Focal dystonia in musicians: phenomenology, pathophysiology and triggering factors

The impact of fine motor activities like playing musical instruments on the thickness and strength of the flexor digitorum muscle

BACKGROUND

This study aimed to explore the impact of occupational activities involving extensive finger movement on the muscular characteristics of the forearms. In particular, the flexor digitorum (FD) muscular thickness and strength asymmetry between right and left hand were compared between musicians and non-musicians.

METHODS

Ultrasonography was employed to measure the thickness of the FD in each hand, while a validated custom-made device was used to assess the strength of the flexor and extensor digitorum (ED). Initially, muscle differences were estimated by computing the asymmetry index between dominant and non-dominant hands. To assess potential occupational disparities, comparisons of the asymmetry index were conducted between 25 right-handed instrumental musicians and 25 right-handed non-musicians.

RESULTS

Musicians exhibited lower asymmetry between dominant and non-dominant hands in both FD thickness and ED strength when compared to non-musicians. This effect was particularly pronounced in musicians playing instruments that extensively use the left-hand fingers (e.g., violinists).

CONCLUSIONS

Occupational activities, such as playing a musical instrument, can alter forearm muscle mass and strength distribution between dominant and non-dominant hands. This underscores the importance of considering occupational parameters in clinical or experimental interventions and musculoskeletal assessments.

Stress in Musicians with and Without Focal Dystonia Is Not Reflected in Limbic Circuit Activation

BACKGROUND

Musicians' dystonia (MD) is a movement disorder with several established risk factors, but the exact pathophysiology remains unknown. Recent research suggests dysfunction in sensory-motor, basal ganglia, cerebellar, and limbic loops as potential causes. Adverse childhood experiences are also considered risk factors.

OBJECTIVE

This study aimed to investigate whether MD patients have experienced more childhood trauma, leading to increased stress reactivity and neural vulnerability to movement disorders.

METHODS

Using functional magnetic resonance imaging and the Montreal Imaging Stress Task, 40 MD patients were compared with 39 healthy musicians (HMs). Whole-brain analysis and regions of interest analysis were performed. Parameter estimates and subjective stress levels were compared between groups and correlated with the Childhood Trauma Questionnaire.

RESULTS

MD patients reported significantly higher childhood trauma scores than healthy control subjects, but they did not differ in their subjective stress experiences. Stress-related activity of limbic areas was neither found in the whole sample nor between the two groups. Instead, increased activity of visual association and temporal areas was observed, but this activation did not differ between patients and HMs. However, patients showed a tendency toward reduced precuneus activity under stress. Adverse childhood experiences were negatively correlated with precuneus, thalamus, and substantia nigra activity across all participants.

CONCLUSIONS

Overall, MD patients and HMs had similar subjective and neurological reactions to stress but differed in childhood trauma experiences and precuneus activity under stress. Further research about the functional connectivity between precuneus, cerebellum, thalamus, and basal ganglia in musicians is needed. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

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.

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

Introduction

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

Methods

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

Results

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

Conclusion

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

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.

Movement patterns in tuba playing: comparison of an embouchure dystonia case with healthy professional tuba players using real-time MRI imaging

Introduction

Musculoskeletal problems in professional brass musicians are very common and often involve the muscles of the embouchure. In rare cases, embouchure dystonia (EmD), a task-specific movement disorder with a wide symptomatic and phenotypic variability, occurs. Following trumpeters and horn players, professional tuba players with and without EmD have now been studied using the latest real-time MRI technology to better understand the underlying pathophysiology.

Materials and methods

In the present study, the tongue movement patterns of 11 healthy professional artists and one subject suffering from EmD were compared. The tongue position in the anterior, intermediary and posterior oral cavity were converted into pixel positions based on seven previously generated profile lines, using the established software MATLAB. These data allow a structured comparison of tongue movement patterns between the patient and the healthy subjects, as well as between individual exercises. The main focus of the analysis was on an ascending 7-note harmonic series performed in different playing techniques (slurred, tongued, tenuto and staccato).

Results

Playing the ascending harmonics, a noticeable ascending tongue movement could be observed in the anterior part of the oral cavity in healthy tubists. In the posterior region, there was a slight decrease in oral cavity space. In the EmD patient, hardly any movement was observed at the tongue apex, but in the middle and posterior regions of the oral cavity there was an increase in size the higher the tone became. These distinct differences are relevant for the characterization and a better understanding of the clinical presentation of EmD. Concerning different playing techniques, it was apparent, that notes played slurred or staccato resulted in a larger oral cavity when compared to notes played tongued or tenuto, respectively.

Conclusion

By using real-time MRI videos, the tongue movements of tuba players can be clearly observed and analyzed. The differences between healthy and diseased tuba players demonstrate the great effects of movement disorders in a small area of the tongue. In order to better understand the compensation of this motor control dysfunction, further studies should investigate further parameters of tone production in all brass players with a larger number of EmD patients additional to the observed movement patterns.

