Literature Review

Benefits of focused ultrasound thalamotomy for essential tremor persist for 3 years



Focused ultrasound thalamotomy provides continued benefits for tremor, disability, and quality of life at 3 years in patients with medically refractory essential tremor, according to data published Nov. 20 in Neurology. Improvement from baseline remains significant at that time point, although the magnitude of effect may decrease. In addition, the treatment is not associated with progressive or delayed complications.

“For people who have disabling essential tremor that is not responding to medication, this treatment should be considered as a safe and effective option,” Casey H. Halpern, MD, assistant professor of neurosurgery at Stanford (Calif.) University, said in a press release.

Long-term follow-up of a prospective trial

Focused ultrasound thalamotomy is an emerging treatment for essential tremor. The procedure, which does not require an incision, is conducted with the guidance of magnetic resonance thermometry and patient feedback. A randomized controlled trial conducted by Elias and colleagues indicated that focused ultrasound ventral intermediate nucleus thalamotomy significantly suppressed tremor, reduced disability, and improved quality of life at 3 months, compared with sham treatment. This improvement was sustained at 12 months, and a follow-up study showed that improvements in tremor and functional disability were sustained at 24 months.

Dr. Halpern and colleagues sought to evaluate the continued safety and efficacy of focused ultrasound thalamotomy at 3 years’ follow-up in patients who participated in the original trial. Movement disorder specialists evaluated participants’ tremor severity and functional impairment using the Clinical Rating Scale for Tremor (CRST) at baseline and at 12, 24, and 36 months after treatment. Patients responded to the Quality of Life in Essential Tremor (QUEST) questionnaire, which assesses quality of life at baseline and at each follow-up visit. Neurologists evaluated and recorded all adverse events that occurred during the trial.

Postural tremor was eliminated

The original population included 75 patients who underwent focused ultrasound thalamotomy during the randomized, blinded phase or in an unblinded fashion during the crossover phase. The mean age of all treated patients was 71 years, and disease duration at treatment was 16.8 years. Fifty-two participants were observed at 36 months, and the 3-year attrition rate thus was 31%.

Dr. Halpern and colleagues found that the hand combined tremor–motor score, which was the trial’s primary endpoint, was significantly improved from baseline at 3 years. The median improvement from baseline was 56%. The median disability score decreased by 63% from baseline. Postural tremor was eliminated at 36 months, and QUEST score improved by 50%.

For patients who were missing at 3-year follow-up, data obtained at 3 months was used for comparison. These patients had less improvement in hand tremor–motor score, less reduction in disability, and less reduction in postural tremor, compared with patients who presented for 3-year follow-up. When the investigators reanalyzed their results to account for missing data, they found that the improvement from baseline remained significant.

Dr. Halpern and colleagues compared scores at 36 months and at 6 months to evaluate the durability of the treatment effect. Data were available for 49 patients at both time points, and their combined tremor–motor score had increased by a median of one point at 36 months. Disability score increased by a median of 2 points at 36 months. Posture and QUEST scores did not change significantly. About 58% of patients had at least 50% improvement in hand combined tremor–motor score at 36 months, compared with 64% at 24 months and 61% at 12 months.

The investigators described all adverse events as mild or moderate. No new procedure-related adverse events occurred between 24 and 36 months of follow-up, and none worsened during this period. Two adverse events, however, resolved between 24 and 36 months: one case of dysarthria and one of imbalance.

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