In a prospective, open-label, multicenter trial, 51 patients with essential tremor who had previously undergone successful unilateral focused ultrasound thalamotomy received contralateral treatment, resulting in significant reductions in tremor severity and functional disability scores.
The study, published in JAMA Neurology, was conducted between July 2020 and October 2021 at seven U.S. academic medical centers. Participants had a mean age of 73 years, and 86.3% were male. All participants had undergone unilateral focused ultrasound thalamotomy at least 9 months prior to enrollment. Inclusion criteria included a Clinical Rating Scale for Tremor (CRST) part A score of 2 or higher for postural or kinetic tremor severity in the upper extremity for the untreated side, and a CRST part C score of 2 or higher in any category.
The primary outcome measure was the change in tremor/motor score (CRST parts A and B) for the treated side at 3 months post-treatment. At 3 months, the mean tremor/motor score improved from 17.4 to 6.4 (66% improvement; 95% confidence interval [CI], 59.8-72.2; P < .001). Secondary outcomes also showed significant improvements, including an 81% reduction in postural tremor (CRST part A; P < .001) and a 73% improvement in functional disability score (CRST part C; P < .001). These improvements persisted at 6 and 12 months post-treatment.
Among participants with baseline voice tremor, 67% (8 of 12) were considered treatment-responsive. For those with head tremor, 71% (12 of 17) were considered responsive to treatment.
Among the 188 reported adverse events, 85% were mild, 13% were moderate, and one event was severe (urinary tract infection related to catheter use during the procedure). The most common adverse events within 30 days of treatment included numbness/tingling (n = 17), dysarthria (n = 15), ataxia (n = 12), unsteadiness/imbalance (n = 10), and dysgeusia (n = 7). At 12 months, eight participants reported numbness, seven reported dysarthria, six reported ataxia, three reported dysgeusia, and one reported gait disturbance; all of these events were mild.
Speech and language pathology assessments revealed that most speech-related adverse events were mild and transient. No participant experienced worsening in all three speech and language measures (phonation, articulation, and swallowing).
By 6 months post-treatment, all six participants who were taking primidone or propranolol at screening had reduced their doses; in three of these six patients, tremor medications were discontinued entirely by 3 months post-treatment.
There were no significant changes in cognition as measured by the Montreal Cognitive Assessment, and Epworth Sleepiness Scale results remained unchanged throughout the study.
The authors concluded that this procedure significantly reduces tremor severity and functional disability, with mostly mild and transient adverse events related to speech, swallowing, and ataxia.
The authors acknowledged the lack of a sham control group and the predominantly male, non-Hispanic White study population as limitations of the study. They suggested that staged bilateral treatment should be considered in patients with ongoing disability from contralateral tremor, even after successful unilateral therapy.
Conflict of interest disclosures can be found in the study.
