Noninvasive Deep Brain Stimulation for Essential Tremor?



Focused ultrasound shows promise as a noninvasive deep brain treatment for patients with essential tremor.

WASHINGTON, DC—Magnetic resonance–guided, focused ultrasound has the potential to safely and effectively control essential tremor, according to preliminary findings from a pilot clinical trial reported by W. Jeffrey Elias, MD, at the 2011 Congress of Neurological Surgeons.

Results from the study’s first 10 patients showed a 78% improvement in contralateral tremor scores in the hand, as assessed with use of the Clinical Rating Scale for Tremor (CRST). Patients’ functional activities scores improved by 92%, as measured in the Disability subsection of the CRST. Outcomes and complications were comparable with other procedures for tremor, including stereotactic thalamotomy and deep brain stimulation.

“So far, this noninvasive treatment has been life-changing for patients,” said Dr. Elias, who is an Associate Professor of Neurological Surgery and Neurology and Director of Stereotactic and Functional Neurosurgery at the University of Virginia in Charlottesville. “All now have the improved ability to use their dominant hand to perform tasks that they couldn’t do before treatment, such as writing legibly, drinking and eating without spilling, and buttoning clothes. It has been exciting to see their immediate improvements.”

Focused Ultrasound in the Thalamus
The researchers are using MRI to guide and monitor the delivery of focused ultrasound to tremor-causing nerve cells in the thalamus. The treatment goal is to reduce tremor in a patient’s dominant hand.

Most study participants have had essential tremor for decades, according to Dr. Elias. As part of the study’s inclusion criteria, all patients had previously taken at least two medications that failed to control their tremor. Despite the severity of their disability, the patients had opted to cope with their symptoms rather than to undergo invasive surgical procedures.

The study marks the first step in determining if magnetic resonance–guided, focused ultrasound is a safe and effective treatment for essential tremor and whether it offers potential benefits beyond current surgical options. The enrolled patients, ages 18 to 80, are followed for three months after treatment, and receive assessments regarding their general health, neurologic status, and tremor measurements. The study is also tracking data about device- or procedure-related side effects that occur within three months of treatment.

Study treatments are performed using the ExAblate Neuro, an investigational device manufactured by InSightec, Ltd (Dallas). The device consists of a specially designed table with a helmet-like unit that contains phased array–focused ultrasound transducers. Treatments are planned with the precision of MRI and then monitored with magnetic resonance thermography, which provides real-time tracking of focused ultrasound delivery. The entire process is noninvasive and does not involve ionizing radiation.

During the study, a series of focused ultrasound pulses is administered through a patient’s intact scalp and skull to a precisely targeted spot in the thalamus. Patients receive no anesthesia and remain awake, providing feedback to clinicians after each pulse. Under the study protocol, only one side of the brain is treated (unilateral thalamotomy), resulting in single hand tremor control.

Long-Term Efficacy Trial Is Anticipated
Conducted under an FDA-approved protocol, the single-arm, nonrandomized, phase 1 study began in February 2011 and is expected to treat 15 patients before concluding. All patients are being followed for three months. If the final results prove successful, Dr. Elias anticipates launching a larger, pivotal trial to study the overall safety and long-term efficacy of magnetic resonance–guided, focused ultrasound in treating medication-refractory essential tremor.

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