Objective: To compare the temporal discrimination threshold (TDT) between musician’s dystonia (MD) patients and healthy controls, and between dystonic and non-dystonic fingers of musicians with hand dystonia respectively.

Background: MD is a task-specific form of isolated focal dystonia with a suggested genetic etiology in up to 30% of patients. Although an abnormal TDT has been established as an endophenotype predisposing to develop the disease in other forms of isolated focal dystonia, the role of TDT in MD remains currently unclear.

Methods: We conducted TDT testing using a previously described visual (VV), tactile (TT) and visual-tactile paradigm (VT). Participants received either pairs of flashlights in the peripheral visual field, electrical stimuli on index and middle finger in both hands or a combination of the two. Inter-stimulus intervals increased in steps of 5ms in three different groups: professional musicians with unilateral hand dystonia, healthy professional musicians and healthy non-musician controls. Additionally, we compared TT and VT-TDT of dystonic and non-dystonic fingers of the affected hand in MD patients. Mean scores were analyzed via repeated measures ANOVA and post-hoc t-Tests.

Results: Preliminary data were collected for 13 MD patients, 6 healthy musicians and 30 non-musician controls balanced for age and gender. ANOVA revealed a significant effect for factor type of stimulation (p < 0.001), and the between subjects factor group (p = 0.008), but no effect for side of stimulation or interaction of any factors. Post-hoc tests (Holm correction) revealed lower TDT in MD (p = 0.031) and healthy musicians (p = 0.035) compared to controls. However, there was no difference between MD and healthy musicians (p = 0.7). T-Tests of dystonic and non-dystonic fingers of the affected hand in eight MD patients revealed higher TDT in the dystonic fingers for tactile (pTT = 0.044), but no difference for visual-tactile TDT (pVT = 0.551).

Conclusions: Our preliminary data show that musicians have lower TDT compared to non-musician controls and that TDT is higher in dystonic compared to non-dystonic fingers. However, to clarify whether TDT is indeed an endophenotype of MD, testing of further patients and healthy family members is needed.

References: Bradley D, Whelan R, Walsh R, Reilly RB, Hutchinson S, Molloy F, Hutchinson M. Temporal discrimination threshold: VBM evidence for an endophenotype in adult onset primary torsion dystonia. Brain. 2009 Sep;132(Pt 9):2327-35. doi: 10.1093/brain/awp156. Epub 2009 Jun 12. Killian O, McGovern EM, Beck R, Beiser I, Narasimham S, Quinlivan B, O’Riordan S, Simonyan K, Hutchinson M, Reilly RB. Practice does not make perfect: Temporal discrimination in musicians with and without dystonia. Mov Disord. 2017 Dec;32(12):1791-1792. doi: 10.1002/mds.27185. Epub 2017 Oct 27.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/temporal-discrimination-threshold-in-musicians-dystonia-an-endophenotype/