Motor training as treatment in focal hand dystonia

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.

Treatment of focal hand dystonia: current status

BACKGROUND

Focal hand dystonia (FHD) is usually adult-onset focal dystonia that can be associated with marked occupational and functional disability leading to reduced quality of life.

METHODS

Relevant studies on treatment options for FHD, their limitations, and current recommendations were reviewed using the PubMed search until March 31, 2021. Besides, the reference lists of the retrieved publications were manually searched to explore other relevant studies.

RESULTS

and conclusion Currently, botulinum toxin has the best evidence for treatment of FHD, and 20-90% of patients experience symptomatic improvement. However, its benefit is often limited by the reduction of muscle tonus acting on the muscle spindle. Different surgical modalities that have been used to treat focal hand dystonia include lesional surgery, deep brain stimulation, and magnetic resonance-guided focused ultrasound thalamotomy. Recent studies exploring the role of behavioral techniques, sensorimotor training, and neuromodulation for the treatment of focal hand dystonia have reported good outcomes, but larger studies are required before implementing these interventions in practice.

Best Practices in the Clinical Management of Progressive Supranuclear Palsy and Corticobasal Syndrome: A Consensus Statement of the CurePSP Centers of Care

Progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS; the most common phenotype of corticobasal degeneration) are tauopathies with a relentless course, usually starting in the mid-60s and leading to death after an average of 7 years. There is as yet no specific or disease-modifying treatment. Clinical deficits in PSP are numerous, involve the entire neuraxis, and present as several discrete phenotypes. They center on rigidity, bradykinesia, postural instability, gait freezing, supranuclear ocular motor impairment, dysarthria, dysphagia, incontinence, sleep disorders, frontal cognitive dysfunction, and a variety of behavioral changes. CBS presents with prominent and usually asymmetric dystonia, apraxia, myoclonus, pyramidal signs, and cortical sensory loss. The symptoms and deficits of PSP and CBS are amenable to a variety of treatment strategies but most physicians, including many neurologists, are reluctant to care for patients with these conditions because of unfamiliarity with their multiplicity of interacting symptoms and deficits. CurePSP, the organization devoted to support, research, and education for PSP and CBS, created its CurePSP Centers of Care network in North America in 2017 to improve patient access to clinical expertise and develop collaborations. The directors of the 25 centers have created this consensus document outlining best practices in the management of PSP and CBS. They formed a writing committee for each of 12 sub-topics. A 4-member Steering Committee collated and edited the contributions. The result was returned to the entire cohort of authors for further comments, which were considered for incorporation by the Steering Committee. The authors hope that this publication will serve as a convenient guide for all clinicians caring for patients with PSP and CBS and that it will improve care for patients with these devastating but manageable disorders.

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.

Treatment of Dystonia: Medications, Neurotoxins, Neuromodulation, and Rehabilitation

Dystonia is a complex disorder with numerous presentations occurring in isolation or in combination with other neurologic symptoms. Its treatment has been significantly improved with the advent of botulinum toxin and deep brain stimulation in recent years, though additional investigation is needed to further refine these interventions. Medications are of critical importance in forms of dopa-responsive dystonia but can be beneficial in other forms of dystonia as well. Many different rehabilitative paradigms have been studied with variable benefit. There is growing interest in noninvasive stimulation as a potential treatment, but with limited long-term benefit shown to date, and additional research is needed. This article reviews existing evidence for treatments from each of these categories. To date, there are many examples of incomplete response to available treatments, and improved therapies are needed.

Botulinum toxin and occupational therapy for Writer's cramp

BACKGROUND

Writer's cramp (WC) is a form of focal hand dystonia, for which focal botulinum neurotoxin (BoNT) injections are the current best therapy. Past studies have shown that some types of rehabilitative therapy can be useful. We hypothesized that BoNT together with a specific type of occupational therapy would be better than BoNT alone for treating WC patients comparing the effects with a patient-rated subjective scale.

METHODS

Twelve WC patients were randomized to two groups. Six received only BoNT therapy and 6 received BoNT & occupational therapy. The occupational therapy involved specific exercises of finger movements in the direction opposite to the dystonic movements during writing. BoNT was injected by movement disorders neurologists in the affected muscles under electromyography-guidance. The primary outcome was the patient-rated subjective scale at 20 weeks. Secondary exploratory outcomes included the writer's cramp rating scale (WCRS), writer's cramp impairment scale (WCIS), the writer's cramp disability scale (WCDS), handgrip strength and kinetic parameters.

RESULTS

The patient-rated subjective scale scores at 20 weeks were not significantly different between the two groups. Significant objective improvement was noted in the BoNT & occupational therapy group, as noted by the decrease (28%) in WCIS scores.

CONCLUSIONS

Improvement of the primary outcome measure, the patient-rated subjective scale, was not achieved. However, significant improvement was found in the BoNT & occupational therapy group in a secondary measure of impairment. Our hypothesis-driven study results are likely limited by small sample size, and further large-scale studies of occupational therapy methods to improve the efficacy of BoNT seems worthwhile.

Systematic Review of Rehabilitation in Focal Dystonias: Classification and Recommendations

Background

Rehabilitation interventions are rarely utilized as an alternative or adjunct therapy for focal dystonias. Reasons for limited utilization are unknown, but lack of conclusive evidence of effectiveness is likely a crucial factor.

