Neuroplasticity in dystonia: Motor symptoms and beyond

This chapter first focuses on the role of altered neuroplasticity mechanisms and their regulation in the genesis of motor symptoms in the various forms of dystonia. In particular, a review of the available literature about focal dystonia suggests that use-dependent plasticity may become detrimental and produce dystonia when practice and repetition are excessive and predisposing conditions are present. Interestingly, recent evidence also shows that functional or psychogenic dystonia, despite the normal plasticity in the sensorimotor system, is characterized by plasticity-related dysfunction within limbic regions. Finally, this chapter reviews the non-motor symptoms that often accompany the motor features of dystonia, including depression and anxiety as well as obsessive-compulsive disorders, pain, and cognitive dysfunctions. Based on the current understanding of these symptoms, we discuss the evidence of their possible relationship to maladaptive plasticity in non-motor basal ganglia circuits involved in their genesis.

Developmental neurobiology of cerebellar and Basal Ganglia connections

BACKGROUND

The high prevalence of mixed phenotypes of Early Onset Ataxia (EOA) with comorbid dystonia has shifted the pathogenetic concept from the cerebellum towards the interconnected cerebellar motor network. This paper on EOA with comorbid dystonia (EOA-dystonia) explores the conceptual relationship between the motor phenotype and the cortico-basal-ganglia-ponto-cerebellar network.

METHODS

In EOA-dystonia, we reviewed anatomic-, genetic- and biochemical-studies on the comorbidity between ataxia and dystonia.

RESULTS

In a clinical EOA cohort, the prevalence of dystonia was over 60%. Both human and animal studies converge on the underlying role for the cortico-basal-ganglia-ponto-cerebellar network. Genetic -clinical and -in silico network studies reveal underlying biological pathways for energy production and neural signal transduction.

CONCLUSIONS

EOA-dystonia phenotypes are attributable to the cortico-basal-ganglia-ponto-cerebellar network, instead of to the cerebellum, alone. The underlying anatomic and pathogenetic pathways have clinical implications for our understanding of the heterogeneous phenotype, neuro-metabolic and genetic testing and potentially also for new treatment strategies, including neuro-modulation.

Sandifer Syndrome: A Case Report

Sandifer syndrome is an extra oesophageal manifestation of gastrointestinal reflux disease that usually presents with torticollis and dystonia (often mimicking epilepsy). Here, we describe a case of a four and a half years old child with convulsion, neck contortion, and irritability. Gastrointestinal reflux disease was suspected on the earlier visit of the patient based on the presenting symptom of vomiting and cough. Electroencephalogram revealed normal findings. A barium meal radiograph was performed which was insignificant for gastrointestinal reflux disease and hiatal hernia. Complete blood count showed results suggestive of iron deficiency anaemia, while the rest of the biochemical parameters and the infection screening were normal. The case was confirmed by a medication trial for gastrointestinal reflux disease. This syndrome is often misdiagnosed as infantile seizure and musculoskeletal disorder. So, physicians need to have a sound knowledge of Sandifer Syndrome while assessing a child presenting with convulsion and torticollis.

Next move in movement disorders (NEMO): developing a computer-aided classification tool for hyperkinetic movement disorders

INTRODUCTION

Our aim is to develop a novel approach to hyperkinetic movement disorder classification, that combines clinical information, electromyography, accelerometry and video in a computer-aided classification tool. We see this as the next step towards rapid and accurate phenotype classification, the cornerstone of both the diagnostic and treatment process.

METHODS AND ANALYSIS

The Next Move in Movement Disorders (NEMO) study is a cross-sectional study at Expertise Centre Movement Disorders Groningen, University Medical Centre Groningen. It comprises patients with single and mixed phenotype movement disorders. Single phenotype groups will first include dystonia, myoclonus and tremor, and then chorea, tics, ataxia and spasticity. Mixed phenotypes are myoclonus-dystonia, dystonic tremor, myoclonus ataxia and jerky/tremulous functional movement disorders. Groups will contain 20 patients, or 40 healthy participants. The gold standard for inclusion consists of interobserver agreement on the phenotype among three independent clinical experts. Electromyography, accelerometry and three-dimensional video data will be recorded during performance of a set of movement tasks, chosen by a team of specialists to elicit movement disorders. These data will serve as input for the machine learning algorithm. Labels for supervised learning are provided by the expert-based classification, allowing the algorithm to learn to predict what the output label should be when given new input data. Methods using manually engineered features based on existing clinical knowledge will be used, as well as deep learning methods which can detect relevant and possibly new features. Finally, we will employ visual analytics to visualise how the classification algorithm arrives at its decision.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from the relevant local ethics committee. The NEMO study is designed to pioneer the application of machine learning of movement disorders. We expect to publish articles in multiple related fields of research and patients will be informed of important results via patient associations and press releases.

