Background: We have observed mild bradykinesia in essential tremor (ET) patients, which do not satisfy the criteria of Parkinson's disease (PD).
Objective: To compare the mean movement time for repetitive movements around distal and proximal joints in ET patients with normal controls by using a simple test paradigm.
Patients and methods: Seventeen patients with ET and 14 control subjects were instructed to tap with the index finger sequentially on push-button microswitches. Movement times around metacarpophalangeal, wrist, elbow, and shoulder joints of the right side were tested. The data collected were stored on a computer and the time elapsed between sequential taps on two keys (ms) and number of taps on the left key for 15 seconds were evaluated offline.
Results: Movement times of the patients with ET were not found to be significantly different from those of the controls at all joints tested despite slight prolongation for movements around the shoulder joint.
Conclusion: The simple test paradigm we have used showed that there is no difference in the movement time for repetitive movements around four joints of the upper extremity between patients with ET and normal control subjects. The slightly prolonged movement time around the shoulder joint noted in patients with ET may be ascribed to tremor, not bradykinesia. Tremor may cause these patients to pay more attention to the performance of goal-directed finger movements and consequently prolong movement time slightly or it may simply delay the time elapsed to reach the goal in the absence of overt intention tremor.