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

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

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

SIGNIFICANCE

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

Focal Dystonia and the Stress Network: The Role of Stress Vulnerability and Adverse Childhood Experiences in the Development of Musician's Dystonia

Musician's dystonia is often described as a neurological disorder, resulting from reduced inhibition in the basal ganglia and the cerebellum and dysfunctional cortical plasticity. However, several studies over the last decades support the hypothesis that psychological factors play an important role in the aetiology of dystonia, contradicting its classification as "purely neurological". Especially adverse childhood experiences (ACEs) such as neglect, maltreatment, or household dysfunction may influence the sensorimotor system, additionally to the impact they have on psychological traits. They are known to alter limbic networks, such as the amygdala, the hippocampus, and the stress response via the hypothalamus-pituitary-adrenal (HPA) axis and might also affect the cortico-striatal-thalamo-cortical loop that is vital for correct motor movement learning. Especially a higher activity of the basolateral amygdala could be important by increasing the consolidation of dysfunctional motor memories in stressful situations.Therefore, this chapter explores how musician's dystonia might be a result of dysfunctional stress-coping mechanisms, additionally to the already established neurological alterations.

Assessing Performing Artists in Medical and Health Practice - The Dancers, Instrumentalists, Vocalists, and Actors Screening Protocol

ABSTRACT

Training in the performing arts exposes individuals to often extreme physical and psychological demands, which are linked to high occupational injury rates. The intense demands of performing artists have been likened to those of sport athletes. However, distinct differences in these demands necessitate specialized approaches to the health care of performing artists. Through the Athletes and the Arts collaboration, the American College of Sports Medicine and Performing Arts Medicine Association identified that the creation of a specialized preparticipation screening tool for performing artists would likely enhance health care for performing artists significantly. Based on a thorough review of established assessments and an extensive consultation process with domain experts, a consensus best-practice screening tool was developed: the Dancer, Instrumentalist, Vocalist, Actor (DIVA) Preparticipation Screening. This screening tool is modeled on the athletic preparticipation examination (PPE) in its structure and 30-min target duration. However, DIVA diverges considerably from the PPE in its content to address the specific risks and needs of performing artists. In particular, screening questions and physical examination procedures focus strongly on musculoskeletal injuries and mental health conditions, in response to the preponderance and interactions of these conditions appearing in performing artists. The DIVA tool presented is intended as a "living tool," which can be modified in the future to include new effective assessment techniques as appropriate. Training in the DIVA preparticipation physical examination is included as a core component of the essentials of performing arts medicine continuing education course described in detail in a companion manuscript in this issue.

Characterizing the temporal discrimination threshold in musician's dystonia

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

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.

Influence of Adverse Childhood Experiences and Perfectionism on Musician's Dystonia: a Case Control Study

Background

Musician's dystonia (MD) is a task-specific movement disorder characterized by muscle cramps and impaired voluntary motor-control whilst playing a musical instrument. Recent studies suggest an involvement of adverse childhood experiences (ACEs) in the development of MD.

Objectives

By investigating the prevalence of ACEs in MD patients with perfectionism as possible mediating factor this study aims to gain further insights into the etiology of MD.

Methods

The Adverse Childhood Experiences Scale (ACE-S), the Childhood Trauma Questionnaire (CTQ) and Frost's Multidimensional Perfectionism Scale (FMPS) were answered by 128 MD patients and 136 healthy musicians. Regression and mediator analyses were conducted to identify relevant predictors of MD and to investigate the role of perfectionism.

Results

The CTQ total score (OR: 1.04; 95% CI [1.01, 1.08]) and the sub-score "emotional neglect" (OR: 1.13; 95% CI [1.02, 1.25]) were identified as two predictors of MD. Patients scored significantly higher on the sub-score emotional neglect, but no significant differences were observed for other forms of ACEs. Perfectionism had no mediating function on the association between ACEs and MD.

Discussion

Though only slight differences between both groups were found, there is a trend towards higher rates of emotional neglect among dystonic musicians. A possible explanation for the association between musician's dystonia and emotional neglect could be a lower stress resilience in musicians with a history of ACEs, which increases vulnerability to acquire dysfunctional movement patterns.These tendencies should be further investigated in future studies in which the MD and HM groups are more evenly matched in sex and age.

Highlights

We investigated the role of Adverse Childhood Experiences in the development of musician's dystonia, comparing a large sample of healthy musicians and dystonia patients. Our findings suggest that experiencing emotional neglect might increase the probability to acquire musician's dystonia. The findings offer new implications for etiology and treatment of dystonia.

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.

Association of the Yips and Musculoskeletal Problems in Highly Skilled Golfers: A Large Scale Epidemiological Study in Japan

The yips are a set of conditions associated with intermittent motor disturbances that affect precision movement, especially in sports. Specifically, skilled golfers suffer from the yips, although its clinical characteristics and pathophysiology have not been well-studied. We surveyed skilled golfers to characterize their yips-related symptoms, to explore potential confounding factors associated with the yips. Golfers’ demographic information, golfing-career-related history, musculoskeletal status and manifestations of the yips are surveyed. Among the 1576 questionnaires distributed, 1457 (92%) responses were received, of which 39% of golfers had experienced the yips. The median age and golfing careers were 48 and 28 years, respectively. Golfers who had experienced the yips were older and had longer golfing careers and more frequent musculoskeletal problems than those without experience of the yips. The multivariate logistic regression analysis revealed that a longer golfing career and musculoskeletal problems were independent factors associated with yips experience. More severe musculoskeletal problems were associated with higher odds of experiencing the yips. A positive association between the yips and musculoskeletal problems was also observed. The yips have similar characteristics to task-specific movement disorders, with a detrimental effect caused by excessive repetition of a routine task. These findings support the notion that the yips are a type of task-specific dystonia.

