movements. The spatiotemporal pattern of coactivation with motor cortex during tics was contrasted with that seen in healthy control subjects during intentional tic-like movements.

RESULTS

Data from 16 adult subjects with tic disorders and 16 matched control subjects, who performed intentional movements similar to the patients' tics, revealed nearly identical patterns of cross-correlation to motor cortex throughout the brain in the two groups. However, the supplementary motor area showed a significantly broader profile of cross-correlation to motor cortex during tics than during intentional movements.

CONCLUSIONS

These findings highlight the importance of the supplementary motor area in tic generation and may point toward novel intervention strategies for individuals suffering with severe tics.

Developmentally regulated and evolutionarily conserved expression of SLITRK1 in brain circuits implicated in Tourette syndrome

Tourette syndrome (TS) is an inherited developmental neuropsychiatric disorder characterized by vocal and motor tics. Multiple lines of neurophysiological evidence implicate dysfunction in the corticostriatal-thalamocortical circuits in the etiology of TS. We recently identified rare sequence variants in the Slit and Trk-like family member 1 (SLITRK1) gene associated with TS. SLITRK1, a single-pass transmembrane protein, displays similarities to the SLIT family of secreted ligands, which have roles in axonal repulsion and dendritic patterning, but its function and developmental expression remain largely unknown. Here we provide evidence that SLITRK1 has a developmentally regulated expression pattern in projection neurons of the corticostriatal-thalamocortical circuits. SLITRK1 is further enriched in the somatodendritic compartment and cytoplasmic vesicles of cortical pyramidal neurons in mouse, monkey, and human brain, observations suggestive of an evolutionarily conserved function in mammals. SLITRK1 is transiently expressed in the striosomal/patch compartment of the mammalian striatum and moreover is associated with the direct output pathway; adult striatal expression is confined to cholinergic interneurons. These analyses demonstrate that the expression of SLITRK1 is dynamic and specifically associated with the circuits most commonly implicated in TS and related disorders, suggesting that SLITRK1 contributes to the development of corticostriatal-thalamocortical circuits.

Brain oscillations forever--neurophysiology in future research of child psychiatric problems

For decades neurophysiology has successfully contributed to research and clinical care in child psychiatry. Recently, methodological progress has led to a revival of interest in brain oscillations (i.e., a band of periodic neuronal frequencies with a wave-duration from milliseconds to several seconds which may code and decode information). These oscillations will nurture future information processing research during normal and pathological brain development, allowing us to investigate basic neuronal connectivity as well as interactions of brain systems and their modulation (e.g., by temporal neuronal synchronisation) as close correlates of behaviour and intermediate phenotypes from genes to behavioural variations. Especially, a systematic neurodynamic look at transitional processes from rest to stimulus-triggered goal-directed performance will aid behavioural understanding and guidance of children. Preliminary data suggest two separate oscillatory mechanisms in this respect. One is ongoing from pre- to post-stimulus processing and related to quantitative modification of behaviour, while another is merely related to qualitative effects of behaviour and reflects 'on-top' post-stimulus processing by temporal neuronal synchronisation of the oscillatory network in question. Suggested neurodynamic models may be tested in multilevel clinical experiments as well as in the framework of computational neuropsychiatry.

Control networks in paediatric Tourette syndrome show immature and anomalous patterns of functional connectivity

Tourette syndrome (TS) is a developmental disorder characterized by unwanted, repetitive behaviours that manifest as stereotyped movements and vocalizations called ‘tics’. Operating under the hypothesis that the brain's control systems may be impaired in TS, we measured resting-state functional connectivity MRI (rs-fcMRI) between 39 previously defined putative control regions in 33 adolescents with TS. We were particularly interested in the effect of TS on two of the brain's task control networks—a fronto-parietal network likely involved in more rapid, adaptive online control, and a cingulo-opercular network apparently important for set-maintenance. To examine the relative maturity of connections in the Tourette subjects, functional connections that changed significantly over typical development were examined. Age curves were created for each functional connection charting correlation coefficients over age for 210 healthy people aged 7–31 years, and the TS group correlation coefficients were compared to these curves. Many of these connections were significantly less ‘mature’ than expected in the TS group. This immaturity was true not only for functional connections that grow stronger with age, but also for those that diminish in strength with age. To explore other differences between Tourette and typically developing subjects further, we performed a second analysis in which the TS group was directly compared to an age-matched, movement-matched group of typically developing, unaffected adolescents. A number of functional connections were found to differ between the two groups. For these identified connections, a large number of connectional differences were found where the TS group value was out of range compared to typical developmental age curves. These anomalous connections were primarily found in the fronto-parietal network, thought to be important for online adaptive control. These results suggest that in adolescents with TS, immature functional connectivity is widespread, with additional, more profound deviation of connectivity in regions related to adaptive online control.

