Task-specific Movement Disorder Research Articles

A model of task-specific focal dystonia

Task-specific focal dystonia is a task-specific movement disorder which manifests itself as a loss of voluntary motor control in extensively trained movements. The condition is most frequent in musicians. Until today, the aetiology of focal hand dystonia is not completely understood, but there is growing evidence for an abnormal cortical processing of sensory information, as well as degraded representation of motor functions. It was demonstrated that in the somatosensory cortex the topographical location of sensory inputs from individual fingers is corrupted. Occasionally, a change in sensory information of the hand may at least temporarily improve the condition. This phenomenon is called sensory trick. In this paper, we propose a model of encoding of sensory stimuli which could explain the task specificity of cortical representations of the fingers or other effectors in the context of dystonia. In the framework of this model a sensory stimulus is encoded as a signal vector of higher dimension. A part of its components directly represents the sensory stimulus, while the remaining components describe the context. This model does not only account for the task specificity, but may also explain some characteristics of the retraining process in this disorder.

Long‐term improvement of musician's dystonia after stereotactic ventro‐oral thalamotomy

Musician's dystonia is a task-specific movement disorder that causes twisting or repetitive abnormal finger postures and movements, which tend to occur only while playing musical instruments. Such a movement disorder will probably lead to termination of the careers of affected professional musicians. Most of the currently available treatments have yet to provide consistent and satisfactory results. We present the long-term follow-up results of ventro-oral thalamotomy for 15 patients with musician's dystonia. Between October 2003 and September 2010, 15 patients with medically intractable task-specific focal hand dystonia that occurred only while playing musical instruments underwent ventro-oral thalamotomy. We used Tubiana's musician's dystonia scale to evaluate the patients' pre- and postoperative neurological conditions. All patients except 1 (93%) experienced dramatic improvement of dystonic symptoms immediately after ventro-oral thalamotomy. The mean follow-up period was 30.8 months (range=4-108 months). None of the patients experienced recurrence or deterioration of symptoms during the follow-up periods. Ventro-oral thalamotomy remarkably improved musician's dystonia, and the effect persisted for a long duration.

Primary Bowing Tremor: A Task-Specific Movement Disorder of String Instrumentalists

Fear of a tremulous or unsteady bow is widespread among string instrumentalists. Faulty technique and performance anxiety have generally been blamed. The cases of 4 high-level violinists and 1 violist, 3 women and 2 men, with uncontrollable bow tremor are presented. Age at onset was from 16 to 75 years, and symptom duration 8 months to 20 years at the time of neurological evaluation. The degree of tremor varied with type of bow stroke and even the portion of the bow contacting the string. Only 1 patient had a slight postural tremor of the opposite limb. In 3 of 5 the tremor was task-specific; the other 2 had mild and nontroubling tremor with other activities. The tremor appeared to worsen over time but then seemed to stabilize. The characteristics of this tremor appear to be distinguishable from the features of both essential tremor and focal dystonia; comparison is made with representative string players afflicted by these other disorders. Analogy of this tremor is made with primary writing tremor, a well-defined task-specific movement disorder also sharing at least some features with both essential tremor and writers' cramp, a focal dystonia. Hence, it was decided to call this primary bowing tremor. Clinical features, family history, diagnostic studies, and responsiveness to treatment of primary writing tremor are discussed to emphasize the similarity to primary bowing tremor. This appears to represent a previously unreported form of task-specific movement disorder of string instrumentalists.

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

Musician's cramp is a task-specific movement disorder that presents itself as muscular incoordination or loss of voluntary motor control of extensively trained movements while a musician is playing the instrument. It is characterized by task specificity and gender bias, affecting significantly more males than females. The etiology is multifaceted: a combination of a genetic predisposition, termed endophenotype, and behavioral triggering factors being the leading features for the manifestation of the disorder. We present epidemiological data from 591 musician patients from our outpatient clinic demonstrating an influence of fine-motor requirements on the manifestation of dystonia. Brass, guitar, and woodwind players were at greater risk than other instrumentalists. High temporospatial precision of movement patterns, synchronous demands on tonic and phasic muscular activation, in combination with fine-motor burdens of using the dominant hand in daily life activities, constitute as triggering factors for the disorder and may explain why different body parts are affected.