Haloperidol-induced isolated lingual dystonia

A 28-year-old woman presenting with agitation and mania with psychotic features developed symptoms of isolated lingual dystonia shortly after the initiation of a haloperidol concentrate regimen.

Spectrum of Movement Disorders in two Movement Disorders Centers in the Philippines

OBJECTIVE

Presently, there are no epidemiologic data on the prevalence of movement disorders in the Philippines. We aim to describe the most common phenomenologies and movement disorders in two specialty centers in Metro Manila dedicated to movement disorders.

METHODS

We investigated the clinical spectrum and etiologies of movement disorders referred to our centers from January 2007-December 2019 using a standardized collection form.

RESULTS

A total of 1438 patients presenting with complaints relating to movement disorders were evaluated between 2007 to 2019. There were 770 (53.5%) men. The mean age was 57.1 ± 17.9 years. The most common movement disorders were parkinsonism (n=677, 47.1%), myoclonus (n=212, 14.7%) and tremor (n=208, 14.5%). The least common was restless legs syndrome (n=4, 0.3%). There were 78 (37.7% of total dystonia cases) X-linked dystonia-parkinsonism patients referred to our clinic. Majority of the botulinum toxin injections were for hemifacial spasms (n=206). A small number of patients (n=41) were also seen at the center for deep brain stimulation programming.

CONCLUSION

The most common movement disorders managed were parkinsonism, myoclonus and tremor. The most common diagnoses were Parkinson's disease, hemifacial spasm and essential tremor. This study highlights the spectrum of movement disorders encountered in two specialty clinics in two Philippine tertiary hospitals. Given these varied cases, there is also a need for more movement specialists and centers dedicated to movement disorders to manage these cases.

Movement Disorders in Children

CONTEXT

Movement disorders represent a common presentation in pediatrics and are often a source of clinical and diagnostic dilemmas. In this review, we provide an overview of common causes along with simplified clinical approach and management options for major movement disorders.

SOURCES

This narrative review is based on contemporary evidence and personal experience. Medline was searched for recent advances, current understanding and consensus on classification, clinical features, diagnosis and treatment.

RESULTS

Movement disorders are classified as hyperkinetic and hypokinetic disorders, the latter being rare in childhood. The hyperkinetic disorders include dystonia, chorea, athetosis, tics and tremor, stereotypies, myoclonus, startle syndromes and functional disorders. Some movement disorders can be benign and developmental. A large proportion of conditions are genetic in origin with a guarded prognosis. Some of the conditions may be post-infectious, immune-mediated or drug induced. Multiple types of movement disorders are present in many conditions. The age at onset, type and distribution of abnormal movements and presence of associated neurological and systemic features help in narrowing the differential diagnosis. The pharmacotherapy of movement disorders is complex and evolving.

CONCLUSION

A synopsis of movement disorders presenting in pediatric age has been provided, incorporating the latest evidence. A simplified approach for clinical diagnosis has been developed for dystonia and chorea.

Metoclopramide-Induced Acute Dystonia: Data From a Pediatric Emergency Unit

OBJECTIVES

Metoclopramide is a commonly used medication in pediatric practice, and dystonia is a common adverse effect of it. The present study aims to evaluate the clinical characteristics of metoclopramide-induced acute dystonic reactions (MIADRs) in pediatric patients admitted to the pediatric emergency unit.

METHODS

Twenty-eight patients were admitted with MIADRs between June 2004 and April 2016; they were enrolled into the study retrospectively.

