Ipsilateral and axial tremor response to focused ultrasound thalamotomy for essential tremor: clinical outcomes and probabilistic mapping

Magnetic Resonance-Guided Focused Ultrasound (MRgFUS)-Thalamotomy for Essential Tremor: Lesion Location and Clinical Outcomes

BACKGROUND

Factors predicting clinical outcomes after MR-guided focused ultrasound (MRgFUS)-thalamotomy in patients with essential tremor (ET) are not well known.

OBJECTIVE

To examine the clinical outcomes and their relationship with patients' baseline demographic and clinical features and lesion characteristics at 6-month follow-up in ET patients.

METHODS

A total of 127 patients were prospectively evaluated at 1 (n = 122), 3 (n = 102), and 6 months (n = 78) after MRgFUS-thalamotomy. Magnetic resonance imaging (MRI) was obtained at 6 months (n = 60). Primary outcomes included: (1) change in the Clinical Rating Scale of Tremor (CRST)-A+B score in the treated hand and (2) frequency and severity of adverse events (AEs) at 6 months. Secondary outcomes included changes in all subitems of the CRST scale in the treated hand, CRST-C, axial tremor (face, head, voice, tongue), AEs, and correlation of primary outcomes at 6 months with lesion characteristics. Statistical analysis included linear mixed, standard, and logistic regression models.

RESULTS

Scores for CRST-A+B, CRST-A, CRST-B in the treated hand, CRST-C, and axial tremor were improved at each evaluation (P < 0.001). Five patients had severe AEs at 1 month that became mild throughout the follow-up. Mild AEs occurred in 71%, 45%, and 34% of patients at 1, 3, and 6 months, respectively. Lesion volume was associated with the reduction in the CRST-A (P = 0.003) and its overlapping with the ventralis intermedius nucleus (Vim) nucleus with the reduction in CRST-A+B (P = 0.02) and CRST-B (P = 0.008) at 6 months.

CONCLUSIONS

MRgFUS-thalamotomy improves hand and axial tremor in ET patients. Transient and mild AEs are frequent. Lesion volume and location are associated with tremor reduction. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Comparative neural correlates of DBS and MRgFUS lesioning for tremor control in essential tremor

BACKGROUND

Given high rates of early complications and non-reversibility, refined targeting is necessitated for magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy for essential tremor (ET). Selection of lesion location can be informed by considering optimal stimulation area from deep brain stimulation (DBS).

METHODS

118 patients with ET who received DBS (39) or MRgFUS (79) of the ventral intermediate nucleus (VIM) underwent stimulation/lesion mapping, probabilistic mapping of clinical efficacy and normative structural connectivity analysis. The efficacy maps were compared, which depict the relationship between stimulation/lesion location and clinical outcome.

RESULTS

Efficacy maps overlap around the VIM ventral border and encompass the dentato-rubro-thalamic tract. While the MRgFUS map extends inferiorly into the posterior subthalamic area, the DBS map spreads inside the VIM antero-superiorly.

CONCLUSION

Comparing the efficacy maps of DBS and MRgFUS suggests a potential alternative location for lesioning, more antero-superiorly. This may reduce complications, without sacrificing efficacy, and individualise targeting.

TRIAL REGISTRATION NUMBER

NCT02252380.

The Optimal Targeting for Focused Ultrasound Thalamotomy Differs between Dystonic and Essential Tremor: A 12-Month Prospective Pilot Study

BACKGROUND

Magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy is increasingly used to treat drug-resistant essential tremor (ET). Data on MRgFUS thalamotomy in dystonic tremor (DT) are anecdotal.

OBJECTIVES

To investigate efficacy, safety, and differences in target coordinates of MRgFUS thalamotomy in DT versus ET.

METHODS

Ten patients with DT and 35 with ET who consecutively underwent MRgFUS thalamotomy were followed for 12 months. Although in both groups the initial surgical planning coordinates corresponded to the ventralis intermediate (Vim), the final target could be modified intraoperatively based on clinical response.

RESULTS

Tremor significantly improved in both groups. The thalamic lesion was significantly more anterior in DT than ET. Considering both ET and DT groups, the more anterior the lesion, the lower the odds ratio for adverse events.

CONCLUSIONS

MRgFUS thalamotomy is safe and effective in DT and ET. Compared to classical Vim coordinates used for ET, more anterior targeting should be considered for DT.

A Systematic Review Comparing Focused Ultrasound Surgery With Radiosurgery for Essential Tremor

BACKGROUND

Focused ultrasound (FUS-T) and stereotactic radiosurgery thalamotomy (SRS-T) targeting the ventral intermediate nucleus are effective incisionless surgeries for essential tremor (ET). However, their efficacy for tremor reduction and, importantly, adverse event incidence have not been directly compared.

OBJECTIVE

To present a comprehensive systematic review with network meta-analysis examining both efficacy and adverse events (AEs) of FUS-T vs SRS-T for treating medically refractory ET.