Interactions between cortical rhythms and spiking activity of single basal ganglia neurons in the normal and parkinsonian state

In order to evaluate the specific interactions between cortical oscillations and basal ganglia-spiking activity under normal and parkinsonian conditions, we examined the relationship between frontal cortex electroencephalographic (EEG) signals and simultaneously recorded neuronal activity in the internal and external segments of the pallidum or the subthalamic nucleus (STN) in 3 rhesus monkeys. After we made recordings in the normal state, hemiparkinsonism was induced with intracarotid injections of the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in one animal, followed by additional recordings. Spiking activity in the pallidum and STN was associated with significant shifts in the level of EEG synchronization. We also found that the spectral power of beta- and gamma-band EEG rhythms covaried positively before the basal ganglia spikes but did not covary or covaried negatively thereafter. In parkinsonism, changes in cortical synchronization and phase coherence were reduced in EEG segments aligned to STN spikes, whereas both were increased in data segments aligned to pallidal spikes. Spiking-related changes in beta/gamma-band covariance were reduced. The findings indicate that basal ganglia and cortex interact in the processing of cortical rhythms that contain oscillations across a broad range of frequencies and that this interaction is severely disrupted in parkinsonism.

Voluntary motor drive: possible reduction in Tourette syndrome

Electrophysiologically, Tourette syndrome (TS) is characterized by shortened cortical silent period (CSP), reflecting decreased motor inhibition. However, voluntary versus involuntary aspects of inhibitory functions in TS are not well understood. Hence, investigating voluntary motor drive (VMD) could help to elucidate this issue. A group of 14 healthy adolescents was compared with subjects of same age suffering from TS with (N = 6) and without (N = 6) presence of distal tics. Basic resting and active motor thresholds (RMT and AMT, respectively) as well as suprathreshold transcranial magnetic stimulation-conditioned RMT and AMT were determined during the CSP. The difference between AMT and RMT was considered as VMD quantum. No group-differences were found in RMT or AMT. Subjects with distal tics showed reduced VMD compared to healthy controls while patients without distal tics did not differ from controls. In the second half of CSP, patients with distal tics showed also diminished VMD compared to tic-patients without distal tics. The findings support the notion, that TS shows possible reduction of VMD and is associated with central motor threshold alterations confined to the very motor networks related to the tics observed.

Deficiency in inhibitory cortical interneurons associates with hyperactivity in fibroblast growth factor receptor 1 mutant mice

BACKGROUND

Motor hyperactivity due to hyper-dopaminergic neurotransmission in the basal ganglia is well characterized; much less is known about the role of the neocortex in controlling motor behavior.

METHODS

Locomotor behavior and motor, associative, and spatial learning were examined in mice with conditional null mutations of fibroblast growth factor receptor 1 (Fgfr1) restricted to telencephalic neural precursors (Fgfr1(f/f;hGfapCre)). Locomotor responses to a dopamine agonist (Amphetamine 2 mg/kg and Methylphenidate 10 mg/kg) and antagonists (SCH233390 .025 mg/kg and Haloperidol .2 mg/kg) were assessed. Stereological and morphological characterization of various monoaminergic, excitatory, and inhibitory neuronal subtypes was performed.

RESULTS

Fgfr1(f/f;hGfapCre) mice have spontaneous locomotor hyperactivity characterized by longer bouts of locomotion and fewer resting points that is significantly reduced by the D1 and D2 receptor antagonists. No differences in dopamine transporter, tyrosine hydroxylase, or serotonin immunostaining were observed in Fgfr1(f/f;hGfapCre) mice. There was no change in cortical pyramidal neurons, but parvalbumin+, somatostatin+, and calbindin+ inhibitory interneurons were reduced in number in the cerebral cortex. The decrease in parvalbumin+ interneurons in cortex correlated with the extent of hyperactivity.

CONCLUSIONS

Dysfunction in specific inhibitory cortical circuits might account for deficits in behavioral control, providing insights into the neurobiology of psychiatric disorders.

