Focal task specific dystonia: a review and update

Musician's dystonia: a perspective on the strongest evidence towards new prevention and mitigation treatments

This perspective article addresses the critical and up-to-date problem of task-specific musician's dystonia (MD) from both theoretical and practical perspectives. Theoretically, MD is explored as a result of impaired sensorimotor interplay across different brain circuits, supported by the most frequently cited scientific evidence-each referenced dozens of times in Scopus. Practically, MD is a significant issue as it occurs over 60 times more frequently in musicians compared to other professions, underscoring the influence of individual training as well as environmental, social, and emotional factors. To address these challenges, we propose a novel application of the FeeSyCy principle (feedback-synchrony-plasticity), which emphasizes the pivotal role of feedback in guiding inter-neuronal synchronization and plasticity-the foundation of learning and memory. This model integrates with established literature to form a comprehensive framework for understanding MD as an impaired FeeSyCy-mediated relationship between the individual and their environment, ultimately leading to trauma. The proposed approach provides significant advantages by enabling the development of innovative therapeutic and preventive strategies. Specifically, it lays the groundwork for multimodal psycho-physical therapies aimed at restoring balance in the neural circuits affected by MD. These strategies include personalized psychotherapy combined with physical rehabilitation to address both the psychological and physiological dimensions of MD. This integration offers a practical and value-added solution to this pressing problem, with potential for broad applicability across similar conditions.

Boundaries of task-specificity: bimanual finger dexterity is reduced in musician's dystonia

Task-specific dystonia leads to loss of sensorimotor control for a particular motor skill. Although focal in nature, it is hugely disabling and can terminate professional careers in musicians. Biomarkers for underlying mechanism and severity are much needed. In this study, we designed a keyboard device that measured the forces generated at all fingertips during individual finger presses. By reliably quantifying overflow to other fingers in the instructed (enslaving) and contralateral hand (mirroring) we explored whether this task could differentiate between musicians with and without dystonia. 20 right-handed professional musicians (11 with dystonia) generated isometric flexion forces with the instructed finger to match 25%, 50% or 75% of maximal voluntary contraction for that finger. Enslaving was estimated as a linear slope of the forces applied across all instructed/uninstructed finger combinations. Musicians with dystonia had a small but robust loss of finger dexterity. There was increased enslaving and mirroring, primarily during use of the symptomatic hand (enslaving p = 0.003; mirroring p = 0.016), and to a lesser extent with the asymptomatic hand (enslaving p = 0.052; mirroring p = 0.062). Increased enslaving and mirroring were seen across all combinations of finger pairs. In addition, enslaving was exaggerated across symptomatic fingers when more than one finger was clinically affected. Task-specific dystonia therefore appears to express along a gradient, most severe in the affected skill with subtle and general motor control dysfunction in the background. Recognition of this provides a more nuanced understanding of the sensorimotor control deficits at play and can inform therapeutic options for this highly disabling disorder.

Incobotulinum Toxin-A in Professional Musicians with Focal Task-Specific Dystonia: A Double Blind, Placebo Controlled, Cross-Over Study

Background

Musician's focal task-specific dystonia is a complex disorder of fine motor control, with incomplete understanding of its etiology. There have been relatively few trials of botulinum toxin in upper limb task-specific dystonia, and prior studies have yielded variable results, leading to skepticism regarding the utility of this approach in elite performers.

Methods

We conducted a double-blind, placebo-controlled, randomized, cross-over study of incobotulinum toxin-A in 21 professional musicians with focal upper extremity task-specific dystonia affecting performance on their instrument, using a novel paradigm of initial injections followed by booster injections at two- and four-week intervals. The primary outcome measure was the change in blinded dystonia rating of the active arm by two expert raters using a Clinical Global Impression numeric scale at week 8 compared to enrollment.

Findings

19 men and 2 women with musicians' dystonia were enrolled over a six-year period. Nineteen patients completed the study. Analysis of the primary outcome measure in comparison to baseline revealed a change in dystonia severity of P = 0.04 and an improvement in overall musical performance of P = 0.027. No clinically significant weakness was observed, and neutralizing antibodies to toxin were not found.

Interpretation

Despite its small sample size, our study demonstrated a statistically significant benefit of incobotulinum toxin-A injections as a treatment for musicians' task-specific dystonia. Tailoring the use of toxin with booster injections allowed refinement of dosing strategy and outcomes, with benefits that were meaningful to patients clearly visible on videotaped evaluations. In addition to its application to musicians' dystonia, this approach may have relevance to optimize application of botulinum toxin in other forms of focal dystonia such as blepharospasm, cervical dystonia, writer's cramp, and spasmodic dysphonia.

Can calcitonin gene-related peptide monoclonal antibodies ameliorate writer's cramp and migraine?

Recently, calcitonin gene-related peptide (CGRP) monoclonal antibodies (mAbs) have become available as a prophylactic treatment for migraine and have shown high efficacy and safety in clinical practice. CGRP mAbs have been reported to be effective not only for migraine but also for other comorbidities, such as psychiatric complications in patients with migraine. However, there are no reports examining the effect of CGRP mAbs on dystonia. We treated a patient with comorbid migraine and focal task-specific dystonia (writer's cramp) with a CGRP mAb (erenumab) because of an increase in monthly migraine days despite the addition of migraine prophylaxis. In this patient, erenumab treatment for 3 months led to improvements in symptoms of both focal dystonia and migraine, suggesting a role for CGRP in the pathophysiology of both conditions.

NSF DARE-Transforming modeling in neurorehabilitation: Four threads for catalyzing progress

We present an overview of the Conference on Transformative Opportunities for Modeling in Neurorehabilitation held in March 2023. It was supported by the Disability and Rehabilitation Engineering (DARE) program from the National Science Foundation's Engineering Biology and Health Cluster. The conference brought together experts and trainees from around the world to discuss critical questions, challenges, and opportunities at the intersection of computational modeling and neurorehabilitation to understand, optimize, and improve clinical translation of neurorehabilitation. We organized the conference around four key, relevant, and promising Focus Areas for modeling: Adaptation & Plasticity, Personalization, Human-Device Interactions, and Modeling 'In-the-Wild'. We identified four common threads across the Focus Areas that, if addressed, can catalyze progress in the short, medium, and long terms. These were: (i) the need to capture and curate appropriate and useful data necessary to develop, validate, and deploy useful computational models (ii) the need to create multi-scale models that span the personalization spectrum from individuals to populations, and from cellular to behavioral levels (iii) the need for algorithms that extract as much information from available data, while requiring as little data as possible from each client (iv) the insistence on leveraging readily available sensors and data systems to push model-driven treatments from the lab, and into the clinic, home, workplace, and community. The conference archive can be found at (dare2023.usc.edu). These topics are also extended by three perspective papers prepared by trainees and junior faculty, clinician researchers, and federal funding agency representatives who attended the conference.

