Bradykinesia in patients with essential tremor.

We compared the level of bradykinesia during rapid alternating movements (RAM) in patients with essential tremor (ET) with that of patients with Parkinson's disease (PD) having either the "tremor dominant" or "akinetic-rigid" form of PD, and 10 healthy controls. We found an increase of pronation-supination cycle duration in the PD and ET group, suggestive of bradykinesia. RAM range was, however, similar between groups. The akinetic-rigid group showed a distinct increase in RAM amplitude fluctuation, suggesting that rigidity modified the characteristics of the observed bradykinesia. In conclusion, slow movements should then be considered as part of the ET symptomatology.