Focused Ultrasound for ET: How Far We’ve Come

MRI-guided Focused Ultrasound (MRgFUS) as a treatment for Essential Tremor (ET) has captured the excitement and imagination of neurologists, neurosurgeons and ET patients. This revolutionary incision-less outpatient procedure uses hundreds of ultrasonic waves to block tremor impulses from the brain to the hand by destroying a very small area of the thalamus called the VIM nucleus. This procedure is called a thalamotomy. It immediately takes effect, and from the patient’s viewpoint, the results are nothing short of miraculous as they regain a quality of life they haven’t known for years!

Progress at a fast pace

From the first clinical testing, the momentum for FDA approval moved quickly, compared to the snail’s pace that such approval for other procedures often takes. The first pilot study ran from Feb. 2011 until Dec. 2013 with 15 patients.1 The results were noteworthy enough to be published in 2013 by the New England Journal of Medicine (NEJM), one of the most prestigious medical journals. It was immediately followed by a prospective, randomized and controlled study that enrolled, treated and followed 76 patients. (A quarter of the cohort was randomly assigned to a sham procedure, while all others underwent MRgFUS. After 3 months, those who received the sham treatment could cross over to the treatment arm.) The NEJM again published this study, in 20162.

The U.S. Food and Drug Administration (FDA) had clearly been following these events. Gaining their approval was nothing less than a triumph for MRgFUS. As Prof. Paul Fishman, MD, PhD (Neurology/University of Maryland) writes:

In July of 2016, the FDA granted approval for MR guided focused ultrasound (MRgFUS) mediated unilateral lesioning of the ventral intermediate nucleus (VIM) of the thalamus for treatment of medically refractory [tremor no longer responds to medication] and disabling essential tremor (ET). The approval was the culmination of decades of progress in scientific and clinical research on the application of FUS to the brain.3

 

What we have learned

In our fast-paced world, we take for granted that this year’s technology will be old hat by the time 12 months have passed. We have only to look at the speed with which cellular phones become outdated and replaced by the next state-of-the-art as one example. In medicine, however, it takes much more time to test, approve and implement new devices because human lives are at stake.

As of this writing, it is barely 7 years since the 2011 pilot study began, and already over 1000 ET patients have been successfully treated. During this period, as the doctors have gained experience, the procedure itself has been efficiently modified and improved. For example, in the early studies the research physicians were relatively cautious in terms of how much focused ultrasound was delivered (how many sonications) and the strength (duration) of each sonication. They weren’t entirely sure of what side effects might occur and whether they would be short- or long-term. What they found back then was that for many of the patients, side effects were minimal and quickly resolved, but the tremor control didn’t last. Within 6-12 months, many of the patients had a recurrence of tremor.

Another area of concern was the precision of the image-based identification of the target, and the delivery of the treatment. Thus, improvements in using MRI to develop a 3-dimensional “atlas” for planning treatment, and confirming accuracy through sub-lethal “sonications” to test the effect on the conscious patient (enabling very small changes in calibration before initiating full treatment) helped increase the confidence of the treating physicians.

Thanks to the accumulation and sharing of physician learning, today’s application of MRgFUS to control ET leads to better tremor control, durable results, and fewer side effects. Refinements will continue into the future, but in a few short years we have already come a long way.

MRgFUS at the Sperling Medical Group

Our Center offers MRgFUS for ET patients using Neuravive technology. Results are immediate and lasting. Learn more about Neuravive at the Sperling Medical Group, or contact us for a consultation.


1 Elias WJ, Huss D, Voss T, Loomba J et al. A pilot study of focused ultrasound thalamotomy for essential tremor. N Engl J Med. 2013 Aug 15;369(7):640-8. doi: 10.1056/NEJMoa1300962.
2 Elias WJ, Lipsman N, Ondo WG, Ghanouni P et al. A randomized trial of focused ultrasound thalamotomy for essential tremor. N Engl J Med. 2016 Aug 25;375(8):730-9. doi: 10.1056/NEJMoa1600159.
3Fishman PS. Thalamotomy for essential tremor: FDA approval brings brain treatment with FUS to the clinic. J Ther Ultrasound. 2017; 5: 19.