Methods and Findings

The purpose of this systematic review was to determine the level of evidence for rehabilitation interventions in focal dystonias. Rehabilitation interventions were classified based upon the underlying theoretical basis of different approaches, and the strength of evidence for each category was evaluated to identify gaps in the field. Prospective studies using rehabilitation methods in cervical, hand, and foot dystonia were reviewed. The key elements of treatments tested were identified and studies were grouped into six categories based on the theoretical basis of the intervention: (1) movement practice, (2) training with constraint, (3) sensory reorganization, (4) normalization of muscle activity with external techniques, (5) neuromodulation with training, and (6) compensatory strategies. Quality of the body of evidence ranged from very low‐to‐low according to the grades of recommendation, assessment, development, and evaluation (GRADE). Despite inconclusive evidence for these rehabilitation approaches, data suggest that intensive movement practice and neuromodulation combined with motor training should be further explored.

Conclusions

This systematic review presents a novel approach to classify studies of rehabilitation in focal dystonias based on the theoretical basis of intervention. The proposed classification system will move toward a unified theoretical understanding of rehabilitation interventions in dystonia. Moreover, it will help provide recommendations for clinical applications and future investigations.

Occupational Health and the Performing Arts: An Introduction

OBJECTIVE

Workplace hazards in the performing arts cause injuries, disabilities, and deaths every year. Occupational health professionals are familiar with most of these hazards and are particularly qualified to contribute to efforts to reduce them. This article reviews current health issues in the performing arts and highlights opportunities for occupational health contributions.

METHODS

Recognized experts in performing arts medicine were consulted and articles illustrating performing arts health issues were reviewed. Literature sources included medical databases, unindexed art-health publications, and popular press articles.

RESULTS

Resources discussing hazards and health issues in theater, dance, voice, and instrumental musicians were located and reviewed.

CONCLUSIONS

Treatment providers have a history of involvement with segments of the performing arts. The occupational health approach to workplace health issues can effectively complement these efforts. Sources of further information on performing arts health concerns are available.

Research Priorities in Limb and Task-Specific Dystonias

Dystonia, which causes intermittent or sustained abnormal postures and movements, can present in a focal or a generalized manner. In the limbs, focal dystonia can occur in either the upper or lower limbs and may be task-specific causing abnormal motor performance for only a specific task, such as in writer’s cramp, runner’s dystonia, or musician’s dystonia. Focal limb dystonia can be non-task-specific and may, in some circumstances, be associated with parkinsonian disorders. The true prevalence of focal limb dystonia is not known and is likely currently underestimated, leaving a knowledge gap and an opportunity for future research. The pathophysiology of focal limb dystonia shares some commonalities with other dystonias with a loss of inhibition in the central nervous system and a loss of the normal regulation of plasticity, called homeostatic plasticity. Functional imaging studies revealed abnormalities in several anatomical networks that involve the cortex, basal ganglia, and cerebellum. Further studies should focus on distinguishing cause from effect in both physiology and imaging studies to permit focus on most relevant biological correlates of dystonia. There is no specific therapy for the treatment of limb dystonia given the variability in presentation, but off-label botulinum toxin therapy is often applied to focal limb and task-specific dystonia. Various rehabilitation techniques have been applied and rehabilitation interventions may improve outcomes, but small sample size and lack of direct comparisons between methods to evaluate comparative efficacy limit conclusions. Finally, non-invasive and invasive therapeutic modalities have been explored in small studies with design limitations that do not yet clearly provide direction for larger clinical trials that could support new clinical therapies. Given these gaps in our clinical, pathophysiologic, and therapeutic knowledge, we have identified priorities for future research including: the development of diagnostic criteria for limb dystonia, more precise phenotypic characterization and innovative clinical trial design that considers clinical heterogeneity, and limited available number of participants.

A Dynamic Circuit Hypothesis for the Pathogenesis of Blepharospasm

Blepharospasm (sometimes called “benign essential blepharospasm,” BEB) is one of the most common focal dystonias. It involves involuntary eyelid spasms, eye closure, and increased blinking. Despite the success of botulinum toxin injections and, in some cases, pharmacologic or surgical interventions, BEB treatments are not completely efficacious and only symptomatic. We could develop principled strategies for preventing and reversing the disease if we knew the pathogenesis of primary BEB. The objective of this study was to develop a conceptual framework and dynamic circuit hypothesis for the pathogenesis of BEB. The framework extends our overarching theory for the multifactorial pathogenesis of focal dystonias (Peterson et al., 2010) to incorporate a two-hit rodent model specifically of BEB (Schicatano et al., 1997). We incorporate in the framework three features critical to cranial motor control: (1) the joint influence of motor cortical regions and direct descending projections from one of the basal ganglia output nuclei, the substantia nigra pars reticulata, on brainstem motor nuclei, (2) nested loops composed of the trigeminal blink reflex arc and the long sensorimotor loop from trigeminal nucleus through thalamus to somatosensory cortex back through basal ganglia to the same brainstem nuclei modulating the reflex arc, and (3) abnormalities in the basal ganglia dopamine system that provide a sensorimotor learning substrate which, when combined with patterns of increased blinking, leads to abnormal sensorimotor mappings manifest as BEB. The framework explains experimental data on the trigeminal reflex blink excitability (TRBE) from Schicatano et al. and makes predictions that can be tested in new experimental animal models based on emerging genetics in dystonia, including the recently characterized striatal-specific D1R dopamine transduction alterations caused by the GNAL mutation. More broadly, the model will provide a guide for future efforts to mechanistically link multiple factors in the pathogenesis of BEB and facilitate simulations of how exogenous manipulations of the pathogenic factors could ultimately be used to prevent and reverse the disorder.

