The natural history of embouchure dystonia

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.

Genetic Update and Treatment for Dystonia

A neurological condition called dystonia results in abnormal, uncontrollable postures or movements because of sporadic or continuous muscular spasms. Several varieties of dystonia can impact people of all ages, leading to severe impairment and a decreased standard of living. The discovery of genes causing variations of single or mixed dystonia has improved our understanding of the disease's etiology. Genetic dystonias are linked to several genes, including pathogenic variations of VPS16, TOR1A, THAP1, GNAL, and ANO3. Diagnosis of dystonia is primarily based on clinical symptoms, which can be challenging due to overlapping symptoms with other neurological conditions, such as Parkinson's disease. This review aims to summarize recent advances in the genetic origins and management of focal dystonia.

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.

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.

Treating the musician rather than the symptom: The holistic tools employed by current practices to attend to the non-motor problems of musicians with task-specific focal dystonia

Musicians Focal Dystonia (MFD) is a task-specific movement disorder affecting highly skilled musicians. The pathophysiology is poorly understood, and the available treatments are unable to fully and reliably rehabilitate the affected skill. Recently, the exclusively neurological nature of the condition has been questioned, and additional psychological, behavioral, and psychosocial contributing factors were identified. However, very little is known about how these factors influence the recovery process, and how, if at all, they are addressed in ongoing practices. For this study, 14 practitioners with substantial experience in working with musicians with MFD were interviewed about the elements in their approach which are directed at the cognition, emotions, attitudes, and behaviors of their patients and clients. A wide variety of tools were reported in three areas: (1) creating a supportive learning environment and addressing anxiety and perfectionism, (2) using body-oriented methods to optimize the playing behaviors and (3) consciously channeling the focus of attention to guide the physical retraining exercises and establishing new habits. The study also revealed that in-depth knowledge of the instrumental technique is profitable to retrain the impaired motor patterns. Therefore, the importance of including music educators in developing new therapeutic approaches will also be highlighted.

Embouchure Dystonia as a Network Disease

While the pathophysiology of embouchure dystonia, a sub-entity of musician's dystonia, is still not fully understood, recent research has shown that it involves alterations of several brain functions and networks. Maladaptive plasticity in sensorimotor integration, sensory perception, and deficient inhibitory mechanisms at cortical, subcortical, and spinal level seem to contribute to its pathophysiology. Furthermore, functional systems of the basal ganglia and the cerebellum are involved, clearly pointing toward a network disorder. We therefore propose a novel network model, based on electrophysiological and recent neuroimaging studies highlighting embouchure dystonia.

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

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

Isolated and combined dystonias: Update

Dystonia is a hyperkinetic movement disorder with a unique motor phenomenology that can manifest as an isolated clinical syndrome or combined with other neurological features. This chapter reviews the characteristic features of dystonia phenomenology and the syndromic approach to evaluating the disorders that may allow us to differentiate the isolated and combined syndromes. We also present the most common types of isolated and combined dystonia syndromes. Since accelerated gene discoveries have increased our understanding of the molecular mechanisms of dystonia pathogenesis, we also present isolated and combined dystonia syndromes by shared biological pathways. Examples of these converging mechanisms of the isolated and combined dystonia syndromes include (1) disruption of the integrated response pathway through eukaryotic initiation factor 2 alpha signaling, (2) disease of dopaminergic signaling, (3) alterations in the cerebello-thalamic pathway, and (4) disease of protein mislocalization and stability. The discoveries that isolated and combined dystonia syndromes converge in shared biological pathways will aid in the development of clinical trials and therapeutic strategies targeting these convergent molecular pathways.

