Focused ultrasound shows promise as a noninvasive deep brain treatment for essential tremor, study shows

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Magnetic resonance-guided focused ultrasound (MRgFUS) therapy has the potential to safely and effectively control essential tremor, according to W Jeffrey Elias, director of Stereotactic and Functional Neurosurgery at University of Virginia, USA, who presented, on 3 October, preliminary results of a pilot clinical trial at the Congress of Neurological Surgeons in Washington, USA.

Results from the study’s first 10 patients showed a 78% improvement in contralateral tremor scores in the hand, as assessed with 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 to other procedures for tremor, including stereotactic thalamotomy and deep brain stimulation.


“So far, this noninvasive treatment has been life-changing for patients,” said Elias, the study’s principal investigator. “All now have improved ability to use their dominant hand to perform tasks that they could not do before treatment, such as writing legibly, drinking and eating without spilling, and buttoning clothes. It has been exciting to see their immediate improvements.”


The study is using magnetic resonance imaging to guide and monitor the delivery of focused ultrasound to tremor-causing nerve cells in the thalamus, a region deep within the brain known to be an effective target for essential tremor and other movement disorders. The treatment goal is to reduce tremor in a patient’s dominant hand.


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


Conducted under an FDA-approved protocol, the single-arm, non-randomised, 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 final results prove successful, Elias anticipates launching a larger, pivotal trial to study the overall safety and long-term efficacy of MR-guided focused ultrasound in treating medication-refractory essential tremor.


Funding for the study is being provided by the Focused Ultrasound Surgery Foundation, which is also underwriting a parallel study at the University of Toronto in Canada. Foundation chairman, Neal Kassell, said the study’s success could lead to other new treatments. “By demonstrating that MR-guided focused ultrasound can treat tissue deep in the brain with great precision and accuracy, we hope to open the door to treating Parkinson’s disease, epilepsy and brain tumors. Much work remains to be done, but the path forward is clear,” he observed.


Kassell added, “Because the brain poses more complex technical challenges than other organs, success in treating essential tremor will spur advancements in developing new focused ultrasound therapies for the breast, liver, pancreas and prostate, which are less complicated to treat.”


Currently, MR-guided focused ultrasound is an FDA-approved therapy for uterine fibroids; it is approved in Europe and elsewhere for the treatment of uterine fibroids and pain associated with bone metastasis. Around the world, clinical trials are treating prostate, breast, bone and uterine tumors.


Study treatments are performed using the ExAblate Neuro, an investigational device manufactured by InSightec. 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 MR imaging and then monitored with MR thermography, which provides real-time tracking of focused ultrasound delivery. The entire process is noninvasive and does not involve ionising radiation. 

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