Focused Ultrasound: How the Non-Invasive Brain Surgery Works


Going into clinical trials around the world is brain surgery that doesn’t require an incision or produce blood, but dramatically improves the lives of people with essential tremor, depression and more. The procedure, known as a focused ultrasound, focuses sound waves at parts of the brain to disrupt faulty brain circuits that cause symptoms.

“Focused ultrasound is a non-invasive therapeutic technology,” said Dr. Neal Kassell, founder and president of the Focused Ultrasound Foundation. “We’ve said that focused ultrasound is the most powerful sound you’ll never hear, but sound that could one day save your life.”

Kassell describes the way it works as “analogous to using a magnifying glass to focus light rays on a point and burn a hole in a leaf.”

“With focused ultrasound, instead of using an optical lens to focus light rays,” he added, “an acoustic lens is used to focus multiple beams of ultrasound energy on targets deep inside the body with a high degree of precision.” and accuracy, the adjacent normal tissue.”

The procedure has been significantly beneficial for people with essential tremor, a neurological condition that causes involuntary and rhythmic shaking. The condition can affect almost any part of the body, but the tremors most commonly occur in the hands — even during simple tasks like eating, drinking, or writing.

Essential tremor is usually more prominent on one side of the body and may worsen with movement. It is most common in people age 40 and older, and affects nearly 25 million people worldwide, according to a 2021 study.

Such was the case with Brenda Hric, 80, who recently underwent focused ultrasound at the University of Virginia, a pioneering institution of the procedure.

Hric’s tremors made her feel uncomfortable in social situations for fear of spilling or knocking something over, she told CNN.

But just 44 seconds of focused ultrasounds relieved her tremor.

“I looked at my hand and I could see it wasn’t moving, and that was the first time I could see my fingers in about 20 years,” Hric said. “I think it’s definitely a miracle, and I thank the Lord for it.”

Focused ultrasound is a form of functional neurosurgery, targeting precise structures deep in the brain to change it, restore function or, in this case, stop a tumor. It is an alternative treatment for those who, like Hric, do not respond to or are no longer affected by conventional drug treatment, experts said.

“In a simplistic sense, you can imagine that there’s a bunch of abnormal neurons in this one target firing out of control, causing the twitches and twitching,” Kassell said.

Focused ultrasound technology uses a transducer to force beams of sound waves to converge at a single point to raise temperatures and destroy tissue.

Before receiving high-intensity focused ultrasound, which is necessary for the treatment of essential tremor, patients should have their heads shaved, as air can sometimes become trapped in the hair follicles.

The patient then undergoes MRI and CT scans so doctors can use the resulting images to map the structure of the brain and the target.

Pictured are scans of Hric's brain.  Focused ultrasound significantly improved the 80-year-old's tremors.

The Insightec Exablate Neuro, a focused ultrasound platform, instructs how many beams to use to deliver the treatment, then neurosurgeons can do what Dr. Jeff Elias calls “test shots,” to make sure we’re aiming right at the bull’s-eye. .”

Elias, a UVA Health neurosurgeon who treated Hric, is a pioneer in treating essential tremors using ultrasound. In 2011, he led the clinical trials that were critical to gaining regulatory approval for this procedure in the United States.

“These (test shots) are very energy efficient, but we want to see if our treatment is exactly where we want it,” he said. “This is our chance to see the gun.”

Four 11-second treatment doses significantly improved Hric’s tremor. The entire procedure took less than two hours, most of which was spent mapping the brain and testing the target.

Beforehand, Hric had trouble drawing within the circle lines. Focused ultrasound helped her color within the lines.

In general, anyone with an essential tremor diagnosis that is unresponsive to medications is a candidate for targeted ultrasound treatment, said Dr. Nir Lipsman, a scientist at the Sunnybrook Health Sciences Center in Toronto and director of Sunnybrook’s Harquail Center for Neuromodulation.

People who can’t have MRI scans because of claustrophobia or metal in their bodies aren’t eligible for targeted ultrasound, said Dr. Noah Philip, a professor of psychiatry and human behavior at Brown University’s Alpert Medical School. Philip is also chief of mental health research at the VA RR&D Center for Neurorestoration and Neurotechnology.

Ideally, the benefits of focused ultrasound are permanent, Lipsman said. “If you are able to destroy the part of the brain responsible for the tremor, it should have a lasting effect,” he said. “However, after a year, some of these patients will have a rebound or recurrence of their tremor, and we don’t know why that is.”

However, such a recurrence can also happen with drug treatment – which is why some essential tremor patients turn to focused ultrasound in the first place.

But according to a 2022 study by Elias, some patients have experienced the benefits five years after receiving focused ultrasound.

Potential side effects of focused ultrasound are why mapping and testing the procedure is so important. Targeting the wrong area or over-treating can harm a patient’s balance and stability in the long run.

“The most common risks we see in patients are temporary numbness or tingling that can sometimes occur in the treated arm or lip area,” Lipsman said. “The vast majority of the time disappears with time.”

Other common, but usually temporary, risks include mild unsteadiness in the feet after the procedure. But doctors don’t use general anesthesia or admit patients for this procedure, he added.

Today, focused ultrasound technology is used worldwide in various stages, including clinical trials and approved regulatory use. There are more than 170 clinical applications — including for neurodegenerative disorders and tumors of the brain, breast, lung, prostate and more — and the field is growing, Kassell said.

“You can see the effect of the ultrasound treatment in real time while the treatment is being delivered, whereas with radiation, the effect of the treatment is invisible while it’s being delivered,” Kassell said. “And it takes weeks or months for the effect of radiation to become visible.”

Use for depression and obsessive-compulsive disorder is on the table, according to a small 2020 study by Lipsman and a team of researchers. They found that focused ultrasound was safe and effective in improving the symptoms of people with major depression and OCD. But further studies are needed.

One limitation of focused ultrasound is that not every person’s skull is created equal, Lipsman said.

“The density of the skull has a major impact on the ability of ultrasound to travel through it,” he added. “It’s rare, but there are some patients that no matter how hard we try, we can’t make an effective lesion in the brain. The skull doesn’t let ultrasound through. So that is a technical limitation of the technology, something we are actively working on.”

Focused ultrasound isn’t available for every condition, but experts said they’re hopeful that “medicine’s best-kept secret” will one day become standard treatment.

“My belief is that in 10 years,” Kassell said, “focused ultrasound will be mainstream therapy, affecting millions of patients around the world every year. It will be widely accepted.”

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