Intraventricular baclofen for palliative management of acquired generalized dystonia in pediatric patients: a case series and literature review

Dystonia represents a significant source of disability in children. Generalized dystonia, which involves multiple body regions, leads to impaired mobility and motor function, resulting in substantial challenges in daily activities. Surgical treatments are used when medical treatments fail. Intrathecal baclofen (ITB) or deep brain stimulations (DBS) are the most employed surgical therapies. When these options are not feasible or ineffective, some authors have explored the use of intraventricular baclofen (IVB). In this report, we present four cases of pediatric patients with generalized dystonia who underwent treatment with IVB, resulting in notable improvements. To further explore the potential of this treatment modality, we conducted a comprehensive literature review. The findings from our study provide a comprehensive overview that can guide palliative management in similar cases.

Treatment of task-specific dystonia in sports: A systematic review

Introduction

Task specific dystonia is a movement disorder only affecting a highly practiced skill and is found in a broad set of expert movements including in sports. Despite affecting many sports, there is no comprehensive review of treatment options, which is in contrast to better studied forms of task specific dystonia in musicians and writers. For this reason, studies involving an intervention to treat task specific dystonia in sports were systematically reviewed, with special attention for the quality of outcome measures.

Methods

The PICO systematic search strategy was employed on task-specific dystonia, and all synonyms. Inclusion criteria were peer reviewed published studies pertaining to sports, studies with a measurement and/or intervention in TSD, all in English. We excluded abstracts, expert opinions, narrative review articles, unpublished studies, dissertations and studies exclusively relating to choking. We included case reports, case studies and case-control studies.

Results

In April 2022 Pubmed, Embase, Web of Science, and Psychinfo were searched. Of the 7000 articles identified, 31 were included that described psychological and invasive and/or pharmacological interventions. There was a lack of formal standardized outcome measures in studies resulting in low quality evidence for the effectiveness of treatment options. A descriptive synthesis showed emotional regulation was effective, but was exclusively tried in golfers. Interventions like botulinum toxin or pharmacology had a similar effectiveness compared to studies in musicians dystonia, however there was almost no formal evidence for these treatments.

Conclusion

The quality of studies was low with a lack of standardized outcome measures. Future studies with larger cohorts and quantitative outcome measures are needed to improve understanding of treatments for task specific dystonia in athletes.

Focal task-specific hand dystonia related to esports in a rhythm gamer: A case report

Herein, we report a novel case of focal task-specific dystonia of the upper extremity that occurred in a 27-year-old man who presented with flexion of the left third, fourth, and fifth fingers exclusively during rhythm gameplay. Dystonia during electronic sports should be recognized as a new type of occupational dystonia.

New-Onset Focal Task Specific Oromandibular Dystonia in Association with Quran Recitation: A Case Series

Background

Focal task-specific dystonia is a form of isolated focal dystonia that occurs during the performance of a specific skilled motor task. The occurrence of oromandibular dystonia (OMD) specifically in association with the recitation of Quranic verses have been rarely reported in the literature, in non-native Arabic-speaking patients. This case series describe a rare type of focal task-specific dystonia that occurs exclusively by reciting Quran in native Arabic-speaking patients, which has never been reported, to the best of our knowledge.

Methods

In this case series, we identified five patients with new-onset OMD that was exclusively induced by reciting Quran. Cases were evaluated in our Movement Disorders outpatient clinic at Ibn Sina hospital; the main tertiary neurology center in Kuwait, between 2015 and 2023.

Results

Five cases (3 males, 2 females) were identified in this study. Mean age of onset of the symptoms was 52.3 ± 4.1 years, while the median duration of the symptoms prior to diagnosis was 3 years. All patients were native Arab-speaking, with no previous history of other types of dystonia. No identifiable risk factors could be obtained including exposure to dopamine blocking agents or antipsychotics, or history of oral or dental surgery. Patients underwent a full clinical, laboratory, and radiological evaluation. All patients had OMD dystonia in varying forms and severity, while two patients had additional spasmodic dysphonia/ blepharospasm on progressive recitation. Most patients had minimal improvement with combination of oral medications and speech therapy. Four patients received botulinum toxin injections with better results.

Discussion

The mental and physical stress in attempting to recite the Quranic verses could have contributed to the development of OMD. Moreover, the increased demand on the muscles of the jaw, lips, and tongue during recitation can trigger the dystonic symptoms.

Highlights

OMD exclusively during Quran recitation is a rare phenomenon, and expands the spectrum of task-specific focal dystonia described in the literature. It was found to be distressing to the patients and a challenge to treat. Prompt recognition could minimize unnecessary testing and procedures, and facilitate earlier treatment.

Function and dysfunction of the dystonia network: an exploration of neural circuits that underlie the acquired and isolated dystonias

Dystonia is a highly prevalent movement disorder that can manifest at any time across the lifespan. An increasing number of investigations have tied this disorder to dysfunction of a broad "dystonia network" encompassing the cerebellum, thalamus, basal ganglia, and cortex. However, pinpointing how dysfunction of the various anatomic components of the network produces the wide variety of dystonia presentations across etiologies remains a difficult problem. In this review, a discussion of functional network findings in non-mendelian etiologies of dystonia is undertaken. Initially acquired etiologies of dystonia and how lesion location leads to alterations in network function are explored, first through an examination of cerebral palsy, in which early brain injury may lead to dystonic/dyskinetic forms of the movement disorder. The discussion of acquired etiologies then continues with an evaluation of the literature covering dystonia resulting from focal lesions followed by the isolated focal dystonias, both idiopathic and task dependent. Next, how the dystonia network responds to therapeutic interventions, from the "geste antagoniste" or "sensory trick" to botulinum toxin and deep brain stimulation, is covered with an eye towards finding similarities in network responses with effective treatment. Finally, an examination of how focal network disruptions in mouse models has informed our understanding of the circuits involved in dystonia is provided. Together, this article aims to offer a synthesis of the literature examining dystonia from the perspective of brain networks and it provides grounding for the perspective of dystonia as disorder of network function.

