Cerebellar transcranial current stimulation – An intraindividual comparison of different techniques

Transcranial current stimulation (tCS) techniques have been shown to induce cortical plasticity. As an important relay in the motor system, the cerebellum is an interesting target for plasticity induction using tCS, aiming to modulate its excitability and connectivity. However, until now it remains unclear, which is the most effective tCS method for inducing plasticity in the cerebellum. Thus, in this study, the effects of anodal transcranial direct current stimulation (tDCS), 50 Hz transcranial alternating current stimulation (50 Hz tACS), and high frequency transcranial random noise stimulation (tRNS) were compared with sham stimulation in 20 healthy subjects in a within-subject design. tCS was applied targeting the cerebellar lobe VIIIA using neuronavigation. We measured corticospinal excitability, short-interval intracortical inhibition (SICI), short-latency afferent inhibition (SAI), and cerebellar brain inhibition (CBI) and performed a sensor-based movement analysis at baseline and three times after the intervention (post1 = 15 min; post2 = 55 min; post3 = 95 min). Corticospinal excitability increased following cerebellar tACS and tRNS compared to sham stimulation. This effect was most pronounced directly after stimulation but lasted for at least 55 min after tACS. Cortico-cortical and cerebello-cortical conditioning protocols, as well as sensor-based movement analyses, did not change. Our findings suggest that cerebellar 50 Hz tACS is the most effective protocol to change corticospinal excitability.

Characterizing the temporal discrimination threshold in musician's dystonia

The temporal discrimination threshold (TDT) has been established as a biomarker of impaired temporal processing and endophenotype in various forms of focal dystonia patients, such as cervical dystonia, writer's cramp or blepharospasm. The role of TDT in musician's dystonia (MD) in contrast is less clear with preceding studies reporting inconclusive results. We therefore compared TDT between MD patients, healthy musicians and non-musician controls using a previously described visual, tactile, and visual-tactile paradigm. Additionally, we compared TDT of the dystonic and non-dystonic hand and fingers in MD patients and further characterized the biomarker regarding its potential influencing factors, i.e. musical activity, disease variables, and personality profiles. Repeated measures ANOVA and additional Bayesian analyses revealed lower TDT in healthy musicians compared to non-musicians. However, TDTs in MD patients did not differ from both healthy musicians and non-musicians, although pairwise Bayesian t-tests indicated weak evidence for group differences in both comparisons. Analyses of dystonic and non-dystonic hands and fingers revealed no differences. While in healthy musicians, age of first instrumental practice negatively correlated with visual-tactile TDTs, TDTs in MD patients did not correlate with measures of musical activity, disease variables or personality profiles. In conclusion, TDTs in MD patients cannot reliably be distinguished from healthy musicians and non-musicians and are neither influenced by dystonic manifestation, musical activity, disease variables nor personality profiles. Unlike other isolated focal dystonias, TDT seems not to be a reliable biomarker in MD.

Diagnosis and classification of blepharospasm: Recommendations based on empirical evidence

BACKGROUND

Blepharospasm is one of the most common subtypes of dystonia, and often spreads to other body regions. Despite published guidelines, the approach to diagnosis and classification of affected body regions varies among clinicians.

OBJECTIVE

To delineate the clinical features used by movement disorder specialists in the diagnosis and classification of blepharospasm according to body regions affected, and to develop recommendations for a more consistent approach.

METHODS

Cross-sectional data for subjects diagnosed with all types of isolated dystonia were acquired from the Dystonia Coalition, an international, multicenter collaborative research network. Data were evaluated to determine how examinations recorded by movement disorder specialists were used to classify blepharospasm as focal, segmental, or multifocal.

RESULTS

Among all 3222 participants with isolated dystonia, 210 (6.5%) had a diagnosis of focal blepharospasm. Among these 210 participants, 34 (16.2%) had dystonia outside of upper face region. Factors such as dystonia severity across different body regions and number of body regions affected influenced the classification of blepharospasm as focal, segmental, or multifocal.

CONCLUSIONS

Although focal blepharospasm is the second most common type of dystonia, a high percentage of individuals given this diagnosis had dystonia outside of the eye/upper face region. These findings are not consistent with existing guidelines for the diagnosis and classification of focal blepharospasm, and point to the need for more specific guidelines for more consistent application of existing recommendations for diagnosis and classification.

