Musician's cramp as manifestation of maladaptive brain plasticity: arguments from instrumental differences

Gender Differences in Task Specific Dystonia: What Can we Learn from Musician's Dystonia?

BACKGROUND

Musician's Dystonia (MD) is a task specific, focal dystonia which usually occurs only at the instrument. The pathophysiology is not fully understood, but several risk factors like over-practice and genetic predisposition are known. Interestingly, 80% of those affected are men, which stands in contrast to the gender distribution in other focal dystonias, such as cervical dystonia.

OBJECTIVES

Our aim was to evaluate the difference in women and men with regard to risk factors leading to MD.

METHODS

We investigated known risk factors for MD in a large cohort of 364 MD patients by retrospectively collecting data on practice behavior and family history.

RESULTS

In line with previous studies, we found a ratio of ~4:1 men to women. Age at onset of MD was significantly lower in women; however, subsequent analysis revealed that it was a positive family history (FH+) and not gender that was associated with a lower age at onset. Furthermore, we found that those with negative family history had accumulated more practice time until onset of MD.

CONCLUSIONS

These results imply that the earlier age at onset in women did not depend on gender but was due to the higher proportion of a positive family history. In contrast, men were less likely to have a positive family history, suggesting that genetic factors may not be the primary reason for the higher prevalence of MD in men. Instead, differences in practice behaviors between men and women may contribute to this gender disparity.

Tribute to the Flute: A Literature Review of Playing-Related Problems in Flautists

Playing musical instruments places unusually high demands on specific parts of the human body. Relative to the instruments they play, musicians may experience instrument-related symptoms, as recorded in flute players. The objective was to provide an overview of the study findings addressing medical problems in flautists to better understand their complaints and pave the way for more personalized healthcare. Several electronic databases (PubMed, Embase, Cochrane Library) were systematically searched in July 2022. Furthermore, the references of all included articles were reviewed for additionally relevant sources. The resulting set of studies was summarized in a table, with quality assessment according to the SIGN grading system. From an initial 433 hits, the search yielded 95 studies with a total of 32,600 musicians, including at least 2134 flautists. Among the latter, evidence was found for musculoskeletal, neurological, dermatological, temporomandibular, and hearing complaints, overuse and reflux symptoms, velopharyngeal insufficiency, as well as upper and lower airway impairment. Other specialists may be consulted equally often and should be sensitive to the particular medical problems in flautists. Future studies would ideally contain specific outcome analyses on an international scale and consider flautists as an individual subgroup within a larger number of total participants.

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.

Hyperkinetic Rat Model Induced by Optogenetic Parafascicular Nucleus Stimulation

OBJECTIVE

The parafascicular nucleus (PF) plays important roles in controlling the basal ganglia. It is not well known whether the PF affects the development of abnormal involuntary movements (AIMs). This study was aimed to find a role of the PF in development of AIMs using optogenetic methods in an animal model.

METHODS

Fourteen rats were underwent stereotactic operation, in which they were injected with an adeno-associated virus with channelrhodopsin (AAV2-hSyn-ChR2-mCherry) to the lateral one third of the PF. Behavior test was performed with and without optical stimulation 14 days after the injection of the virus. AIM of rat was examined using AIM score. After the behavior test, rat's brain was carefully extracted and the section was examined using a fluorescence microscope to confirm transfection of the PF.

RESULTS

Of the 14 rats, seven rats displayed evident involuntary abnormal movements. AIM scores were increased significantly after the stimulation compared to those at baseline. In rats with AIMs, mCherry expression was prominent in the PF, while the rats without AIM lacked with the mCherry expression.

CONCLUSION

AIMs could be reversibly induced by stimulating the PF through an optogenetic method.

Electrically Induced Sensory Trick in a Patient with Musician's Dystonia: A Case Report

A sensory trick is a specific maneuver that temporarily improves focal dystonia. We describe a case of musician's dystonia in the right-hand fingers of a patient, who showed good and immediate improvement after using an electrical stimulation-mimicking sensory trick. A 49-year-old professional guitarist presented with chronic involuntary flexion of the right-hand third and fourth fingers that occurred during guitar performances. Electrical stimulation with a frequency of 40 Hz and an intensity of 1.5 times the sensory threshold was administered on the third and fourth fingernails of the right hand, which facilitated fluent guitar playing. While he played guitar with and without electrical stimulation, we measured the surface electromyograms (sEMG) of the right extensor digitorum and flexor digitorum superficialis muscles to evaluate the sensory-trick-like effects of electrical stimulation. This phenomenon can offer clues for developing electrical stimulation-based treatment devices for focal dystonia. Electrical stimulation has the advantage that it can be turned off to avoid habituation. Moreover, the device is easy to use and portable. These findings warrant further investigation into the use of sensory stimulation for treating focal dystonia.

Sensorimotor Incoordination in Musicians' Dystonia

To acquire and maintain outstanding sensorimotor skills for playing musical instruments inevitably requires extensive training from childhood. However, on the way toward musical excellence, musicians sometimes develop serious disorders, such as tendinitis, carpal tunnel syndrome, and task-specific focal dystonia. Particularly, task-specific focal dystonia in musicians, which is referred to as musician's dystonia (MD), has no perfect cure and therefore often terminates professional careers of musicians. To better understand its pathological and pathophysiological mechanisms, the present article focuses on malfunctions of the sensorimotor system at the behavioral and neurophysiological levels. Based on emerging empirical evidence, we propose that the aberrant sensorimotor integration, possibly which occurs in both cortical and subcortical systems, underlies not only movement incoordination between the fingers (i.e., maladaptive synergy) but also failure of long-term retention of intervention effects in the patients with MD.