Kinematic and kinetic assessment of upper limb movements in patients with writer's cramp

Background

The assessment and treatment of writer’s cramp is complicated due to the variations in the forces and angles of involved joints. Additionally, in some cases compensatory movements for cramp relief further complicates assessment. Currently these variables are subjectively measured with clinical scales and visual assessments. This subjectivity makes it difficult to successfully administer interventions such as Botulinum toxin injection or orthotics resulting in poor efficacy and significant side effects.

Method

A multi-sensor system was used to record finger and wrist forces along with deviation angles at the wrist, elbow and shoulder while 9 patients with writer's cramp performed a series of standardized tasks on surfaces inclined at different angles. Clinical, kinetic, and kinematic information regarding cramping was collected.

Results

First, four tasks appeared to best predict cramp occurrence. Second, unique biomechanical profiles emerged for patients regarding force, angles and cramp severity. Third, cluster analyses using these features showed a clear separation of patients into two severity classes. Finally, a relationship between severity and kinetic-kinematic information suggested that primary cramping versus compensatory movements could be potentially inferred.

Conclusions

The results demonstrate that using a set of standardized tasks and objective measures, individual profiles for arm movements and applied forces associated with writer’s cramp can be generated. The clinician can then accurately target the biomechanics specifically, whether it is with injection or other rehabilitative measures, fulfilling an important unmet need in the treatment of writer’s cramp.

Electronic supplementary material

The online version of this article (doi:10.1186/s12984-016-0122-0) contains supplementary material, which is available to authorized users.

Diagnosis and treatment of dystonia

The dystonias are a group of disorders characterized by excessive involuntary muscle contractions leading to abnormal postures and/or repetitive movements. A careful assessment of the clinical manifestations is helpful for identifying syndromic patterns that focus diagnostic testing on potential causes. If a cause is identified, specific etiology-based treatments may be available. In most cases, a specific cause cannot be identified, and treatments are based on symptoms. Treatment options include counseling, education, oral medications, botulinum toxin injections, and several surgical procedures. A substantial reduction in symptoms and improved quality of life is achieved in most patients by combining these options.

Sensory-motor integration in focal dystonia

Traditional definitions of focal dystonia point to its motor component, mainly affecting planning and execution of voluntary movements. However, focal dystonia is tightly linked also to sensory dysfunction. Accurate motor control requires an optimal processing of afferent inputs from different sensory systems, in particular visual and somatosensory (e.g., touch and proprioception). Several experimental studies indicate that sensory-motor integration - the process through which sensory information is used to plan, execute, and monitor movements - is impaired in focal dystonia. The neural degenerations associated with these alterations affect not only the basal ganglia-thalamic-frontal cortex loop, but also the parietal cortex and cerebellum. The present review outlines the experimental studies describing impaired sensory-motor integration in focal dystonia, establishes their relationship with changes in specific neural mechanisms, and provides new insight towards the implementation of novel intervention protocols. Based on the reviewed state-of-the-art evidence, the theoretical framework summarized in the present article will not only result in a better understanding of the pathophysiology of dystonia, but it will also lead to the development of new rehabilitation strategies.

Are movement disorders and sensorimotor injuries pathologic synergies? When normal multi-joint movement synergies become pathologic

The intact nervous system has an exquisite ability to modulate the activity of multiple muscles acting at one or more joints to produce an enormous range of actions. Seemingly simple tasks, such as reaching for an object or walking, in fact rely on very complex spatial and temporal patterns of muscle activations. Neurological disorders such as stroke and focal dystonia affect the ability to coordinate multi-joint movements. This article reviews the state of the art of research of muscle synergies in the intact and damaged nervous system, their implications for recovery and rehabilitation, and proposes avenues for research aimed at restoring the nervous system’s ability to control movement.

Proprioceptive dysfunction in focal dystonia: from experimental evidence to rehabilitation strategies

Dystonia has historically been considered a disorder of the basal ganglia, mainly affecting planning and execution of voluntary movements. This notion comes from the observation that most lesions responsible for secondary dystonia involve the basal ganglia. However, what emerges from recent research is that dystonia is linked to the dysfunction of a complex neural network that comprises basal ganglia–thalamic–frontal cortex, but also the inferior parietal cortex and the cerebellum. While dystonia is clearly a motor problem, it turned out that sensory aspects are also fundamental, especially those related to proprioception. We outline experimental evidence for proprioceptive dysfunction in focal dystonia from intrinsic sensory abnormalities to impaired sensorimotor integration, which is the process by which sensory information is used to plan and execute volitional movements. Particularly, we will focus on proprioceptive aspects of dystonia, including: (i) processing of vibratory input, (ii) temporal discrimination of two passive movements, (iii) multimodal integration of visual-tactile and proprioceptive inputs, and (iv) motor control in the absence of visual feedback. We suggest that these investigations contribute not only to a better understanding of dystonia pathophysiology, but also to develop rehabilitation strategies aimed at facilitating the processing of proprioceptive input.