RESULTS

The study group was composed of 13 females and 15 males with the mean ± SD age of the females higher than that of the males, 12.3 ± 4.5 and 7.8 ± 4.3 years, respectively. Only 9 (32.1%) of the patients were diagnosed as MIADRs at the time of admission. Seventeen patients (60.7%) received over the recommended daily dose of metoclopramide. Dystonia was focal in most of the patients, with the most affected parts consisting of the neck, eyes, and orolingual regions. In 9 of the patients, the dystonia was episodic in nature. Pharmacological treatment was used for 18 patients. No patients died, and none suffered long-term injury related to MIADRs.

CONCLUSIONS

Metoclopramide administration may be associated with the occurrence of acute dystonic reaction. Metoclopramide-induced acute dystonic reactions may be misdiagnosed, so detailed medical history gathering and a high index of suspicion are warranted. Our data suggest that MIADRs may be dose related and that there may be age- and sex-related differences in the epidemiology of MIADRs.

Case Report: Secondary bilateral parkinsonism and dystonia treated with dronabinol

Drug abuse may damage basal ganglia that are essential for planning and execution of movements. We report about the case of a 38-year old patient with ischemic lesions of the basal ganglia presenting with bilateral painful dystonia and parkinsonism caused by polyintoxication. Dronabinol resulted in improvement of pain and gait disturbance, suggesting a novel therapeutic strategy in these challenging patients.

Personality Profile in Focal Hand Dystonia: A Cross-Sectional Study

It has been suggested that focal hand dystonia (FHD) should be viewed as a neuropsychiatric disorder rather than as a pure movement disorder. We aimed to compare the personality factors that are common to people with FHD and evaluate how personality factors could affect the functionality of the upper limbs and community participation. We conducted a cross-sectional case-control study in which 12 people with FHD were matched with 12 age and gender matched healthy control participants. The Big Five Questionnaire; the Quick Disabilities, Arm, Shoulder, and Hand questionnaire; and the Jebsen-Taylor Test of Hand Function were used as assessment measures. Control of emotions was the only variable for which a significant difference was found, with participants with FHD displaying lesser control. Correlations were not observed between different personality profiles, the functionality of the upper limbs and the perceived participation of people with FHD in activities of daily living. People with FHD may present with low emotional stability, but this does not have a negative impact on the functionality of the upper limbs and activities of daily living. These findings have clinical implications to be considered for interventions, as they suggest that personality aspects, such as extraversion, may not predict for better functionality and perceived participation in activities of daily living.

X-Linked Parkinsonism: Phenotypic and Genetic Heterogeneity

X-linked parkinsonism encompasses rare heterogeneous disorders mainly inherited as a recessive trait, therefore being more prevalent in males. Recent developments have revealed a complex underlying panorama, including a spectrum of disorders in which parkinsonism is variably associated with additional neurological and non-neurological signs. In particular, a childhood-onset encephalopathy with epilepsy and/or cognitive disability is the most common feature. Their genetic basis is also heterogeneous, with many causative genes and different mutation types ranging from "classical" coding variants to intronic repeat expansions. In this review, we provide an updated overview of the phenotypic and genetic spectrum of the most relevant X-linked parkinsonian syndromes, namely X-linked dystonia-parkinsonism (XDP, Lubag disease), fragile X-associated tremor/ataxia syndrome (FXTAS), beta-propeller protein-associated neurodegeneration (BPAN, NBIA/PARK-WDR45), Fabry disease, Waisman syndrome, methyl CpG-binding protein 2 (MeCP2) spectrum disorder, phosphoglycerate kinase-1 deficiency syndrome (PGK1) and X-linked parkinsonism and spasticity (XPDS). All clinical and radiological features reported in the literature have been reviewed. Epilepsy occasionally represents the symptom of onset, predating parkinsonism even by a few years; action tremor is another common feature along with akinetic-rigid parkinsonism. A focus on the genetic background and its pathophysiological implications is provided. The pathogenesis of these disorders ranges from well-defined metabolic alterations (PGK1) to non-specific lysosomal dysfunctions (XPDS) and vesicular trafficking alterations (Waisman syndrome). However, in other cases it still remains poorly defined. Recognition of the phenotypic and genetic heterogeneity of X-linked parkinsonism has important implications for diagnosis, management, and genetic counseling. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

[A toddler with status dystonicus due to medication]

BACKGROUND

Status dystonicus (SD) is a severe episode of generalized dystonia, potentially complicated by respiratory and metabolic disruption. Triggers can be infection, medication, or metabolic disturbance. The prognosis is variable and mortality is approximately 10%.