Error monitoring is altered in musician's dystonia: evidence from ERP‐based studies

Musician's dystonia (MD) is a task-specific movement disorder characterized by a loss of voluntary motor control in highly trained movements like piano playing. Its underlying pathophysiology is defined by deficient functioning of neural pathways at different levels of the central nervous system. However, a few studies have examined the brain responses associated with executive functions such as error monitoring in MD. We recorded the electroencephalogram (EEG) in professional pianists during the performance of memorized music sequences at fast tempi. Event-related potentials (ERPs) locked to pitch errors were investigated in MD and a control group. In MD patients, significantly larger error-related brain responses before and following errors were observed as compared with healthy pianists. Our results suggest that in MD, the generalized degraded neural activity at all levels of the central nervous system is manifested in specific neural correlates of the executive functions that monitor an overlearned sensorimotor performance.

Phenotypic spectrum of musician's dystonia: A task‐specific disorder?

Musician's dystonia (MD) is traditionally considered a sporadic and task-specific movement disorder. The phenotypic spectrum of the disorder was studied in 116 patients suffering from MD including videotaping. Based on the movement disorders observed, we categorized our patients into two different groups: (i) 65 patients with isolated MD, that is only present when playing the instrument and (ii) 51 patients with MD and one or more additional features of primary dystonia independent of MD (complex MD). Patients with a positive family history of movement disorders had an increased risk to develop complex MD [odds ratio = 4.80; 95% confidence interval: 1.94-11.92; P = 0.001]. In previous studies, we recently identified 22 relatives with different types of movement disorders in the families of 28 MD patients. Taken together, our results further support a genetic contribution to MD with a broad individual and familial phenotypic spectrum consisting of MD, other dystonias and even other, non-dystonic movement disorders.

Single-session tDCS-supported retraining does not improve fine motor control in musician's dystonia

Focal dystonia in musicians (MD) is a task-specific movement disorder with a loss of voluntary motor control during instrumental playing. Defective inhibition on different levels of the central nervous system is involved in the pathophysiology. Sensorimotor retraining is a therapeutic approach to MD and aims to establish non-dystonic movements. Transcranial direct current stimulation (tDCS) modulates cortical excitability and alters motor performance. In this study, tDCS of the motor cortex was expected to assist retraining at the instrument. Nine professional pianists suffering from MD were included in a placebo-controlled double-blinded study. Retraining consisted of slow, voluntarily controlled movements on the piano and was combined with tDCS. Patients were treated with three stimulation protocols: anodal tDCS, cathodal tDCS and placebo stimulation. No beneficial effects of single-session tDCS-supported sensorimotor retraining on fine motor control in pianists with MD were found in all three conditions. The main cause of the negative result of this study may be the short intervention time. One retraining session with a duration of 20 min seems not sufficient to improve symptoms of MD. Additionally, a single tDCS session might not be sufficient to modify sensorimotor learning of a highly skilled task in musicians with dystonia.

Focal dystonia in musicians: phenomenology, pathophysiology and triggering factors

Musician's dystonia is a task-specific movement disorder that manifests itself as a loss of voluntary motor control in extensively trained movements. In many cases, the disorder terminates the careers of affected musicians. Approximately, 1% of all professional musicians are affected. The pathophysiology of the disorder is still unclear. Findings include: (i) reduced inhibition in different levels of the central nervous system, (ii) maladaptive plasticity, e.g. in the somatosensory cortex and in the basal ganglia and (iii) alterations in sensorimotor processing. Review of the literature. Epidemiological data demonstrated a higher risk for those musicians who play instruments requiring maximal fine-motor skills. For instruments where workload differs across hands, focal dystonia appears more often in the more intensely used hand. In psychological studies, musicians with dystonia had more perfectionist tendencies than healthy musicians. These findings strengthen the assumption that behavioural factors may be involved in the etiology of musician's dystonia. Hereditary factors may play a greater role than previously assumed. We propose a heuristic model that may explain the relatively high incidence of focal dystonia in musicians. This model assumes the coactions between a predominantly genetically determined predisposition and intrinsic and extrinsic triggering factors.

