Abstract
BackgroundMusician’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.MethodsVideo 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.ResultsFor 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%).ConclusionsThis 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.
Highlights
Musician’s Dystonia (MD) by impaired or complete loss of fine motor control in extensively trained movements at the instrument
Regression models The best models with respect to expected log pointwise predictive density [30] for the outcomes irregularity and impairment contained in both cases no interactions for the population effects time point and therapy. Since this interaction was of special interest to answer the question of how large the impact of each therapy was over time on the two outcomes, we looked at those models with elpd values closest to the top model and that included an interaction term
Rating reliability Analysis of the intra-rater reliability of student ratings revealed a significant average Pearson’s product moment correlation both for irregularity and impairment of r = 0.84 (95%-confidence interval [0.81-0.86], p < 0.01) and a significant average intra-class correlation (ICC) for irregularity of 0.86 and for impairment of 0.88 (0.86, 0.90)
Summary
Musician’s Dystonia (MD) by impaired or complete loss of fine motor control in extensively trained movements at the instrument. Common symptoms are either impaired or complete loss of task-relevant voluntary motor control, leading to stiffness or cramping, the latter resulting in involuntary movements of affected fingers, i.e. flexion or extension [2, 3]. Most studies of focal dystonia reveal abnormalities in three main areas: a) reduced inhibition in the motor system at cortical, subcortical and spinal levels; b) altered sensory perception and integration; and c) impaired sensorymotor integration. All of these changes are believed to primarily originate from altered synaptic plasticity and dysfunctional brain plasticity [6,7,8]. Overuse, chronic stress and traumatic life experiences might trigger MD, given a genetic susceptibility [9, 10]
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