Movement disorders of the mouth: a review of the common phenomenologies

Movement disorders of the mouth encompass a spectrum of hyperactive movements involving the muscles of the orofacial complex. They are rare conditions and are described in the literature primarily in case reports originating from neurologists, psychiatrists, and the dental community. The focus of this review is to provide a phenomenological description of different oral motor disorders including oromandibular dystonia, orofacial dyskinesia and orolingual tremor, and to offer management strategies for optimal treatment based on the current literature. A literature search of full text studies using PubMed/Medline and Cochrane library combined with a manual search of the reference lists was conducted until June 2021. Results from this search included meta-analyses, systematic reviews, reviews, clinical studies, case series, and case reports published by neurologists, psychiatrists, dentists and oral and maxillofacial surgeons. Data garnered from these sources were used to provide an overview of most commonly encountered movement disorders of the mouth, aiding physicians in recognizing these rare conditions and in initiating appropriate therapy.

Oromandibular dystonia – A systematic review

Oromandibular dystonia (OMD) is a clinical problem which is commonly encountered in the practice of movement disorders. OMD results from a variety of genetic and acquired etiologies and can occur as an isolated manifestation, or as part of an isolated generalized or a combined dystonia syndrome. There are only very few systematic reviews on this condition which often causes significant disability. We review here the etiology, clinical features, diagnostic approach and management of OMD.

Occupational Injuries in Musicians: A Literature Review

INTRODUCTION

The U.S. Department of Defense employs more musicians than any other organization in the USA with over 6,000 musicians employed. Musculoskeletal pathologies, behavioral health disorders, hearing loss, and dystonias account for the majority of reasons a musician seek medical care. The aim of this study is to review recent medical literature documenting occupational hazards in musicians.

MATERIALS AND METHODS

Authors performed a literature review of publications related to musician performance-related musculoskeletal disorders (PRMDs) and performance-related pain (PRP), behavioral health disorders, dystonias, and hearing loss, published from 2004 to 2019 PubMed.

RESULTS

The search returned 174 possible articles which, after review and exclusion, yielded 88 articles.

CONCLUSIONS

Medical literature suggests several risk factors for multiple disease categories. Practice time and history of PRMD/PRP were both associated with development of PRMD/PRP and focal dystonia. A history of behavioral health disorder was associated with development of focal dystonia. Clinicians should counsel their musician patients on strategies to minimize risks, and additional research is needed to identify specific causes of illnesses in musician populations.

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.

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

INTRODUCTION

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

EVIDENCE ACQUISITION

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

EVIDENCE SYNTHESIS

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

CONCLUSIONS

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

Facial Muscle Activity Patterns in Clarinet Players: A Key to Understanding Facial Muscle Physiology and Dysfunction in Musicians

OBJECTIVES

Facial muscle activity is crucial to controlling musical performance in wind instrument playing. Facial muscle dysfunctions are common in wind instrument players, dramatically affecting their professional musical activity and potentially leading to disabling symptoms.The aim of this pilot study on a cohort of healthy clarinetists was to use surface electromyography to identify the facial muscle activity patterns involved in stabilizing the mouthpiece, controlling emission and articulation during musical tasks in physiological conditions, also comparing muscle activity between less and more experienced clarinetists (students vs postgraduates/professionals).

METHODS

Surface electromyographic measures of the sternocleidomastoid, masseter, mentalis, mylohyoid and buccinator muscles were obtained from eight healthy clarinet players (four students and four postgraduates/professionals) performing two standardized musical tasks.

RESULTS

Overall, mean IEMG activity was significantly lower for the sternocleidomastoid than for the other muscles (P = .000), and for the mouthpiece-stabilizing muscles (masseter and mentalis) than for those directly involved in controlling emission and articulation (buccinator and mylohyoid muscles) (P = .000).Regardless of the musical task, the mean IEMG values were significantly higher in the students for the masseter (P = .0007), buccinator (P = .0001) and mylohyoid (0.000), while they were significantly higher in the postgraduates/professionals for the mentalis (P = .000). No significant differences emerged between the two groups for the sternocleidomastoid (P = .207).

CONCLUSIONS

These preliminary data reflect a significantly higher overall facial muscle activity in the less-experienced group, potentially resulting in an overload, whereas the more expert players had more optimized muscle activity patterns.