A novel task-specific dystonia type: Hemifacial spasm in a photographer

A 67-year-old male photographer who used traditional cameras that necessitated monocular focusing developed intermittent blepharospasms, evident only during and shortly after the voluntary contraction of the left eyelids while using the camera, a form of a task-specific blepharospasm. The spasms gradually progressed to involve the entire hemiface resulting in a task-specific hemifacial spasm that eventually evolved into a persistent hemifacial spasm. Our case report highlights the fact that focal dystonia may also develop in the facial muscles following chronic and repetitive muscle contractions, such as those performed by an older photographer who used traditional cameras that necessitated monocular focusing. To our knowledge, hemifacial spasm has not yet been recognized as a form of focal, task-specific dystonia. Moreover, occupational, focal dystonia has not been described in photographers.

Tongue involvement in embouchure dystonia: new piloting results using real-time MRI of trumpet players

Background

The embouchure of trumpet players is of utmost importance for tone production and quality of playing. It requires skilled coordination of lips, facial muscles, tongue, oral cavity, larynx and breathing and has to be maintained by steady practice. In rare cases, embouchure dystonia (EmD), a highly task specific movement disorder, may cause deterioration of sound quality and reduced control of tongue and lip movements. In order to better understand the pathophysiology of this movement disorder, we use real-time MRI to analyse differences in tongue movements between healthy trumpet players and professional players with embouchure dystonia.

Methods

Real-time MRI videos (with sound recording) were acquired at 55 frames per second, while 10 healthy subjects and 4 patients with EmD performed a defined set of exercises on an MRI-compatible trumpet inside a 3 Tesla MRI system. To allow for a comparison of tongue movements between players, temporal changes of MRI signal intensities were analysed along 7 standardized positions of the tongue using a customised MATLAB toolkit. Detailed results of movements within the oral cavity during performance of an ascending slurred 11-note harmonic series are presented.

Results

Playing trumpet in the higher register requires a very precise and stable narrowing of the free oral cavity. For this purpose the anterior section of the tongue is used as a valve in order to speed up airflow in a controlled manner. Conversely, the posterior part of the tongue is much less involved in the regulation of air speed. The results further demonstrate that healthy trumpet players control movements of the tongue rather precisely and stable during a sustained tone, whereas trumpet players with EmD exhibit much higher variability in tongue movements.

Conclusion

Control of the anterior tongue in trumpet playing emerges as a critical feature for regulating air speed and, ultimately, achieving a high-quality performance. In EmD the observation of less coordinated tongue movements suggests the presence of compensatory patterns in an attempt to regulate (or correct) pitch. Increased variability of the anterior tongue could be an objective sign of dystonia that has to be examined in further studies and extended to other brass instruments and may be also a potential target for therapy options.

Skater's Cramp: A Possible Task-Specific Dystonia in Dutch Ice Skaters

Background

Skater's cramp is an involuntary lower leg movement in skilled speed skaters. We aim to evaluate whether skater's cramp is compatible with task‐specific dystonia.

Methods

A case‐control study tested 5 speed skaters exhibiting symptoms of skater's cramp and 5 controls. Affected skaters completed a standardized questionnaire and neurological examination. Video analyses included skating normally, intensely, and with extra mass around the skater's ankles. An Inertial Motion Capturing (IMC) device mounted on both skates provided angular velocity data for both feet.

Results

Median time of onset of skater's cramp occurred after 12 (range 3–22) years of speed skating. Skater's cramp appeared as task specific; its onset was sudden and correlated to stress and aberrant proprioception. Symptoms presented acutely and consistently during skating, unilaterally in 4 and bilaterally in 1 skater. Visually, skater's cramp was an active, patterned, and person‐specific jerking of a skater's foot, either exo‐ or endorotationally. It presented asymmetrically, repeating persistently as the foot neared the end of the swing phase. The skater's affected leg had a longer swing phase (median, 1.37 [interquartile range {IQR}, 0.35]/1.18 [IQR, 0.24] seconds; P < 0.01), a shorter glide phase (median, 1.09 [IQR, 0.25]/1.26 (IQR, 0.29) seconds; P < 0.01), and higher angular velocity during the jerking motion. Symptoms remained constant irrespective of speed or extra mass around the ankle (P > 0.05). No significant differences between legs were detected in the control group.

Conclusions

Observed clinical, visual, and kinematic data could be an early and tentative indication of task‐specific dystonia.

