By Harini Sarva, MD
This open-label study demonstrated the safety and efficacy of staged bilateral magnetic resonance imaging-guided focused ultrasound thalamotomy for bilateral essential tremor with excellent efficacy rates at one year. Most adverse events were mild, but greater real-world experience is needed to understand its true safety profile.
Kaplitt MG, Krishna V, Eisenberg HM, et al. Safety and efficacy of staged, bilateral focused ultrasound thalamotomy in essential tremor: An open-label clinical trial. JAMA Neurol. 2024;81(9):939-946.
Sheth SA, Ostrem JL, Hariz M. Bilateral focused ultrasound thalamotomy for tremor — is it really safe? JAMA Neurol. 2024;81(9):914-915.
This was an open-label clinical trial of 51 subjects who previously had one side treated by magnetic resonance imaging (MRI)-guided focused ultrasound thalamotomy at least nine months prior to enrollment. They had to have no significant side effects from the original procedure and a score of at least 2 on either the postural or kinetic tremor item on the standardized Clinical Rating Scale for Tremor (CRST) and a score of 2 or more on one of the CRST functional disability questions.
The subjects had baseline speech pathology assessments. They were followed and evaluated at one week, one month, three months, six months, and one-year time points. Most of the subjects were white and had their left-hand tremor treated. Efficacy evaluation demonstrated a 62% reduction in tremor scores, an 80% reduction in upper extremity tremor score, and a 73% reduction in functional impairment scores at the one-year mark. Adverse events mostly were mild to moderate. The three most common adverse events were paresthesia, dysarthria, and gait issues, but most improved or resolved by six months. Five moderate adverse events mostly improved by six months and one serious adverse event resulted from urinary catheter placement.
Commentary
Essential tremor can be challenging to treat and leads to functional impairment. Having effective therapies for bilateral essential tremor is important. Although deep brain stimulation has a long history of efficacy, the incisionless lesion approach without implantable hardware with MRI-guided focused ultrasound is proving to be more desirous among medically refractory patients. This study demonstrated good efficacy and safety data in a staged bilateral thalamotomy approach. Functional disability improved by more than 70%, and many of the side effects were mild with few moderate events.
Although this is exciting, there are several caveats to consider. Patients were appropriately selected by movement disorders specialists. The surgeons performing the procedure are experts in the field, contributing to the excellent side effect profile. Patients also were followed closely by a speech pathologist.
As a recent editorial of this study pointed out, real world data with less experienced clinicians in terms of patient selection and procedure performance will determine the true side effect profile of staged bilateral MRI-guided focused ultrasound thalamotomies. Proper training of neurologists for appropriate patient selection and special training for neurosurgeons who are not as experienced will allow for good safety outcomes.
In addition, setting practical guidelines for speech evaluations both in terms of pre-procedure and follow-up is important, since dysarthria was more common with bilateral procedures than unilateral procedures. In addition, postoperative care guidelines need to be established in terms of physical and occupational therapies because some patients had gait problems for three to six months.
Although these are important considerations for its long-term applicability, the study demonstrated good safety and efficacy results from focused ultrasound, giving clinicians another option for treating medically refractory essential tremor.
Harini Sarva, MD, is Assistant Professor of Clinical Neurology, Weill Cornell Medical College.