Oromandibular dystonia: a diagnosis not to miss

Oromandibular dystonia (OMD) is characterised by sustained or repetitive involuntary movements of the jaw, face, and tongue. People with the condition may present to their dentist, general practitioner, or a secondary care specialist with non-specific symptoms including jaw or facial pain, bruxism, subluxations or dislocations of the jaw; fractured teeth or dental restorations, or both; or jaw tremor. Many clinicians are not aware of the disorder and this can lead to delayed diagnoses, unnecessary complications, and inappropriate treatment. OMD is an important diagnosis not to miss because referral for specialist management can provide good long-term results. To aid early, accurate diagnosis, this paper focuses on the key clinical features of the disorder and its dental and medical mimics.

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.

Abnormalities in grey matter structure in embouchure dystonia

INTRODUCTION

Embouchure dystonia (ED) is a debilitating movement disorder in professional brass players leading to involuntary muscle contractions/spasms during play. To date, activity changes in sensorimotor cortices during motor tasks and tactile processing, as well as connectivity changes at rest in sensorimotor and auditory brain networks have been described in the disease.

OBJECTIVE

To characterize differences in grey matter volume and asymmetry between brass musicians suffering from ED, healthy brass musicians and healthy nonmusicians.

METHODS

High-resolution structural magnetic resonance imaging was obtained from 24 brass musicians with ED, 23 healthy brass musicians and 24 healthy nonmusicians. Whole-brain voxel-wise morphometry and asymmetry analyses, as well as region-of-interest-based volumetry analysis were performed on the subjects' images and compared between groups. Further, correlations with clinical parameters were investigated.

RESULTS

ED patients showed increased grey matter volume in the primary sensorimotor cortex in relation to both healthy brass players and nonmusicians. Both healthy and diseased musicians showed increased thalamic symmetry in relation to nonmusicians; diseased brass musicians additionally showed increased basal ganglia symmetry compared to nonmusicians. There was an inverse correlation of disease duration with both mean putaminal volume and the extent of basal ganglia asymmetry.

CONCLUSION

This work provides first evidence for structural abnormalities in task-specific orofacial (musician's) dystonia. Somatotopy-related structural primary sensorimotor cortex changes underlying previously observed functional abnormalities underscore the role of maladaptive plasticity in the disease. The study further shows subcortical brain (a)symmetry changes in healthy brass players and hints at a possible role of such changes in focal dystonia.

Personality profiles are different in musician's dystonia and other isolated focal dystonias

Psychological abnormalities have been reported in patients with musician's dystonia. To further differentiate these abnormalities, we evaluated personality traits in musician's dystonia and compared them to those in other isolated focal dystonias. Therefore patients with musician's dystonia (n = 101) and other isolated focal dystonias (n = 85) underwent the Neuroticism Extraversion Openness Five-Factor Inventory (NEO-FFI). Women with musician's dystonia had higher NEO-FFI neuroticism scores, and men significantly higher openness scores compared to women and men with other isolated focal dystonias, respectively. There were negative correlations in men with musician's dystonia between duration of dystonia and the NEO-FFI openness and extraversion scores and between age and extraversion scores. Women with other isolated focal dystonias showed correlations between age and agreeableness and conscientiousness scores. Patients with musician's dystonia are characterized by a specific personality profile with increased neuroticism and openness compared to other isolated focal dystonias. Whether this profile can be traced back to specific underlying disease mechanisms should be further investigated.

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.

Functional facial and tongue movement disorders

Functional movement disorders (FMDs) affecting the eyelids, tongue, and other facial muscles are often underrecognized because their phenomenology has not been fully characterized. Nevertheless, these disorders are more common than previously thought. In this chapter we will discuss the phenomenology as well as the clinical and instrumental diagnosis of facial FMDs. Facial FMDs should be considered when a patient exhibits any combination of the following features: (1) fixed unilateral facial contractions, especially with lower lip, with or without ipsilateral jaw involvement, of maximal severity at onset; (2) inconsistent features such as changes in side and pattern during or between examination; (3) associated somatoform or nonphysiologic sensory or motor findings; (4) reduction or abolition of facial spasm with distraction; (5) response to suggestion or psychotherapy; (6) rapid onset and/or spontaneous remissions; and (7) normal neurologic examination. Supportive features are young age, female gender, and associated medical conditions such as depression, headaches, facial pain, fibromyalgia, or irritable-bowel syndrome. Finally, the differential diagnosis with the organic counterparts will be also addressed, particularly with respect to blepharospasm, oromandibular dystonia, and hemifacial spasm.

