Ultrasound-guided thalamotomy calms essential tremor

By Liz Meszaros, MDLinx
Published August 31, 2016

Key Takeaways

Patients with essential tremor (ET)—estimated to affect 10 million people in the US—may gain improvement in their tremors and quality of life after treatment with MRI-guided focused ultrasound, according to researchers from the University of Maryland School of Medicine (UM SOM), Baltimore, MD, who published their results in the August 25, 2016 issue of The New England Journal of Medicine.

“We are very excited to have this new noninvasive treatment option for patients who struggle every day with this debilitating neurological disorder,” says study co-author Howard M. Eisenberg, MD, the RK Thompson Professor and Chair of Neurosurgery at the UM SOM. “We saw an impressive reduction in tremors in hands and arms and an improvement in quality of life in patients who experienced no relief from medication.”

This procedure lasts 2 to 4 hours, and involves focusing ultrasound waves—with a 1-mm wide focus and guided by MRI—through intact skin and the skull to surgically and precisely ablate tissue in the thalamus, which is thought to play a vital role in ET.

“You are raising the temperature in a very restricted area of the brain and that destroys the tissue,” says Dr. Eisenberg. “The ultrasound creates a heat lesion that you monitor through MRI.”

During the procedure, patients—who remain awake—are asked to draw spirals with pencil and paper. A comparison between these and those they drew before the treatment helped researchers determine whether their tremors had decreased.

For this multicenter study (completed in eight sites worldwide, five in the US), Dr. Eisenberg and colleagues enrolled 76 patients with moderate-to-severe essential tremor who had no response to at least two previous trials of medical therapy. They randomized subjects 3:1 to either unilateral focused ultrasound thalamotomy or sham. The primary outcome of the study was the between-group difference in change from baseline to 3 months in hand tremor, which they rated on a 32-point scale, from least to greatest. After the initial 3 months, subjects who underwent the sham procedure were allowed to crossover to active treatment, as an open-label extension cohort.

From baseline to 3 months, hand-tremor scores improved more after focused ultrasound thalamotomy compared to sham (18.1 to 9.6 vs 16.0 to 15.8, respectively for the groups, for a mean between-group change of 8.3 points (95% CI: 5.9-10.7; P < 0.001). At 12 months, subjects in the thalamotomy group had maintained this improvement (change from baseline: 7.2 points; 95% CI: 6.1-8.3).

Compared with subjects who underwent the sham procedures, those treated with thalamotomy also showed improvements in secondary outcomes measures, including disability and quality of life (P < 0.001 for both).

In 36% of patients treated with thalamotomy, gait disturbance occurred, and persisted at 12 months in 9%; and in 38%, paresthesias or numbness occurred, which persisted in 14% at 12 months.

“This groundbreaking study clearly demonstrates that focused ultrasound can be transmitted with precision through the human skull to target areas deep within the brain – and improve the quality of life of patients with essential tremor who have difficulty performing tasks that most of us take for granted,” commented UM SOM Dean E. Albert Reece, MD, PhD, MBA, also Vice President of Medical Affairs, University of Maryland and the John Z. and Akiko Bowers Distinguished Professor at UM SOM.

The study was funded by the Focused Ultrasound Foundation, BIRD Foundation and Insightec, the equipment’s manufacturer. Dr. Eisenberg is a consultant to both the Focused Ultrasound Foundation and Insightec.

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