Evaluation of the efficacy and safety of MRI-guided focused ultrasound (MRgFUS) for focal hand dystonia: study protocol for an open-label non-randomised clinical trial

Introduction

MRI-guided focused ultrasound (MRgFUS) thalamotomy provides an exciting development in the field of minimally invasive stereotactic neurosurgery. Current treatment options for focal hand dystonia are limited, with potentially more effective invasive stereotactic interventions, such as deep brain stimulation or lesional therapies, rarely used. The advent of minimally invasive brain lesioning provides a potentially safe and effective treatment approach with a recent pilot study establishing MRgFUS Vo-complex thalamotomy as an effective treatment option for focal hand dystonia. In this study, we undertake an open-label clinical trial to further establish MRgFUS Vo-complex thalamotomy as an effective treatment for focal hand dystonia with greater attention paid to potential motor costs associated with this treatment. To elucidate pathophysiology of dystonia and treatment mechanisms, neurophysiological and MRI analysis will be performed longitudinally to explore the hypothesis that neuroplastic and structural changes that may underlie this treatment benefit.

Methods and analysis

A total of 10 participants will be recruited into this open-label clinical trial. All participants will undergo clinical, kinemetric, neurophysiological and radiological testing at baseline, followed by repeated measures at predesignated time points post MRgFUS Vo-complex thalamotomy. Further, to identify any underlying structural or neurophysiological abnormalities present in individuals with focal hand dystonia, 10 age and gender matched control participants will be recruited to undergo comparative investigation. These results will be compared with the intervention participants both at baseline and at 12 months to assess for normalisation of these abnormalities, if present.

Ethics and dissemination

This trial was reviewed and approved by the St Vincent's Health Network Sydney Human Research Ethics Committee (2022/ETH00778). Study results will be published in peer-reviewed journals and presented at both national and international conferences.

Trial registration number

CTRN12622000775718.

Personality in speed skaters with skater's cramp: A preliminary cross-sectional study

OBJECTIVE

Skater's cramp is a debilitating disorder in expert speedskaters and recent evidence from muscle and movement studies nominate it is a task-specific dystonia (TSD). Building on these studies we investigated clinical features and personality in skater's cramp, hypothesizing that similar to other TSDs, trait emotionality would be higher in affected skaters.

METHODS

In a cross-sectional study we employed the HEXACO inventory to examine the personality of a cohort of skaters with skater's cramp (n = 26) compared to age, sex, and experience-matched controls (n = 28). Affected skaters were selected based on relevant clinical features important to the diagnosis of TSD.

RESULTS

Sentimentality (a sub-factor of emotionality) was higher in affected skaters, but only in the male population. Extraversion was lower in skaters with skater's cramp. Clinical findings resembled other forms of TSD.

DISCUSSION

Higher sentimentality is in line with previous studies in TSD. Lower Extraversion in affected skaters was an unexpected finding that may be a new feature of skater's cramp and TSD. Due to our small sample size and cross-sectional design, these findings are preliminary, but offer tentative evidence of personality differences in skater's cramp in line with TSD.

Pistol Shooting Dystonia Treated with Thalamotomy

Background

Neurosurgical treatment for pistol shooting dystonia has not been studied.

Case report

The patient was a 41-year-old woman who participated in the Olympic Games four times as a shooting player. Five months after the final Tokyo Olympic trials, she developed dystonia of the right index finger when shooting. Stereotactic thalamotomy was performed, and a complete resolution of dystonia was achieved. She garnered her personal best score and placed fifth in the Tokyo Olympics.

Discussion

Thalamotomy along with deep brain stimulation can be a surgical modality for patients with task-specific dystonia who fail oral medications or botulinum toxin therapy.

[Abnormal movements "Motare" in Kyudo have the characteristics of task-specific focal dystonia]

Among the abnormal kyudo movements ("yips"), "motare" is the inability to release the arrow at the intended timing if aiming the target. We hypothesized that "motare" is a task-specific focal dystonia (TSFD). We interviewed three participants with "motare," three participants with "hayake", and three controls without "motare" nor "hayake". Moreover, we conducted a surface electromyography (sEMG) examination and found that "motare" was characterized by stereotypy, sensory tricks, and morning benefit; however, these findings were not observed in "hayake". Abnormal co-contraction of the upper extremity antagonist muscles was observed in one of the three "motare" participants. Overall, these findings suggest that "motare" have the characteristics of TSFD not previously reported.

Long-Term Muscular Atrophy and Weakness Following Cessation of Botulinum Toxin Type A Injections in the Flexor Digitorum Muscle of Musicians with Focal Hand Dystonia

The present study assessed muscular atrophy and weakness of the flexor digitorum superficialis (FDS) and profundus (FDP) muscle as possible long-term side effects of botulinum toxin (BoNT) injections in hand dystonia patients after the termination of their treatment. For the assessment of both parameters, a group of 12 musicians diagnosed with focal hand dystonia was compared with a group of 12 healthy matched musicians. The minimum and maximum times since the last injection across patients were 0.5 to 3.5 years, respectively. The thickness and strength of the FDS and FDP were assessed via ultrasonography and a strength measurement device. Group differences were estimated through the calculation of the symmetry index between the dominant and non-dominant hand. The results revealed that compared to the control group, thickness and flexion strength of the injected FDS and FDP were decreased by 10.6% ± 5.3% (95% CI) and 12.5% ± 6.4% (95% CI), respectively, in the patient group. The amount of weakness and atrophy was predicted significantly by the total amount of BoNT injected throughout the entire treatment period. In contrast, the time after the last injection did not predict the amount of strength and muscle mass recovery after the cessation of the treatment. The current study revealed that even up to 3.5 years after the termination of BoNT injections, long-term side effects such as weakness and atrophy can still be observed. We suggest that the total BoNT dose should remain as small as possible to reduce long-lasting side effects to the minimum. Although side effects differ significantly among patients, a potential full recovery of atrophy and weakness after the cessation of BoNT treatment might be observed after periods longer than 3.5 years.