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.

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.

Laterality of proprioception in the orofacial muscles and temporomandibular joint

Laterality of function in the orofacial musculature suggests there may be side-to-side asymmetry of proprioceptive acuity in lip movement compared to the temporomandibular joint (TMJ). In the present work, 14 young adults were tested for acuity of lip and TMJ closure movements onto plugs varying from 5 to 8mm without visual feedback. Testing was conducted on both left and right sides, using the same psychophysical task and stimuli. Results showed superior proprioceptive acuity at the lips, with no significant side effect. However, there was side-to-side asymmetry in the correlations between proprioceptive performance for the two anatomical structures, with performance on the right side strongly correlated but not on the left. This is consistent with the need for coordination between structures during chewing. When acuity at different points in the stimulus range was examined, the right side lips were better with small stimuli. Overall, results support enhanced use-specific proprioception.

Embouchure dystonia: a video guide to diagnosis and evaluation

Background

Embouchure dystonia is an unusual focal task-specific dystonia affecting the muscles that control the flow of air into the mouthpiece of a brass or woodwind instrument. The complexity of the embouchure and the relative rarity of the condition pose barriers for recognition and management of the disorder.

Methods

Case review and video survey.

Results

This paper presents four video compilations that illustrate the rich phenomenology of embouchure dystonia, in order to enhance recognition and diagnosis.

Conclusion

The phenomenology of embouchure dystonia is discussed.

Electronic supplementary material

The online version of this article (doi:10.1186/s40734-016-0035-x) contains supplementary material, which is available to authorized users.

Activity and topographic changes in the somatosensory system in embouchure dystonia

BACKGROUND

Embouchure dystonia is a highly disabling focal task-specific dystonia affecting professional brass players.

OBJECTIVE

This study was designed to analyze activity changes along with topographic representations in primary and nonprimary centers for somatosensory processing in patients with embouchure dystonia.

METHODS

We used event-related functional magnetic resonance imaging with automized tactile stimulation of dystonic (upper lip) and nondystonic (forehead and dorsal hand) body regions in 15 professional brass players with and without embouchure dystonia. Statistical analyses included whole-brain between-group comparisons of stimulation-induced activation and region-of-interest-based single patient analyses of topographic activation characteristics.

RESULTS

Affected musicians revealed increased stimulation-induced activity in contralateral primary and bilateral secondary somatosensory representations of dystonic and nondystonic body regions as well as in the cerebellum ipsilateral to the left dystonic upper lip. Changes of somatotopic organization with altered intracortical distances and between-group differences of the centers of representations were found in the right primary and the bilateral secondary somatosensory cortex and in the left cerebellum. Positional variability of dystonic and nondystonic body regions was reduced with an emphasis on face representations.

CONCLUSIONS

The present findings are supportive of the concept of an abnormal processing of somatosensory information in embouchure dystonia affecting multiple domains. The underlying neurophysiological mechanisms (eg, changes in inhibition, maladaptive plasticity, changes in baseline activity) remain unclear. The involvement of nondystonic body areas can be viewed in the context of possible compensation or an endophenotypic predisposition. © 2016 International Parkinson and Movement Disorder Society.

