LAS VEGAS – according to two presentations delivered at the annual meeting of the North American Neuromodulation Society. The techniques’ surgical procedures, associated risks, and adverse event profiles may influence neurologists and patients in their choice of treatment.
Dr. Kathryn L. Holloway
FUS allows neurosurgeons to apply thermal ablation to create a lesion on the thalamus. MRI guidance enables precise control of the lesion location (within approximately 1 mm) and of the treatment intensity. The surgery can be performed with high-resolution stereotactic framing.
DBS entails the surgical implantation of a neurostimulator and attached leads and electrodes. The neurosurgeon drills a hole of approximately 14 mm in diameter into the skull so that the electrode can be inserted stereotactically while the patient is awake or asleep. The neurostimulator is installed separately.
Both treatments provide functional benefits
Dr. W. Jeff Elias
In 2016, W. Jeff Elias, MD, director of stereotactic and functional neurosurgery at the University of Virginia in Charlottesville, and his colleagues published the results of a randomized controlled trial that compared FUS with sham treatment in 76 patients with essential tremor. At three months, hand tremor had improved by approximately 50% among treated patients, but controls had no significant benefit(N Engl J Med. 2016 Aug 25;375[8]:730-9). The improvement among treated patients was maintained for 12 months. Disability and quality of life also improved after FUS.
A study by Schuurman et al. published in 2000 (N Engl J Med. 2000 Feb 17;342[7]:461-8) showed that DBS and FUS had similar efficacy at 1 year, said Kathryn L. Holloway, MD, professor of neurosurgery at Virginia Commonwealth University in Richmond. It included 45 patients with Parkinson’s disease, 13 with essential tremor, and 10 with multiple sclerosis who were randomized 1:1 to FUS or DBS. The primary outcome was activities of daily living, and blinded physicians assessed patient videos. Most of the patients who improved had received DBS, and most of the ones who worsened had received FUS, said Dr. Holloway. Among patients with essential tremor, tremor improved by between 94% and 100% with either treatment.
To find more recent data about these treatments, Dr. Holloway searched the literature for studies of FUS or DBS for essential tremor. She analyzed only studies that included unselected populations, blinded evaluations within 1 or 2 years of surgery, and tremor scores for the treated side. She found two studies of FUS, including Dr. Elias’s 2016 trial and a 2018 follow-up (Ann Neurol. 2018 Jan;83[1]:107-14). Dr. Holloway also identified three trials of DBS.
In these studies, reduction of hand tremor was 55% with FUS and between 63% and 69% with DBS. Reduction of postural tremor was approximately 72% with FUS and approximately 67% with DBS. Reduction of action tremor was about 52% with FUS and between 65% and 71% with DBS. Overall, DBS appears to be more effective, said Dr. Holloway.
A 2015 study (Mov Disord. 2015 Dec;30[14]:1937-43) that compared bilateral DBS, unilateral DBS, and unilateral FUS for essential tremor indicated that the treatments provide similar benefits on hand tremor, disability, and quality of life, said Dr. Elias. FUS is inferior to DBS, however, for total tremor and axial tremor.
Furthermore, the efficacy of FUS wanes over time, said Dr. Elias. He and his colleagues conducted a pilot study of 15 patients with essential tremor who received FUS (N Engl J Med. 2013 Aug 15;369[7]:640-8). At 6 years, 6 of 13 patients whose data were available still had a 50% improvement in tremor. “Some went on to [receive] DBS,” said Dr. Elias. “Functional improvements persisted more than the tremor improvement.”