Impaired feedforward control of movements in pianists with focal dystonia

Learning accurate and fast movements typically accompanies the modulation of feedforward control. Nevertheless, it remains unclear how motor skill learning modulates feedforward control, such as through maladaptation of the sensorimotor system by extensive training (e.g., task-specific dystonia). Here, we examined the modulation of feedforward control through motor skill learning while focusing on the motion of piano playing at either a natural tempo or the fastest tempo. The current study compared the kinematics and keypress data among individuals in three groups: healthy and well-trained pianists (i.e., subjects with skill learning), non-musicians (i.e., subjects without skill learning), and patients with focal-hand dystonia (FHD) (i.e., subjects with maladaptation by skill learning). Compared to healthy pianists, patients with FHD showed impairment in some feedforward motion components that are relevant to classifying the two playing tempi. However, while focusing on motion components that are irrelevant to the tempo classification, patients with FHD showed movements comparable to those of healthy pianists. Furthermore, patients with FHD demonstrated significantly slower movement times than healthy pianists. Our results suggest that maladaptation by skill learning affects parts of feedforward control rather than its entirety. Nevertheless, the affected feedforward components are relevant to performing movements as fast as possible, which may underlie the speed dependence of dystonic symptoms.

Video-based long-term follow up of musician’s dystonia in pianists reveals similar improvements following different treatment strategies: a retrospective observational study

Background

Musician’s Dystonia (MD) by impaired or complete loss of fine motor control in extensively trained movements at the instrument. In pianists, it frequently leads to involuntary flexion or extension of one or more fingers. Treatment remains challenging, although local injections with Botulinum toxin, anticholinergic medication and pedagogical retraining seem to be helpful in individual cases. Evaluation of therapies however is frequently hampered by lack of practicability, or validity. This retrospective observational study aims to assess the long-term development of MD and efficacy of therapies in keyboard players by means of a simple video-rating procedure by informed expert raters.

Methods

Video rating is characterisedwas done by 6 carefully instructed pianists, rating a total of 266 videos from 80 patients, recorded over a period of almost 20 years. These showed the affected hand playing a C-major scale as “regularly” as possible at a moderate tempo on a grand piano. Raters assessed the acoustic irregularity of scale playing and any visible movement impairment on visual analogue scales. Influence of patient-specific factors including applied treatment was estimated in a Bayesian multilevel beta regression.

Results

For ratings of irregularity and impairment intra-rater reliability was strong and inter-rater concordance was moderate. The average estimated improvement across all therapies was 14% in irregularity and 15% in impairment. Highest improvement rates in ratings of irregularity were found after the combined treatment with Botulinum toxin and Trihexyphenidyl (45%) as well as in retraining (29% improvement) as single therapy. In ratings of impairment the highest improvement was shown for retraining in combination with Trihexyphenidyl (36% improvement) as well as retraining as single therapy (23%).

Conclusions

This study provides a new perspective on the course of MD in keyboard players in a larger cohort using methods other than self-report. Video rating of scale-playing was shown to be a reliable and useful method to evaluate MD in keyboard players. Average improvement rates were different to previous studies using patient-subjective questionnaires. Treatment options showed different effects in the two rating criteria, with retraining showing the highest improvement rates in single and combined use.

Aberrant Cerebello-Cortical Connectivity in Pianists With Focal Task-Specific Dystonia

Musician's dystonia is a type of focal task-specific dystonia (FTSD) characterized by abnormal muscle hypercontraction and loss of fine motor control specifically during instrument playing. Although the neuropathophysiology of musician's dystonia remains unclear, it has been suggested that maladaptive functional abnormalities in subcortical and cortical regions may be involved. Here, we hypothesized that aberrant effective connectivity between the cerebellum (subcortical) and motor/somatosensory cortex may underlie the neuropathophysiology of musician's dystonia. Using functional magnetic resonance imaging, we measured the brain activity of 30 pianists with or without FTSD as they played a magnetic resonance imaging-compatible piano-like keyboard, which elicited dystonic symptoms in many but not all pianists with FTSD. Pianists with FTSD showed greater activation of the right cerebellum during the task than healthy pianists. Furthermore, patients who reported dystonic symptoms during the task demonstrated greater cerebellar activation than those who did not, establishing a link between cerebellar activity and overt dystonic symptoms. Using multivoxel pattern analysis, moreover, we found that dystonic and healthy pianists differed in the task-related effective connectivity between the right cerebellum and left premotor/somatosensory cortex. The present study indicates that abnormal cerebellar activity and cerebello-cortical connectivity may underlie the pathophysiology of FTSD in musicians.

Rescue of striatal long-term depression by chronic mGlu5 receptor negative allosteric modulation in distinct dystonia models

An impairment of long-term synaptic plasticity is considered as a peculiar endophenotype of distinct forms of dystonia, a common, disabling movement disorder. Among the few therapeutic options, broad-spectrum antimuscarinic drugs are utilized, aimed at counteracting abnormal striatal acetylcholine-mediated transmission, which plays a crucial role in dystonia pathophysiology. We previously demonstrated a complete loss of long-term synaptic depression (LTD) at corticostriatal synapses in rodent models of two distinct forms of isolated dystonia, resulting from mutations in the TOR1A (DYT1), and GNAL (DYT25) genes. In addition to anticholinergic agents, the aberrant excitability of striatal cholinergic cells can be modulated by group I metabotropic glutamate receptor subtypes (mGlu1 and 5). Here, we tested the efficacy of the negative allosteric modulator (NAM) of metabotropic glutamate 5 (mGlu) receptor, dipraglurant (ADX48621) on striatal LTD. We show that, whereas acute treatment failed to rescue LTD, chronic dipraglurant rescued this form of synaptic plasticity both in DYT1 mice and GNAL rats. Our analysis of the pharmacokinetic profile of dipraglurant revealed a relatively short half-life, which led us to uncover a peculiar time-course of recovery based on the timing from last dipraglurant injection. Indeed, striatal spiny projection neurons (SPNs) recorded within 2 h from last administration showed full expression of synaptic plasticity, whilst the extent of recovery progressively diminished when SPNs were recorded 4-6 h after treatment. Our findings suggest that distinct dystonia genes may share common signaling pathway dysfunction. More importantly, they indicate that dipraglurant might be a potential novel therapeutic agent for this disabling disorder.

