Objective: To compare the Temporal Discrimination Thresholds (TDT) of Musician’s Dystonia (MD) patients with those of healthy control musicians.

Background: The TDT is a measure of the shortest time interval at which two stimuli are perceived as different and is abnormal in several movement disorders including Adult-Onset Isolated Focal Dystonias (AOIFD). The reported frequency of abnormal TDTs in MD subjects is considerably lower than that found in other forms of AOIFD. Previous studies found intact timing abilities in MD patients when compared with control musicians but did not use TDT as a metric. 

Methods: Participants were recruited from two centres in New York and Dublin with retrospective inclusion of results from previous TDT studies and prospective testing of additional subjects. Three cohorts were recruited: subjects with clinically diagnosed MD, healthy professional musicians without a family history of movement disorders and healthy Non-musician Controls. TDT testing was conducted using a visual TDT paradigm consisting of a pair of flashing lights, which began synchronously and became asynchronous in 5 ms increments. Z-scores were calculated in order to compare the performance of individual subjects to the control groups’ means. 

Results: Data were collected from 20 MD subjects, 20 Musician Controls and 94 Non-musician Controls. Age and gender were balanced across groups. Comparison of MD subjects to non-musician controls resulted in 4 (20%) MD subjects being identified as abnormal (statistically insignificant using Fisher’s Exact Test; p = 0.09), in line with previous studies. However, use of a Z-score, derived from Musician Controls, resulted in the detection of 9 (45%) abnormal MD subjects and 21 (22%) abnormal Non-musician controls. Both these results were statistically significant when applying Fisher’s Exact Test (p<0.001 and p=0.02, respectively).

Conclusions: Healthy musicians have faster temporal discrimination than non-musicians. These results further support the model of abnormal temporal discrimination in AOIFD suggesting similar pathophysiological mechanisms between MD and other Focal Dystonias. They also challenge previous findings of normal or intact timing abilities in MD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-comparison-of-temporal-discrimination-thresholds-in-musicians-with-and-without-dystonia/