Focal Dystonia in Musicians: Phenomenology, Pathophysiology, Triggering Factors, and Treatment

Musician's dystonia is a task-specific movement disorder that manifests itself as a loss of voluntary motor control in extensively trained movements. Approximately 1% of all professional musicians develop musician's dystonia, and in many cases, the disorder terminates the careers of affected musicians. The pathophysiology of the disorder is not completely clarified. Findings include 1) reduced inhibition at different levels of the central nervous system, 2) maladaptive plasticity and altered sensory perception, and 3) alterations in sensorimotor integration. Epidemiological data demonstrate a higher risk for those musicians who play instruments requiring maximal fine-motor skills. For instruments where workload differs across hands, focal dystonia appears more often in the more intensely used hand. In psychological studies, musicians with dystonia have more anxiety and perfectionist tendencies than healthy musicians. These findings strengthen the assumption that behavioral factors may be involved in the etiology of musician's dystonia. Preliminary findings also suggest a genetic contribution to focal task-specific dystonia with phenotypic variations including musician's dystonia. Treatment options include pharmacological interventions, such as trihexyphenidyl or botulinum toxin-A, as well as retraining programs and ergonomic changes in the instrument. Patient-tailored treatment strategies may significantly improve the situation of musicians with focal dystonia. Positive results after retraining and unmonitored technical exercises underline the benefit of an active involvement of patients in the treatment process. Only a minority of musicians, however, return to normal motor control using the currently available therapies.

Failure of cathodal direct current stimulation to improve fine motor control in musician's dystonia

Musician's dystonia (MD) is a task-specific movement disorder with a loss of voluntary motor control in highly trained movements. Defective inhibition on different levels of the central nervous system is involved in its pathophysiology. Cathodal transcranial direct current stimulation (ctDCS) diminishes excitability of the motor cortex and improves performance in overlearned tasks in healthy subjects. The aim of this study was to investigate whether ctDCS improves fine motor control in MD. Professional guitarists (n = 10) with MD played exercises before, directly after ctDCS, and 60 min after ctDCS. ctDCS (2 mA, 20 min) was applied on the primary motor cortex contralateral to the affected hand. Guitar exercises were video-documented and symptoms were evaluated by three independent experts. No beneficial effect of ctDCS on fine motor control was found for the entire group. However, motor control of one guitarist improved after stimulation. This patient suffered from arm dystonia, whereas the other guitarists suffered from hand dystonia.

Focal hand dystonia in musicians: phenomenology, etiology, and psychological trigger factors

Narrative Review Musician's dystonia is a task-specific movement disorder, which manifests itself as a loss of voluntary motor control in extensively trained movements. In many cases, the disorder terminates the careers of affected musicians. Approximately 1% of all professional musicians are affected. In the past, focal dystonia (FD) was classified as a psychological disorder. Over time, the problem was classified as a neurological problem. Although the specific pathophysiology of the disorder is still unclear, it appears the etiology is multifactorial. While there may be a family history, neurophysiological, physical, and environmental factors, trauma and stress contribute to the phenotypic development of FD. This manuscript analyzes the evidence supporting the potential contribution of the emotional brain systems in the etiology of focal hand dystonia in musicians. In addition, the psychological findings from a large descriptive study comparing healthy musicians, musicians with dystonia, and musicians with chronic pain. Information about psychogenic characteristics might be used to modify intervention strategies and music instruction to reduce the incidence of musician's dystonia.