Dystonia in Performing Artists: Beyond Focal Hand Dystonia

Overuse of specific muscles in perfecting movements in performing arts makes an artist prone to many medical conditions. Musicians' hand dystonia is focal task-specific dystonia (FTSD) of hand among musicians that has been extensively studied. However, embouchure, lower limbs, and laryngeal muscles can also be affected among musicians. Embouchure dystonia (ED) refers to dystonia of the perioral and facial muscles that occurs in musicians while playing embouchure instruments. It is essential to identify ED since the dystonia might become persistent and non-task-specific if the musician continues to play the instrument. Task-specific dystonia of lower limbs among musicians has been exclusively reported among drummers. The diagnosis rests on electromyogram (EMG) of the involved muscles during the task. Singer's dystonia (SD) refers to task-specific laryngeal dystonia that occurs only while singing. The diagnosis of SD is based on laryngeal EMG and spectrographic analysis. Cortical hyperexcitability, loss of inhibition, and aberrant plasticity are central to the pathogenesis in both ED and musicians' hand dystonia. The pathophysiological studies in SD are limited. This review aims to discuss the lesser known dystonias among performing artists - ED, FTSD of lower limb, and SD.

Brain connectivity in patients with dystonia during motor tasks

OBJECTIVE

This study aims to investigate alterations of brain connectivity using multivariate electroencephalographic data to provide new insights of the brain connectivity dynamics of dystonia.

APPROACH

We recorded electroencephalography (EEG) of patients with right upper limb idiopathic focal dystonia and paired controls during resting state, writing-from-memory, and finger-tapping tasks. We applied power spectrum analyses considering the mu, beta and gamma rhythms of the motor cortex and analyzed brain connectivity networks and microstates (MS).

MAIN RESULTS

The power spectra results showed that patients had a loss of desynchronization of the beta rhythm during the writing task. We observed differences in the structure of the connective core in beta rhythm, as well as, in the intensity of the patient's hubs observed with basis in path length measures in mu and beta rhythms. Abnormalities were also identified in MS of default mode networks of patients associated with its performances during motor tasks.

SIGNIFICANCE

The EEG connectivity analyses provided interesting insights about the cortical electrophysiological patterns in dystonia, such as loss of event-related desynchronization, changes in the effective connectivity with similar signature to other neurological diseases, indications of alterations in the default-mode-network. Our findings are consistent with previously described connectivity abnormalities in neuroimaging studies confirming that dystonia is a network disorder.

Does the Side Onset of Parkinson's Disease Influence the Time to Develop Levodopa-Induced Dyskinesia?

BACKGROUND

Aberrant plasticity is closely linked to the development of levodopa-induced dyskinesia (LID) in Parkinson's disease (PD).

OBJECTIVE

This study investigated whether dominant-side patients with PD exhibit a shorter time to LID development, based on the hypothesis that the dominant hemisphere may have greater plasticity than non-dominant-side patients.

METHODS

We analyzed data from 387 right-handed patients with PD who exhibited asymmetric motor deficits and received PD medications for ≥2 years (191 dominant-side and 196 non-dominant-side patients). The influence of side onset on time for LID development was assessed by Kaplan-Meier estimates and time-dependent Cox regression models based on the 5-year time point, after adjusting for age at PD onset, dopamine transporter activity in the posterior putamen, and daily levodopa dose.

RESULTS

LID developed in 46 (23.4%) patients with non-dominant-side PD and in 35 (18.1%) patients with dominant-side PD. The Kaplan-Meier analyses revealed that non-dominant-side patients developed LID earlier than dominant-side patients (p = 0.027). The time-dependent Cox regression models showed that the risk of LID within 5 years of treatment was significantly higher in non-dominant-side than in dominant-side patients (hazard ratio 1.954; p = 0.034), whereas the risk after 5 years was similar between groups (p = 0.528).

CONCLUSIONS

The present study demonstrated that LID developed earlier in non-dominant-side than in dominant-side patients with PD. These results suggested a greater potential of synaptic plasticity in the dominant hemisphere that may exert a protective role for the development of LID compared to the non-dominant hemisphere.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Brain Activity Underlying Muscle Relaxation

Fine motor control of not only muscle contraction but also muscle relaxation is required for appropriate movements in both daily life and sports. Movement disorders such as Parkinson’s disease and dystonia are often characterized by deficits of muscle relaxation. Neuroimaging and neurophysiological studies suggest that muscle relaxation is an active process requiring cortical activation, and not just the cessation of contraction. In this article, we review the neural mechanisms of muscle relaxation, primarily utilizing research involving transcranial magnetic stimulation (TMS). Several studies utilizing single-pulse TMS have demonstrated that, during the relaxation phase of a muscle, the excitability of the corticospinal tract controlling that particular muscle is more suppressed than in the resting condition. Other studies, utilizing paired-pulse TMS, have shown that the intracortical inhibition is activated just before muscle relaxation. Moreover, muscle relaxation of one body part suppresses cortical activities controlling other body parts in different limbs. Therefore, the cortical activity might not only be a trigger for muscle relaxation of the target muscles but could also bring about an inhibitory effect on other muscles. This spread of inhibition can hinder the appropriate contraction of muscles involved in multi-limb movements such as those used in sports and the play of musical instruments. This may also be the reason why muscle relaxation is so difficult for beginners, infants, elderly, and the cognitively impaired.

