Analysis of dystonic tremor in musicians using empirical mode decomposition

Test the hypotheses that tremor amplitude in musicians with task-specific dystonia is higher at the affected finger (dystonic tremor, DT) or the adjacent finger (tremor associated with dystonia, TAD) than (1) in matched fingers of healthy musicians and non-musicians and (2) within patients in the unaffected and non-adjacent fingers of the affected side within patients.

We measured 21 patients, 21 healthy musicians and 24 non-musicians. Participants exerted a flexion-extension movement. Instantaneous frequency and amplitude values were obtained with empirical mode decomposition and a Hilbert-transform, allowing to compare tremor amplitudes throughout the movement at various frequency ranges.

We did not find a significant difference in tremor amplitude between patients and controls for either DT or TAD. Neither differed tremor amplitude in the within-patient comparisons.

Both hypotheses were rejected and apparently neither DT nor TAD occur in musician's dystonia of the fingers.

This is the first study assessing DT and TAD in musician's dystonia. Our finding suggests that even though MD is an excellent model for malplasticity due to excessive practice, it does not seem to provide a good model for DT. Rather it seems that musician's dystonia may manifest itself either as dystonic cramping without tremor or as task-specific tremor without overt dystonic cramping.