Sustained activation in basal ganglia and cerebellum after repetitive movement in a non-task-specific dystonia

We previously observed sustained fMRI BOLD signal in the basal ganglia in focal hand dystonia patients after a repetitive finger tapping task. Since this was observed in a task-specific dystonia, for which excessive task repetition may play a role in pathogenesis, in the current study we asked if this effect would be observed in a focal dystonia (cervical dystonia [CD]) that is not considered task-specific or thought to result from overuse. We evaluated fMRI BOLD signal time courses before, during, and after the finger tapping task in CD patients. We observed patient/control differences in post-tapping BOLD signal in left putamen and left cerebellum during the non-dominant (left) hand tapping condition, reflecting abnormally sustained BOLD signal in CD. BOLD signals in left putamen and cerebellum were also abnormally elevated in CD during tapping itself and escalated as tapping was repeated. There were no cerebellar differences in the previously studied FHD cohort, either during or after tapping. We conclude that some elements of pathogenesis and/or pathophysiology associated with motor task execution/repetition may not be limited to task-specific dystonias, but there may be regional differences in these effects across dystonias, associated with different types of motor control programs.

Muscular and kinematic features in speed skaters indicate a task-specific dystonia

OBJECTIVE

Skater's cramp is a movement disorder in speed skaters. We investigated whether affected skaters matched the disease profile of task-specific dystonia, specifically whether there was evidence of maladaptive muscle activity occurring simultaneously with aberrant movements (jerking). We further examined different skating intensities, positing no change would be more indicative of task-specific dystonia.

METHODS

We analyzed video, kinematic and muscle activity in 14 affected skaters. We measured the angular velocity and electromyographic activity of normalized speed skating strokes using one dimensional statistical non-parametric mapping. Skaters were matched with comparably skilled controls, and filled out a bespoke clinical questionnaire.

RESULTS

Skaters' impacted leg showed over-activation in the peroneus longus, tibialis anterior and gastrocnemius that coincided with higher foot movement compared to their healthy leg and controls. This pattern persisted regardless of skating intensity. Clinical features indicated it was task-specific and painless with common trigger factors including stress, equipment change, and falling.

CONCLUSIONS

We showed aberrant muscular and kinematic activity in a movement disorder in speed skaters indicative of task-specific dystonia.

SIGNIFICANCE

Understanding skater's cramp as a task-specific dystonia could reduce the damage that misdiagnosis and unsuccessful invasive operations have caused. Our quantitative method has value in testing future treatment efficacy.

Inter-muscular coherence in speed skaters with skater's cramp

INTRODUCTION

Skater's cramp is a career-ending movement disorder in expert speed skaters noted to be a likely task-specific dystonia. In other movement disorders, including task-specific dystonia, studies have found evidence of central dysregulation expressed as higher inter-muscular coherence. We looked at whether inter-muscular coherence was higher in affected skaters as a possible indicator that it is centrally driven, and by extension further evidence it is a task-specific dystonia.

METHODS

In 14 affected and 14 control skaters we calculated inter-muscular coherence in the theta-band in a stationary task where tonic muscle activation was measured at 10%, 20% and 50% of maximum voluntary contraction. Additionally, we calculated wavelet coherence while skating at key moments in the stroke cycle.

RESULTS

Coherence did not differ in the stationary activation task. While skating, coherence was higher in the impacted leg of affected skaters compared to their non-impacted leg, p = .05, η² = 0.031, and amplitude of electromyography correlated with coherence in the impacted leg, p = .009, R²_adjusted = 0.41. A sub-group of severely affected skaters (n = 6) had higher coherence in the impacted leg compared to the left and right leg of controls, p = .02, Cohen's d = 1.59 and p = .01, Cohen's d = 1.63 respectively. Results were less clear across the entire affected cohort probably due to a diverse case-mix.

CONCLUSION

Our results of higher coherence in certain severe cases of skater's cramp is preliminary evidence of a central dysregulation, making the likelihood it is a task-specific dystonia higher.

Is Behavioural Therapy a New Treatment Option for Task-Specific Dystonia in Athletes? A Case Series

Background

Task-specific dystonia is a movement disorder of the central nervous system characterized by focal involuntary spasms and muscle contractions, which can negatively affect performance of a specific task. It can affect a wide range of fine motor skills, also in athletes. Current management of task-specific dystonia includes mainly prescribing drugs, exercise therapy or botulinum injections to the affected muscles. Psychological interventions for athletes suffering from task-specific dystonia have not been described extensively so far.

Methods

We present a case-series of 4 different advanced skill-level athletes with suspected task-specific dystonia, which had a major impact on their performance. They all received treatment consisting of a combination of standardized behavioural therapy and relaxation techniques in the form of hypnosis in a total of 8 sessions in a 16-week time period.

Results

After treatment, all athletes returned to their original high level of sport performance without further symptoms of their suspected task-specific dystonia.

Discussion

Behavioural therapy in combination with a relaxation technique seems to be a safe and promising treatment for athletes with suspected task-specific dystonia. Further studies in a larger, preferably randomized controlled trial, are warranted to evaluate if this treatment strategy is effective in athletes with suspected task-specific dystonia.

Alterations in dexterity and manual function in patients with focal hand dystonia

INTRODUCTION

Focal hand dystonia is a movement disorder whose symptoms cause alterations in the performance of tasks requiring a high level of dexterity. Currently, there is no model for interpreting the disease and few studies have identified the difficulties of patients with dystonia in carrying out activities of daily living (ADL). This study aims to describe manipulative dexterity and its influence on ADLs in patients with focal hand dystonia.

MATERIALS AND METHODS

We performed an observational, cross-sectional, case-control study including 24 participants (12 patients with focal hand dystonia and 12 controls). The patients were referred by the neurology department of Hospital Ramón y Cajal. We gathered sociodemographic data, as well as retrospective clinical data for patients. We subsequently administered evaluation tests, in the following order: Nine-Hole Peg Test (NHPT), Box and Blocks Test (BBT), Purdue Pegboard Test (PPT), and Jebsen-Taylor Test of Hand Function (JTTHF).

RESULTS

The study sample included a total of 24 participants, 7 women and 17 men, with a mean age (standard deviation) of 50.79 (14.40) years. In the patient group, neuromuscular involvement or psycho-emotional problems were not detected in half of cases; smaller numbers of patients presented difficulties associated with the right shoulder (25%) and anxious state (33.3%).

CONCLUSIONS

Our results indicate that focal hand dystonia affects manipulative dexterity in these patients, who showed poorer performance and required more time to complete the tasks.