Detection of Traumatic and Postoperative Nerve Lesions following Upper Extremity Fractures in a Pediatric Cohort Using MR Neurography

INTRODUCTION

 Fractures of the upper extremity are common traumatic injuries in children. Nerve lesions are a rare but typical complication of these fractures. Additional to physical, electrophysiological, and sonographic examinations, magnetic resonance neurography (MRN) can be used to assess the degree and exact localization of nerve damage. This retrospective study was conducted to evaluate the potential role of this examination technique for children and to test a proposed MRN classification of traumatic nerve injury according to Chhabra in a pediatric cohort.

MATERIALS AND METHODS

 Pediatric patients undergoing MRN for traumatic nerve injury from January 2016 to December 2020 were retrospectively identified. A total of 12 consecutive patients with sufficient clinical data, an MRN, and if available follow-up examination were enrolled and analyzed.

RESULTS

 In 10 of 12 cases one or more nerve lesions could be identified by MRN using the classification proposed by Chhabra et al. MRN was used to assess nerve injuries, imaging results were compared with clinical course. Clinical follow-up examinations of 10 patients showed an overall good clinical recovery, even in one case with severe trauma and nerve surgery.

CONCLUSION

 MRN as a noninvasive procedure can help in the evaluation of nerve injury, especially for the identification of lower grade nerve damage and to objectify suspected nerve damage in case of uncertain clinical examination results; thus, can help in decision making whether surgical revision or conservative treatment is preferable.

Clinical relevance and translational impact of reduced penetrance in genetic movement disorders

Reduced penetrance is an important but underreported aspect in monogenic diseases. It refers to the phenomenon that carriers of pathogenic variants do not manifest with an overt disease. Clinical expressivity, on the other hand, describes the degree to which certain disease characteristics are present. In this article, we discuss the implications of reduced penetrance on genetic testing and counseling, outline how penetrance can be estimated in rare diseases using large cohorts and review the ethical, legal and social implications of studying non-manifesting carriers of pathogenic mutations. We highlight the interplay between reduced penetrance and the prodromal phase of a neurodegenerative disorder through the example of monogenic Parkinson's disease and discuss the therapeutic implications.

[Treatment of Sialorrhea with Botulinum Neurotoxin Type A - Consensus Practice Recommendations for Children and Adults]

Sialorrhea, uncontrolled, excessive drooling, accompanies different, mostly neurological disorders from childhood to adulthood. With incobotulinumtoxinA (Xeomin, IncoBoNT/A, Merz Pharmaceuticals GmbH), an approved medication for the treatment of sialorrhea has been available since 2019. Patient selection, possible therapy goals, treatment and the management of specific treatment situations build the focus of this interdisciplinary expert consensus recommendations with the intent to facilitate access to treatment and to contribute to qualified botulinum toxin therapy.

[Therapy of Sialorrhea with Botulinum Toxin - An Update]

The most important salivary glands are the paired parotid and submandibular glands. Adults produce 1 to 1.5 liters of saliva which are then regularly swallowed. When the act of swallowing is disturbed, salivation occurs. More rarely, the cause can be found in increased saliva production, for example, when caused through medication. Sialorrhea impairs the quality of life substantially and is frequently often socially stigmatizing. Therapy includes conservative measures such as functional dysphagia therapy, oral or transdermal application of anticholinergics, as well as, in selected cases, radiation and surgical measures. Over the last 20 years, local injection of botulinum toxin has been successfully applied in the treatment of this condition. With approval of incobotulinumtoxinA toxin for children and adults, this procedure will become the therapy of choice for chronic sialorrhea. The results of the phase III registration trials have demonstrated high efficacy and good safety of the injection treatment in both children and adults.

Longitudinal evaluations of somatosensory-motor inhibition in Dopa-responsive dystonia

INTRODUCTION

GCH1 mutations have been linked to decreased striatal dopamine and development of dopa-responsive dystonia (DRD) and Parkinsonism. Sensory and sensorimotor integration impairments have been documented in various forms of dystonia. DRD patients with confirmed GCH1 mutations have demonstrated normal short-latency afferent inhibition (SAI), a measure of sensorimotor inhibition, under chronic dopaminergic replacement therapy (DRT), but reduced inhibition after a single l-dopa dose following 24 h withdrawal. Studies have revealed normal SAI in other forms of dystonia but reductions with DRT in Parkinson's disease. Longitudinal changes in sensorimotor inhibition are unknown.