The anatomical basis of upper limb dystonia: lesson from secondary cases

Upper limb dystonia is a focal dystonia that may affect muscles in the arm, forearm and hand. The neuroanatomical substrates involved in upper limb dystonia are not fully understood. Traditionally, dysfunction of the basal ganglia is presumed to be the main cause of dystonia but a growing body of evidence suggests that a network of additional cortical and subcortical structures may be involved. To identify the brain regions that are affected in secondary upper limb dystonia may help to better understand the neuroanatomical basis of the condition. We considered only patients with focal upper limb dystonia associated with a single localized brain lesion. To identify these patients, we conducted a systematic review of the published literature as well as the medical records of 350 patients with adult-onset dystonia seen over past 15 years at our movement disorder clinic. The literature review revealed 36 articles describing 72 cases of focal upper limb dystonia associated with focal lesions. Among patients at our clinic, four had focal lesions on imaging studies. Lesions were found in multiple regions including thalamus (n = 39), basal ganglia (n = 17), cortex (n = 4), brainstem (n = 4), cerebellum (n = 1), and cervical spine (n = 7). Dystonic tremor was not associated with any particular site of lesion, whereas there was a trend for an inverse association between task specificity and thalamic involvement. These data in combination with functional imaging studies of idiopathic upper limb dystonia support a model in which a network of different regions plays a role in pathogenesis.

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.

Idiopathic Radiographic Apical Root Resorption in Wind Instrument Players

Root resorption of the permanent teeth involves an elaborate interaction among inflammatory cells resulting in loss of dental hard tissues. This report describes three clinical cases where idiopathic root resorption occurred in wind instrument playing patients. These patients produce adequate non-orthodontic forces, while playing their instruments, to expose their teeth to root resorbing force. Careful clinical monitoring of patients' teeth should be undertaken, as the additive effects of orthodontic treatment and musical habits are unknown. CPD/Clinical Relevance: This paper advises that questioning about wind instrument playing during case history-taking would be beneficial to clinicians. Furthermore, careful clinical monitoring of these patients' teeth during orthodontic treatment should be undertaken.

Evaluation of embouchure dysfunction: Experience of 139 patients at a single center

OBJECTIVES/HYPOTHESIS

Our aims are to 1) illustrate the complexity and phenomenological richness of the embouchure; 2) delineate the main clinical features of non-dystonic embouchure problems (NED) versus embouchure dystonia (ED); and 3) provide a practical framework for physicians who may encounter a patient with embouchure dysfunction.

STUDY DESIGN

We performed retrospective chart and video review and report 139 instrumentalists with embouchure dysfunction evaluated over a 15-year period.

RESULTS

Included in this group are 109 ED patients (20 newly reported and 89 previously published) and 30 NED patients. Non-dystonic embouchure problems included the overuse syndrome, infraorbital neuropathy, and orbicularis oris tears, among others.

CONCLUSIONS

Based on this experience, the largest series presented to date, we propose a practical guide to help evaluate patients with embouchure dysfunction in the office.

LEVEL OF EVIDENCE

4. Laryngoscope, 126:1327-1333, 2016.

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.

Sensory trick phenomenon improves motor control in pianists with dystonia: prognostic value of glove-effect

Musician’s dystonia (MD) is a task-specific movement disorder that causes loss of voluntary motor control while playing the instrument. A subgroup of patients displays the so-called sensory trick: alteration of somatosensory input, e.g., by wearing a latex glove, may result in short-term improvement of motor control. In this study, the glove-effect in pianists with MD was quantified and its potential association with MD-severity and outcome after treatment was investigated. Thirty affected pianists were included in the study. Music instrument digital interface-based scale analysis was used for assessment of fine motor control. Therapeutic options included botulinum toxin, pedagogical retraining and anticholinergic medication (trihexyphenidyl). 19% of patients showed significant improvement of fine motor control through wearing a glove. After treatment, outcome was significantly better in patients with a significant pre-treatment sensory trick. We conclude that the sensory trick may have a prognostic value for the outcome after treatment in pianists with MD.

