LAS VEGAS – In addition, sensors worn on the wrist can provide objective measures of tremor in the home environment, said the investigators, who presented their research at the annual meeting of the North American Neuromodulation Society.
Dr. Rajesh Pahwa
The current hypothesis is that tremulous activity within a central tremor network causes essential tremor, but the specific mechanisms are unknown. Research suggests that invasive neuromodulation of deep brain structures within this tremor network provides clinical benefit. The question of whether noninvasive neuromodulation of the peripheral nerve inputs connected to this network is beneficial has received comparatively little attention, however.
Rajesh Pahwa, MD, movement disorders division chief at the University of Kansas Medical Center in Kansas City, and his colleagues examined the safety and efficacy of noninvasive neuromodulation for hand tremor in patients with essential tremor. To provide treatment, they used a wristband with three electrodes that targeted the median and radial nerves. The stimulation pattern was adjusted to interrupt each patient’s tremulous signal in the clinical setting and at home. Participants were asked to hold a certain posture for 20 seconds while the device recorded tremor frequency. After determining the peak tremor frequency, the device was able to adapt stimulation parameters to each patient.
Dr. Pahwa and his colleagues conducted an acute in-office study and an at-home study. In the in-office study, 77 participants were randomized to peripheral nerve treatment or sham stimulation of the tremor-dominant hand. The researchers evaluated tremor before and after one stimulation session using the Essential Tremor Rating Assessment Scale (TETRAS) Upper Limb Tremor Scale and the TETRAS Archimedes Spiral Rating Scale. In the at-home study, 61 participants were randomized to stimulation, sham, or standard of care for 2 weeks. After that point, all participants underwent two to five 40-minute stimulation sessions daily for 2 weeks. Patients in the treatment and sham groups had at least two sessions per day.
In the in-office study, the researchers randomized 40 patients to stimulation and 37 patients to sham. Dr. Pahwa and his colleagues determined that participants had been blinded successfully. The investigators observed a mean improvement in forward posture of approximately 0.75 points among treated patients, compared with a mean improvement of 0.3 points in the sham group. The difference between groups was statistically significant. Treated patients had significant improvements in upper limb tremor score and total performance score, compared with the sham group. The investigators also observed greater mean improvements in spiral drawing, lateral posture, and movement among treated patients, compared with the sham group, but the differences were not statistically significant.
Participants in the in-office study rated their improvement on activities of daily living. Average improvement across tasks was significantly greater for the treated group, compared to the sham group. Improvement on each individual task also was greater for the treated group than the sham group. The differences in improvement were significant for holding a cup of tea, dialing a telephone, picking up change, and unlocking a door with a key.
In the at-home study, the decrease in tremor amplitude, as measured by the wrist-worn device, was significantly greater among participants who received stimulation than in the sham group. “These randomized, controlled studies suggest that noninvasive peripheral neuromodulation may offer meaningful symptomatic relief from hand tremor in essential tremor with a favorable safety profile, compared to other available therapies,” noted Dr. Pahwa and his colleagues. “At-home monitoring may provide key insights into evaluating and treating tremor,” they added.
The studies were supported by Cala Health.