Deep brain stimulation in Tourette's syndrome

A 48-year-old man with severe, lifelong Tourette's syndrome (TS) characterized by forceful self-injurious motor tics and obsessive-compulsive disorder was treated with bilateral deep brain stimulation (DBS). The decision to treat was based on his progressive neurological impairment (left sided weakness secondary to spinal cord injury) because of his relentless, violent head jerks. Electrodes were implanted at the level of the medial part of the thalamus (centromedian nucleus, the substantia periventricularis, and the nucleus ventro-oralis internus). DBS resulted in a substantial reduction of tics. These data show that bilateral DBS of the thalamus can have a good effect on severe tics in adult patients suffering from intractable TS.

Is onset of Tourette syndrome influenced by life events?

The aim of this study is to investigate the possible relationship between stressful life events, personality, and onset of Tourette syndrome in children. The study group included 93 subjects aged 7-18 years: 41 with Tourette syndrome (TS), 28 with obsessive-compulsive disorder (OCD), and 24 healthy controls. Diagnoses were based on the Child Schedule for Schizophrenia and Affective Disorders (K-SADS). All children were tested with the Screen for Child Anxiety Related Emotional Disorders, Children's Yale Brown Obsessive Compulsive Scale, Beck Depression Inventory or Children's Depression Inventory, the Life Experience Survey, and the Junior Temperament and Character Inventory. The findings were compared among the groups. Subjects with Tourette syndrome and healthy controls had significantly less stressful life events than subjects with (OCD). There were no significant differences between the TS subjects and the healthy controls. This finding applied to total lifetime events, total lifetime negative events, and events in the year before and after illness onset. Subjects with TS and the healthy controls also showed a significantly lesser impact of life events than subjects with OCD. The Tourette syndrome group showed a significantly lesser impact of stressful life events than controls. Harm avoidance tended to be higher in the patients with Tourette syndrome and comorbid attention deficit hyperactivity disorder and obsessive-compulsive disorder than in patients with Tourette syndrome only. There seemed to be no association between life events, diagnosis, and personality. Although there is some research suggesting that tics can be influenced by the environment, the onset of Tourette syndrome does not seem to be related to stressful life events, nor to an interaction between stressful life events and personality.

Attentional functions in children and adolescents with attention-deficit/hyperactivity disorder with and without comorbid tic disorder

Although the coexistence of attention-deficit/hyperactivity disorder (ADHD) and tic disorder (TD) is common, the nature of association is yet not fully understood. Thus, the aim of the present study was to explore attentional dysfunction in children with pure ADHD compared to children with comorbid ADHD + TD. Three groups of 20 children each, aged 8-15 years with either ADHD, ADHD + chronic tic disorder or Tourette syndrome (ADHD + TD) and a healthy control group were compared in their performance on three computerized attention tasks. Tasks of sustained attention, selective attention and interference control were employed. In addition, parental ratings of ADHD symptom severity and behaviour problems were obtained. Both clinical groups were rated as equally inattentive, however, externalising symptoms were more severe in the ADHD group. Objective measures of attentional performance revealed differences between the groups: whereas the ADHD group was markedly impaired in sustaining attention and selective attention/inhibitory control, the ADHD + TD group only showed marginal deficits in selective attention/inhibitory control. Possible explanations for the superior performance of the comorbid group are discussed: In particular, the results may indicate that in some patients, the tic disorder produces behavioural symptoms of ADHD, but not the broad neurocognitive deficits that usually are associated with ADHD. Alternatively, compensatory neural mechanisms of TD patients may result in a better neuropsychological performance of comorbid patients relative to patients suffering from pure ADHD.

Tourette syndrome and tic disorders: a decade of progress

OBJECTIVE

This is a review of progress made in the understanding of Tourette syndrome (TS) during the past decade including models of pathogenesis, state-of-the-art assessment techniques, and treatment.

METHOD

Computerized literature searches were conducted under the key words "Tourette syndrome," "Tourette disorder," and "tics." Only references from 1996-2006 were included.

RESULTS

Studies have documented the natural history of TS and the finding that tics usually improve by the end of the second decade of life. It has also become clear that TS frequently co-occurs with attention-deficit/hyperactivity disorder), obsessive-compulsive disorder, and a range of other mood and anxiety disorders. These comorbid conditions are often the major source of impairment for the affected child. Advances have also been made in understanding the underlying neurobiology of TS using in vivo neuroimaging and neurophysiology techniques. Progress on the genetic front has been less rapid. Proper diagnosis and education (involving the affected child and his or her parents, teachers, and peers) are essential prerequisites to the successful management of children with TS. When necessary, modestly effective antitic medications are available, although intervening to treat the comorbid attention-deficit/hyperactivity disorder and/or obsessive-compulsive disorder is usually the place to start.