Focal dystonia in musicians: From phenomenology to therapy

Background: Musician’s dystonia is a task-specific movement disorder which manifests itself as a loss of voluntary motor control in extensively trained movements. In many cases, the disorder terminates the careers of affected musicians. Approximately 1% of all professional musicians are affected. Etiology and Pathophysiology: The pathophysiology of the disorder is still unclear. Findings include (a) reduced inhibition in different levels of the central nervous system, (b) maladaptive plasticity, e.g. in the somatosensory cortex and in the basal ganglia, and (c) alterations in sensorimotor processing. Epidemiological data demonstrated a higher risk for those musicians who play instruments requiring maximal fine-motor skills. For instruments where workload differs across hands, focal dystonia appears more often in the more intensely used hand. In psychological studies, musicians with dystonia had more perfectionist tendencies than healthy musicians. These findings strengthen the assumption that behavioral factors may be involved in the etiology of musician’s dystonia. Hereditary factors may play a greater role than previously assumed. Preliminary findings suggest a genetic contribution to focal task-specific dystonia with phenotypic variations including musician’s dystonia. Treatment: Treatment options for musician’s dystonia include pharmacological interventions such as administration of Trihexyphenidyl or Botulinum Toxin-A as well as retraining programs and ergonomic changes in the instrument. A long-term follow-up study was performed in 144 patients with musician’s dystonia. The outcome was revealed on average 8.4 years after onset of symptoms. Outcome was assessed by patients’ subjective rating of cumulative treatment response and response to individual therapies. Seventy-seven patients (54%) reported an alleviation of symptoms: 33% of the patients with Trihexyphenidyl, 49% with Botulinum Toxin, 50% with pedagogical retraining, 56% with unmonitored technical exercises, and 63% with ergonomic changes. In embouchure dystonia, only 15% of patients reported improvement. The results demonstrate that the situation of musicians with focal hand dystonia may be significantly improved. Positive results after retraining and unmonitored technical exercises underline the benefit of an active involvement of patients in the treatment process. Only exceptionally, however, can musicians with focal dystonia return to normal motor control using the currently available therapies.

Anxiety as an Aggravating Factor During Onset of Focal Dystonia in Musicians

Focal dystonia in musicians is a task-specific movement disorder that in many cases leads to the end of musical careers. In a recent study, perfectionism and anxious traits were found to be elevated in musicians with dystonia. Dynamics of different anxiety disorders and their possible role during the development of musician’s dystonia still are unclear. Dystonic musicians (n = 20) were investigated by means of self-estimation and compared with healthy musicians (n = 30) and musicians with chronic pain syndromes (n = 20). Participants completed a questionnaire focusing on different anxiety disorders, particularly with regard to their dynamics. Musicians with focal dystonia more often reported social phobia and specific phobias than healthy musicians. In the retrospective analysis, these differences already were present before onset of dystonia. Musicians who later developed focal dystonia more often suffered from specific phobias than musicians who later developed chronic pain. Musicians with chronic pain more often reported free-floating anxiety compared with healthy musicians. In the subscale stage fright, no significant differences were observed between the groups. The pattern of specific phobias and social phobia were reported to have been preexisting before the onset of dystonia. Anxiety and perfectionism may be aggravating factors during the development of musician’s dystonia.

Quantification of focal dystonia in pianists using scale analysis.

Focal dystonia in pianists is a task-specific movement disorder that causes loss of pianistic skills and provokes irregularities in playing. So far, no method has been available for objective quantification of the disorder. Eight professional pianists with focal dystonia and eight healthy professional pianists matched by age, gender, and handedness were examined, using a newly developed MIDI-based Scale Analysis as well as the Arm Dystonia Disability Scale (ADDS). Key velocities and timing parameters were analyzed. In 5 pianists with dystonia, follow-up examinations were carried out after treatment with botulinum toxin-A. In affected hands, significantly higher mean standard deviations of timing parameters were seen compared with healthy reference hands. After treatment with botulinum toxin-A, significant improvements in performance parameters were monitored by Scale Analysis. Mean standard deviations of inter-onset intervals correlated with ADDS scores. We conclude that Scale Analysis is an effective and precise tool for quantification of focal dystonia in pianists and provides fine resolution. It is independent of rating methods and allows reliable follow-up examinations during treatment.

Aberrant Sensorimotor Integration in Musicians' Cramp Patients

AbstractSimple tapping and complex movements (Luria finger apposition task) were performed unimanually and bimanually by two groups of professional guitarists while EEG was recorded from electrodes over the sensorimotor cortex. One group had a task-specific movement disorder (focal dystonia or musicians' cramp), while the other group did not (controls). There were no significant group interactions in the task-related power (TRPow) within the alpha range of 8-10Hz (mu1). In contrast, there was a significant group interaction within the alpha range of 10-12Hz (mu2); these latter frequencies are associated with task-specific sensorimotor integration. The significant group interaction included task (simple and complex) by hand (left, right, and both) by electrodes (10 electrodes over the sensorimotor areas). In the rest conditions, the alpha power (10-12Hz) was comparable between the groups; during movement, however, compared to the controls, patients demonstrated the greatest TRPow (10-12Hz) over all conditions. This was particularly evident when patients used their affected hand and suggests that patients with musicians' cramp have impaired task-specific sensorimotor integration.