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.

Background: Systematic perceptual distortions of tactile space have been documented in healthy adults. In isolated focal dystonia impaired spatial somatosensory processing is suggested to be a central pathophysiological finding, but the structure of tactile space for different body parts has not been previously explored. Objectives: The objective of this study was to assess tactile space organization with a novel behavioral paradigm of tactile distance perception in patients with isolated focal dystonia and controls. Methods: Three groups of isolated focal dystonia patients (cervical dystonia, blepharospasm/Meige syndrome, focal hand dystonia) and controls estimated perceived distances between 2 touches across 8 orientations on the back of both hands and the forehead. Results: Stimulus size judgments differed significantly across orientations in all groups replicating distortions of tactile space known for healthy individuals. There were no differences between groups in the behavioral parameters we assessed on the hands and forehead. Conclusions: Tactile space organization is comparable between isolated focal dystonia and healthy controls in dystonic and unaffected body parts.

Tourette syndrome (TS) is characterized by the presence of involuntary movements (tics) which are, at least partly, generated within 'voluntary' motor pathways. Here we reassess 16 TS patients (age 19±2.3 years) who participated in a mental chronometry study of volition 5.5 years previously (Ganos C et al. Cortex. 2015 Mar;64:47-54), and 16 age-matched controls.Participants estimated the time of their own voluntary movements (Libet's M judgement), or of conscious intention to make voluntary movements (Libet's W judgement), in separate blocks.We considered M judgement as a control condition. Therefore, the experience of an intention to move occurring prior to actual movement onset, as measured by the W-M gap, was taken as the cardinal feature of volition. Time estimates of the TS group did not differ significantly from controls, for either M or W judgement. Further, M and W time estimates in the TS group had not changed significantly between the two assessments. However, exploratory analyses revealed a strong relation between disease duration and the development of M-and W-judgements: the longer was the disease duration, the less was the developmental increase in the W-M gap (linear regression, p=0.003). In conclusion, our results suggest compromised development of experience of volition in developing TS patients. The developmental difficulty in processing internal premotor signals for voluntary actions could reflect the chronic persistence of tics from adolescence to adulthood.

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