Characterizing Movement Fluency in Musical Performance: Toward a Generic Measure for Technology Enhanced Learning

Virtuosity in music performance is often associated with fast, precise, and efficient sound-producing movements. The generation of such highly skilled movements involves complex joint and muscle control by the central nervous system, and depends on the ability to anticipate, segment, and coarticulate motor elements, all within the biomechanical constraints of the human body. When successful, such motor skill should lead to what we characterize as fluency in musical performance. Detecting typical features of fluency could be very useful for technology-enhanced learning systems, assisting and supporting students during their individual practice sessions by giving feedback and helping them to adopt sustainable movement patterns. In this study, we propose to assess fluency in musical performance as the ability to smoothly and efficiently coordinate while accurately performing slow, transitionary, and rapid movements. To this end, the movements of three cello players and three drummers at different levels of skill were recorded with an optical motion capture system, while a wireless electromyography (EMG) system recorded the corresponding muscle activity from relevant landmarks. We analyzed the kinematic and coarticulation characteristics of these recordings separately and then propose a combined model of fluency in musical performance predicting music sophistication. Results suggest that expert performers' movements are characterized by consistently smooth strokes and scaling of muscle phasic coactivation. The explored model of fluency as a function of movement smoothness and coarticulation patterns was shown to be limited by the sample size, but it serves as a proof of concept. Results from this study show the potential of a technology-enhanced objective measure of fluency in musical performance, which could lead to improved practices for aspiring musicians, instructors, and researchers.

Task-specificity in focal dystonia is shaped by aberrant diversity of a functional network kernel

OBJECTIVES

Task-specific focal dystonia selectively affects the motor control during skilled and highly learned behaviors. Recent data suggest the role of neural network abnormalities in the development of the pathophysiological dystonic cascade.

METHODS

We used resting-state functional MRI and analytic techniques rooted in network science and graph theory to examine the formation of abnormal subnetwork of highly influential brain regions, the functional network kernel, and its influence on aberrant dystonic connectivity specific to affected body region and skilled motor behavior.

RESULTS

We found abnormal embedding of sensorimotor cortex and prefrontal thalamus in dystonic network kernel as a hallmark of task-specific focal dystonia. Dependent on the affected body region, aberrant functional specialization of the network kernel included regions of motor control management in focal hand dystonia (writer's cramp, musician's focal hand dystonia) and sensorimotor processing in laryngeal dystonia (spasmodic dysphonia, singer's laryngeal dystonia). Dependent on skilled motor behavior, the network kernel featured altered connectivity between sensory and motor execution circuits in musician's dystonia (musician's focal hand dystonia, singer's laryngeal dystonia) and abnormal integration of sensory feedback into motor planning and executive circuits in non-musician's dystonia (writer's cramp, spasmodic dysphonia).

CONCLUSIONS

Our study identified specific traits in disorganization of large-scale neural connectivity that underlie the common pathophysiology of task-specific focal dystonia while reflecting distinct symptomatology of its different forms. Identification of specialized regions of information transfer that influence dystonic network activity is an important step for future delineation of targets for neuromodulation as a potential therapeutic option of task-specific focal dystonia. © 2018 International Parkinson and Movement Disorder Society.

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.

State anxiety disorganizes finger movements during musical performance

Skilled performance, in many situations, exposes an individual to psychological stress and fear, thus triggering state anxiety and compromising motor dexterity. Suboptimal skill execution in people under pressure affects the future career prospects of trained individuals, such as athletes, clinicians, and musicians. However, it has not been elucidated in what manner state anxiety affects multijoint movements and thereby degrades fine motor control. Using principal component analysis of hand kinematics recorded by a data glove during piano performances, we tested whether state anxiety affects the organization of movements of multiple joints or merely constrains the amplitude of the individual joints without affecting joint movement coordination. The result demonstrated changes in the coordination of movements across joints in piano performances by experts under psychological stress. Overall, the change was characterized by reduction of synergistic movements between the finger responsible for the keypress and its adjacent fingers. A regression analysis further identified that the attenuation of the movement covariation between the fingers was associated with an increase in temporal error during performance under pressure. In contrast, neither the maximum nor minimum angles of the individual joints of the hand were susceptible to induced anxiety. These results suggest that degradation of fine motor control under pressure is mediated by incoordination of movements between the fingers in skilled piano performances. NEW & NOTEWORTHY A key issue in neuromuscular control of coordinated movements is how the nervous system organizes multiple degrees of freedom for production of skillful motor behaviors. We found that state anxiety disorchestrates the organization of finger movements so as to decrease synergistic motions between the fingers in musical performance, which degrades fine motor control. The findings are important to shed light on mechanisms underlying loss of motor dexterity under pressure.