Range of voluntary neck motility predicts outcome of pallidal DBS for cervical dystonia

BACKGROUND

The effectiveness of pallidal deep brain stimulation (GPi DBS) for cervical dystonia has been extensively described, but controversies exist about which prognostic factor is clinically useful. We previously reported that classification of tonic- or phasic-type cervical dystonia is useful for predicting clinical prognosis; however, the approach used by physicians to distinguish between the two types remains subjective.

OBJECTIVE

The aim of this study was to develop a prognostic factor of GPi DBS for cervical dystonia.

METHODS

By identifying distributions of range of motion scores between phasic- and tonic-type cervical dystonia, a new prognostic factor group was developed based on whether the patients could voluntarily move their head to the opposite side against dystonic motions. The prognosis for GPi DBS in the two groups was analyzed according to the time sequence.

RESULTS

Patients who were able to move their head past the midline had a better long-term prognosis after GPi DBS than did those who could not. In the early post-operative phase, there were no significant differences in the clinical outcomes between the two groups.

CONCLUSION

A range of voluntary neck motility with respect to the midline is an objective factor that is useful in predicting the prognosis of patients with cervical dystonia. This result renders needs for future study addressing neuroplastic changes in the brain network caused by GPi DBS.

Simultaneous dual-plane, real-time magnetic resonance imaging of oral cavity movements in advanced trombone players

Background

This paper describes the use of real-time magnetic resonance imaging to simultaneously obtain magnetic resonance imaging (MRI) videos in both a sagittal and coronal plane during the performance of a musical exercise in five advanced trombone players.

Methods

Dual-slice recordings were implemented in a frame-interleaved manner with 20 ms acquisitions per frame to achieve two interleaved videos at a rate of 25 frames per second. A customized MATLAB toolkit was used for the extraction of line profiles from MRI videos to quantify tongue movements associated with exercise performance from both perspectives.

Results

Across all subjects, the analyses revealed precise coupling of vertical movements of the dorsal tongue surface (DTS), viewed from a sagittal perspective, with reduction in the vertical and horizontal dimensions of the air channel formed between the DTS and the hard palate, viewed from a coronal perspective. The cross-correlation between these movements was very strong (mean R=0.967).

Conclusions

These results demonstrate the unique utility of this dual-slice technology in describing the coordination of complex tongue movements occurring in two planes (i.e., three directions) simultaneously, lending a deeper understanding of lingual motor control during trombone performance.

Testing rTMS-Induced Neuroplasticity: A Single Case Study of Focal Hand Dystonia

Focal hand dystonia in musicians is a neurological motor disorder in which aberrant plasticity is caused by excessive repetitive use. This work's purposes were to induce plasticity changes in a dystonic musician through five daily thirty-minute sessions of 1 Hz repetitive transcranial magnetic stimulation (rTMS) applied to the left M1 by using neuronavigated stimulation and to reliably measure the effect of these changes. To this aim, the relationship between neuroplasticity changes and motor recovery was investigated using fine-grained kinematic analysis. Our results suggest a statistically significant improvement in motor coordination both in a task resembling the dystonic-inducing symptoms and in a reach-to-grasp task. This single case study supports the safe and effective use of noninvasive brain stimulation in neurologic patients and highlights the importance of evaluating outcomes in measurable ways. This issue is a key aspect to focus on to classify the clinical expression of dystonia. These preliminary results promote the adoption of kinematic analysis as a valuable diagnostic tool.

Aberrant cortical excitability reflects the loss of hand dexterity in musician's dystonia

KEY POINTS

Dystonia is a movement disorder characterized by abnormalities at multifaceted aspects of motor dexterity and neural functions. Evidence bridging between pathophysiology and movement abnormalities is limited. A novel finding was that in focal task-specific dystonia (FTSD), an aberrantly reduced inhibition at the motor cortex was related to the temporal imprecision of the dexterous finger movements, whereas an elevated facilitation was associated with an abnormally sluggish transition of finger movements from flexion to extension. We newly identified two sets of behavioural-physiological covariations as hallmarks of hand FTSD, which is clinically significant because these findings provide novel evidence connecting distinct types of malfunctions within the motor cortex at rest with distinct aspects of motor dexterity degradation in FTSD patients.

ABSTRACT

Focal task-specific dystonia (FTSD) compromises dexterous movements. A proposed pathophysiological mechanism of FTSD involves malfunction of the motor cortex (M1). However, no evidence is yet available regarding whether and how malfunctions of M1 are responsible for the loss of motor dexterity. Here, we addressed this issue by assessing both M1 excitability and detailed movement parameters, as well as their relationships. Transcranial magnetic stimulation was applied over M1 in 20 pianists with FTSD, 20 healthy pianists and 20 non-musicians. The patients demonstrated both reduced short-interval intracortical inhibition (SICI) and elevated intracortical facilitation (ICF) compared with the healthy controls. This indicates that the abnormal cortical excitability reflects pathophysiology but not current skills. Hand motor dexterity was evaluated by position sensors during piano playing at two tempi. The patients showed delayed transition from finger flexion to extension at the fastest tempo and greater timing variability of the finger movements. Furthermore, multivariate analyses identified distinct sets of covariation between cortical excitability and dexterity measures. Namely, the SICI measure and ICF measure were associated with the temporal variability of the movements and the quickness of the transition from flexion to extension, respectively. Specifically, the reduced inhibition and elevated facilitation at M1 in pianists was related to the temporal imprecision and impairment of quick transitions in the sequential finger movements. The present study provides novel evidence associating M1 malfunctions with dexterity loss.

Anatomy, Physiology, and Clinical Syndromes of the Basal Ganglia: A Brief Review

Movement disorders typically arise from dysfunction of the basal ganglia (BG), cerebellum, or both. The BG-a group of deep, subcortical structures-form complex circuits that shape motor control and motor learning, as well as limbic and associative functions. In this article, we summarize the anatomy and physiology of the BG and cerebellum, and briefly highlight the clinical syndromes that may arise in the context of their injury or dysfunction.