Proprioceptive rehabilitation of upper limb dysfunction in movement disorders: a clinical perspective

Movement disorders (MDs) are frequently associated with sensory abnormalities. In particular, proprioceptive deficits have been largely documented in both hypokinetic (Parkinson’s disease) and hyperkinetic conditions (dystonia), suggesting a possible role in their pathophysiology. Proprioceptive feedback is a fundamental component of sensorimotor integration allowing effective planning and execution of voluntary movements. Rehabilitation has become an essential element in the management of patients with MDs, and there is a strong rationale to include proprioceptive training in rehabilitation protocols focused on mobility problems of the upper limbs. Proprioceptive training is aimed at improving the integration of proprioceptive signals using “task-intrinsic” or “augmented feedback.” This perspective article reviews the available evidence on the effects of proprioceptive stimulation in improving upper limb mobility in patients with MDs and highlights the emerging innovative approaches targeted to maximizing the benefits of exercise by means of enhanced proprioception.

Emerging concepts in the physiological basis of dystonia

Work over the past 2 decades has led to substantial changes in our understanding of dystonia pathophysiology. Three general abnormalities appear to underlie the pathophysiological substrate. The first is a loss of inhibition. This makes sense considering that it may be responsible for the excess of movement and for the overflow phenomena seen in dystonia. A second abnormality is sensory dysfunction which is related to the mild sensory complaints in patients with focal dystonias and may be responsible for some of the motor dysfunction. Third, evidence from animal models of dystonia as well as from patients with primary dystonia has revealed significant alterations of synaptic plasticity characterized by a disruption of homeostatic plasticity, with a prevailing facilitation of synaptic potentiation, together with the loss of synaptic inhibitory processes. We speculate that during motor learning this abnormal plasticity may lead to an abnormal sensorimotor integration, leading to consolidation of abnormal motor engrams. If so, then removing this abnormal plasticity might have little immediate effect on dystonic movements because bad motor memories have already been ''learned'' and are difficult to erase. These considerations might explain the delayed clinical effects of deep brain stimulation (DBS) in patients with generalized dystonia. Current lines of research will be discussed from a network perspective. © 2013 Movement Disorder Society.

Sensitive Training Through Body Awareness to Improve the Writing of Patients with Writer's Cramp

The aim of this article is to evaluate if body awareness is important to improve the writing ability before using the splints. Twelve patients with writer's cramp were evaluated by a specialist in movement disorders. The Burke-Fahn-Marsden Scale (BFM), the Jedynak Protocol and the Analog Pain Scale were used. The rehabilitation training was administered over an eight-week period, in two phases of four weeks each, twice a week. Each session would last 60 minutes. A significant improvement was shown, not only in the motor, but also in the pain perception, through the BFM scale, the Jedynak Protocol and the Analog Pain Scale. Therefore, we conclude that the motor training, thanks to the body awareness and immobilization by splints of the affected dystonic musculature, led to an important improvement in the writer's cramp writing.

Task specific grip force control in writer's cramp

OBJECTIVE

Writer's cramp is defined as a task specific focal dystonia generating hypertonic muscle co-contractions during handwriting resulting in impaired writing performance and exaggerated finger force. However, little is known about the generalisation of grip force across tasks others than writing. The aim of the study was to directly compare regulation of grip forces during handwriting with force regulation in other fine-motor tasks in patients and control subjects.

METHODS

Handwriting, lifting and cyclic movements of a grasped object were investigated in 21 patients and 14 controls. The applied forces were registered in all three tasks and compared between groups and tasks. In addition, task-specific measures of fine-motor skill were assessed.

RESULTS

As expected, patients generated exaggerated forces during handwriting compared to control subjects. However there were no statistically significant group differences during lifting and cyclic movements. The control group revealed a generalisation of grip forces across manual tasks whereas in patients there was no such correlation.

CONCLUSION

We conclude that increased finger forces during handwriting are a task-specific phenomenon that does not necessarily generalise to other fine-motor tasks.

SIGNIFICANCE

Force control of patients with writer's cramp in handwriting and other fine-motor tasks is characterised by individualised control strategies.

The focal dystonias: current views and challenges for future research

The most common forms of dystonia are those that develop in adults and affect a relatively isolated region of the body. Although these adult-onset focal dystonias are most prevalent, knowledge of their etiologies and pathogenesis has lagged behind some of the rarer generalized dystonias, in which the identification of genetic defects has facilitated both basic and clinical research. This summary provides a brief review of the clinical manifestations of the adult-onset focal dystonias, focusing attention on less well understood clinical manifestations that need further study. It also provides a simple conceptual model for the similarities and differences among the different adult-onset focal dystonias as a rationale for lumping them together as a class of disorders while at the same time splitting them into subtypes. The concluding section outlines some of the most important research questions for the future. Answers to these questions are critical for advancing our understanding of this group of disorders and for developing novel therapeutics.

Transcranial magnetic stimulation in dystonia

Transcranial magnetic stimulation (TMS) is a method of noninvasive brain stimulation that directly affects the cerebral cortex but not deep structures. TMS has been used extensively in patients with primary dystonia to test the excitability of connections within and among motor areas of the cortex, and has provided useful information on pathophysiology; however, interindividual variability in the responses has resulted in difficulties in translating this method into a clinically applicable diagnostic use. In addition, TMS studies have disclosed that dystonia is a disorder linked to a disruption of synaptic "scaling," with an excess of synaptic plasticity that is in keeping with findings obtained in animal models of dystonia. This alteration is a unique feature of organic dystonia and may be helpful in differentiating patients with psychogenic dystonia. Finally, TMS can potentially be used as a therapeutic tool to treat some forms of dystonia, such as focal hand dystonia, where pharmacological options or injections of botulinum toxin are often ineffective.