CASE DESCRIPTION

An 18 month old girl presented to the ER with clinical suspicion of a febrile status epilepticus and was evaluated according to APLS principles. Eventually, a SD became apparent, with generalized dystonic features at examination. Most likely, the episode was provoked by a single dose of metoclopramide. Her clinical state improved rapidly, possibly aided by administration of biperiden.

CONCLUSION

Treatment of SD encompasses elimination or treatment of the trigger, stabilization of vital functions, possible administration of sedatives and dystonia specific medication. Metoclopramide holds a relatively high risk for extrapyramidal complications (1-10%) and dystonia (0.1-1.5%), even within therapeutic range. The use of anti-emetics with less alarming side effect profiles, for example ondansetron, is recommended.

Genotype-Phenotype Relations for Isolated Dystonia Genes: MDSGene Systematic Review

This comprehensive MDSGene review is devoted to 7 genes - TOR1A, THAP1, GNAL, ANO3, PRKRA, KMT2B, and HPCA - mutations in which may cause isolated dystonia. It followed MDSGene's standardized data extraction protocol and screened a total of ~1200 citations. Phenotypic and genotypic data on ~1200 patients with 254 different mutations were curated and analyzed. There were differences regarding age at onset, site of onset, and distribution of symptoms across mutation carriers in all 7 genes. Although carriers of TOR1A, THAP1, PRKRA, KMT2B, or HPCA mutations mostly showed childhood and adolescent onset, patients with GNAL and ANO3 mutations often developed first symptoms in adulthood. GNAL and KMT2B mutation carriers frequently have 1 predominant site of onset, that is, the neck (GNAL) or the lower limbs (KMT2B), whereas site of onset in DYT-TOR1A, DYT-THAP1, DYT-ANO3, DYT-PRKRA, and DYT-HPCA was broader. However, in most DYT-THAP1 and DYT-ANO3 patients, dystonia first manifested in the upper half of the body (upper limb, neck, and craniofacial/laryngeal), whereas onset in DYT-TOR1A, DYT-PRKRA and DYT-HPCA was frequently observed in an extremity, including both upper and lower ones. For ANO3, a segmental/multifocal distribution was typical, whereas TOR1A, PRKRA, KMT2B, and HPCA mutation carriers commonly developed generalized dystonia. THAP1 mutation carriers presented with focal, segmental/multifocal, or generalized dystonia in almost equal proportions. GNAL mutation carriers rarely showed generalization. This review provides a comprehensive overview of the current knowledge of hereditary isolated dystonia. The data are also available in an online database (http://www.mdsgene.org), which additionally offers descriptive summary statistics. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Modified Graded Motor Imagery for Musicians' Focal Dystonia: A Case Series

PURPOSE

This study aimed to assess the effectiveness of the "modified graded motor imagery" (mGMI) protocol as a rehabilitative treatment of musician's focal dystonia (MFD).

METHODS

Six musicians with MFD (age 43.83±17.24 yrs) performed the home-based mGMI protocol (laterality training, imagined hand movements and visual mirror feedback) once a day for 4 weeks. The mMGI protocol was designed to sequentially activate cortical motor networks and improve cortical organization. Subjects were evaluated before and after treatment with the dystonia evaluation scale (DES), arm dystonia disability scale (ADDS), Tubiana-Chamagne scale (TCS), and performing scale (PS).

RESULTS

All participants were compliant with the mGMI treatment protocol without any adverse events. A significant improvement was measured in ADDS (p=0.047) and TCS scores (p=0.014) but not in DES (p=0.157). The severity of MFD decreased from moderate to mild in four patients. After mGMI treatment, all musicians were able to play easy pieces (TCS: median 3.5, IR 3.5-4).

CONCLUSION

The findings from this pilot study suggest that home-based mGMI treatment is a feasible and promising rehabilitative approach for patients with mild to moderate MFD.