A unifying motor control framework for task-specific dystonia

Task-specific dystonia is a movement disorder characterized by a painless loss of dexterity specific to a particular motor skill. This disorder is prevalent among writers, musicians, dancers and athletes. No current treatment is predictably effective, and the disorder generally ends the careers of affected individuals. Traditional disease models of dystonia have a number of limitations with regard to task-specific dystonia. We therefore discuss emerging evidence that the disorder has its origins within normal compensatory mechanisms of a healthy motor system in which the representation and reproduction of motor skill are disrupted. We describe how risk factors for task-specific dystonia can be stratified and translated into mechanisms of dysfunctional motor control. The proposed model aims to define new directions for experimental research and stimulate therapeutic advances for this highly disabling disorder.

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.

Clinical and Epidemiological Correlates of Task-Specific Dystonia in a Large Cohort of Brazilian Music Players

Musician’s dystonia is a task-specific dystonia (TSD) worldwide disabling disorder, and most of the affected individuals may have severe difficulty to play their instrument. Many professional music players may have to quit working as a player. The objective of the present study was to evaluate the clinical characteristics and frequency of TSD in Brazilian music players and to promote awareness of this condition among musicians. We visited orchestras and music schools delivering lectures on TSD and about the scope of our survey. Musicians were invited to answer a questionnaire, and those with possible neurological dysfunction associated with musical performance were recorded by video while playing the instrument. We visited 51 orchestras and music schools in 19 Brazilian cities between March 2013 and March 2015. We collected 2,232 questionnaires, and 72 subjects with suspicion of dystonia were video recorded during specific tasks and evaluated regarding motor impairment. Forty-nine individuals (2.2%) were diagnosed as having TSD (mean age 36.4 years; 92% male). The instruments most associated with TSD were acoustic guitar (36.7%) and brass instruments (30.6%). We concluded that Brazilian TSD music players are mainly male, classical music professionals, around 30 years of age, with arms, hands, or oromandibular muscles affected. TSD is a neurological condition that can impair musical performance and should receive more attention from musicians, teachers, and health professionals.

Skilful force control in expert pianists

Dexterous object manipulation in skilful behaviours such as surgery, craft making, and musical performance involves fast, precise, and efficient control of force with the fingers. A challenge in playing musical instruments is the requirement of independent control of the magnitude and rate of force production, which typically vary in relation to loudness and tempo. However, it is unknown how expert musicians skilfully control finger force to elicit tones with a wide range of loudness and tempi. Here, we addressed this issue by comparing the variation of spatiotemporal characteristics of force during repetitive and simultaneous piano keystrokes in relation to the loudness and tempo between pianists and musically untrained individuals. While the peak key-descending velocity varied with loudness but not with tempo in both groups, the peak and impulse of the key-depressing force were smaller in pianists than in the non-musicians, specifically when eliciting loud tones, suggesting superior energetic efficiency in the trained individuals. The key-depressing force was more consistent across strikes in pianists than in the non-musicians at all loudness levels but only at slow tempi, confirming expertise-dependency of precise force control. A regression analysis demonstrated that individual differences in the keystroke rates when playing at the fastest tempo across the trained pianists were negatively associated with the force impulse during the key depression but not with the peak force only at the loudest tone. This suggests that rapid reductions of force following the key depression plays a role in considerably fast performance of repetitive piano keystrokes.

Neural plasticity and network remodeling: From concepts to pathology

Neuroplasticity has been subject to a great deal of research in the last century. Recently, significant emphasis has been placed on the global effect of localized plastic changes throughout the central nervous system, and on how these changes integrate in a pathological context. Specifically, alterations of network functionality have been described in various pathological contexts to which corresponding structural alterations have been proposed. However, considering the amount of literature and the different pathological contexts, an integration of this information is still lacking. In this paper we will review the concepts of neural plasticity as well as their repercussions on network remodeling and provide a possible explanation to how these two concepts relate to each other. We will further examine how alterations in different pathological contexts may relate to each other and will discuss the concept of plasticity diseases, its models and implications.

Task-Specific Dystonia in Professional Musicians. A Systematic Review of the Importance of Intensive Playing as a Risk Factor

BACKGROUND

Focal dystonia in professional musicians is a movement disorder that manifests itself during playing. It is a multifactorial condition in which a genetic predisposition and exogenous factors both play a role. Evidence suggests that intensive playing is a risk factor for the development of task-specific dystonia in professional musicians.

METHODS

This review is based on pertinent publications (1950-2013) retrieved by a systematic search in medical and musicological databases. The references of the retrieved publications were also considered in the search.

RESULTS

16 articles with clinical information on a total of 1144 affected musicians were reviewed systematically. Their overall quality was intermediate to poor, and a meta-analysis was therefore not possible. The Bradford Hill criteria were applied to study a possible causative link between intensive playing and musician's dystonia. Musician's dystonia generally arises after at least ten years of intensive playing (corresponding to roughly 10 000 hours of practice). An association was found between the affected limb and the type of instrument: the limb that is subject to the greatest fine motor demands is the one most commonly affected. The average age of onset is 28 to 44 years.

CONCLUSION

The Bradford Hill causality criteria indicate that intensive playing is related to the development of musician's dystonia. In particular, the association of the type of instrument with the site of dystonia supports this thesis. The findings imply that task-specific dystonia in professional musicians should be included in the list of occupational diseases in Germany.

Changes in resting-state connectivity in musicians with embouchure dystonia

OBJECTIVE

Embouchure dystonia is a highly disabling task-specific dystonia in professional brass musicians leading to spasms of perioral muscles while playing the instrument. As they are asymptomatic at rest, resting-state functional magnetic resonance imaging in these patients can reveal changes in functional connectivity within and between brain networks independent from dystonic symptoms.