Hand pain other than carpal tunnel syndrome (CTS): the role of occupational factors

Some occupational factors have been implicated in the development of disorders manifested as hand pain. The associations seem to be well documented in processes such as hand-arm vibration syndrome (HAVS) or writer's cramp. There are contradictory data in the literature about the relationships of trigger finger, De Quervain's tenosynovitis (DQT) and tenosynovitis of the wrist with occupational factors. In this article, we review current knowledge about clinical manifestations, case definition, implicated occupational factors, diagnosis and treatment of the most relevant hand pain disorders that have been associated with occupational factors, excluding carpal tunnel syndrome (CTS).

Milestones in clinical neurophysiology

Over the last 25 years, clinical neurophysiology has made many advances in the understanding, diagnosis, and even treatment of different movement disorders. Transcranial magnetic stimulation has been the biggest technical advance. Progress in pathophysiology includes improved knowledge about bradykinesia in Parkinson's disease, loss of inhibition and increased plasticity in dystonia, abnormal startle in hyperekplexia, and various features of psychogenic movement disorders that can aid diagnosis. Studies have been done looking at the use of noninvasive brain stimulation for therapy, but effects are generally small.

Amplitude and timing of somatosensory cortex activity in task-specific focal hand dystonia

OBJECTIVE

Task-specific focal hand dystonia (tspFHD) is a movement disorder diagnosed in individuals performing repetitive hand behaviors. The extent to which processing anomalies in primary sensory cortex extend to other regions or across the two hemispheres is presently unclear.

METHODS

In response to low/high rate and novel tactile stimuli on the affected and unaffected hands, magnetoencephalography (MEG) was used to elaborate activity timing and amplitude in the primary somatosensory (S1) and secondary somatosensory/parietal ventral (S2/PV) cortices. MEG and clinical performance measures were collected from 13 patients and matched controls.

RESULTS

Compared to controls, subjects with tspFHD had increased response amplitude in S2/PV bilaterally in response to high rate and novel stimuli. Subjects with tspFHD also showed increased response latency (low rate, novel) of the affected digits in contralateral S1. For high rate, subjects with tspFHD showed increased response latency in ipsilateral S1 and S2/PV bilaterally. Activation differences correlated with functional sensory deficits (predicting a latency shift in S1), motor speed and muscle strength.

CONCLUSIONS

There are objective differences in the amplitude and timing of activity for both hands across contralateral and ipsilateral somatosensory cortex in patients with tspFHD.

SIGNIFICANCE

Knowledge of cortical processing abnormalities across S1 and S2/PV in dystonia should be applied towards the development of learning-based sensorimotor interventions.

Reaching and writing movements: sensitive and reliable tools to measure genetic dystonia in children

The aim of this study was to provide a quantitative assessment of pure dystonia in a group of children. Kinematic and muscular characteristics of unconstrained movements of the upper limb, reaching and writing, were investigated. During reaching, the distinguishing factors of dystonic movement were reduced velocity, loss of muscular activation focalization, and impairment of rest-movement modulation. Muscular parameters were able to linearly discriminate the different levels of severity. These results support the hypothesis that basal ganglia dysfunction is responsible for compromising the motor activity focusing. The handwriting movement revealed that the kinematic coordination was altered depending on dystonia severity scores. The 2 protocols revealed themselves feasible and sensitive for detecting even local and subclinical signs. Hence, this work provides a contribution toward a reliable assessment of pure dystonia, crucial for clinical characterization of patients and evaluation of the different treatment options.

Transcranial direct current stimulation for the treatment of focal hand dystonia

The treatment of writer's cramp, a task-specific focal hand dystonia, needs new approaches. A deficiency of inhibition in the motor cortex might cause writer's cramp. Transcranial direct current stimulation modulates cortical excitability and may provide a therapeutic alternative. In this randomized, double-blind, sham-controlled study, we investigated the efficacy of cathodal stimulation of the contralateral motor cortex in 3 sessions in 1 week. Assessment over a 2-week period included clinical scales, subjective ratings, kinematic handwriting analysis, and neurophysiological evaluation. Twelve patients with unilateral dystonic writer's cramp were investigated; 6 received transcranial direct current and 6 sham stimulation. Cathodal transcranial direct current stimulation had no favorable effects on clinical scales and failed to restore normal handwriting kinematics and cortical inhibition. Subjective worsening remained unexplained, leading to premature study termination. Repeated sessions of cathodal transcranial direct current stimulation of the motor cortex yielded no favorable results supporting a therapeutic potential in writer's cramp.

Neurophysiology of dystonia: The role of inhibition

The pathophysiology of dystonia has been best studied in patients with focal hand dystonia. A loss of inhibitory function has been demonstrated at spinal, brainstem and cortical levels. Many cortical circuits seem to be involved. One consequence of the loss of inhibition is a failure of surround inhibition, and this appears to directly lead to overflow and unwanted muscle spasms. There are mild sensory abnormalities and deficits in sensorimotor integration; these also might be explained by a loss of inhibition. Increasing inhibition may be therapeutic. A possible hypothesis is that there is a genetic loss of inhibitory interneurons in dystonia and that this deficit is a substrate on which other factors can act to produce dystonia. This article is part of a Special Issue entitled "Advances in dystonia".