The Collicular-Pulvinar-Amygdala Axis and Adult-Onset Idiopathic Focal Dystonias

Adult-onset idiopathic focal dystonias (AOIFD) are the most common type of dystonia. It has varied expression including multiple motor (depending on body part affected) and non-motor symptoms (psychiatric, cognitive and sensory). The motor symptoms are usually the main reason for presentation and are most often treated with botulinum toxin. However, non-motor symptoms are the main predictors of quality of life and should be addressed appropriately, as well as treating the motor disorder. Rather than considering AOIFD as a movement disorder, a syndromic approach should be taken, one that accommodates all the symptoms. Dysfunction of the collicular-pulvinar-amygdala axis, with the superior colliculus as a central node, can explain the diverse expression of this syndrome.

The Dystonias

PURPOSE OF REVIEW

This article discusses the most recent findings regarding the diagnosis, classification, and management of genetic and idiopathic dystonia.

RECENT FINDINGS

A new approach to classifying dystonia has been created with the aim to increase the recognition and diagnosis of dystonia. Molecular biology and genetic studies have identified several genes and biological pathways involved in dystonia.

SUMMARY

Dystonia is a common movement disorder involving abnormal, often twisting, postures and is a challenging condition to diagnose. The pathophysiology of dystonia involves abnormalities in brain motor networks in the context of genetic factors. Dystonia has genetic, idiopathic, and acquired forms, with a wide phenotypic spectrum, and is a common feature in complex neurologic disorders. Dystonia can be isolated or combined with another movement disorder and may be focal, segmental, multifocal, or generalized in distribution, with some forms only occurring during the performance of specific tasks (task-specific dystonia). Dystonia is classified by clinical characteristics and presumed etiology. The management of dystonia involves accurate diagnosis, followed by treatment with botulinum toxin injections, oral medications, and surgical therapies (mainly deep brain stimulation), as well as pathogenesis-directed treatments, including the prospect of disease-modifying or gene therapies.

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.

Dystonia, chorea, hemiballismus and other dyskinesias

Hyperkinesias are heterogeneous involuntary movements that significantly differ in terms of clinical and semeiological manifestations, including rhythm, regularity, speed, duration, and other factors that determine their appearance or suppression. Hyperkinesias are due to complex, variable, and largely undefined pathophysiological mechanisms that may involve different brain areas. In this chapter, we specifically focus on dystonia, chorea and hemiballismus, and other dyskinesias, specifically, levodopa-induced, tardive, and cranial dyskinesia. We address the role of neurophysiological studies aimed at explaining the pathophysiology of these conditions. We mainly refer to human studies using surface and invasive in-depth recordings, as well as spinal, brainstem, and transcortical reflexology and non-invasive brain stimulation techniques. We discuss the extent to which the neurophysiological abnormalities observed in hyperkinesias may be explained by pathophysiological models. We highlight the most relevant issues that deserve future research efforts. The potential role of neurophysiological assessment in the clinical context of hyperkinesia is also discussed.

Task-specific dystonia in hairdressers: a questionnaire survey and review of the literature

Hairdresser dystonia is one of the occupational dystonias and task-specific movement disorders occurring as a result of long-term repetitive cutting with scissors. The task-specific dystonia manifests itself as a loss of voluntary motor control during extensive practice of cutting requiring a high level of technical proficiency. The prevalence rate of hairdresser dystonia is not well-known worldwide. A questionnaire regarding dystonia was prepared for hairdressers. After sending the questionnaires to 800 hairdressers by direct mail, 134 answers were received by mail. Five of the 134 were suspected to have hairdresser-associated focal dystonia. Thus, 3.7% of hairdressers might have task-specific dystonia. This report was limited because of the small number of participants. However, this research is valuable because it was difficult to find a patient with suspected dystonia due to concerns related to job security.

The Technical Ability and Performing Scale (TAPS): A newly developed patient-reported functional rating scale for Musician's focal dystonia

BACKGROUND

Musician's Focal Dystonia (MFD) is the most common adult-onset dystonia involving the hand and can cause a professional music career to end. MFD affects about 1% of professional musicians and is a challenging clinical condition to treat. This work aimed to validate the Technical Ability and Performing Scale (TAPS), a newly-developed patient-reported functional rating scale for the clinical assessment of the MFD burden.

METHODS

Seventy-seven musicians with MFD (40.84 ± 13.14 years) who accessed "Sol Diesis Service" were consecutively enrolled. Each subject filled in the TAPS after playing six technical passages of different complexity for 45 s each. The clinicians also collected the Arm Dystonia Disability Scale (ADDS) and Tubiana-Chamagne Scale (TCS). Cronbach's α coefficient was used to assess reliability; concurrent validity was measured using correlation with validated tools (ADDS and TCS).

RESULTS

Our results showed that the symptoms of dystonia appeared at around 33 years of age and lasted for at least three years. The Cronbach's α displayed good internal consistency (0.817) for Technical Ability (TA). The two TAPS scores, TA and Performing Score (PS), positively correlated with TCS total score and negatively with ADDS total score (concurrent validity).

CONCLUSIONS

The TAPS is a reliable and valid tool for the clinical assessment of the MFD burden. This patient-reported outcome measure may facilitate patient engagement in decision-making about their care and can help healthcare professionals to monitor the musician's change during the rehabilitative intervention.

Symptom Locus and Symptom Origin Incongruity in Runner's Dystonia - Case Study of an Elite Female Runner

Objectives: Runner's dystonia is a task-specific dystonia that occurs in the lower limbs and trunk, with diverse symptomatology. We aimed to identify the origin of a dystonic movement abnormality using combined three-dimensional kinematic analysis and electromyographic (EMG) assessment during treadmill running. Participant: A 20-year-old female runner who complained of right-foot collision with the left-leg during right-leg swing-phase, which mimicked right-ankle focal dystonia. Results: Kinematic and EMG assessment of her running motion was performed, which showed a significant drop of the left pelvis during right-leg stance-phase, and a simultaneous increase of right hip adductor muscle activity. This resulted in a pronounced adduction of the entire right lower limb with respect to the pelvis segment. Trajectories of right foot were seen to encroach upon left-leg area. Discussion: These findings suggested that the symptom of this runner was most likely a form of segmental dystonia originating from an impaired control of hip and pelvis, rather than a distal focal ankle dystonia. Conclusion: We conclude that, for individualized symptom assessment, deconstructing the symptom origin from its secondary compensatory movement is crucial for characterizing dystonia. Kinematic and EMG evaluation will therefore be a prerequisite to distinguish symptom origin from secondary compensatory movement.