METHODS

We therefore compared embouchure dystonia patients to healthy musicians with resting-state functional magnetic resonance imaging in combination with independent component analyses.

RESULTS

Patients showed increased functional connectivity of the bilateral sensorimotor mouth area and right secondary somatosensory cortex, but reduced functional connectivity of the bilateral sensorimotor hand representation, left inferior parietal cortex, and mesial premotor cortex within the lateral motor function network. Within the auditory function network, the functional connectivity of bilateral secondary auditory cortices, right posterior parietal cortex and left sensorimotor hand area was increased, the functional connectivity of right primary auditory cortex, right secondary somatosensory cortex, right sensorimotor mouth representation, bilateral thalamus, and anterior cingulate cortex was reduced. Negative functional connectivity between the cerebellar and lateral motor function network and positive functional connectivity between the cerebellar and primary visual network were reduced.

CONCLUSIONS

Abnormal resting-state functional connectivity of sensorimotor representations of affected and unaffected body parts suggests a pathophysiological predisposition for abnormal sensorimotor and audiomotor integration in embouchure dystonia. Altered connectivity to the cerebellar network highlights the important role of the cerebellum in this disease. © 2016 International Parkinson and Movement Disorder Society.

Maladaptive Plasticity Induces Degradation of Fine Motor Skills in Musicians

Abstract. Performing music at a professional level is probably one of the most complex human accomplishments requiring extensive training periods. The superior skills of musicians are mirrored in plastic adaptations of the brain involving gray and white matter increase in sensory motor and auditory areas and enlargement of receptive fields. Motor disturbances in musicians are common and include mild forms, such as temporary motor fatigue, painful overuse injuries following prolonged practice, anxiety-related motor failures during performances, and more persistent losses of motor control, termed “dynamic stereotypes.” Musician’s dystonia is characterized by a permanent loss of motor control when playing a musical instrument linked to genetic susceptibility and to maladaptive plasticity. In this review article, we argue that these motor failures developing on a continuum from motor fatigue to musician’s dystonia require client tailored treatment and accordingly specific psychological and neurological interventions.

The curse of motor expertise: Use-dependent focal dystonia as a manifestation of maladaptive changes in body representation

Focal task-specific dystonia (FTSD) impairs not only motor dexterity, but also somatosensory perception involved in well-trained behavioral tasks. Occupations that carry a risk of developing FTSD include musician, writer, painter, surgeon, and golfer, which are characterized by repetitive and precise motor actions over a prolonged period. Behavioral studies have uncovered various undesirable effects of FTSD on sensorimotor functions, such as a loss of independent movement control, unintended muscular co-activation, awkward limb posture, and impairment of fine discrimination of tactile and proprioceptive sensations. Studies using neuroimaging and noninvasive brain stimulation techniques have related such sensorimotor malfunctions to maladaptive neuroplastic changes in the sensorimotor system, including the primary motor and somatosensory areas, premotor area, cerebellum, and basal ganglia. In this review, we summarize recent empirical findings regarding phenomenological and pathophysiological abnormalities associated with the development of FTSD. We particularly focused on maladaptive alterations of body representations underlying the degradation of fine motor control and somatosensory perception in FTSD patients.

Divergent oral cavity motor strategies between healthy elite and dystonic horn players

BACKGROUND

This paper describes the use of real-time magnetic resonance imaging in visualizing and quantifying oral cavity motor strategies employed by 6 healthy, elite horn players and 5 horn players with embouchure dystonia.

METHODS

Serial images with an acquisition time of 33.3 ms were obtained from each performer during execution of an 11-note harmonic series encompassing 2.5 octaves on a magnetic resonance imaging-compatible horn. A customized MATLAB toolkit was employed for the extraction of line profiles from magnetic resonance imaging films allowing comparative analyses between elite and dystonic horn players.

RESULTS

The data demonstrate differing motor strategies, particularly in moving from the 6th through 9th harmonics. The elite horn player strategy features elevation and anterior displacement of the tongue during ascending sequences, whereas dystonic players showed significantly less movement. The elite horn players thus narrowed the air channel on higher notes, presumably affording faster airflow for vibration of the lips at higher frequencies.

CONCLUSIONS

We postulate that failure to employ this strategy by dystonic horn players may require greater tension in the embouchure muscles to compensate for slower air speed. Though this may simply be an expression of or adaptation for dystonia, the possibility that it may be a contributing factor in the development of embouchure dystonia is suggested.

Losing dexterity: patterns of impaired coordination of finger movements in musician's dystonia

Extensive training can bring about highly-skilled action, but may also impair motor dexterity by producing involuntary movements and muscular cramping, as seen in focal dystonia (FD) and tremor. To elucidate the underlying neuroplastic mechanisms of FD, the present study addressed the organization of finger movements during piano performance in pianists suffering from the condition. Principal component (PC) analysis identified three patterns of fundamental joint coordination constituting finger movements in both patients and controls. The first two coordination patterns described less individuated movements between the “dystonic” finger and key-striking fingers for patients compared to controls. The third coordination pattern, representing the individuation of movements between the middle and ring fingers, was evident during a sequence of strikes with these fingers in controls, which was absent in the patients. Consequently, rhythmic variability of keystrokes was more pronounced during this sequence of strikes for the patients. A stepwise multiple-regression analysis further identified greater variability of keystrokes for individuals displaying less individuated movements between the affected and striking fingers. The findings suggest that FD alters dexterous joint coordination so as to lower independent control of finger movements, and thereby degrades fine motor control.