METHODS

We analyzed sensorimotor inhibition using two different measures: SAI and somatosensory-motor inhibition using dual-site transcranial magnetic stimulation (ds-TMS). SAI was measured using digit stimulation 25 ms prior to contralateral primary motor cortex (M1) TMS. DS-TMS was measured using TMS over the somatosensory cortex 1 or 2.5 ms prior to ipsilateral M1 stimulation. A total of 20 GCH1 mutation carriers and 20 age-matched controls were included in the study. SAI and ds-TMS were evaluated in GCH1 mutation carriers both OFF and ON DRT compared to controls. Furthermore, longitudinal changes of SAI were examined in a subset of the same individuals that were measured ∼five years earlier.

RESULTS

Neither SAI nor ds-TMS were significantly different in GCH1 mutation carriers relative to controls. No effects of DRT on SAI or ds-TMS were seen but SAI decreased over time in mutation carriers OFF DRT.

CONCLUSION

Our longitudinal results suggest changes in SAI that could be associated with plasticity changes in sensorimotor networks.

Questioning the definition of Tourette syndrome-evidence from machine learning

Tics in Tourette syndrome are often difficult to discern from single spontaneous movements or vocalizations in healthy people. In this study, videos of patients with Tourette syndrome and healthy controls were taken and independently scored according to the Modified Rush Videotape Rating Scale. We included n = 101 patients with Tourette syndrome (71 males, 30 females, mean age 17.36 years ± 10.46 standard deviation) and n = 109 healthy controls (57 males, 52 females, mean age 17.62 years ± 8.78 standard deviation) in a machine learning-based analysis. The results showed that the severity of motor tics, but not vocal phenomena, is the best predictor to separate and classify patients with Tourette syndrome and healthy controls. This finding questions the validity of current diagnostic criteria for Tourette syndrome requiring the presence of both motor and vocal tics. In addition, the negligible importance of vocalizations has implications for medical practice, because current recommendations for Tourette syndrome probably also apply to the large group with chronic motor tic disorders.

Predictive modeling of spread in adult-onset isolated dystonia: Key properties and effect of tremor inclusion

BACKGROUND AND PURPOSE

Several clinical and demographic factors relate to anatomic spread of adult-onset isolated dystonia, but a predictive model is still lacking. The aims of this study were: (i) to develop and validate a predictive model of anatomic spread of adult-onset isolated dystonia; and (ii) to evaluate whether presence of tremor associated with dystonia influences model predictions of spread.

METHODS

Adult-onset isolated dystonia participants with focal onset from the Dystonia Coalition Natural History Project database were included. We developed two prediction models, one with dystonia as sole disease manifestation ("dystonia-only") and one accepting dystonia OR tremor in any body part as disease manifestations ("dystonia OR tremor"). Demographic and clinical predictors were selected based on previous evidence, clinical plausibility of association with spread, or both. We used logistic regressions and evaluated model discrimination and calibration. Internal validation was carried out based on bootstrapping.

RESULTS

Both predictive models showed an area under the curve of 0.65 (95% confidence intervals 0.62-0.70 and 0.62-0.69, respectively) and good calibration after internal validation. In both models, onset of dystonia in body regions other than the neck, older age, depression and history of neck trauma were predictors of spread.

CONCLUSIONS

This predictive modeling of spread in adult-onset isolated dystonia based on accessible predictors (demographic and clinical) can be easily implemented to inform individuals' risk of spread. Because tremor did not influence prediction of spread, our results support the argument that tremor is a part of the dystonia syndrome, and not an independent or coincidental disorder.

Increased scale-free and aperiodic neural activity during sensorimotor integration-a novel facet in Tourette syndrome