Temporal exploration in sequential movements shapes efficient neuromuscular control

The interaction of early and deliberate practice with genetic predisposition endows experts with virtuosic motor performance. However, it has not been known whether ways of practicing shape motor virtuosity. Here, we addressed this issue by comparing the effects of rhythmic variation in motor practice on neuromuscular control of the finger movements in pianists. With the use of a novel electromyography system with miniature active electrodes, we recorded the activity of the intrinsic hand muscles of 27 pianists while they played the piano and analyzed it by using a nonnegative matrix factorization algorithm and cluster analysis. The result demonstrated that practicing a target movement sequence with various rhythms reduced muscular activity, whereas neither practicing a sequence with a single rhythm nor taking a rest without practicing changed the activity. In addition, practice with rhythmic variation changed the patterns of simultaneous activations across muscles. This alteration of muscular coordination was associated with decreased activation of muscles not only relevant to, but also irrelevant to the task performance. In contrast, piano practice improved the maximum speed of the performance, the amount of which was independent of whether rhythmic variation was present. These results suggest that temporal variation in movement sequences during practice co-optimizes both movement speed and neuromuscular efficiency, which emphasizes the significance of ways of practice in the acquisition of motor virtuosity. NEW & NOTEWORTHY A key question in motor neuroscience is whether "ways of practicing" contribute to shaping motor virtuosity. We found both attenuation of activities and alteration of coordination of the intrinsic hand muscles of pianists, specifically through practicing a movement sequence with various rhythms. The maximum speed of the finger movements was also enhanced following the practice. These results emphasize the importance of ways of practicing in facilitating multiple skills: efficiency and speed.

Quantitative, clinically relevant acoustic measurements of focal embouchure dystonia

BACKGROUND

Focal embouchure dystonia impairs orofacial motor control in wind musicians and causes professional disability. A paucity of quantitative measures or rating scales impedes the objective assessment of treatment efficacy.

OBJECTIVES

We quantified specific features of focal embouchure dystonia using acoustic measures and developed a metric to assess severity across multiple domains of symptomatic impairment.

METHODS

We recruited 9 brass musicians with and 6 without embouchure dystonia. The following 4 domains of symptomatic dysfunction in focal embouchure dystonia were identified: pitch inaccuracy, sound instability and tremor, sound breaks, and timing variability. Musicians performed sustained tones and sequences, and then acoustic variables within each domain were quantified. A composite brass acoustic severity score composed of these variables was validated against clinical global impressions of severity.

RESULTS

Musicians with dystonia performed worse in acoustic domains of pitch inaccuracy (median: dystonia = 100%, control = 62%), instability (median shimmer: dystonia = 3%, control = 2%), and breaks (median: dystonia = 0.34%, control = 0.05%). Tremor in embouchure dystonia was 5 to 8 Hz, intermittent, and variable in amplitude. Rhythmic variability did not differ between groups. Participants with embouchure dystonia had different patterns of impairment across variables. Composite severity scores strongly predicted clinical global impression of severity (R2  = 0.95).

CONCLUSIONS

Acoustic variables distinguish musicians with embouchure dystonia from controls and reflect different types of symptomatic impairments. Our composite acoustic severity score predicts severity of clinical global impression for musicians with different patterns of symptomatic impairment and may provide a foundation for developing a clinical rating scale. © 2018 International Parkinson and Movement Disorder Society.

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.

Clinical and Phenomenological Characteristics of Patients with Task-Specific Lingual Dystonia: Possible Association with Occupation

BACKGROUND

Lingual dystonia is a subtype of oromandibular dystonia, which is a movement disorder characterized by involuntary sustained or intermittent contraction of the masticatory and/or tongue muscles. Lingual dystonia interferes with important daily activities, such as speaking, chewing, and swallowing, resulting in vocational and social disability.

OBJECTIVE

The aim of this study was to investigate a possible relationship between occupation and the development of lingual dystonia.

METHODS

Phenomenological and clinical characteristics of 95 patients [53 females (55.8%) and 42 males (44.2%), mean age 48.0 years] with task-specific, speech-induced lingual dystonia were analyzed. Structured interviews were carried out to obtain information regarding primary occupation, including overtime work and stress during work. The factors that might have influenced the development of lingual dystonia were estimated using multivariate logistic regression analysis of the 95 patients with lingual dystonia and 95 controls [68 females (71.6%) and 27 males (28.4%), mean age 47.2 years] with temporomandibular disorders.

RESULTS

Overall, 84.2% of the patients had regular occupations; 73.8% of the patients with regular occupations reported working overtime more than twice a week, and 63.8% of them experienced stress at the workplace. Furthermore, 82.1% of the patients had engaged in occupations that required them to talk to customers or other people under stressful situations over prolonged periods of time for many years (mean: 15.6 years). The most common occupation was sales representative (17.9%), followed by telephone operator (13.7%), customer service representative (10.5%), health care worker (9.5%), waiter or waitress (5.3%), receptionist (5.3%), and cashier (5.3%). Twenty-nine patients (30.5%) had tardive lingual dystonia. Logistic regression analyses revealed that frequent requirements for professional speaking (p = 0.011, odds ratio: 5.66), high stress during work (p = 0.043, odds ratio: 5.4), and neuroleptic use (p = 0.032, odds ratio: 2.52) were significant contributors to the manifestation of lingual dystonia.

CONCLUSION

Professions in which conversations in stressful situations are unavoidable may trigger lingual dystonia. Therefore, speech-induced lingual dystonia can be regarded as occupational dystonia in certain cases.