Acquisition and reacquisition of motor coordination in musicians

Precise control of movement timing plays a key role in musical performance. This motor skill requires coordination across multiple joints and muscles, which is acquired through extensive musical training from childhood. However, extensive training has a potential risk of causing neurological disorders that impair fine motor control, such as task-specific tremor and focal dystonia. Recent technological advances in measurement and analysis of biological data, as well as noninvasive manipulation of neuronal activities, have promoted the understanding of computational and neurophysiological mechanisms underlying acquisition, loss, and reacquisition of dexterous movements through musical practice and rehabilitation. This paper aims to provide an overview of the behavioral and neurophysiological basis of motor virtuosity and disorder in musicians, representative extremes of human motor skill. We also report novel evidence of effects of noninvasive neurorehabilitation that combined transcranial direct-current stimulation and motor rehabilitation over multiple days on musician's dystonia, which offers a promising therapeutic means.

A practical approach to management of focal hand dystonia

Dystonia can be focal, segmental, multifocal, generalized, or hemidystonia. Focal dystonia is localized to a specific part of the body. Overall upper limb is more commonly involved in focal dystonia than lower limb and since it starts from hand, focal hand dystonia (FHD) is a more accepted terminology. Writer's cramp and musician dystonia are commonest types of FHD. Typically this dystonia is task specific, but in some patients this specificity may be lost over a period of time. Segmental or generalized dystonia may also start as FHD, so a detailed clinical assessment is required, which should be supplemented by relevant investigations. Treatment includes oral medications, injection botulinum toxin, neurosurgery including neurostimulation, and rehabilitation. Role of injection botulinum toxin has been extensively studied in writer's cramp patients and found to be effective; however, selection of muscles and techniques of injection are crucial in getting best results.

A multifactorial conceptual model of peripheral neuromusculoskeletal predisposing factors in task-specific focal hand dystonia in musicians: etiologic and therapeutic implications

A model is presented showing how peripheral factors may cause a process of movement adaptation that leads to task-specific focal hand dystonia in musicians (FHDM). To acquire a playing technique, the hand must find effective and physiologically sustainable movements within a complex set of functional demands and anatomic, ergonomic, and physiological constraints. In doing so, individually discriminating constraints may become effective, such as limited anatomic independence of finger muscles/tendons, limited joint ranges of motion, or (subclinical) neuromusculoskeletal defects. These factors may, depending on the instrument-specific playing requirements, compromise or exclude functional playing movements. The controller (i.e., the brain) then needs to develop alternative motions to execute the task, which is called compensation. We hypothesize that, if this compensation process does not converge to physiologically sustainable muscle activation patterns that satisfy all constraints, compensation could increase indefinitely under the pressure of practice. Dystonic symptoms would become manifest when overcompensation occurs, resulting in motor patterns that fail in proper task execution. The model presented in this paper only concerns the compensatory processes preceding such overcompensations and does not aim to explain the nature of the dystonic motions themselves. While the model considers normal learning processes in the development of compensations, neurological predispositions could facilitate developing overcompensations or further abnormal motor programs. The model predicts that if peripheral factors are involved, FHDM symptoms would be preceded by long-term gradual changes in playing movements, which could be validated by prospective studies. Furthermore, the model implies that treatment success might be enhanced by addressing the conflict between peripheral factors and playing tasks before decompensating/retraining the affected movements.

Apollo's curse: neurological causes of motor impairments in musicians

Performing music at a professional level is probably one of the most complex human accomplishments. Extremely fast and complex, temporo-spatially predefined movement patterns have to be learned, memorized, and retrieved with high reliability in order to meet the expectations of listeners. Performing music requires not only the integration of multimodal sensory and motor information, and its precise monitoring via auditory and kinesthetic feedback, but also emotional communicative skills, which provide a "speaking" rendition of a musical masterpiece. To acquire these specialized auditory-sensory-motor and emotional skills, musicians must undergo extensive training periods over many years, which start in early childhood and continue on through stages of increasing physical and strategic complexities. Performance anxiety, linked to high societal pressures such as the fear of failure and heightened self-demands, frequently accompanies these learning processes. Motor disturbances in musicians are common and include mild forms, such as temporary motor fatigue with short-term reduction of motor skills, painful overuse injuries following prolonged practice, anxiety-related motor failures during performances (choking under pressure), as well as more persistent losses of motor control, here termed "dynamic stereotypes" (DSs). Musician's dystonia (MD), which is characterized by the permanent loss of control of highly skilled movements when playing a musical instrument, is the gravest manifestation of dysfunctional motor programs, frequently linked to a genetic susceptibility to develop such motor disturbances. In this review chapter, we focus on different types of motor failures in musicians. We argue that motor failures in musicians develop along a continuum, starting with subtle transient degradations due to fatigue, overuse, or performance stress, which transform by and by into more permanent, still fluctuating motor degradations, the DSs, until a more irreversible condition, MD manifests. We will review the epidemiology and the principles of medical treatment of MD and discuss prevention strategies.

Rating scales for musician's dystonia: the state of the art

Musician's dystonia (MD) is a focal adult-onset dystonia most commonly involving the hand. It has much greater relative prevalence than non-musician's focal hand dystonias, exhibits task specificity at the level of specific musical passages, and is a particularly difficult form of dystonia to treat. For most MD patients, the diagnosis confirms the end of their music performance careers. Research on treatments and pathophysiology is contingent upon measures of motor function abnormalities. In this review, we comprehensively survey the literature to identify the rating scales used in MD and the distribution of their use. We also summarize the extent to which the scales have been evaluated for their clinical utility, including reliability, validity, sensitivity, specificity to MD, and practicality for a clinical setting. Out of 135 publications, almost half (62) included no quantitative measures of motor function. The remaining 73 studies used a variety of choices from among 10 major rating scales. Most used subjective scales involving either patient or clinician ratings. Only 25% (18) of the studies used objective scales. None of the scales has been completely and rigorously evaluated for clinical utility. Whether studies involved treatments or pathophysiologic assays, there was a heterogeneous choice of rating scales used with no clear standard. As a result, the collective interpretive value of those studies is limited because the results are confounded by measurement effects. We suggest that the development and widespread adoption of a new clinically useful rating scale is critical for accelerating basic and clinical research in MD.