Tourette syndrome is a common neurodevelopmental disorder defined by multiple motor and phonic tics. Tics in Tourette syndrome resemble spontaneously occurring movements in healthy controls and are therefore sometimes difficult to distinguish from these. Tics may in fact be mis-interpreted as a meaningful action, i.e. a signal with social content, whereas they lack such information and could be conceived a surplus of action or 'motor noise'. These and other considerations have led to a 'neural noise account' of Tourette syndrome suggesting that the processing of neural noise and adaptation of the signal-to-noise ratio during information processing is relevant for the understanding of Tourette syndrome. So far, there is no direct evidence for this. Here, we tested the 'neural noise account' examining 1/f noise, also called scale-free neural activity as well as aperiodic activity, in n = 74 children, adolescents and adults with Tourette syndrome and n = 74 healthy controls during task performance using EEG data recorded during a sensorimotor integration task. In keeping with results of a previous study in adults with Tourette syndrome, behavioural data confirmed that sensorimotor integration was also stronger in this larger Tourette syndrome cohort underscoring the relevance of perceptual-action processes in this disorder. More importantly, we show that 1/f noise and aperiodic activity during sensorimotor processing is increased in patients with Tourette syndrome supporting the 'neural noise account'. This implies that asynchronous/aperiodic neural activity during sensorimotor integration is stronger in patients with Tourette syndrome compared to healthy controls, which is probably related to abnormalities of GABAergic and dopaminergic transmission in these patients. Differences in 1/f noise and aperiodic activity between patients with Tourette syndrome and healthy controls were driven by high-frequency oscillations and not lower-frequency activity currently discussed to be important in the pathophysiology of tics. This and the fact that Bayesian statistics showed that there is evidence for the absence of a correlation between neural noise and clinical measures of tics, suggest that increased 1/f noise and aperiodic activity are not directly related to tics but rather represents a novel facet of Tourette syndrome.

An Integrated clinical pathway for diagnosis, treatment and care of rare diseases: model, operating procedures, and results of the project TRANSLATE-NAMSE funded by the German Federal Joint Committee

BACKGROUND

Diagnosis, treatment, and care of patients with rare diseases require multidisciplinary cooperation between medical and paramedical specialities and with patients and families. Innovative genetic diagnostics, whole exome and whole genome sequencing (WES, WGS) has enlarged the diagnostic toolkit but also increased the complexity of the endeavour. Structured multidisciplinary clinical pathways (CPW) can guide diagnosis, treatment, and care of patients with rare diseases, link scientific evidence to clinical practice and optimise clinical outcomes whilst maximising clinical efficiency.

RESULTS

In contrast to the common approach of appending disease-specific CPWs to disease-specific guidelines, we suggest a generic CPW manoeuvring the patient along the way of finding the correct diagnosis by applying the best diagnostic strategy into an appropriate system of treatment and care. Available guidelines can be integrated into the generic CPW in the course of its application. The approach also applies to situations where a diagnosis remains unsolved. The backbone of the generic CPW is a set of multidisciplinary structured case conferences projecting and evaluating diagnostic and/or therapeutic steps, enforcing to integrate best scientific evidence with clinical experience. The generic CPW is stated as a flowchart and a checklist which can be used to record and document parsimoniously the structure, process and results of a patient's pathway, but also as a data model for research. It was applied in a multicentre setting with 587 cases each with a presumptive diagnosis of a rare disease. In 369 cases (62.8%) a diagnosis could be confirmed, and multidisciplinary treatment and/or care was initiated. The median process time from first contact until confirmation of diagnosis by WES was 109 days and much shorter than diagnostic delays reported in the literature. Application of the CPW is illustrated by two case reports.

CONCLUSIONS

Our model is a tool to change the diagnostic odyssey into an organised and trackable route. It can also be used to inform patients and families about the stages of their individual route, to update health care providers only partially involved or attending specialised treatment and care, like the patient's or family's primary physician, and finally to train novices in the field.

Using Probabilistic Movement Primitives in Analyzing Human Motion Differences Under Transcranial Current Stimulation

In medical tasks such as human motion analysis, computer-aided auxiliary systems have become the preferred choice for human experts for their high efficiency. However, conventional approaches are typically based on user-defined features such as movement onset times, peak velocities, motion vectors, or frequency domain analyses. Such approaches entail careful data post-processing or specific domain knowledge to achieve a meaningful feature extraction. Besides, they are prone to noise and the manual-defined features could hardly be re-used for other analyses. In this paper, we proposed probabilistic movement primitives (ProMPs), a widely-used approach in robot skill learning, to model human motions. The benefit of ProMPs is that the features are directly learned from the data and ProMPs can capture important features describing the trajectory shape, which can easily be extended to other tasks. Distinct from previous research, where classification tasks are mostly investigated, we applied ProMPs together with a variant of Kullback-Leibler (KL) divergence to quantify the effect of different transcranial current stimulation methods on human motions. We presented an initial result with 10 participants. The results validate ProMPs as a robust and effective feature extractor for human motions.