Functional Characterization of Rare RAB12 Variants and Their Role in Musician's and Other Dystonias

Mutations in RAB (member of the Ras superfamily) genes are increasingly recognized as cause of a variety of disorders including neurological conditions. While musician’s dystonia (MD) and writer’s dystonia (WD) are task-specific movement disorders, other dystonias persistently affect postures as in cervical dystonia. Little is known about the underlying etiology. Next-generation sequencing revealed a rare missense variant (c.586A>G; p.Ile196Val) in RAB12 in two of three MD/WD families. Next, we tested 916 additional dystonia patients; 512 Parkinson’s disease patients; and 461 healthy controls for RAB12 variants and identified 10 additional carriers of rare missense changes among dystonia patients (1.1%) but only one carrier in non-dystonic individuals (0.1%; p = 0.005). The detected variants among index patients comprised p.Ile196Val (n = 6); p.Ala174Thr (n = 3); p.Gly13Asp; p.Ala148Thr; and p.Arg181Gln in patients with MD; cervical dystonia; or WD. Two relatives of MD patients with WD also carried p.Ile196Val. The two variants identified in MD patients (p.Ile196Val; p.Gly13Asp) were characterized on endogenous levels in patient-derived fibroblasts and in two RAB12-overexpressing cell models. The ability to hydrolyze guanosine triphosphate (GTP), so called GTPase activity, was increased in mutants compared to wildtype. Furthermore, subcellular distribution of RAB12 in mutants was altered in fibroblasts. Soluble Transferrin receptor 1 levels were reduced in the blood of all three tested p.Ile196Val carriers. In conclusion, we demonstrate an enrichment of missense changes among dystonia patients. Functional characterization revealed altered enzyme activity and lysosomal distribution in mutants suggesting a contribution of RAB12 variants to MD and other dystonias.

Focal task specific dystonia: a review and update

In this review, we summarize recent advances in understanding the etiology, risk factors and pathophysiology of focal task specific dystonia (FTSD), movement disorders characterized by abnormal motor activation during the performance of specific, repetitive actions. We focus on two common FTSD, musician’s dystonia and writer’s cramp. FTSD may pose a threat to the patient’s livelihood, and improved therapeutic treatments are needed.

Mental rotation and working memory in musicians' dystonia

BACKGROUND

Mental rotation of body parts engages cortical-subcortical areas that are actually involved in the execution of a movement. Musicians' dystonia is a type of focal hand dystonia that is grouped together with writer's cramp under the rubric of "occupational dystonia", but it is unclear to which extent these two disorders share common pathophysiological mechanisms. Previous research has demonstrated patients with writer's cramp to have deficits in mental rotation of body parts. It is unknown whether patients with musicians' dystonia would display similar deficits, reinforcing the concept of shared pathophysiology.

METHODS

Eight patients with musicians' dystonia and eight healthy musicians matched for age, gender and musical education, performed a number of tasks assessing mental rotation of body parts and objects as well as verbal and spatial working memories abilities.

RESULTS

There were no differences between patients and healthy musicians as to accuracy and reaction times in any of the tasks.

CONCLUSIONS

Patients with musicians' dystonia have intact abilities in mentally rotating body parts, suggesting that this disorder relies on a highly selective disruption of movement planning and execution that manifests only upon playing a specific instrument. We further demonstrated that mental rotation of body parts and objects engages, at least partially, different cognitive networks.

Sun exposure is an environmental factor for the development of blepharospasm

BACKGROUND

Adult-onset isolated focal dystonia may present with various phenotypes including blepharospasm and cervical dystonia. Although inherited in an autosomal dominant manner with a markedly reduced penetrance, environmental factors are considered important in disease penetrance and expression. We observed a marked variation by latitude in the reports of the frequency of patients with blepharospasm relative to those with cervical dystonia; we hypothesised that sun exposure is an environmental risk factor for the development of blepharospasm in genetically susceptible individuals.

METHODS

From published clinic cohorts and epidemiological reports, the ratio of the number of cases of blepharospasm to cervical dystonia (phenotype case ratio) at each study site was analysed with regard to latitude and measures of annual insolation. Meta-regression analyses of the phenotype case ratio to these environmental factors were performed.

RESULTS

The phenotype case ratio in 15 eligible study sites over 41° of latitude demonstrated a statistically significant inverse association with latitude (p=0.0004, R(2)=53.5%). There were significant positive associations between the phenotype case ratio and quarter-one (January-March) insolation (p=0.0005, R(2)=53%) and average annual insolation (p=0.003, R(2)=40%).

CONCLUSION

The increase in the blepharospasm: cervical dystonia case ratio with decreasing latitude and increasing insolation suggests that sunlight exposure is an environmental risk factor for the development of blepharospasm (rather than cervical dystonia) in individuals genetically susceptible to adult-onset dystonia.

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.

