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Essential tremor (ET) is the most common movement disorder that includes postural tremor and action tremor. This study investigates whether sensory electrical stimulation (SES) is effective on the action tremor in patients with ET. One task in the clinical testing of action tremor, "Archimedes spiral drawing", was performed in 18 patients for three sessions, which were named as pre-stimulation (PRE), stimulation on (ON), and 5min after stimulation (POST). SES (sub-motor threshold) was applied on the muscles of the elbow and wrist only at ON session. Three-dimensional (3D) angular velocities were measured on three segments (index finger, hand, and forearm) from which movements of metacarpophalangeal (MP) and wrist joints were derived. Average tremor intensity in each session was represented by root mean square of the vector sum of 3D angular velocities. Tremor intensities in ON session were smaller than in PRE session in one segment (finger) and two joints (MP and wrist) (p<0.05). Tremor intensities in POST session were even smaller than in ON session in all segments and one joint (wrist) (p<0.05). The results indicate that SES suppresses action tremor and the effect continues and even improves 5min after the termination of stimulation. The findings of this study may contribute to the improvement of the quality of life in patients with ET., SCOPUS: cp.j, info:eu-repo/semantics/published

Essential tremor is an involuntary trembling of body limbs in people without tremor-related disease. In previous study, suppression of tremor by sensory electrical stimulation was confirmed on the index finger. This study investigates the effect of sensory stimulation on multiple segments and joints of the upper limb. It denotes the observation regarding the effect's continuity after halting the stimulation. 18 patients with essential tremor (8 men and 10 women) participated in this study. The task, "arms stretched forward", was performed and sensory electrical stimulation was applied on four muscles of the upper limb (Flexor Carpi Radialis, Extensor Carpi Radialis, Biceps Brachii, and Triceps Brachii) for 15 seconds. Three 3-D gyro sensors were used to measure the angular velocities of segments (finger, hand, and forearm) and joints (metacarpophalangeal and wrist joints) for three phases of pre-stimulation (Pre), during-stimulation (On), and 5 minute post-stimulation (P5). Three characteristic variables of root-mean-squared angular velocity, peak power, and peak power frequency were derived from the vector sum of the sensor signals. At On phase, RMS velocity was reduced from Pre in all segments and joints while peak power was reduced from Pre in all segments and joints except for forearm segment. Sensory stimulation showed no effect on peak power frequency. All variables at P5 were similar to those at On at all segments and joints. The decrease of peak power of the index finger was noted by 90% during stimulation from that of On phase, which was maintained even after 5 min. The results indicate that sensory stimulation may be an effective clinical method to treat the essential tremor., SCOPUS: ar.j, info:eu-repo/semantics/published