Diagnostic criteria for blepharospasm: A multicenter international study

BACKGROUND

There are no widely accepted criteria to aid the physician in diagnosing BSP.

OBJECTIVE

To validate recently proposed diagnostic criteria for blepharospasm in a larger and geographically diverse population and to develop a screening system for blepharospasm.

METHODS

Video-recordings from 211 blepharospasm patients and 166 healthy/disease controls were examined by 8 raters. Agreement for presence of orbicularis oculi spasms, sensory trick, and increased blinking was measured by k statistics. Inability to voluntarily suppress the spasms was asked by the examiner but not captured in the video. Patients/controls were also requested to fill a self-administered questionnaire addressing relevant blepharospasm clinical aspects. The diagnosis at each site was the gold standard for sensitivity/specificity.

RESULTS

All the study items yielded satisfactory inter/intra-observer agreement. Combination of items rather than each item alone reached satisfactory sensitivity/specificity. The combined algorithm started with recognition of spasms followed by sensory trick. In the absence of a sensory trick, including "increased blinking" or "inability to voluntarily suppress the spasms" or both items yielded 88-92% sensitivity and 79-83% specificity. No single question of the questionnaire yielded high sensitivity/specificity. Serial application of the questionnaire to our blepharospasm and control subjects and subsequent clinical examination of subjects screening positive by the validated diagnostic algorithms yielded 78-81% sensitivity and 83-91% specificity.

CONCLUSION

These results support the use of proposed diagnostic criteria in multi-ethnic, multi-center cohorts. We also propose a case-finding procedure to screen blepharospasm in a given population with less effort than would be required by examination of all subjects.

Pandemic Tic-like Behaviors Following Social Media Consumption

BACKGROUND

Currently, there is a marked increase of young people with sudden onset of tic-like behaviors (TLBs) resembling movements and vocalizations presented on social media videos as "Tourette's syndrome."

OBJECTIVE

To delineate clinical phenomenology of TLBs after social media exposure in comparison with clinical features of Tourette's syndrome.

METHODS

We compared demographic and clinical variables between 13 patients with TLBs and 13 age- and sex-related patients with Tourette's syndrome.

RESULTS

Patients with TLBs had several characteristics allowing to distinguish them from patients with Tourette's syndrome, some of which discriminated perfectly (ie, abrupt symptom onset, lack of spontaneous symptom fluctuations, symptom deterioration in the presence of others) and some nearly perfectly (ie, predominantly complex movements involving trunk/extremities). Also, symptom onset was significantly later.

CONCLUSIONS

TLBs after social media consumption differ from tics in Tourette's syndrome, strongly suggesting that these phenomena are categorically different conditions. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Oromandibular Dystonia: A Clinical Examination of 2,020 Cases

Objective: The goal of this study is to better characterize the phenotypic heterogeneity of oromandibular dystonia (OMD) for the purpose of facilitating early diagnosis. Methods: First, we provide a comprehensive summary of the literature encompassing 1,121 cases. Next, we describe the clinical features of 727 OMD subjects enrolled by the Dystonia Coalition (DC), an international multicenter cohort. Finally, we summarize clinical features and treatment outcomes from cross-sectional analysis of 172 OMD subjects from two expert centers. Results: In all cohorts, typical age at onset was in the 50s and 70% of cases were female. The Dystonia Coalition cohort revealed perioral musculature was involved most commonly (85%), followed by jaw (61%) and tongue (17%). OMD more commonly appeared as part of a segmental dystonia (43%), and less commonly focal (39%) or generalized (10%). OMD was found to be associated with impaired quality of life, independent of disease severity. On average, social anxiety (LSA score: 33 ± 28) was more common than depression (BDI II score: 9.7 ± 7.8). In the expert center cohorts, botulinum toxin injections improved symptom severity by more than 50% in ~80% of subjects, regardless of etiology. Conclusions: This comprehensive description of OMD cases has revealed novel insights into the most common OMD phenotypes, pattern of dystonia distribution, associated psychiatric disturbances, and effect on QoL. We hope these findings will improve clinical recognition to aid in timely diagnosis and inform treatment strategies.

Evaluation of Individualized Multi-Disciplinary Inpatient Treatment for Functional Movement Disorders

BACKGROUND

Functional movement disorders (FMD) are associated with considerable morbidity and impairment of quality of life. Specialized treatment is scarce and data on efficacy of different therapies are limited.