Dystonia and Paroxysmal Dyskinesias: Under-Recognized Movement Disorders in Domestic Animals? A Comparison with Human Dystonia/Paroxysmal Dyskinesias

Dystonia is defined as a neurological syndrome characterized by involuntary sustained or intermittent muscle contractions causing twisting, often repetitive movements, and postures. Paroxysmal dyskinesias are episodic movement disorders encompassing dystonia, chorea, athetosis, and ballism in conscious individuals. Several decades of research have enhanced the understanding of the etiology of human dystonia and dyskinesias that are associated with dystonia, but the pathophysiology remains largely unknown. The spontaneous occurrence of hereditary dystonia and paroxysmal dyskinesia is well documented in rodents used as animal models in basic dystonia research. Several hyperkinetic movement disorders, described in dogs, horses and cattle, show similarities to these human movement disorders. Although dystonia is regarded as the third most common movement disorder in humans, it is often misdiagnosed because of the heterogeneity of etiology and clinical presentation. Since these conditions are poorly known in veterinary practice, their prevalence may be underestimated in veterinary medicine. In order to attract attention to these movement disorders, i.e., dystonia and paroxysmal dyskinesias associated with dystonia, and to enhance interest in translational research, this review gives a brief overview of the current literature regarding dystonia/paroxysmal dyskinesia in humans and summarizes similar hereditary movement disorders reported in domestic animals.

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.

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 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.

Pain sensitivity and tactile spatial acuity are altered in healthy musicians as in chronic pain patients

Extensive training of repetitive and highly skilled movements, as it occurs in professional classical musicians, may lead to changes in tactile sensitivity and corresponding cortical reorganization of somatosensory cortices. It is also known that professional musicians frequently experience musculoskeletal pain and pain-related symptoms during their careers. The present study aimed at understanding the complex interaction between chronic pain and music training with respect to somatosensory processing. For this purpose, tactile thresholds (mechanical detection, grating orientation, two-point discrimination) and subjective ratings to thermal and pressure pain stimuli were assessed in 17 professional musicians with chronic pain, 30 pain-free musicians, 20 non-musicians with chronic pain, and 18 pain-free non-musicians. We found that pain-free musicians displayed greater touch sensitivity (i.e., lower mechanical detection thresholds), lower tactile spatial acuity (i.e., higher grating orientation thresholds) and increased pain sensitivity to pressure and heat compared to pain-free non-musicians. Moreover, we also found that musicians and non-musicians with chronic pain presented lower tactile spatial acuity and increased pain sensitivity to pressure and heat compared to pain-free non-musicians. The significant increment of pain sensitivity together with decreased spatial discrimination in pain-free musicians and the similarity of results found in chronic pain patients, suggests that the extensive training of repetitive and highly skilled movements in classical musicians could be considered as a risk factor for developing chronic pain, probably due to use-dependent plastic changes elicited in somatosensory pathways.

[Focal dystonia in musicians: Phenomenology and musical triggering factors]

Dystonias are defined as a joint sustained and involuntary contraction of agonist and antagonist muscles, which can cause torsion, repetitive abnormal involuntary movements, and/or abnormal postures. One special group of dystonias are those known as occupational, which include dystonia disorders triggered by a repetitive motor activity associated with a specific professional activity or task. Musicians are a population particularly vulnerable to these types of dystonia, which are presented as a loss of coordination and voluntary motor control movements highly trained in musical interpretation. Our aim is to describe a clinical series of focal dystonias in musicians evaluated and treated in our centre.

PATIENTS AND METHODS

Data is presented on a clinical series of 12 musicians with occupational dystonia. Their history and phenomenology are described, as well as well as their outcome after therapy.

RESULTS

Demographic details: Mean age 34.8 ± 11.8 years, 10 males (83.3%) and 2 females (16.7%).

CLINICAL HISTORY

History of trauma in dystonic segment, 6 patients (50%); family history of neurological diseases in first-degree relatives, 6 patients (50%); occupational history according to music category, 8 patients (66.6%) were classical musicians and 4 patients (33.3%) were popular musicians.

PHENOMENOLOGY

The dystonia syndrome was characterised by having a mean age of onset of 28.2 ± 11.3 years (range 18-57 years). The segment affected was the hand (91.7%) in 11 patients. Of all the musicians seen in the clinic, 9 of them (75%) received therapy. The majority of patients appeared to have triggering factors specific to musical execution and linked to the requirement of fine motor control. It should be mentioned that 50% of the musicians treated maintained their professional activity or position in the orchestra to which they belonged.

CONCLUSIONS

The majority of our phenomenological findings are consistent with those reported in the current literature. However, it is worth mentioning the presence of triggering factors attributed to the specific requirements of performing music, linked to the participation of fine motor control.

Evidence-informed physical therapy management of performance-related musculoskeletal disorders in musicians

Playing a musical instrument at an elite level is a highly complex motor skill. The regular daily training loads resulting from practice, rehearsals and performances place great demands on the neuromusculoskeletal systems of the body. As a consequence, performance-related musculoskeletal disorders (PRMDs) are globally recognized as common phenomena amongst professional orchestral musicians. These disorders create a significant financial burden to individuals and orchestras as well as lead to serious consequences to the musicians’ performance and ultimately their career. Physical therapists are experts in treating musculoskeletal injuries and are ideally placed to apply their skills to manage PRMDs in this hyper-functioning population, but there is little available evidence to guide specific injury management approaches. An Australia-wide survey of professional orchestral musicians revealed that the musicians attributed excessively high or sudden increase in playing-load as major contributors to their PRMDs. Therefore, facilitating musicians to better manage these loads should be a cornerstone of physical therapy management. The Sound Practice orchestral musicians work health and safety project used formative and process evaluation approaches to develop evidence-informed and clinically applicable physical therapy interventions, ultimately resulting in favorable outcomes. After these methodologies were employed, the intervention studies were conducted with a national cohort of professional musicians including: health education, onsite injury management, cross-training exercise regimes, performance postural analysis, and music performance biomechanics feedback. The outcomes of all these interventions will be discussed alongside a focussed review on the existing literature of these management strategies. Finally, a framework for best-practice physical therapy management of PRMDs in musicians will be provided.