Impact of Psychic Traumatization on the Development of Musicians' Dystonia: Six Exploratory Case Studies

OBJECTIVE

Musician's dystonia represents a special case of focal dystonia. It is described as a task-specific movement disorder which presents itself as muscular incoordination or loss of voluntary fine-motor control of extensively trained movements while a musician is playing the instrument. Several triggering factors have been identified, such as overuse, chronic pain, perfectionism, and anxiety disorders. As a common feature, dysfunctional self-management and stress-coping mechanisms are at the root of the aforementioned behaviors. Based on long-term experience from our musicians' medicine outpatient clinic, we hypothesized that early psychic or somatic traumatization may be an underlying mechanism and therefore contribute essentially to focal dystonia.

METHODS

In a qualitative study, we investigated the role of early traumatization as a potential cause of motor failures, such as musician's dystonia, employing an episodic interview on a sample of six professional musicians (age 30-57 yrs, 5:1 M:F) suffering from musician's dystonia.

RESULTS

Using grounded theory methodology, we were able to derive one generalized etiological model describing contributing factors in the etiological understanding of focal dystonia from the six case studies. The qualitative interviews clearly revealed that all patients experienced early psychic traumatizations, including violence and parents' substance abuse.

CONCLUSIONS

In this small sample, we theorize that in-depth, early traumatization most probably led to a dysfunctional stress-coping mechanism. We therefore propose in our model that there are two types of motor failures, one linked to stressful experiences, dysfunctional coping behaviors, and increased muscle tone, and one linked to genetic susceptibility of the motor-system without psychological triggering factors.

Reversal of Temporal Discrimination in Cervical Dystonia after Low-Frequency Sensory Stimulation

BACKGROUND

Somatosensory temporal discrimination is abnormal in dystonia and reflects reduced somatosensory inhibition. In healthy individuals, both the latter are enhanced by high-frequency repetitive somatosensory stimulation, whereas opposite effects are observed in patients with cervical dystonia.

OBJECTIVES

We tested whether low-frequency repetitive sensory stimulation, which in healthy individuals worsens discrimination, might have the opposite effect in patients with cervical dystonia at the physiological level and, in turn, improve their perceptual performance.

METHODS

Somatosensory temporal discrimination and several electrophysiological measures of sensorimotor inhibition were collected before and after 45 minutes of low-frequency repetitive sensory stimulation.

RESULTS

As predicted, and opposite to what happened in controls, low-frequency repetitive sensory stimulation in patients enhanced sensorimotor inhibition and normalized somatosensory temporal discrimination.

CONCLUSIONS

Patients with cervical dystonia have an abnormal response to repetitive sensory stimulation, which we hypothesize is attributed to abnormally sensitive homeostatic mechanisms of inhibitory circuitry in both sensory and motor systems. © 2020 International Parkinson and Movement Disorder Society.

Design of an Interactive Mind Calligraphy System by Affective Computing and Visualization Techniques for Real-Time Reflections of the Writer's Emotions

A novel interactive system for calligraphy called mind calligraphy that reflects the writer's emotions in real time by affective computing and visualization techniques is proposed. Differently from traditional calligraphy, which emphasizes artistic expression, the system is designed to visualize the writer's mental-state changes during writing using audio-visual tools. The writer's mental state is measured with a brain wave machine to yield attention and meditation signals, which are classified next into the four types of emotion, namely, focusing, relaxation, calmness, and anxiety. These emotion types then are represented both by animations and color palettes for by-standing observers to appreciate. Based on conclusions drawn from data collected from on-site observations, surveys via Likert-scale questionnaires, and semi-structured interviews, the proposed system was improved gradually. The participating writers' cognitive, emotional, and behavioral engagements in the system were recorded and analyzed to obtain the following findings: (1) the interactions with the system raise the writer's interest in calligraphy; (2) the proposed system reveals the writer's emotions during the writing process in real time via animations of mixtures of fish swimming and sounds of raindrops, insects, and thunder; (3) the dynamic visualization of the writer's emotion through animations and color-palette displays makes the writer understand better the connection of calligraphy and personal emotions; (4) the real-time audio-visual feedback increases the writer's willingness to continue in calligraphy; and (5) the engagement of the writer in the system with interactions of diversified forms provides the writer with a new experience of calligraphy.