Paramedical treatment in primary dystonia: a systematic review

Dystonia is a disabling movement disorder with a significant impact on quality of life. The current therapeutic armamentarium includes various drugs, botulinum toxin injections, and occasionally (neuro)surgery. In addition, many patients are referred for paramedical (including allied health care) interventions. An enormous variation in the paramedical treatment is provided, largely because evidence-based, accepted treatment regimes are not available. We have conducted a systematic review of studies that explored the effect of various paramedical interventions in primary dystonia. Only studies that have used clinical outcome measures were included. There were no class A1 or A2 studies and therefore, level 1 or 2 practice recommendations for a specific intervention could not be deducted. Many papers were case reports, mostly with a very limited number of patients and a clear publication bias for beneficial effects of a particular paramedical intervention. Some potentially interesting interventions come from class B studies, which include physical therapy in addition to botulinum toxin injections (BoNT-A) in cervical dystonia; sensorimotor training and transcutaneous electrical nerve stimulation (TENS) in writer's cramp; and speech therapy added to BoNT-A injections in laryngeal dystonia. Good quality clinical studies are therefore warranted, which should have the aim to be generally applicable. A design in which the paramedical intervention is added to a current gold standard, for example, BoNT-A injections in cervical dystonia, is recommended.

A new therapeutic proposal for writer's cramp: a case report

CONTEXT

Writer's cramp is a kind of focal hand dystonia that appears when individuals are writing. Since pharmacological treatment has not shown the desired therapeutic response, a study on immobilization of the damaged musculature was performed on two individuals with writer's cramp, using splints with the objective of reducing the handwriting abnormalities.

CASE REPORT

Two patients presenting writer's cramp who had previously undergone different therapies, including botulinum toxin, without an adequate response, participated in a body awareness program, followed by immobilization of the hand musculature damaged by dystonia, by means of splints, with handwriting training. At the end of the procedure, objective and subjective improvements in the motor pattern of writing could be observed. The immobilization of the dystonic musculature of the hand by means of splints and the motor training of handwriting helped to improve and consequently to reduce the dystonic component observed in the writer's cramp.

Regaining motor control in musician's dystonia by restoring sensorimotor organization

Professional musicians are an excellent model of long-term motor learning effects on structure and function of the sensorimotor system. However, intensive motor skill training has been associated with task-specific deficiency in hand motor control, which has a higher prevalence among musicians (musician's dystonia) than in the general population. Using a transcranial magnetic stimulation paradigm, we previously found an expanded spatial integration of proprioceptive input into the hand motor cortex [sensorimotor organization (SMO)] in healthy musicians. In musician's dystonia, however, this expansion was even larger. Whereas motor skills of musicians are likely to be supported by a spatially expanded SMO, we hypothesized that in musician's dystonia this might have developed too far and now disrupts rather than assists task-specific motor control. If so, motor control should be regained by reversing the excessive reorganization in musician's dystonia. Here, we test this hypothesis and show that a 15 min intervention with proprioceptive input (proprioceptive training) restored SMO in pianists with musician's dystonia to the pattern seen in healthy pianists. Crucially, task-specific motor control improved significantly and objectively as measured with a MIDI (musical instrument digital interface) piano, and the amount of behavioral improvement was significantly correlated to the degree of sensorimotor reorganization. In healthy pianists and nonmusicians, the SMO and motor performance remained essentially unchanged. These findings suggest that the differentiation of SMO in the hand motor cortex and the degree of motor control of intensively practiced tasks are significantly linked and finely balanced. Proprioceptive training restored this balance in musician's dystonia to the behaviorally beneficial level of healthy musicians.

Clinical relevance of neuromuscular findings and abnormal movement patterns: a comparison between focal hand dystonia and upper extremity entrapment neuropathies

NARRATIVE REVIEW: Patients with focal hand dystonia and upper extremity entrapment neuropathies may present with similar symptoms and risk factors making it difficult to distinguish between the two diagnoses. Evaluating for the presence of neuromuscular findings and abnormal movement patterns can help assist the hand therapist in identifying the presence of focal hand dystonia or peripheral motor axon involvement in the absence of pronounced muscle atrophy. The purposes of this review article are twofold. First, to describe selected neuromuscular signs and symptoms characteristic of patients presenting with repetitive overuse syndromes of the upper limb leading to either a nerve entrapment syndrome or a focal hand dystonia. The selected topics will be limited to an overview of ectopic neuronal activity with an emphasis on fasciculations, muscle spasms/cramps, and sensation (including pain). Second, the article will conclude with a brief synopsis of focal hand dystonia and compression neuropathies, highlighting general assessment and treatment principles.

Novel nonpharmacologic perspectives for the treatment of task-specific focal hand dystonia

NARRATIVE REVIEW: The pathophysiology of focal hand dystonia (FHD) has not yet been completely clarified. Although there is a loss of inhibition at multiple levels of the central nervous system, maladaptive plasticity of the cerebral cortex as well as impairments in sensory and motor representations have also been reported. All of these abnormalities can be viewed as an epiphenomenon of the primary--still unknown--abnormality underlying focal dystonia. The purpose of this review is to describe the underlying constructs of novel nonpharmacologic approaches for the treatment of FHD. Alternative or complementary approaches to botulinum toxin injections such as behavioral training strategies and brain stimulation techniques are reviewed. None of the proposed treatments appears to be definitive and applicable to all patients with FHD. Each treatment strategy elicited some benefit in a fraction of patients. The combination of more than one approach (retraining, immobilization, botulinum toxin, neuromodulation, etc.) could lead to a better control of FHD.

