Nancy A. Melville

May 05, 2016

CHICAGO — Magnetic-resonance (MR)-guided ultrasound thalamotomy in the treatment of essential tremor shows significant benefit in reducing upper-limb tremor and improving functionality on several measures, a new study shows.

"Based on these findings, we showed that focused ultrasound thalamotomy improves hand tremor in essential tremor," said lead investigator William Jeffrey Elias, MD, from the University of Virginia's Department of Neurosurgery, in Charlottesville.

Dr Elias and colleagues previously reported in a smaller open-label pilot study, published in the New England Journal of Medicine, important benefits of the investigational approach of high-intensity focused ultrasound thalamotomy for essential tremor in 15 patients.

They presented the new data here at the 2016 American Association of Neurological Surgeons (AANS) Annual Scientific Meeting.

In this analysis, the researchers expanded the study to include 72 patients with moderate to severe essential tremor at a level of severity of 2 or higher in postural or intention tremor and 2 or higher in disability in functional activity.

The participants, who were evenly matched in patient and demographic characteristics, were randomly assigned 3 to 1 to receive a unilateral, focused ultrasound thalamotomy (n = 56) or sham procedure (n = 20).

Measures for tremor improvement included the Friedman test for change in hand tremor score and secondary outcome scores on the total and disability subsections of the Clinical Rating Score for Tremor, the Dynamic Gait Index, grip strength, Physical Performance Test, and its simulated eating task.

In terms of the study's primary outcome of upper-limb tremor improvements between the two groups, the ultrasound treatment group had improvement of tremor scores, assessed by independent neurologists, of as much as 47% at 3 months, compared with nearly no improvement in the sham group. This finding was "highly statistically significant" (P < .001), Dr Elias said.

The secondary outcome of durability in terms of upper-limb tremor at 12 months showed some reduction in improvement in the ultrasound group, from 47% at 3 months to approximately 40% at 12 months, but the improvement was still highly statistically different from baseline, Dr Elias said.

In addition, those receiving the ultrasound treatment had statistical improvements in functional measures of disability and quality of life at 3 and 12 months, including speaking, feeding, hygiene, dressing, writing, and social activities, compared with no changes in the sham group.

The treatments for the focused ultrasound group consisted of 18.5 sonications delivering roughly 15,000 joules of energy and creating temperatures of approximately 55°C. The sham group received 15.3 sonications that did not deliver heat. Approximately 70% of patients in the ultrasound group had intraprocedural adjustments, with a mean adjustment of 1.6 mm.

Treatments in five patients were considered technical failures because of difficulties in heating the thalamic target and failure to achieve the desired therapeutic ablation.

In terms of side effects, 21 patients in the ultrasound group reported paresthesia or numbness, dropping to 8 at 12 months; 11 patients reported gait disturbances, dropping to 2 at 12 months. In addition, 9 reported having an unsteady gait, dropping to 3 at 12 months.

There were two reports of contralateral weakness, with one persisting, Dr Elias said.

"We found that the focused ultrasound thalamotomy improves hand tremor in essential tremor," Dr Elias said.

"There are some issues with transcranial sonication — not everyone sonicates as efficiently and some skulls are simply different from others and that's currently being worked out," he said.

The study was funded by Insightec. Dr Elias has received funding from Insightec, the Focused Ultrasound Foundation, and the BIRD Foundation.

2016 American Association of Neurological Surgeons (AANS) Annual Scientific Meeting. Abstract 728. Presented May 3, 2016.

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