Delineating the electrophysiological signature of dystonia

Over the last 30 years, the concept of dystonia has dramatically changed, from being considered a motor neurosis, to a pure basal ganglia disorder, to finally reach the definition of a network disorder involving the basal ganglia, cerebellum, thalamus and sensorimotor cortex. This progress has been possible due to the collaboration between clinicians and scientists, and the development of increasingly sophisticated electrophysiological techniques able to non-invasively investigate pathophysiological mechanisms in humans. This review is a chronological excursus of the electrophysiological studies that laid the foundation for the understanding of the pathophysiology of dystonia and delineated its electrophysiological signatures. Evidence for neurophysiological abnormalities is grouped according to the neural system involved, and a unifying theory, bringing together all the hypothesis and evidence provided to date, is proposed at the end.

Normal Temporal Discrimination in Musician's Dystonia Is Linked to Aberrant Sensorimotor Processing

OBJECTIVES

Alterations in sensory discrimination are a prominent nonmotor feature of dystonia. Abnormal temporal discrimination in focal dystonia is considered to represent its mediational endophenotype, albeit unclear pathophysiological correlates. We examined the associations between the visual temporal discrimination threshold (TDT) and brain activity in patients with musician's dystonia, nonmusician's dystonia, and healthy controls.

METHODS

A total of 42 patients and 41 healthy controls participated in the study. Between-group differences in TDT z scores were computed using inferential statistics. Statistical associations of TDT z scores with clinical characteristics of dystonia and resting-state functional brain activity were examined using nonparametric rank correlations.

RESULTS

The TDT z scores of healthy controls were significantly different from those of patients with nonmusician's dystonia, but not of patients with musician's dystonia. Healthy controls showed a significant relationship between normal TDT levels and activity in the inferior parietal cortex. This relationship was lost in all patients. Instead, TDT z scores in musician's dystonia established additional correlations with activity in premotor, primary somatosensory, ventral extrastriate cortices, inferior occipital gyrus, precuneus, and cerebellum, whereas nonmusician's dystonia showed a trending correlation in the lingual gyrus extending to the cerebellar vermis. There were no significant relationships between TDT z scores and dystonia onset, duration, or severity.

CONCLUSIONS

TDT assessment as an endophenotypic marker may only be relevant to nonmusician forms of dystonia because of the lack of apparent alterations in musician's dystonia. Compensatory adaptation of neural circuitry responsible for TDT processing likely adjusted the TDT performance to the behaviorally normal levels in patients with musician's dystonia, but not nonmusician's dystonia. © 2020 International Parkinson and Movement Disorder Society.

Elevated Forearm Coactivation Levels and Higher Temporal Variability in String Players with Musicians' Dystonia During Demanding Playing Conditions

AIMS

There is a lack of an objective measurement tool for evaluating the quality of bowing performance in string players. The present study aimed to assess kinematic features of bow strokes performed by violinists and violists affected by bow arm dystonia, compared to healthy controls.

METHODS

Seven musicians with musician's dystonia and 20 healthy controls participated in the study. A 3D motion capture system was used to record repetitive bowing on a single string at fixed velocities. Temporal variability, an indirect indicator for motor disturbances, was computed in order to evaluate the musicians' performance during the repetitive movements. Simultaneously, muscular activity of essential flexors and extensors of the right arm was recorded using surface electromyography. Antagonistic muscular coactivation and temporal variability were analyzed in a multilevel linear model framework.

RESULTS

The results revealed generally higher forearm coactivation during upstrokes as compared to downstrokes in both groups. Whereas coactivation levels of the upper arm did not significantly differ between groups, we found increased forearm coactivation in patients during the more demanding playing conditions. Increased coactivation may represent an adaptive motor control strategy that is applied in order to reduce noise entering the motor system. Furthermore, affected musicians executed bow strokes with higher temporal variability than healthy controls, especially during fast playing.

CONCLUSIONS

Building on these results we introduce a novel approach using simple kinematic measures to quantifying dystonic symptoms in string players. Even though dystonia patients showed higher temporal variability and elevated forearm coactivation, both variables were not correlated. This finding is discussed with respect to the heterogeneity of musicians' dystonia and its individual-specific manifestations in dystonic symptoms.