CONCLUSIONS

Prospective longitudinal studies and randomized clinical trials have led to the refinement of several models of pathogenesis and advanced our evidence base regarding treatment options. However, fully explanatory models are needed that would allow for more accurate prognosis and the development of targeted and efficacious treatments.

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.

Comorbidity of tic disorders & ADHD: conceptual and methodological considerations

BACKGROUND

The causes and pathophysiological mechanisms of the common comorbidity of tic disorders and Attention-deficit/Hyperactivity disorder (TD + ADHD; about 50% of TD, about 20% of ADHD) still remain unclear. Studies with a 2 x 2 design comparing groups of children with TD, ADHD, TD + ADHD and healthy controls are in need and may disentangle the influences of TD versus ADHD in the case of comorbidity. Unfortunately, conceptual and methodological problems can restrain possible conclusions from these studies.

METHOD

A review of the literature on artifactual and non-artifactual models of comorbidity in general and specially for TD + ADHD was conducted.

RESULTS

The first section describes various possible models of comorbidity and their corresponding hypotheses concerning expected patterns of findings comparing groups of children with TD, ADHD, TD + ADHD and healthy controls. In the second part research results concerning psychopathological, neuropsychological, neurophysiological, structural and functional imaging, as well as genetic characteristics are summarized. In the third section possible conclusions and their limitations due to conceptual and methodological problems possibly contributing to the ambiguous results are discussed. Finally, future research strategies and the need for full causal models are outlined.

CONCLUSION

Some components of the etiological pathways of TD + ADHD may well be shared with the 'pure' conditions while others may be unique.

Sleep patterns in children with attention-deficit/hyperactivity disorder, tic disorder, and comorbidity

BACKGROUND

In children, attention-deficit/hyperactivity disorder (ADHD), tic disorder (TD), and their coexistence (ADHD + TD comorbidity) are very common and clinically important. Associated sleep patterns and their clinical role are still insufficiently investigated. This study aimed at characterizing these sleep patterns in children with ADHD, TD, and ADHD + TD comorbidity and determining whether, in ADHD + TD, the factors ADHD and TD may affect the sleep pattern in an independent (additive) or in a complex (interactive) manner.

METHOD

By means of polysomnography, sleep patterns were investigated in 4 groups of unmedicated 8.0-16.4-year-old children (healthy controls, ADHD-only, TD-only, and ADHD + TD). Each group consisted of 18 subjects matched for age, gender, and intelligence.

RESULTS

ADHD was primarily characterized by increase in rapid eye movement (REM) sleep, whereas TD patients displayed lower sleep efficiency and elevated arousal index in sleep. In children with ADHD + TD, both effects appeared. No interaction between the ADHD and TD factors was found for any of the sleep parameters. Significant correlations between sleep patterns and clinical symptoms were found.

CONCLUSIONS

ADHD and TD are characterized by specific sleep alterations. When coexisting, the two disorders alter the sleep pattern in an additive manner, suggesting a high impact on clinical and therapeutic perspectives.

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).

Co-existence of tic disorders and attention-deficit/hyperactivity disorder-recent advances in understanding and treatment

In daily clinical practice of child psychiatry tic disorders (TD) and attention-deficit/hyperactivity disorder (ADHD) as well as their co-existence are common and need careful evidence-based approaches in differential diagnostics and treatment choice. Hence, their relationship at different levels (e.g., psychopathology, neuropsychology, neurobiology, treatment) needs to be elucidated in more detail. The articles of this supplement deal with this subject. It is unclear if TD + ADHD represents an own clinical entity and which component (TD vs. ADHD) is most important in case of co-existence with respect to accompanying problems like emotional or cognitive disturbances. This editorial gives a short overview of the essential research topics concerning TD + ADHD and shows where (in this ECAP supplement and other literature) empirically based answers can be found. Probably, the identification of separate or common "endophenotypes" for TD-only, ADHD-only and for TD + ADHD would help to sort out the complexities and this supplement may nurture such a perspective of future research for a better understanding and treatment of youths with TD + ADHD and their families.

Behavior therapy in tic-disorders with co-existing ADHD

OBJECTIVES

To give an overview concerning the behavioral treatment approaches for Chronic Tic Disorder (CTD) and Attention-Deficit/Hyperactivity Disorder (ADHD) and to provide some suggestions for the behavioral treatment of children and adolescents with a combination of both disorders.