Bayesian Interpretation of Essential Tremor Plus

Essential tremor (ET) plus is a new tremor classification that was introduced in 2018 by a task force of the International Parkinson and Movement Disorder Society. Patients with ET plus meet the criteria for ET but have one or more additional systemic or neurologic signs of uncertain significance or relevance to tremor (“soft signs”). Soft signs are not sufficient to diagnose another tremor syndrome or movement disorder, and soft signs in ET plus are known to have poor interrater reliability and low diagnostic sensitivity and specificity. Therefore, the clinical significance of ET plus must be interpreted probabilistically when judging whether a patient is more likely to have ET or a combined tremor syndrome, such as dystonic tremor. Such a probabilistic interpretation is possible with Bayesian analysis. This review presents a Bayesian analysis of ET plus in patients suspected of having ET versus a dystonic tremor syndrome, which is the most common differential diagnosis in patients referred for ET. Bayesian analysis of soft signs provides an estimate of the probability that a patient with possible ET is more likely to have an alternative diagnosis. ET plus is a distinct tremor classification and should not be viewed as a subtype of ET. ET plus covers a more-comprehensive phenotyping of people with possible ET, and the clinical interpretation of ET plus is enhanced with Bayesian analysis of associated soft signs.

Botulinum Toxin Therapy in Writer's Cramp and Musician's Dystonia

Task-specific focal dystonia is characterized by muscle contraction(s) during a specific task, resulting in abnormal postures or movements. Specifically, writer’s cramp involves the upper extremity during the act of writing. Musician’s dystonia has a highly variable presentation, and thus makes therapeutic options more limited. Treatments include oral pharmacologic agents, neuromodulation, surgery and, most often, botulinum toxin (BoNT) injection. Selection of target muscles for toxin injection continues to be an area of active research for these task-specific movements. We present a review of the literature selected from a predefined search of the MEDLINE and ClinicalTrials.gov databases. We include six controlled studies of botulinum toxin for the management of writer’s cramp and focal task-specific dystonia (FTSD), including musician’s dystonia. Overall, 139 patients were included across all studies, with 99 individuals injected for writer’s cramp and the remaining 40 individuals with FTSD. The age range of all patients was 18–80 years old. We included studies that utilized only the BoNT-A serotype. These studies utilized various severity scales to quantify response to toxin injection, with ratings of instrument or pen control included as subjective ratings. Of the included 139 patients in this review, pooled data for toxin response show that 73% of patients who received the drug demonstrated improvement. Specific techniques for muscle localization and targeting were difficult to study as variable methods were employed. This remains an area of ongoing exploration.

Henry Meige: The man and his understanding of dystonia, at the turn of the 19th to 20th century

BACKGROUND

Henry Meige (1866-1940), a French neurologist, the pupil of Charcot, is remembered for the eponym, the Meige syndrome, describing the clinical picture of craniocervical dystonia. This historical review highlights the controversies from his essay on "Le Juif Errant" (the Wandering Jew), and the evolution of his understanding of the movement disorders of the face and neck at the time of the encephalitis lethargica.

RESULTS

His thesis reported 5 patients from Eastern Europe, presenting with functional neurological disorders following traumatic life experiences. He wrote with Feindel the first book on movement disorders "Les tics et leur traitement". He pioneered the concept of focal dystonia and distinguished the facial median spasm as a dystonic movement disorder of the face. He highlighted the co-existence of psychopathology and the influence of the mental on tics and dystonia. He coined with Brissaud and Feindel the term "geste antagoniste" in cervical dystonia. He emphasized the importance of self-management and psycho-motor retraining for focal dystonia.

CONCLUSION

Meige made an invaluable contribution to our understanding of movement disorders, during his long medical career. The eponym Meige syndrome should be retained to describe an individual clinical entity.

Deep Brain Stimulation of the Ventral Intermediate Nucleus of the Thalamus in Writer's Cramp: A Case Report

Background

Globus pallidus internus (GPi) deep brain stimulation (DBS) and thalamotomy are interventions for writer's cramp (WC). Ventralis intermedius nucleus (VIM) DBS is targeted for tremor, however, many aspects of VIM DBS remained underexplored in WC.

Case Report

A 62-year-old man with WC underwent DBS. Dystonic tremor improved intraoperatively with ventralis oralis anterior (VoA)/ventral oralis posterior (VoP) and with subthalamic nucleus stimulation; although greatest benefit was obtained with VIM stimulation. Sustained benefit with VIM DBS at ten months post-operative was obtained.

Discussion

This case demonstrates an intraoperative approach in target selection and supports benefits of VIM DBS for WC.

Highlights

This case highlights the intraoperative approach and clinical effects of VIM DBS in the treatment of medically refractory writer's cramp (WC). We contextualize our results from this case with previous reports of VoA/VoP stimulation for WC.

Task specific dystonia - a patients' perspective

BACKGROUND

Task specific dystonia (TSD) is a subtype of dystonia with no cure and significant limitations on treatments. Few studies have investigated the outcomes of rehabilitative therapy from the patient's perspective.

PURPOSE OF THE STUDY

This study explored the interventions that patients have utilized and their perceived effectiveness in treating and managing their TSD, specifically musicians' dystonia (MD) and writer's dystonia (WD). Symptoms and the effect of TSD on the perceived performance of every day and specific tasks, and possible reasons why the condition developed, were also investigated.

STUDY DESIGN

Descriptive survey.

METHODS

Patients diagnosed with TSD, treated at a private hand therapy unit, who had consented to being contacted for research purposes, were emailed a link to an online survey (or posted if email was not available), administered via KwikSurveys. The survey consisted of 4 subsections: personal information, general medical history, dystonia medical history and dystonia treatment history.

RESULTS

Invitations were sent to 105 patients of whom 90% (n = 95/105) responded. Results for both the MD and WD groups were similar. There was a significant association between the 2 groups as to what they viewed may have led to the development of TSD (a change in technique; P < .001) and the most effective treatments (massage P< .043, modifications to the instrument P< .002; ultrasound therapy P< .013.) All reported that daily activities were affected by their condition.

DISCUSSION

Although full levels of task specific function (playing their instrument or writing) were not usually regained, participants with both MD and WD perceived improvement in symptoms with rehabilitation intervention. Three treatments were perceived to be most effective in achieving this, suggesting that these should be considered for inclusion within treatment plans.