Focal dystonia and the Sensory-Motor Integrative Loop for Enacting (SMILE)

Performing accurate movements requires preparation, execution, and monitoring mechanisms. The first two are coded by the motor system, the latter by the sensory system. To provide an adaptive neural basis to overt behaviors, motor and sensory information has to be properly integrated in a reciprocal feedback loop. Abnormalities in this sensory-motor loop are involved in movement disorders such as focal dystonia, a hyperkinetic alteration affecting only a specific body part and characterized by sensory and motor deficits in the absence of basic motor impairments. Despite the fundamental impact of sensory-motor integration mechanisms on daily life, the general principles of healthy and pathological anatomic–functional organization of sensory-motor integration remain to be clarified. Based on the available data from experimental psychology, neurophysiology, and neuroimaging, we propose a bio-computational model of sensory-motor integration: the Sensory-Motor Integrative Loop for Enacting (SMILE). Aiming at direct therapeutic implementations and with the final target of implementing novel intervention protocols for motor rehabilitation, our main goal is to provide the information necessary for further validating the SMILE model. By translating neuroscientific hypotheses into empirical investigations and clinically relevant questions, the prediction based on the SMILE model can be further extended to other pathological conditions characterized by impaired sensory-motor integration.

Genome-wide association study in musician's dystonia: a risk variant at the arylsulfatase G locus?

Musician's dystonia (MD) affects 1% to 2% of professional musicians and frequently terminates performance careers. It is characterized by loss of voluntary motor control when playing the instrument. Little is known about genetic risk factors, although MD or writer's dystonia (WD) occurs in relatives of 20% of MD patients. We conducted a 2-stage genome-wide association study in whites. Genotypes at 557,620 single-nucleotide polymorphisms (SNPs) passed stringent quality control for 127 patients and 984 controls. Ten SNPs revealed P < 10(-5) and entered the replication phase including 116 MD patients and 125 healthy musicians. A genome-wide significant SNP (P < 5 × 10(-8) ) was also genotyped in 208 German or Dutch WD patients, 1,969 Caucasian, Spanish, and Japanese patients with other forms of focal or segmental dystonia as well as in 2,233 ethnically matched controls. Genome-wide significance with MD was observed for an intronic variant in the arylsulfatase G (ARSG) gene (rs11655081; P = 3.95 × 10(-9) ; odds ratio [OR], 4.33; 95% confidence interval [CI], 2.66-7.05). rs11655081 was also associated with WD (P = 2.78 × 10(-2) ) but not with any other focal or segmental dystonia. The allele frequency of rs11655081 varies substantially between different populations. The population stratification in our sample was modest (λ = 1.07), but the effect size may be overestimated. Using a small but homogenous patient sample, we provide data for a possible association of ARSG with MD. The variant may also contribute to the risk of WD, a form of dystonia that is often found in relatives of MD patients.

From embouchure problems to embouchure dystonia? A survey of self-reported embouchure disorders in 585 professional orchestra brass players

OBJECTIVES

Data concerning embouchure problems in professional brass players are scarce. Embouchure problems can potentially lead to focal dystonia. The aim of this study was to investigate the frequency of distinct embouchure problems in professional brass players. Furthermore, the frequency of "cramping", a distinct symptom of embouchure dystonia, was evaluated in the context of established embouchure dystonia risk factors.

METHODS

Five hundred and eighty-five professional brass players participated in a cross-sectional study concerning embouchure problems. A self-administered questionnaire was developed to evaluate embouchure fatigue, embouchure disorders and their consequences. To study the association between risk factors and cramping (a symptom of embouchure dystonia), a log-binomial regression analysis was conducted, enabling estimation of prevalence ratios (PR) and 95 % confidence intervals (95 % CI).

RESULTS

Thirty percent (95 % CI 25.9-33.3) reported embouchure fatigue. The relative frequency of embouchure disorders was 59 % (95 % CI 54.6-63.6), with 26 % (95 % CI 22.4-29.5) reporting embouchure cramping. Embouchure disorders resulted in sick leave in 16 % (95 % CI 12.7-20.6). Female brass players (PR 2.0, 95 % CI 0.98-3.98) and musicians with a prior change in their embouchure (PR 2.4, 95 % CI 1.38-4.05) or breathing technique (PR 2.2, 95 % CI 1.25-3.72) and musicians with embouchure fatigue (PR 1.9, 95 % CI 1.18-2.93) presented more frequently with embouchure cramping than musicians with other or without risk factors.

CONCLUSION

This study shows a high relative frequency of embouchure problems in professional brass players. Given that embouchure dystonia is often preceded by embouchure problems, these findings may assist in gaining further insight into the characteristics of embouchure dystonia and the development of preventive strategies.