Flexibility of movement organization in piano performance

Piano performance involves a large repertoire of highly skilled movements. The acquisition of these exceptional skills despite innate neural and biomechanical constraints requires a sophisticated interaction between plasticity of the neural system and organization of a redundant number of degrees of freedom (DOF) in the motor system. Neuroplasticity subserving virtuosity of pianists has been documented in neuroimaging studies investigating effects of long-term piano training on structure and function of the cortical and subcortical regions. By contrast, recent behavioral studies have advanced the understanding of neuromuscular strategies and biomechanical principles behind the movement organization that enables skilled piano performance. Here we review the motor control and biomechanics literature, introducing the importance of describing motor behaviors not only for understanding mechanisms responsible for skillful motor actions in piano playing, but also for advancing diagnosis and rehabilitation of movement disorders caused by extensive piano practice.

Focal dystonia in musicians: linking motor symptoms to somatosensory dysfunction

Musician's dystonia (MD) is a neurological motor disorder characterized by involuntary contractions of those muscles involved in the play of a musical instrument. It is task-specific and initially only impairs the voluntary control of highly practiced musical motor skills. MD can lead to a severe decrement in a musician's ability to perform. While the etiology and the neurological pathomechanism of the disease remain unknown, it is known that MD like others forms of focal dystonia is associated with somatosensory deficits, specifically a decreased precision of tactile and proprioceptive perception. The sensory component of the disease becomes also evident by the patients' use of “sensory tricks” such as touching dystonic muscles to alleviate motor symptoms. The central premise of this paper is that the motor symptoms of MD have a somatosensory origin and are not fully explained as a problem of motor execution. We outline how altered proprioceptive feedback ultimately leads to a loss of voluntary motor control and propose two scenarios that explain why sensory tricks are effective. They are effective, because the sensorimotor system either recruits neural resources normally involved in tactile-proprioceptive (sensory) integration, or utilizes a fully functioning motor efference copy mechanism to align experienced with expected sensory feedback. We argue that an enhanced understanding of how a primary sensory deficit interacts with mechanisms of sensorimotor integration in MD provides helpful insights for the design of more effective behavioral therapies.

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.

Finger-specific loss of independent control of movements in musicians with focal dystonia

The loss of independent control of finger movements impairs the dexterous use of the hand. Focal hand dystonia is characterised by abnormal structural and functional changes at the cortical and subcortical regions responsible for individuated finger movements and by the loss of surround inhibition in the finger muscles. However, little is known about the pathophysiological impact of focal dystonia on the independent control of finger movements. Here we addressed this issue by asking pianists with and without focal dystonia to repetitively strike a piano key with one of the four fingers as fast as possible while the remaining digits kept the adjacent keys depressed. Using principal component analysis and cluster analysis to the derived keystroke data, we successfully classified pianists according to the presence or absence of dystonic symptoms with classification rates and cross-validation scores of approximately 90%. This confirmed the effects of focal dystonia on the individuated finger movements. Interestingly, the movement features that contributed to successful classification differed across fingers. Compared to healthy pianists, pianists with an affected index finger were characterised predominantly by stronger keystrokes, whereas pianists with affected middle or ring fingers exhibited abnormal temporal control of the keystrokes, such as slowness and rhythmic inconsistency. The selective alternation of the movement features indicates a finger-specific loss of the independent control of finger movements in focal dystonia of musicians.

Focal hand dystonia in musicians: a synopsis

Focal hand dystonia in musicians (FHDM), also known as 'musicians' cramp', is a relatively rare, task-specific, pain-free disorder of control, causing unintentional, abnormal movements and/or positions in a part of the body directly involved in playing a musical instrument. Few physicians are familiar with the diagnosis, yet the exact cause of the disorder remains unknown and there is no generally effective therapy. In this synopsis, the authors present their experience with the diagnosis and treatment of FHDM and their aetiology hypothesis that musicians' cramp is caused by a loss of central motor control initiated by a failure of coping mechanisms, which (try to) compensate for the effects of peripheral local movement disturbing factors in the hand. Recent publications focus on the role of the central nervous system and on motor pattern relearning. We recommend further (prospective) research of the results of operative (peripheral) therapy, followed by (central) motor pattern relearning, and of neuropsychological contributions.

Task-specific dystonias: historical review--a new look at the classics

Although task-specific dystonias (TSD) have been described for almost two centuries, few entities have been characterised so variously as TSD. Over time TSD have been described as pure motor phenomena, "neurasthenic" symptoms, occupational hazards akin to repetitive strain, hysterical symptoms and finally… back to pure motor phenomena. A review of the classic literature can shed light on this subject and show that the same disease can be classified of different ways according to the dominant contemporary concepts over time. In any case, classic authors already defined TSD as motor phenomena of central origin.

Introduction to The neurosciences and music IV: learning and memory

The conference entitled "The Neurosciences and Music-IV: Learning and Memory'' was held at the University of Edinburgh from June 9-12, 2011, jointly hosted by the Mariani Foundation and the Institute for Music in Human and Social Development, and involving nearly 500 international delegates. Two opening workshops, three large and vibrant poster sessions, and nine invited symposia introduced a diverse range of recent research findings and discussed current research directions. Here, the proceedings are introduced by the workshop and symposia leaders on topics including working with children, rhythm perception, language processing, cultural learning, memory, musical imagery, neural plasticity, stroke rehabilitation, autism, and amusia. The rich diversity of the interdisciplinary research presented suggests that the future of music neuroscience looks both exciting and promising, and that important implications for music rehabilitation and therapy are being discovered.