Ultrasound Used to Treat Parkinson's Tremors

New study shows ultrasound therapy could help Parkinson's patients, explains Jack Coles.

Jack Coles
13th November 2017
Deep brain stimulation is used to treat the symptoms of Parkinson's. Image courtesy of Massachusetts General Hospital and Draper Labs [Public domain], via Wikimedia Commons.

Parkinson’s disease is a neurodegenerative disorder that occurs almost exclusively in older patients. People with Parkinson’s have problems with walking (and movement in general), as well as tremors and dementia. The cause of the disease is unknown, but genetics, smoking, and exposure to pesticides are thought to be the main risk factors involved.

There is no known cure for Parkinson’s disease so far. Common treatments often focus on increasing the levels of dopamine in the brain, either by supplying extra dopamine precursor molecules, or by preventing the degradation of dopamine by enzymes between neurones.

A more expensive treatment is surgery; to just cut out problematic parts of the brain. A less expensive (but more time consuming) treatment is on-going physiotherapy sessions. There’s also deep brain stimulation, which is like having a pacemaker installed into your brain (and nobody’s sure why it works).

Imperial College London is trialling a new method; blasting affected parts of the brain using ultrasound, which is usually too high-pitched for humans to hear at over 20,000 Hz. One focused “beam” of ultrasound does nothing to your brain, but where over a thousand beams converge, the surrounding tissue is damaged through heat.

After a single day of treatment, a patient came out of the machine with a hand steady enough to continue his job as a decorator.

There has already been a success with the ultrasound; Selwyn Lucas, a 52-year-old man from Cornwall who had tremors in his right hand. Although not a Parkinson’s disease patient, he suffered from essential tremor, which has a similar pathophysiology to Parkinson’s disease, but can occur in younger people.

Around 4% of 40-year-olds have this condition, and the percentage only increases the older your sample. After spending a single day in treatment, Selwyn came out of the machine with a hand that was steady enough for him to continue his job as a decorator.

While the machine used to do this is still a prototype, clinical trials for this sort of treatment are well underway and showing promising results. Just over 30 patients have been treated with this in clinical trials, and most of them have showed a temporary, if not permanent improvement to their motor control. Furthermore, the procedure was non-invasive and only took five hours; traditional brain surgery usually takes over a day to complete and usually destroys non-target tissue.

Traditional deep brain stimulation techniques are more invasive than ultrasound therapy. Image: Zhang Q, Kim Y-C and Narayanan NS [CC BY 4.0], via Wikimedia Commons.

Traditional deep brain stimulation techniques are more invasive than ultrasound therapy. Image: Zhang Q, Kim Y-C and Narayanan NS [CC BY 4.0], via Wikimedia Commons.

The ultrasound surgery also avoids some of the adverse effects that pharmaceutical treatment can create, such as erratic moods and heart problems. The new procedure doesn’t seem to produce as many neurological issues as deep brain stimulation and doesn’t require any drilling, just a shaved head.

There are some issues, of course. For one thing, the procedure is pretty much permanent. You can adjust drug dosage or wiggle the deep brain stimulator around a bit, but you can’t undo the damage you’ve caused to the brain. Sometimes the effects are only temporary, and there are no long-term studies on what any chronic adverse effects may be.

Blasting away bits of the brain – when we're not entirely sure what they do – is somewhat terrifying...

Also, neurosurgeons haven’t entirely agreed on which part of the brain to destroy to prevent tremors. Some perform surgery on the subthalamic nucleus, others ablate the globus pallidus, and some burn the pallidothalamic tract between the first two. All of them show similar results, but a lack of standardised testing means that the finer points are lost during comparisons. This also is somewhat terrifying when you consider they are blasting away bits of the brain when we’re not entirely sure what exactly these bits do.

Overall, though, this is an encouraging step for treatment of Parkinson’s and other tremors. At the very least, this is a massive upgrade from traditional brain surgery, to the extent that traditional methods may eventually be phased out over time.

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