Clinical outcomes after MRI connectivity-guided radiofrequency thalamotomy for tremor.

OBJECTIVE: Radiofrequency thalamotomy (RF-T) is an established treatment for refractory tremor. It is unclear whether connectivity-guided targeting strategies could further augment outcomes. The aim of this study was to evaluate the efficacy and safety of MRI connectivity-guided RF-T in severe tremor. METHODS: Twenty-one consecutive patients with severe tremor (14 with essential tremor [ET], 7 with Parkinson's disease [PD]) underwent unilateral RF-T at a single institution between 2017 and 2020. Connectivity-derived thalamic segmentation was used to guide targeting. Changes in the Fahn-Tolosa-Marin Rating Scale (FTMRS) were recorded in treated and nontreated hands as well as procedure-related side effects. RESULTS: Twenty-three thalamotomies were performed (with 2 patients receiving a repeated intervention). The mean postoperative assessment time point was 14.1 months. Treated-hand tremor scores improved by 63.8%, whereas nontreated-hand scores deteriorated by 10.1% (p < 0.01). Total FTMRS scores were significantly better at follow-up compared with baseline (mean 34.7 vs 51.7, p = 0.016). Baseline treated-hand tremor severity (rho = 0.786, p < 0.01) and total FTMRS score (rho = 0.64, p < 0.01) best correlated with tremor improvement. The most reported side effect was mild gait ataxia (n = 11 patients). CONCLUSIONS: RF-T guided by connectivity-derived segmentation is a safe and effective option for severe tremor in both PD and ET.

Cost-Effectiveness of Magnetic Resonance-Guided Focused Ultrasound for Essential Tremor.

BACKGROUND: Radiofrequency thalamotomy and deep brain stimulation are current treatments for moderate to severe medication-refractory essential tremor. However, they are invasive and thus carry risks. Magnetic resonance-guided focused ultrasound is a new, less invasive surgical option. The objective of the present study was to determine the cost-effectiveness of magnetic resonance-guided focused ultrasound compared with standard treatments in Canada. METHODS: We conducted a cost-utility analysis using a Markov cohort model. We compared magnetic resonance-guided focused ultrasound with no surgery in people ineligible for invasive neurosurgery and with radiofrequency thalamotomy and deep brain stimulation in people eligible for invasive neurosurgery. In the reference case analysis, we used a 5-year time horizon and a public payer perspective and discounted costs and benefits at 1.5% per year. RESULTS: Compared with no surgery in people ineligible for invasive neurosurgery, magnetic resonance-guided focused ultrasound cost $21,438 more but yielded 0.47 additional quality-adjusted life years, producing an incremental cost-effectiveness ratio of $45,817 per quality-adjusted life year gained. In people eligible for invasive neurosurgery, magnetic resonance-guided focused ultrasound was slightly less effective but much less expensive compared with the current standard of care, deep brain stimulation. The results were sensitive to assumptions regarding the time horizon, cost of magnetic resonance-guided focused ultrasound, and probability of recurrence. CONCLUSIONS: In people ineligible for invasive neurosurgery, the incremental cost-effectiveness ratio of magnetic resonance-guided focused ultrasound versus no surgery is comparable to many other tests and treatments that are widely adopted in high-income countries. In people eligible for invasive neurosurgery, magnetic resonance-guided focused ultrasound is also a reasonable option. © 2018 International Parkinson and Movement Disorder Society.

Stereotactic radiosurgery for medically refractory multiple sclerosis-related tremor.