OBJECTIVE

To evaluate a multi-modal inpatient treatment program for patients with FMD.

METHODS

Thirty-one patients with FMD were analyzed before (t1) and after multi-modal inpatient treatment (t2) by a blinded video rating using the Psychogenic Movement Disorder Rating Scale (PMDRS), the simplified Functional Movement Disorder Rating Scale (S-FMDRS), and the Clinical Global Impression Scale of Severity (CGI-S), as well as patients' self-rating. In 23 out of 31 patients a 5 months follow-up investigation was performed (t3). Wilcoxon signed-rank test and Friedman test were used for rating scale and self-rating comparisons over time. Spearman correlation was used for correlation of symptom improvement and clinical characteristics.

RESULTS

Video rating revealed significant reduction of scores after therapy (median PMDRS t1 = 24, t2 = 8, P = 0.0006; S-FMDRS t1 = 11, t2 = 4, P = 0.008; CGI-S t1 = 4, t2 = 3, P = 0.000136) with sustained score decrease in follow-up evaluations (PMDRS t1 = 31, t2 = 8, t3 = 7, P = 0.000032; S-FMDRS t1 = 12, t2 = 4, t3 = 3, P = 0.000888; CGI-S t1 = 4, t2 = 3, t3 = 3, P = 0.000032). Patients reported a stable reduction of symptoms in the self-rating (CGI-S t1 = 5, t2 = 4, t3 = 4, P = 0.016). Age correlated with treatment response with older patients showing better improvement, but disease duration did not correlate with outcome. Patients who suffered from physical trauma, sexual or physical abuse had smaller score reductions.

CONCLUSION

Blinded video and self-rating assessment showed significant score reduction in patients with FMD after an individualized interdisciplinary inpatient intervention.

Distinct Brain-Oscillatory Neuroanatomical Architecture of Perception-Action Integration in Adolescents With Tourette Syndrome

Background

Gilles de la Tourette Syndrome (GTS) is a neurodevelopmental disorder with a peak of symptom severity around late childhood and early adolescence. Previous findings in adult GTS suggest that changes in perception-action integration, as conceptualized in the theory of event coding framework, are central for the understanding of GTS. However, the neural mechanisms underlying these processes in adolescence are elusive.

Methods

A total of 59 children/adolescents aged 9 to 18 years (n = 32 with GTS, n = 27 typically developing youths) were examined using a perception-action integration task (event file task) derived from the theory of event coding. Event-related electroencephalogram recordings (theta and beta band activity) were analyzed using electroencephalogram–beamforming methods.

Results

Behavioral data showed robust event file binding effects in both groups without group differences. Neurophysiological data showed that theta and beta band activity were involved in event file integration in both groups. However, the functional neuroanatomical organization was markedly different for theta band activity between the groups. The typically developing group mainly relied on superior frontal regions, whereas the GTS group engaged parietal and inferior frontal regions. A more consistent functional neuroanatomical activation pattern was observed for the beta band, engaging inferior parietal and temporal regions in both groups.

Conclusions

Perception-action integration processes lag behind in persisting GTS but not in the GTS population as a whole, underscoring differences in developmental trajectories and the importance of longitudinal investigations for the understanding of GTS. The findings corroborate known differences in the functional/structural brain organization in GTS and suggest an important role of theta band activity in these patients.

A Multi-center Genome-wide Association Study of Cervical Dystonia

BACKGROUND

Several monogenic causes for isolated dystonia have been identified, but they collectively account for only a small proportion of cases. Two genome-wide association studies have reported a few potential dystonia risk loci; but conclusions have been limited by small sample sizes, partial coverage of genetic variants, or poor reproducibility.

OBJECTIVE

To identify robust genetic variants and loci in a large multicenter cervical dystonia cohort using a genome-wide approach.

METHODS

We performed a genome-wide association study using cervical dystonia samples from the Dystonia Coalition. Logistic and linear regressions, including age, sex, and population structure as covariates, were employed to assess variant- and gene-based genetic associations with disease status and age at onset. We also performed a replication study for an identified genome-wide significant signal.

