Wrist-Worn Device Reduces Hand Tremor

LOS ANGELES -- Custom, non-invasive nerve stimulation appears to reduce hand tremors in essential tremor patients, according to data from two trials that will be reported here next week.

The wrist-worn neuromodulation device stimulated median and radial nerves in the wrist and delivered a stimulation pattern tuned to interrupt a patient's tremulous signal. Two early release abstracts about this research from the American Academy of Neurology's annual meeting, which will begin April 21, were made available Thursday.

The company that developed the device is pioneering a new class of electrical medicine called neuroperipheral therapy, which potentially can address chronic disease like essential tremor by externally stimulating peripheral nerves with body-worn electronics.

"Our research suggests that this non-invasive therapy may offer meaningful relief from the symptoms of hand tremor for people with essential tremor," study author Rajesh Pahwa, MD, of the University of Kansas Medical Center in Kansas City, said in a statement, noting that the treatment was safe and produced significant improvements in both physician-rated and patient-rated measures of tremor severity.

This represents a novel approach to treating essential tremor, noted Vicki Shanker, MD, of the Icahn School of Medicine at Mount Sinai in New York City, who was not involved in the study.

"There are a limited amount of medications available to patients with essential tremor, and use is often limited by side effects," she told MedPage Today.

"While there are surgical options available, many patients are looking for options that are less invasive. This study by Pahwa and colleagues offers a non-invasive alternative to medications using neuromodulation therapy where treated patients had improved tremor and had improvement in their activities of daily living. In addition, the side effect profile was minimal."

Essential tremor is thought to be caused by tremulous activity within a central tremor network. Evidence has supported invasive neuromodulation of deep brain structures in the network, but few studies have explored non-invasive neuromodulation of the connecting peripheral nerve inputs.

Pahwa and colleagues conducted two randomized controlled trials of essential tremor patients: an acute (in-clinic) study and a chronic (at-home) study. In the acute study, the researchers randomized 77 patients to receive either treatment or sham stimulation to the wrist of the tremor dominant hand; they evaluated tremor before and after a single stimulation session. In the chronic study, the team randomized 61 participants to treatment, sham, or standard-of-care for two therapy sessions a day for up to 1 month.

In the acute study, physician assessments showed that patients who wore the device had a 65% improvement in tremor severity in their entire arm, compared with a 32% improvement in the sham group. And in patient-rated assessments, those who received treatment stimulation showed a 27% improvement after performing certain activities of daily living in the clinic, compared with a 16% improvement for patients who received sham stimulation. Overall, 88% of patients who wore the device reported tremor improvement.

In the chronic study, the researchers measured tremor severity before and after each therapy session through sensors on the device. The sensors showed that patients who wore the device had a reduction in their tremor severity after 89.5% of the at-home treatment stimulation sessions.

Patients experienced no serious side effects. In the acute study, 3% of participants had mild effects like skin redness and irritation, which resolved spontaneously.

"These randomized controlled studies suggest that non-invasive peripheral neuromodulation may offer meaningful symptomatic relief from hand tremor in [essential tremor] with a favorable side effect profile compared to other available therapies, and that at-home monitoring may provide key insights into evaluating and treating tremor," Pahwa and co-authors wrote.

One limitation of the studies is that treatment was tested in small groups of people for short durations; future studies will include more people and longer periods of time.

While it's unclear whether patients will have sustained benefits from this therapy, "the initial finding certainly warrants larger studies and will likely be met with great enthusiasm by the essential tremor community," Shanker noted.

Pahwa will present these findings at 5:30 p.m. PT on Wednesday, April 25, in the West Exhibit Hall A at the Los Angeles Convention Center.

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