Focal hand dystonia: effectiveness of a home program of fitness and learning-based sensorimotor and memory training

STUDY DESIGN

This was a pre post test design.

INTRODUCTION

Retraining the brain is one approach to remediate movement dysfunction resulting from task specific focal hand dystonia (FHD(TSP)).

PURPOSE

Document change in task specific performance (TSP) for patients with FHD(TSP) after 8 weeks of comprehensive home training (fitness activities, task practice, learning based memory and sensorimotor training).

METHODS

Thirteen subjects were admitted and evaluated at baseline, immediately and 6 months post treatment for task specific performance, functional independence, sensory discrimination, fine motor speed and strength. In Phase I, 10 subjects were randomly assigned to home training alone or supervised practice prior to initiating the home training. In phase II, 2 subjects crossed over and 3 new subjects were added (18 hands). The intent to treat model was followed. Outcomes were summarized by median, effect size, and proportion improving with nonparametric analysis for significance.

RESULTS

Immediately post-intervention, TSP, sensory discrimination, and fine motor speed improved 60-80% (p<0.00l respectively). Functional independence and strength improved by 50%. Eleven subjects (16 hands) were re-evaluated at 6 months; all but one subject reported a return to work. Task-specific performance was scored 84-90%. Supervised practice was associated with greater compliance and greater gains in performance.

CONCLUSIONS

Progressive task practice plus learning based memory and sensorimotor training can improve TSP in patients with FHD(TSP). Compliance with home training is enhanced when initiated with supervised practice.

Auditory grip force feedback in the treatment of Writer's cramp

STUDY DESIGN

Pre-post, single-group.

INTRODUCTION

Writer's cramp (WC) is a focal dystonia causing impairments in daily life. Behavioral treatment approaches have been shown to improve handwriting performance, though outcomes remain sub-optimal.

PURPOSE OF THE STUDY

To examine the effects of the handwriting training and auditory grip force feedback in seven patients with WC.

METHODS

Handwriting performance was examined before and after treatment. Writing frequency, fluency, and pressure were recorded with a digitizing tablet and grip forces during handwriting were recorded. Subjective writing performance and pain were rated on visual analog scales.

RESULTS

The treatment resulted in significant reductions in writing pressure and pain, while writing performance was significantly improved.

CONCLUSIONS

Patients in this study with WC, who exhibit grip force and pressure problems, benefit from feedback-supported handwriting training.

Differences in physical characteristics and response to rehabilitation for patients with hand dystonia: musicians' cramp compared to writers' cramp

STUDY DESIGN

Pre-Post, Mixed Factorial Trial.

INTRODUCTION

Focal hand dystonia is a challenging movement disorder to rehabilitate in musicians and writers.

PURPOSE OF THE STUDY

To compare the neuromusculoskeletal characteristics of those with writers' cramp (WC) and musicians' cramp (MC), and evaluate responsiveness to learning-based sensorimotor training.

METHODS

Twenty-seven individuals (14 musicians, 13 writers) participated in 8 weeks of supervised therapy supplemented with a home program. Between-group differences on measures of musculoskeletal (physical), sensory, and motor performance were evaluated at baseline and post-intervention.

RESULTS

Subjects with MC had a higher level of functional independence and better range of motion, but less strength in the affected upper limb than those of subjects with WC. Subjects with MC demonstrated greater accuracy on graphesthesia, kinesthesia, and localization at baseline. No between-group differences in motor performance were noted at baseline or post-intervention. Following individually adapted learning-based sensorimotor training, both groups improved in musculoskeletal (physical) parameters, sensory processing, and motor control; however, improvements on certain subtests differed by group. At follow-up, differences in posture, ROM, strength, graphesthesia, and kinesthesia persisted between the groups.

CONCLUSIONS

Subjects with WC have different physical and performance risk factors compared with those of subjects with MC. Intervention paradigms are efficacious, but variable responses to rehabilitation occur.

Slow pre-movement cortical potentials do not reflect individual response to therapy in writer's cramp

OBJECTIVE

To investigate whether movement-related cortical potentials (MRCP) provide a physiological correlate that indicates the response to treatment in patients with writer's cramp.

METHODS

In 21 patients with writer's cramp, who underwent 4 weeks of limb immobilization followed by re-training for 8 weeks, we recorded MRCPs preceding a self-initiated brisk finger abduction movement. MRCP measurements of pre-movement activity were performed at baseline, after the end of immobilization and four and 8 weeks of re-training. We examined 12 controls, who received no intervention, twice 4 weeks apart.

RESULTS

Patients benefited from the therapeutical intervention (Zeuner et al., 2008). They showed no abnormalities of the MRCPs at baseline. In controls, MRCPs did not significantly change after 4 weeks. In patients, immobilization and re-training had no effect on MRCPs. There was no correlation between the severity of dystonic symptoms or the individual treatment response and MRCPs.

CONCLUSION

MRCPs are stable measures for interventional studies. However, they do not reflect clinical severity of dystonic symptoms or improvement after therapeutic interventions.

SIGNIFICANCE

This is the first study to investigate MRCPs in a large cohort of patients with writer's cramp compared to a control group at different time points. These potentials do not reflect the motor control disorder in patients with writer's cramp.