CONCLUSIONS

From the perspective of people with TSD, a range of rehabilitation interventions are effective in enhancing symptom management, providing further evidence to support their use.

Perception of yips among professional Japanese golfers: perspectives from a network modelled approach

'Yips' in golf is a complex spectrum of anxiety and movement-disorder that affects competitive sporting performance. With unclear etiology and high prevalence documented in western literature, the perception and management of this psycho-neuromuscular problem among Japanese elite golfers is unknown. The objective of this study was to explore factors associated with yips, investigate the performance deficits and the strategies implemented to prevent yips. We surveyed approx. 1300 professional golfers on their golfing habits, anxiety and musculoskeletal problems, kinematic deficits, changes in training and their outcomes. Statistical procedures included multiple logistic regression and network analysis. 35% of the respondents had experienced yips in their career, their odds increasing proportionally to their golfing experience. Regardless of musculoskeletal symptoms, about 57% of all yips-golfers attributed their symptoms to psychological causes. Network analysis highlighted characteristic movement patterns, i.e. slowing, forceful or freezing of movement for putting, approach and teeing shots respectively. Golfers' self-administered strategies to relieve yips were mostly inconsequential. Within the limits of our self-reported survey, most golfers perceived yips as a psychological phenomenon despite evidence pointing to a movement-disorder. While self-administered interventions were satisfactory at best, it may be imperative to sensitize golfers from a movement-disorder standpoint for early management of the problem.

Splice-variant specific effects of a CACNA1H mutation associated with writer's cramp

The CACNA1H gene encodes the α1 subunit of the low voltage-activated Ca_v3.2 T-type calcium channel, an important regulator of neuronal excitability. Alternative mRNA splicing can generate multiple channel variants with distinct biophysical properties and expression patterns. Two major splice variants, containing or lacking exon 26 (± 26) have been found in different human tissues. In this study, we report splice variant specific effects of a Ca_v3.2 mutation found in patients with autosomal dominant writer’s cramp, a specific type of focal dystonia. We had previously reported that the R481C missense mutation caused a gain of function effect when expressed in Ca_v3.2 (+ 26) by accelerating its recovery from inactivation. Here, we show that when the mutation is expressed in the short variant of the channel (− 26), we observe a significant increase in current density when compared to wild-type Ca_v3.2 (− 26) but the effect on the recovery from inactivation is lost. Our data add to growing evidence that the functional expression of calcium channel mutations depends on which splice variant is being examined.

Combined treatment with C16 peptide and angiopoietin-1 confers neuroprotection and reduces inflammation in 3-nitropropionic acid-induced dystonia mice

Dystonia is a disorder associated with abnormalities in many brain regions including the basal ganglia and cerebellum. The toxin 3-Nitropropionic acid (3-NP) can induce neuropathologies in the mice striatum and nigra substance, including excitotoxicity, neuroinflammation, and extensive neuronal atrophy, characterized by progressive motor dysfunction, dystonia, and memory loss, mimicking those observed in humans. We established a mouse model of dystonia by administering 3-NP. Given the reported neuroprotective effects of the endothelial growth factor angiopoietin-1 (Ang-1) and the anti-inflammatory integrin αvβ3 binding peptide C16, we performed this study to evaluate their combined effects on 3-NP striatal toxicity and their therapeutic potential with multiple methods using an in vivo mouse model. Sixty mice were equally and randomly divided into three groups: control, 3-NP treatment, and 3-NP+C16+Ang-1 treatment. Behavioral and electrophysiological tests were conducted and the effect of the combined C16+Ang-1 treatment on neural function recovery was determined. We found that C16+Ang-1 treatment alleviated 3-NP-induced behavioral, biochemical, and cellular alterations in the central nervous system and promoted function recovery by restoring vascular permeability and reducing inflammation in the micro-environment. In conclusion, our results confirmed the neuroprotective effect of combined C16+Ang-1 treatment and suggest their potential as a complementary therapeutic against 3-NP-induced dystonia.

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.

Low-frequency oscillations in cortical level to help diagnose task-specific dystonia

Task-specific dystonia is a neurological movement disorder that abnormal contractions of muscles result in the twisting of fixed postures or muscle spasm during specific tasks. Due to the rareness and the pathophysiology of the disease, there is no test to confirm the diagnosis of task-specific dystonia, except comprehensive observations by the experts. Evidence from neural electrophysiological data suggests that enhanced low frequency (4-12 Hz) oscillations in the subcortical structure of the globus pallidus were associated with the pathological abnormalities concerning β and γ rhythms in motor areas and motor cortical network in patients with task-specific dystonia. However, whether patients with task-specific dystonia have any low-frequency abnormalities in motor cortical areas remains unclear. In this study, we hypothesized that low-frequency abnormalities are present in core motor areas and motor cortical networks in patients with task-specific dystonia during performing the non-symptomatic movements and those low-frequency abnormalities can help the diagnosis of this disease. We tested this hypothesis by using EEG, effective connectivity analysis, and a machine learning method. Fifteen patients with task-specific dystonia and 15 healthy controls were recruited. The machine learning method identified 8 aberrant movement-related network connections concerning low frequency, β and γ frequencies, which enabled the separation of the data of patients from those of controls with an accuracy of 90%. Importantly, 7 of the 8 aberrant connections engaged the premotor area contralateral to the affected hand, suggesting an important role of the premotor area in the pathological abnormities. The patients exhibited significantly lower low frequency activities during the movement preparation and significantly lower β rhythms during movements compared with healthy controls in the core motor areas. Our findings of low frequency- and β-related abnormalities at the cortical level and aberrant motor network could help diagnose task-specific dystonia in the clinical setting, and the importance of the contralesional premotor area suggests its diagnostic potential for task-specific dystonia.

The Dutch Yips Study: Results of a Survey Among Golfers

Background:

The yips in golf is currently regarded as a task-specific movement disorder, with variable phenomenology and of unclear etiology. There is some overlap with task-specific dystonia (TSD), which has also been reported in other sports. The objective was to further characterize the yips in terms of its prevalence and related factors.

Methods:

Recreational golfers from one of the larger golf clubs in the Netherlands aged 18 years or older, filled in an anonymous, web-based questionnaire with items on demographic, medical and lifestyle factors, specific yips-relevant items, as well as fanaticism, familial presence of yips, obsessive-compulsive traits, and a dystonia questionnaire.

