Essential tremor (ET) is the most common movement disorder in the United States, afflicting an estimated 10 million Americans.
“Although the condition does not shorten life expectancy, ET can have a dramatic effect on quality of life, functional activities, mood, and socialization,” says Binit B. Shah, MD. “Medications and/or surgery for ET can be effective for some patients, but many still have disabling tremors and some may wish to avoid surgery because of its invasiveness.”
Testing a New Treatment
Dr. Shah and colleagues have experimented with using ultrasound energy, a scalpel-free alternative treatment option for ET. For a study published in the New England Journal of Medicine, they assessed the safety and efficacy of MRI-guided focused ultrasound thalamotomy to treatment of medication-refractory ET. The prospective, sham-controlled trial included 76 patients with moderate-to-severe ET, with 75% of participants receiving the focused ultrasound guided by MRI. The remaining 25% of participants served as the control group and received a sham procedure.
Results of the analysis showed that patients receiving the scalpel-free approach had dramatic improvements that continued throughout the study period. “Recipients of the treatment had their ET improve by 47% at 3 months and 40% at 12 months,” says Dr. Shah. “They also reported major improvements in quality of life.” Conversely, the control group that received the sham procedure exhibited no significant improvements.
“The most important findings of our study were that patients receiving focused ultrasound had significant gains in improvements in disabilities and quality of life for an extended period of time,” Dr. Shah says. “The most commonly reported side effects among those receiving focused ultrasound were gait disturbances and numbness in the hand or face, but these side effects were transient in nature in most cases.”
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A Big Step Forward
According to Dr. Shah, the study represents a major advance for neurosurgery, treatment of brain disease, and treatment of ET. The data demonstrate that ultrasound can be precisely delivered through the intact human skull to treat a difficult neurological disease. Based on data from this trial, the FDA has since approved a focused ultrasound device manufactured by InSightec Inc. for the treatment of ET.
Importantly, the study notes that MRI-guided focused ultrasound thalamotomy is not for all patients with ET. For example, it is contraindicated in patients who cannot undergo MRI imaging, including those with implanted metallic devices like pacemakers. Other conditions in which this treatment may not be feasible include pregnancy, cardiac conditions, kidney diseases, clotting disorders, and a history of stroke, brain tumors, and/or substance abuse, among other exclusions to consider.
Dr. Shah says it is critical to better identify ideal candidates for this focused ultrasound in the future. “We also need Medicare and private insurance companies to adopt this treatment as a reimbursable therapeutic option for patients with refractory ET,” he says. “Studies are also been conducted to explore the use of MRI-guided focused ultrasound thalamotomy in patients with Parkinson’s disease, but this is a very different disease so there are other factors besides tremor to consider.”
Elias WJ, Lipsman N, Ondo WG, et al. A randomized trial of focused ultrasound thalamotomy for essential tremor. N Eng J Med. 2016;375:730-739. Available at: http://www.nejm.org/doi/full/10.1056/NEJMoa1600159#t=article.
Elias WJ, Huss D, Voss T, et al. A pilot study of focused ultrasound thalamotomy for essential tremor. N Engl J Med. 2013;369:640-648.
Elias WJ, Shah BB. Tremor. JAMA. 2014;311:948-954.
Elias WJ, Khaled M, Hilliard JD, et al. A magnetic resonance imaging, histological, and dose modeling comparison of focused ultrasound, radiofrequency, and Gamma Knife radiosurgery lesions in swine thalamus. J Neurosurg. 2013;119:307-317.