Tricks in dystonia: ordering the complexity

Sensory tricks are various manoeuvres that can ameliorate dystonia. Common characteristics are well known, but their variety is wide, sensory stimulation is not necessarily the critical feature, and their physiology is unknown. To enumerate the various forms of sensory tricks and describe their nature, research findings and theories that may elucidate their neurophysiologic mechanism, we reviewed the literature pertaining to sensory tricks, including variants like motor tricks, imaginary tricks, forcible tricks and reverse sensory tricks. On the basis of this information, we propose a new classification of sensory tricks to include its variants. We highlight neurophysiologic evidence suggesting that sensory tricks work by decreasing abnormal facilitation. We tie this with established dystonia pathogenesis and postulate that sensory tricks decrease abnormally increased facilitation to inhibition ratios in the dystonic brain. It appears worthwhile for patients to search for possible sensory tricks.

[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.

Analysis of dystonic tremor in musicians using empirical mode decomposition

OBJECTIVE

Test the hypotheses that tremor amplitude in musicians with task-specific dystonia is higher at the affected finger (dystonic tremor, DT) or the adjacent finger (tremor associated with dystonia, TAD) than (1) in matched fingers of healthy musicians and non-musicians and (2) within patients in the unaffected and non-adjacent fingers of the affected side within patients.

METHODS

We measured 21 patients, 21 healthy musicians and 24 non-musicians. Participants exerted a flexion-extension movement. Instantaneous frequency and amplitude values were obtained with empirical mode decomposition and a Hilbert-transform, allowing to compare tremor amplitudes throughout the movement at various frequency ranges.

RESULTS

We did not find a significant difference in tremor amplitude between patients and controls for either DT or TAD. Neither differed tremor amplitude in the within-patient comparisons.

CONCLUSION

Both hypotheses were rejected and apparently neither DT nor TAD occur in musician's dystonia of the fingers.

SIGNIFICANCE

This is the first study assessing DT and TAD in musician's dystonia. Our finding suggests that even though MD is an excellent model for malplasticity due to excessive practice, it does not seem to provide a good model for DT. Rather it seems that musician's dystonia may manifest itself either as dystonic cramping without tremor or as task-specific tremor without overt dystonic cramping.

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.

Fixed dystonia of the left hand in a violinist: a rare functional disorder

BACKGROUND

Fixed dystonia leads to an immobile abnormal posturing of the affected limb. There is an ongoing debate whether this condition is psychogenic in origin.

CASE REPORT

We present a 21-year-old violinist with fixed dystonia after an acute overuse injury with a transient cyanosis but no signs for psychological trauma. After Incobotulinumtoxin injection, symptoms subsided within 8 hours.

DISCUSSION

Our case corroborates the notion that fixed dystonias after minor injuries are functional disorders. It underlines the necessity of a biopsychosocial approach to functional disorders, considering the possibility of an overlay between organic and non-organic disorders.

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.

What is It? Difficult to Pigeon Hole Tremor: a Clinical-Pathological Study of a Man with Jaw Tremor

Background

The phenomenology of tremor is broad and its classification is complicated. Furthermore, the full range of tremor phenomenology with respect to specific neurological and neurodegenerative diseases has not been fully elaborated.

Case Report

This right-handed man had a chief complaint of jaw tremor, which began approximately 20 years prior to death at age 101 years. He had been diagnosed with essential tremor (ET) by a local doctor. His examination at age 100 years was notable for marked jaw tremor at rest in the absence of other clear features of parkinsonism, mild kinetic tremor of the hands and, in the last year of life, a score of 22/41 on a cognitive screen. A senior movement disorder neurologist raised doubt about the “ET” diagnosis. The history and videotaped examination were reviewed by three additional senior tremor experts, who raised a number of diagnostic possibilities. A complete postmortem examination was performed by a senior neuropathologist, and was notable for the presence of tufted astrocytes, AT8-labeled glial cytoplasmic inclusions, and globose neuronal tangles. These changes were widespread and definitive. A neuropathological diagnosis of progressive supranuclear palsy was assigned.

Discussion

This case presents with mixed and difficult to clinically classify tremor phenomenology and other neurological findings. The postmortem diagnosis was not predicted based on the clinical features, and it is possible that it does not account for all of the features. The case raises many interesting issues and provides a window into the complexity of the interpretation, nosology, and classification of tremor phenomenology.

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.