Researchers have devised a way to shoot focused beams of ultrasound through the skull to calm essential tremor, potentially the first non-invasive approach for hard-to-treat forms of the involuntary-shaking disorder.
As many as 10 million people in the U.S. have essential tremor, which is four times more common than its close cousin Parkinson’s disease. The condition often begins in young adults, worsening over time. While drugs help, deep-brain stimulation and surgery are used for those with disabling symptoms.
A study of 15 patients published yesterday in the New England Journal of Medicine shows that technological advances in the past decade allow doctors to deliver the focused ultrasound-beam therapy into the brain without removing a portion of the skull. Word of the small clinical trial spread among patients, creating waiting lists with dozens of people who want to participate in the next wave of research, doctors said.
“This was the first trial to treat a movement disorder, a neurologic disease, in which we suppressed essential tremor,” Jeffrey Elias, the lead researcher and an associate professor of neurosurgery at the University of Virginia Health Sciences Center in Charlottesville, said in a telephone interview. “It’s one of the first to use ultrasound to treat something in the brain, not just provide images.”
The technology was developed by InSightec Ltd., a closely held Israeli company owned by General Electric Co., Elbit Medical Technologies Ltd., MediTech Advisors LLC and its employees. The system, called ExAblate Neuro, is approved in Europe for essential tremor, Parkinson’s disease and neuropathic pain. A similar product is approved in the U.S. for treating uterine fibroids and cancer that has spread to the bone.
The device uses a helmet-like transducer that shoots more than 1,000 ultrasound beams. The procedure is guided by MRI to ensure the beams hit the same 1-millimeter spot inside the thalamus where the tremors form. The energy caused a lesion at the location, stopping the aberrant electrical signals in the circuit from outside the skull.
Elias compared it to using a magnifying glass to focus the sun’s rays onto a leaf.
“That’s what’s so incredible,” Elias said. “We took 1,000 beams, sent them through the skull non-invasively, focused them all to one specific spot about the size of a grain of rice deep in the middle of the brain and stopped most of the tremors. It didn’t appear to damage any of the intervening brain, just the point of convergence.”
Essential tremor typically affects the hands and arms, though it can develop anywhere in the body.
Neuroscientists have been trying since the 1950s to get ultrasound into the brain to make lesions that could ease suffering. The approach stumbled because of limitations of the technology and the need to cut through the skull. Development of high-intensity ultrasound, coupled with high-resolution magnetic resonance imaging for precise targeting, revived the field.
The patients in the study were in their 60s, and had tremors for more than three decades on average. The procedure, which was performed while the patients were awake and alert, targeted the tremors in the dominant hand by ablating a tiny spot in the thalamus on only one side of the brain.
All 15 patients had significant improvements. There was no change in the untreated opposite hand. Five of nine patients with vocal tremors also improved, though those tremors weren’t intentionally targeted by the therapy. Four patients whose tremors were so severe that they struggled to eat were able to feed themselves after the procedure.
“This is really a game-changer of a trial for essential tremor,” said Travis Tierney, director of Stereotactic & Functional Neurosurgery at Boston’s Brigham & Women’s Hospital, who wasn’t involved in the study. “It basically means we can treat the disease without an incision in the scalp.”
Side effects included unsteadiness, tingling and numbness in the face and fingers. A larger study involving at least 72 patients at seven medical centers is being planned, Elias said.
The study was funded by the Focused Ultrasound Surgery Foundation.
Essential tremor affects as many as 4 percent of U.S. adults. About half may not respond to medicine or may eventually grow tolerant of the drugs, leaving surgery as the only treatment option. Neurosurgeons currently create lesions in the brain after burring through the skull, or implant deep-brain stimulation devices from companies including Medtronic Inc. to disrupt the unwanted electrical activity.
“Quality of life is pretty much destroyed with the progression toward the end of life,” Tierney said. “Patients can’t eat, they have trouble performing simple activities of daily living. They don’t want to go out in public. It’s those limitations that prompt patients to seek surgical solutions.”