Why is it so Hard to Develop a Universal Tremor Control Device?

Millions of people have essential tremor (ET), a movement disorder characterized by involuntary shaking. Voluntary movement tends to aggravate the tremors; however, since ET is often observed to be progressive, in later stages resting tremors can occur even when the affected part of the body is relaxed.

ET of the hands and arms disrupts normal activities. Eating, drinking, dressing, writing, using a keyboard or cell phone buttons and apps—hundreds of daily tasks become frustrating challenges that cause feelings ranging from annoyance and impatience to desperation and depression. The cause for ET is unknown, and there is no cure.

The standard approach to managing tremors uses medications like propranolol, primidone and others. Sadly, drugs don’t work for about half of people. Much research has gone into developing devices that either compensate for tremors (e.g. weighted utensils, or a “smart” computer mouse that cancels the tremor effects during use) or control tremors by wearing devices that mechanically or electrically lessen the tremors themselves (e.g. cumbersome robotic exoskeletons, or wrist worn electrical stimulation devices). Here we focus on tremor control devices.

 

A crash course in individuality

It’s not far-fetched to say that no two ET cases are exactly alike. The latest scientific theory that ET is a group or family of conditions comes from its many variables: family history or not, age of onset, pace of progression, affected part(s) of the body, tremor speed and force, tremor breadth or range of motion, non-motor symptoms, etc. In short, ET is highly variable.

This makes it difficult to design a device, set up a study to test it, and recruit participants for the study. There’s also the question of who’s doing the research: a device manufacturer (commercial), a university research center (academic), or a collaboration of both? A commercial entity has an obvious economic interest in bringing a device to the marketplace, but so does an academic site that may own patents. It would be a mistake, however, to stereotype the development of tremor control devices as simply profit-oriented, because there’s always an underlying motive of compassion and the desire to make life better.

To return to the issue of variance, if there’s no universal tremor state, it’s really hard to come up with a universal tremor control device. Here’s an example from published literature.

 

A multi-national experiment

In 2017, an academic multi-national team published their investigation into electrical stimulation for tremor suppression. Their work was based on results from nine previous studies showing that bursts of muscle activity associated with hand/arm tremors could be influenced by electrically stimulating the active muscle(s) in the wrist, finger, or elbow. However, in those studies the underlying nerve pathways or mechanisms weren’t identified, nor were there different stimulation settings. Therefore, the 2017 study was designed to systematically apply various electrical settings to both surface (on the skin) and intramuscular (within the muscle) pathways to test which offered the best hand tremor control.

For skin surface trials, electrodes were placed on the skin over targeted nerve locations, while the intramuscular trials used very thin electrode wires placed into muscle nerve pathways via hypodermic needle. Note: the degree of stimulation in all cases was kept below a certain threshold, but adjustments were made if a test caused discomfort or pain, or a participant wanted to stop a trial.

The participants were 5 Parkinson’s disease (PD) patients and 4 ET patients, all having hand tremors at the wrist. They were given actions or tasks that would activate their tremors. A total of 10 trials were planned per participant for a total of 90 trials, with at least 2 minutes of rest between each trial, during which electrical stimulation at a different intensity and timing was applied, and effects measured.

 

Results

A total of 76 out of the planned 90 trials were completed. The authors wrote that 3 of the 4 intramuscular group members and 3 of the 5 surface group members exhibited significant tremor control during a total of 21 trials—but the results were not consistent. As they write, “The efficiency for each stimulation setting, however, varied substantially across patients and it was not possible to identify a single set of stimulation parameters that yielded positive results in all patients.”

This 2017 paper is just one illustration of why today, just as with medication, there is not a single device that controls tremors for everyone. There are other design, production and sale challenges as well, things like practicality, comfort, affordability, etc. The most consistent promise today is not a drug or device, but a noninvasive neurosurgical procedure called Neuravive®, that uses MRI-guided focused ultrasound to control tremors by shutting down a pathway in the brain. When the tremor circuit is interrupted before it leaves the brain toward the hand, tremors are effectively controlled.

No more drugs, no more devices. So far, it appears universally effective. For more information about Neuravive, visit our website.

NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.

 

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