Results:

In total, 234 golfers (26%) completed the questionnaire, among whom 52 (22%, 95% CI: 17–28%) reported to suffer from the yips. In comparison to their non-yips counterparts, the yips group was characterized by a larger proportion of men, more current or past smoking, better golf skills, longer history of playing golf, and more familial yips occurrence.

Discussion:

Golfer’s self-reported yips may be very frequent in a group of responding amateur golfers and associated factors seems to include male gender, current or past smoking, extensive golf experience and skills, and a positive family history of the yips. Further work to better understand the origin and nature of the yips is needed.

Magnetic Resonance-Guided Focused Ultrasound Thalamotomy for Focal Hand Dystonia: A Pilot Study

Background

The efficacy of magnetic resonance‐guided focused ultrasound (MRgFUS) thalamotomy for the treatment of focal hand dystonia (FHD) is not well known.

Objective

We aimed to prospectively investigate the efficacy of MRgFUS thalamotomy for the treatment of FHD.

Methods

We performed MRgFUS thalamotomy of the ventro‐oral (Vo) nucleus in 10 patients with FHD. We evaluated the scores of the Writer's Cramp Rating Scale (WCRS, 0–30; higher scores indicating greater severity), Tubiana Musician's Dystonia Scale (TMDS, 0–5; lower scores indicating greater severity), and Arm Dystonia Disability Scale (ADDS, 0%–100%; lower scores indicating greater disability) at baseline and 3 and 12 months post‐treatment.

Results

WCRS, TMDS, and ADDS scores significantly improved from 6.3 ± 2.7, 1.4 ± 0.5, and 58.7% ± 14.3% at baseline to 1.6 ± 3.1 (P = 0.011), 5.0 ± 0 (P = 0.0001), and 81.6% ± 22.9% (P = 0.0229) at 12 months, respectively. There was one prolonged case of dysarthria at 12 months.

Conclusion

We show that MRgFUS Vo‐thalamotomy significantly improved FHD. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Evidence of rehabilitation therapy in task-specific focal dystonia: a systematic review

INTRODUCTION

Task-specific dystonias are primary focal dystonias characterized by excessive muscle contractions producing abnormal postures during selective motor activities that often involve highly skilled, repetitive movements. Based on the idea of excessive motor excitability and aberrant sensorimotor integration in the pathophysiology of task-specific dystonia, sensorimotor retraining may hold promise. The purpose of this systematic review was to investigate the available evidence about the role of rehabilitation therapy as a treatment for task-specific dystonia.

EVIDENCE ACQUISITION

A systematic review was performed of studies identified through Pubmed and Embase in a structured search strategy by independent author screening. The JBI (Joanna Briggs Institute) Critical Appraisal Checklist and RoB 2 were used to evaluate their methodological quality.

EVIDENCE SYNTHESIS

21 studies were included for qualitative synthesis. Most of the reports are small single group pre-/post-test study designs with a variability in the type of task-specific dystonia and the type of evaluated outcome measures. Rehabilitation interventions were grouped into six categories based upon the underlying theoretical basis of different approaches: 1) movement practice, 2) training with constraint, 3) sensory reorganization, 4) biofeedback training, 5) neuromodulation with training and 6) compensatory strategies.

CONCLUSIONS

Although it appears that a number of task-specific dystonia patients may improve with rehabilitation therapy, no definitive conclusions can be drawn. More research in this field is needed, using standardized approaches and clearly defined outcome measures in larger cohorts of task-specific dystonia patients that are clinically and diagnostically well characterized.

Anisotropy of the Drawing Plane in Focal Hand Dystonia: A Case Report and a Novel Postulate of Dysfunctional Tensorial Networks

The pathophysiology of the dystonias has been associated with loss of inhibition in the sensory-motor cortex, brainstem and spinal cord, abnormal motor preparation in the pre-motor cortex, abnormal sensory processing in the sensory cortex, maladaptive plasticity and abnormal sensory-motor integration in the cerebral cortex. We present a case of focal hand dystonia with variance of spiral drawing in the horizontal and vertical planes, that is amelioration of spiral drawing in the vertical plane compared to the horizontal plane. We refer to this phenomenon as "anisotropy". We seize upon this unique finding and postulate a novel mechanism for the generation of the dystonias. The anisotropy referred to can only be explained by a breakdown of the tensorial transformation of a covariant vector to a contravariant vector in the frequency hyperspace of the brain. This novel hypothesis is based on the unequivocal invariance of tensorial transformation, a mathematical fact in differential geometry, the very geometry of the most celebrated and sublime General Theory of Relativity, and the model of dynamic brain function proposed by Pellionisz and Llinas.

Functional Dystonia: Differentiation From Primary Dystonia and Multidisciplinary Treatments

Dystonia is a common movement disorder, involving sustained muscle contractions, often resulting in twisting and repetitive movements and abnormal postures. Dystonia may be primary, as the sole feature (isolated) or in combination with other movement disorders (combined dystonia), or as one feature of another neurological process (secondary dystonia). The current hypothesis is that dystonia is a disorder of distributed brain networks, including the basal ganglia, cerebellum, thalamus and the cortex resulting in abnormal neural motor programs. In comparison, functional dystonia (FD) may resemble other forms of dystonia (OD) but has a different pathophysiology, as a subtype of functional movement disorders (FMD). FD is the second most common FMD and amongst the most diagnostically challenging FMD subtypes. Therefore, distinguishing between FD and OD is important, as the management of these disorders is distinct. There are also different pathophysiological underpinnings in FD, with for example evidence of involvement of the right temporoparietal junction in functional movement disorders that is believed to serve as a general comparator of internal predictions/motor intentions with actual motor events resulting in disturbances in self-agency. In this article, we present a comprehensive review across the spectrum of FD, including oromandibular and vocal forms and discuss the history, clinical clues, evidence for adjunctive "laboratory-based" testing, pathophysiological research and prognosis data. We also provide the approach used at the Massachusetts General Hospital Dystonia Center toward the diagnosis, management and treatment of FD. A multidisciplinary approach, including neurology, psychiatry, physical, occupational therapy and speech therapy, and cognitive behavioral psychotherapy approaches are frequently required; pharmacological approaches, including possible targeted use of botulinum toxin injections and inpatient programs are considerations in some patients. Early diagnosis and treatment may help prevent unnecessary investigations and procedures, while facilitating the appropriate management of these highly complex patients, which may help to mitigate frequently poor clinical outcomes.