RESULTS

Pharmacotherapy plays an important role in the treatment of both ADHD and CTD. However, behavior therapy has also been proven to ameliorate the core symptoms of both disorders. The most prominent behavioral technique to reduce tics is habit reversal training. In ADHD behavioral interventions, especially parent training and behavioral interventions in preschool/school, are effective in reducing ADHD core symptoms and comorbid problems. In children and adolescents with ADHD plus CTD both ADHD and tic symptoms can be treated by behavioral interventions alone or in combination with pharmacotherapy. However, most of the published studies on behavioral interventions in children with ADHD or CTD do not give detailed information on comorbidity and many studies excluded patients with comorbid problems.

CONCLUSIONS

Clinical experience suggests that in CTD+ADHD success may be easier to achieve using behavioral treatment of ADHD first. Adherence to the habit reversal procedure to reduce tics in daily living is the most important problem in the behavioral treatment of tics especially in children with comorbid ADHD. Practical suggestions to overcome these difficulties are presented.

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.

Annotation: what electrical brain activity tells us about brain function that other techniques cannot tell us - a child psychiatric perspective

BACKGROUND

Monitoring brain processes in real time requires genuine subsecond resolution to follow the typical timing and frequency of neural events. Non-invasive recordings of electric (EEG/ERP) and magnetic (MEG) fields provide this time resolution. They directly measure neural activations associated with a wide variety of brain states and processes, even during sleep or in infants. Mapping and source estimation can localise these time-varying activation patterns inside the brain.

METHODS

Recent EEG/ERP research on brain functions in the domains of attention and executive functioning, perception, memory, language, emotion and motor processing in ADHD, autism, childhood-onset schizophrenia, Tourette syndrome, specific language disorder and developmental dyslexia, anxiety, obsessive-compulsive disorder, and depression is reviewed.

RESULTS

Over the past two decades, electrophysiology has substantially contributed to the understanding of brain functions during normal development, and psychiatric conditions of children and adolescents. Its time resolution has been important to measure covert processes, and to distinguish cause and effect.

CONCLUSIONS

In the future, EEG/ERP parameters will increasingly characterise the interplay of neural states and information processing. They are particularly promising tools for multilevel investigations of etiological pathways and potential predictors of clinical treatment response.

Neurobiologie bei Tic- und Zwangsstörungen

Zusammenfassung. Erst in den letzten Jahren wird auch in der Forschung vermehrtes Augenmerk auf die Überschneidung von Tic- und Zwangsstörungen gerichtet. Während in Übersichtsarbeiten zum gemeinsamen Auftreten von Tic- und Zwangsstörungen die zahlreichen Befunde zu Phänomenologie, begleitender Psychopathologie, Epidemiologie und daraus resultierenden Therapieimplikationen breiten Raum einnehmen, sind die Untersuchungsergebnisse hinsichtlich ätiologischer und pathophysiologischer Gemeinsamkeiten in entsprechenden Arbeiten unterrepräsentiert. Daher wird mit dieser Arbeit ein Überblick über den aktuellen neurobiologischen Forschungsstand zu den Gemeinsamkeiten und Unterschieden von Tic- und Zwangsstörungen gegeben.

Annotation: neurofeedback - train your brain to train behaviour

BACKGROUND

Neurofeedback (NF) is a form of behavioural training aimed at developing skills for self-regulation of brain activity. Within the past decade, several NF studies have been published that tend to overcome the methodological shortcomings of earlier studies. This annotation describes the methodical basis of NF and reviews the evidence base for its clinical efficacy and effectiveness in neuropsychiatric disorders.

METHODS

In NF training, self-regulation of specific aspects of electrical brain activity is acquired by means of immediate feedback and positive reinforcement. In frequency training, activity in different EEG frequency bands has to be decreased or increased. Training of slow cortical potentials (SCPs) addresses the regulation of cortical excitability.

RESULTS

NF studies revealed paradigm-specific effects on, e.g., attention and memory processes and performance improvements in real-life conditions, in healthy subjects as well as in patients. In several studies it was shown that children with attention-deficit hyperactivity disorder (ADHD) improved behavioural and cognitive variables after frequency (e.g., theta/beta) training or SCP training. Neurophysiological effects could also be measured. However, specific and unspecific training effects could not be disentangled in these studies. For drug-resistant patients with epilepsy, significant and long-lasting decreases of seizure frequency and intensity through SCP training were documented in a series of studies. For other child psychiatric disorders (e.g., tic disorders, anxiety, and autism) only preliminary investigations are available.

CONCLUSIONS

There is growing evidence for NF as a valuable treatment module in neuropsychiatric disorders. Further, controlled studies are necessary to establish clinical efficacy and effectiveness and to learn more about the mechanisms underlying successful training.

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.