Motor re-training does not need to be task specific to improve writer's cramp

Previous studies showed a beneficial effect of motor re-training in task-specific hand dystonia. Here we examined whether re-training needs to specifically focus on the task affected by dystonia. 21 patients with writer's cramp were randomly assigned to two types of re-training: One group of patients trained drawing and writing movements using a pen attached to the bottom of a finger splint. The second group used therapeutic putty to train finger movements without exercises of drawing and writing movements. Training lasted for 8 weeks. Before re-training, affected hand and forearm were immobilized for 4 weeks to facilitate the responsiveness to re-training. Dystonia was assessed during handwriting using the Writer's Cramp Rating Scale. Although no clinical improvement was observed immediately after immobilization, 8 weeks of re-training improved task-specific dystonia relative to baseline (P = 0.005). Both training modalities were equally effective. More severely affected patients benefited most. There was no correlation between disease duration and the individual treatment response. Re-training also improved hand function as indexed by the Arm Dystonia Disability Scale (P = 0.008). Kinematic handwriting analysis showed that re-training lowered vertical force level and enhanced the fluency of handwriting. We conclude that re-training does not need to specifically focus on the task affected by dystonia to be clinically effective.

Neuroimaging characteristics of patients with focal hand dystonia

NARRATIVE REVIEW: Advances in structural and functional imaging have provided both scientists and clinicians with information about the neural mechanisms underlying focal hand dystonia (FHd), a motor disorder associated with aberrant posturing and patterns of muscle contraction specific to movements of the hand. Consistent with the hypothesis that FHd is the result of reorganization in cortical fields, studies in neuroimaging have confirmed alterations in the topography and response properties of somatosensory and motor areas of the brain. Noninvasive stimulation of these regions also demonstrates that FHd may be due to reductions in inhibition between competing sensory and motor representations. Compromises in neuroanatomical structure, such as white matter density and gray matter volume, have also been identified through neuroimaging methods. These advances in neuroimaging have provided clinicians with an expanded understanding of the changes in the brain that contribute to FHd. These findings should provide a foundation for the development of retraining paradigms focused on reversing overlapping sensory representations and interactions between brain regions in patients with FHd. Continued collaborations between health professionals who treat FHd and research scientists who examine the brain using neuroimaging tools are imperative for answering difficult questions about patients with specific movement disorders.

Therapeutic immobilisation for small guitar player's dystonia: a case report

The development of focal hand dystonia through repetitive tasks is a result of degradation of cortical somatosensory representation due to repetitive fast stimuli sufficient to alter the sensory-motor stimulus, harming the motor control. A sensory-motor training program can modify this disorder. A behavioural intervention focusing on movement could help reduce or eliminate these conditions.

The pathophysiology of focal hand dystonia

NARRATIVE REVIEW: Focal hand dystonia is a disabling movement disorder, often task specific, that leads to impaired hand use. In addition to a genetic predisposition, environmental risk factors including repetitive use and musculoskeletal constraints are contributory. Although the underlying cause is unknown, recent studies have identified several key mechanisms that may play a part in its genesis. Failure of inhibition, abnormal sensorimotor integration, and maladaptive plasticity seem to be important. Understanding the underlying physiology may lead to the design of novel therapies.

Treatment of focal dystonias with botulinum neurotoxin

This is a review on the use of injections of botulinum toxin for the treatment of focal dystonias. Disorders covered include cranial dystonia, cervical dystonia, spasmodic dysphonia, and focal hand dystonia. Considered are clinical aspects, alternative treatment strategies and principles of use of botulinum toxin injections.

Research priorities in spasmodic dysphonia

OBJECTIVE

To identify research priorities to increase understanding of the pathogenesis, diagnosis, and improved treatment of spasmodic dysphonia.

STUDY DESIGN AND SETTING

A multidisciplinary working group was formed that included both scientists and clinicians from multiple disciplines (otolaryngology, neurology, speech pathology, genetics, and neuroscience) to review currently available information on spasmodic dysphonia and to identify research priorities.

RESULTS

Operational definitions for spasmodic dysphonia at different levels of certainty were recommended for diagnosis and recommendations made for a multicenter multidisciplinary validation study.

CONCLUSIONS

The highest priority is to characterize the disorder and identify risk factors that may contribute to its onset. Future research should compare and contrast spasmodic dysphonia with other forms of focal dystonia. Development of animal models is recommended to explore hypotheses related to pathogenesis. Improved understanding of the pathophysiology of spasmodic dysphonia should provide the basis for developing new treatment options and exploratory clinical trials.

SIGNIFICANCE

This document should foster future research to improve the care of patients with this chronic debilitating voice and speech disorder by otolaryngology, neurology, and speech pathology.

Clinical features of dystonia: a pathophysiological revisitation

PURPOSE OF REVIEW

To elucidate the pathophysiology of some clinical features of dystonic patients and to provide some new insight into the mechanisms underlying task-specific dystonia.

RECENT FINDINGS

There are three general lines of work at the present time that may indicate the physiological substrate for dystonia. All three are persuasive and it is not clear whether they are related to each other or whether one is more important than the others. According to the first line of research, a loss of inhibition at different levels of the central nervous system might contribute for the excessive movement seen in dystonia. Another field of research suggests that dystonic patients may have faulty processing within the lemniscal pathway with abnormalities in the sensory-motor integration. Finally, another convincing line of evidence is that in some susceptible individuals, during the acquisition of new motor skills, the mechanisms of neuroplasticity are subtly abnormal. In the presence of such predisposition, several environmental factors, such as repetitive training or peripheral nervous system injury, can trigger an abnormal maladaptive plasticity, which can lead to an overt dystonia.

SUMMARY

These findings may be relevant in the development of new therapeutic strategies in dystonia.