RESULTS

After quality control, 919 cervical dystonia patients compared with 1491 controls of European ancestry were included in the analyses. We identified one genome-wide significant variant (rs2219975, chromosome 3, upstream of COL8A1, P-value 3.04 × 10^-8 ). The association was not replicated in a newly genotyped sample of 473 cervical dystonia cases and 481 controls. Gene-based analysis identified DENND1A to be significantly associated with cervical dystonia (P-value 1.23 × 10^-6 ). One low-frequency variant was associated with lower age-at-onset (16.4 ± 2.9 years, P-value = 3.07 × 10^-8 , minor allele frequency = 0.01), located within the GABBR2 gene on chromosome 9 (rs147331823).

CONCLUSION

The genetic underpinnings of cervical dystonia are complex and likely consist of multiple distinct variants of small effect sizes. Larger sample sizes may be needed to provide sufficient statistical power to address the presumably multi-genic etiology of cervical dystonia. © 2021 International Parkinson and Movement Disorder Society.

Inter-individual differences in urge-tic associations in Tourette syndrome

Premonitory urges are a cardinal feature in Tourette syndrome (GTS) and are commonly viewed as a driving force of tics. However, inter-individual differences in experimentally measured urges, tics and urge-tic associations, as well as possible relations to clinical characteristics and abnormal perception-action processing recently demonstrated in these patients have not been investigated in detail. Here, we analyze the temporal associations between urges and tics in 21 adult patients with GTS including inter-individual differences and the relation of such associations with clinical measures and experimentally tested perception-action coupling. At the group level, our results confirm known positive associations between subjective urges and tics, with increased tic frequency and tic intensity during periods of elevated urge. Inter-individual differences in the associations between urges and tics were, however, substantial. While most participants (57-66 % depending on the specific measure) showed positive associations as expected, several participants did not, and two even had negative associations with tic occurrence and intensity being reduced at times of increased urges. Subjective urge levels and tic occurrence correlated with corresponding clinical scores, providing converging evidence. Measures of the strength of urge-tic associations did not correlate with clinical measures nor the strength of perception-action coupling. Taken together, urge-tic associations in GTS are complex and heterogenous, casting doubt on the notion that tics are primarily driven by urges.

Intact Organization of Tactile Space Perception in Isolated Focal Dystonia

BACKGROUND

Systematic perceptual distortions of tactile space have been documented in healthy adults. In isolated focal dystonia impaired spatial somatosensory processing is suggested to be a central pathophysiological finding, but the structure of tactile space for different body parts has not been previously explored.

OBJECTIVES

The objective of this study was to assess tactile space organization with a novel behavioral paradigm of tactile distance perception in patients with isolated focal dystonia and controls.

METHODS

Three groups of isolated focal dystonia patients (cervical dystonia, blepharospasm/Meige syndrome, focal hand dystonia) and controls estimated perceived distances between 2 touches across 8 orientations on the back of both hands and the forehead.

RESULTS

Stimulus size judgments differed significantly across orientations in all groups replicating distortions of tactile space known for healthy individuals. There were no differences between groups in the behavioral parameters we assessed on the hands and forehead.

CONCLUSIONS

Tactile space organization is comparable between patients with isolated focal dystonia and healthy controls in dystonic and unaffected body parts. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Networks in the Field of Tourette Syndrome

Gilles de la Tourette syndrome (TS) is a neuropsychiatric neurodevelopmental disorder with the cardinal clinical features of motor and phonic tics. Clinical phenomenology can be complex since, besides tics, there are other features including premonitory urges preceding tics, pali-, echo-, and coprophenomena, hypersensitivity to external stimuli, and symptom dependency on stress, attention, and other less well-defined factors. Also, the rate of comorbidities, particularly attention deficit hyperactivity disorder and obsessive-compulsive disorder, is high. Mirroring the complexities of the clinical course and phenomenology, pathophysiological findings are very diverse, and etiology is disputed. It has become clear, though, that abnormalities in the basal ganglia and their connections with cortical areas are key for the understanding of the pathophysiology and as regards etiology, genetic factors are crucial. Against this background, both adequate clinical management of TS and TS-related research require multidisciplinary preferably international cooperation in larger groups or networks to address the multiple facets of this disorder and yield valid and useful data. In particular, large numbers of patients are needed for brain imaging and genetic studies. To meet these requirements, a number of networks and groups in the field of TS have developed over the years creating an efficient, lively, and supportive international research community. In this review, we will provide an overview of these groups and networks.