OBJECTIVE Multiple sclerosis (MS) is a neurodegenerative disease that can lead to severe intention tremor in some patients. In several case reports, conventional radiotherapy has been reported to possibly exacerbate MS. Radiosurgery dramatically limits normal tissue irradiation to potentially avoid such a problem. Gamma Knife thalamotomy (GKT) has been established as a minimally invasive technique that is effective in treating essential tremor and Parkinson's disease-related tremor. The goal in this study was to analyze the outcomes of GKT in patients suffering from medically refractory MS-related tremor. METHODS The authors retrospectively studied the outcomes of 15 patients (mean age 46.5 years) who had undergone GKT over a 15-year period (1998-2012). Fourteen patients underwent GKT at a median maximum dose of 140 Gy (range 130-150 Gy) using a single 4-mm isocenter. One patient underwent GKT at a dose of 140 Gy delivered via two 4-mm isocenters (3 mm apart). The posteroinferior region of the nucleus ventralis intermedius (VIM) was the target for all GKTs. The Fahn-Tolosa-Marin clinical tremor rating scale was used to evaluate tremor, handwriting, drawing, and drinking. The median time to the last follow-up was 39 months. RESULTS After GKT, 13 patients experienced tremor improvement on the side contralateral to surgery. Four patients noted tremor arrest at a median of 4.5 months post-GKT. Seven patients had excellent tremor improvement and 6 had good tremor improvement. Four patients noted excellent functional improvement, 8 noted good functional improvement, and 1 noted satisfactory functional improvement. Three patients experienced diminished tremor relief at a median of 18 months after radiosurgery. Two patients experienced temporary adverse radiation effects. Another patient developed a large thalamic cyst 60 months after GKT, which was successfully managed with Ommaya reservoir placement. CONCLUSIONS Gamma Knife thalamotomy was found to be a minimally invasive and beneficial procedure for medically refractory MS tremor.

Is staged bilateral thalamic radiosurgery an option for otherwise surgically ineligible patients with medically refractory bilateral tremor?

OBJECTIVE Unilateral Gamma Knife thalamotomy (GKT) is a well-established treatment for patients with medically refractory tremor who are not eligible for invasive procedures due to increased risk of compications. The purpose of this study was to evaluate whether staged bilateral GKT provides benefit with acceptable risk to patients suffering from disabling medically refractory bilateral tremor. METHODS Eleven patients underwent staged bilateral GKT during a 17-year period (1999-2016). Eight patients had essential tremor (ET), 2 had Parkinson's disease (PD)-related tremor, and 1 had multiple-sclerosis (MS)-related tremor. For the first GKT, a median maximum dose of 140 Gy was delivered to the posterior-inferior region of the nucleus ventralis intermedius (VIM) through a single isocenter with 4-mm collimators. Patients who benefitted from unilateral GKT were eligible for a contralateral GKT 1-2 years later (median 22 months). For the second GKT, a median maximum dose of 130 Gy was delivered to the opposite VIM nucleus to a single 4-mm isocenter. The Fahn-Tolosa-Marin (FTM) clinical tremor rating scale was used to score tremor, drawing, and drinking before and after each GKT. The FTM writing score was assessed only for the dominant hand before and after the first GKT. The Karnofsky Performance Status (KPS) was used to assess quality of life and activities of daily living before and after the first and second GKT. RESULTS The median time to last follow-up after the first GKT was 35 months (range 11-70 months). All patients had improvement in at least 1 FTM score after the first GKT. Three patients (27.3%) had tremor arrest and complete restoration of function (noted via FTM tremor, writing, drawing, and drinking scores equaling zero). No patient had tremor recurrence or diminished tremor relief after the first GKT. One patient experienced new temporary neurological deficit (contralateral lower-extremity hemiparesis) from the first GKT. The median time to last follow-up after the second GKT was 12 months (range 2-70 months). Nine patients had improvement in at least 1 FTM score after the second GKT. Two patients had tremor arrest and complete restoration of function. No patient experienced tremor recurrence or diminished tremor relief after the second GKT. No patient experienced new neurological or radiological adverse effect from the second GKT. Statistically significant improvements were noted in the KPS score following the first and second GKT. CONCLUSIONS Staged bilateral GKT provided effective relief for medically refractory, disabling, bilateral tremor without increased risk of neurological complications. It is an appropriate strategy for carefully selected patients with medically refractory bilateral tremor who are not eligible for deep brain stimulation.