METHODS

We conducted a systematic review and network meta-analysis according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, using the PubMed and Embase databases. We included all primary FUS-T/SRS-T studies with approximately 1-year follow-up, with unilateral Fahn-Tolosa-Marin Tremor Rating Scale or Clinical Rating Scale for Tremor scores prethalamotomy/post-thalamotomy and/or AEs. The primary efficacy outcome was Fahn-Tolosa-Marin Tremor Rating Scale A+B score reduction. AEs were reported as an estimated incidence.

RESULTS

Fifteen studies of 464 patients and 3 studies of 62 patients met inclusion criteria for FUS-T/SRS-T efficacy comparison, respectively. Network meta-analysis demonstrated similar tremor reduction between modalities (absolute tremor reduction: FUS-T: -11.6 (95% CI: -13.3, -9.9); SRS-T: -10.3 (95% CI: -14.2, -6.0). FUS-T had a greater 1-year adverse event rate, particularly imbalance and gait disturbances (10.5%) and sensory disturbances (8.3%). Contralateral hemiparesis (2.7%) often accompanied by speech impairment (2.4%) were most common after SRS-T. There was no correlation between efficacy and lesion volume.

CONCLUSION

Our systematic review found similar efficacy between FUS-T and SRS-T for ET, with trend toward higher efficacy yet greater adverse event incidence with FUS-T. Smaller lesion volumes could mitigate FUS-T off-target effects for greater safety.

Essential Tremor - Deep Brain Stimulation vs. Focused Ultrasound

INTRODUCTION

Essential Tremor (ET) is one of the most common tremor syndromes typically presented as action tremor, affecting mainly the upper limbs. In at least 30-50% of patients, tremor interferes with quality of life, does not respond to first-line therapies and/or intolerable adverse effects may occur. Therefore, surgery may be considered.

AREAS COVERED

In this review, the authors discuss and compare unilateral ventral intermedius nucleus deep brain stimulation (VIM DBS) and bilateral DBS with Magnetic Resonance-guided Focused Ultrasound (MRgFUS) thalamotomy, which comprises focused acoustic energy generating ablation under real-time MRI guidance. Discussion includes their impact on tremor reduction and their potential complications. Finally, the authors provide their expert opinion.

EXPERT OPINION

DBS is adjustable, potentially reversible and allows bilateral treatments; however, it is invasive requires hardware implantation, and has higher surgical risks. Instead, MRgFUS is less invasive, less expensive, and requires no hardware maintenance. Beyond these technical differences, the decision should also involve the patient, family, and caregivers.

Focused ultrasound thalamotomy for tremor treatment impacts the cerebello-thalamo-cortical network

High-intensity Magnetic Resonance-guided Focused Ultrasound (MRgFUS) is a recent, non-invasive line of treatment for medication-resistant tremor. We used MRgFUS to produce small lesions in the thalamic ventral intermediate nucleus (VIM), an important node in the cerebello-thalamo-cortical tremor network, in 13 patients with tremor-dominant Parkinson's disease or essential tremor. Significant tremor alleviation in the target hand ensued (t(12) = 7.21, p < 0.001, two-tailed), which was strongly associated with the functional reorganization of the brain's hand region with the cerebellum (r = 0.91, p < 0.001, one-tailed). This reorganization potentially reflected a process of normalization, as there was a trend of increase in similarity between the hand cerebellar connectivity of the patients and that of a matched, healthy control group (n = 48) after treatment. Control regions in the ventral attention, dorsal attention, default, and frontoparietal networks, in comparison, exhibited no association with tremor alleviation and no normalization. More broadly, changes in functional connectivity were observed in regions belonging to the motor, limbic, visual, and dorsal attention networks, largely overlapping with regions connected to the lesion targets. Our results indicate that MRgFUS is a highly efficient treatment for tremor, and that lesioning the VIM may result in the reorganization of the cerebello-thalamo-cortical tremor network.

A phase 1 open-label trial evaluating focused ultrasound unilateral anterior thalamotomy for focal onset epilepsy

OBJECTIVE

Focused ultrasound ablation (FUSA) is an emerging treatment for neurological and psychiatric diseases. We describe the initial experience from a pilot, open-label, single-center clinical trial of unilateral anterior nucleus of the thalamus (ANT) FUSA in patients with treatment-refractory epilepsy.

METHODS

Two adult subjects with treatment-refractory, focal onset epilepsy were recruited. The subjects received ANT FUSA using the Exablate Neuro (Insightec) system. We determined the safety and feasibility (primary outcomes), and changes in seizure frequency (secondary outcome) at 3, 6, and 12 months. Safety was assessed by the absence of side effects, that is, new onset neurological deficits or performance deterioration on neuropsychological testing. Feasibility was defined as the ability to create a lesion within the anterior nucleus. The monthly seizure frequency was compared between baseline and postthalamotomy.

RESULTS

The patients tolerated the procedure well, without neurological deficits or serious adverse events. One patient experienced a decline in verbal fluency, attention/working memory, and immediate verbal memory. Seizure frequency reduced significantly in both patients; one patient was seizure-free at 12 months, and in the second patient, the frequency reduced from 90-100 seizures per month to 3-6 seizures per month.

SIGNIFICANCE

This is the first known clinical trial to assess the safety, feasibility, and preliminary efficacy of ANT FUSA in adult patients with treatment-refractory focal onset epilepsy.