Role of deep brain stimulation therapy in the magnetic resonance-guided high-frequency focused ultrasound era: current situation and future prospects

Magnetic resonance-guided focused ultrasound ventral intermediate thalamotomy for Tremor-Dominant Parkinson's disease: a systematic review and meta-analysis

INTRODUCTION

Tremor-dominant Parkinson's Disease (TDPD) has a slower neurological decline compared to other phenotypes of the disease, but significantly impacts daily activities and is often less responsive to standard medications. Magnetic Resonance-guided Focused Ultrasound (MRgFUS) lesioning of the Ventral Intermediate (VIM) nucleus of the thalamus may alleviate symptoms for these patients.

METHODS

A systematic review and meta-analysis of English-language studies from PubMed, Cochrane, and Embase were conducted, assessing the efficacy and safety of MRgFUS VIM thalamotomy in TDPD patients. Tremor scores were evaluated using the Clinical Scale Rating for Tremor and the Movement Disorders Society - Unified Parkinson's Disease Rating Scale (MDS-UPDRSIII). Neuropsychological outcomes were measured using the Parkinson Disease Questionnaire (PDQ) and the Montreal Cognitive Assessment. This analysis adhered to Cochrane and PRISMA guidelines.

RESULTS

Thirteen studies with 211 patients were included. MDS-UPDRSIII scores showed significant improvement at 1, 6, and 12 months post-MRgFUS, respectively: (MD -8.92 points, 95% CI: -15.44 to -2.40, p < 0.01; MD -7.39 points, 95% CI: -11.47 to -3.30, p < 0.01; MD -10.66 points, 95% CI: -16.89 to -4.43, p < 0.01). PDQ scores at baseline compared to 6 months post-treatment also indicated a significant improvement (SMD - 0.86, 95% CI: -1.21 to -0.50, p < 0.01). Neurological adverse events were generally mild and transient, with gait instability and sensory deficits being the most common.

CONCLUSION

This meta-analysis demonstrates significant improvements in tremor and neuropsychological outcomes following MRgFUS VIM thalamotomy in TDPD patients, with adverse events being typically mild and transient.

MRI-Guided Focused Ultrasound for the Treatment of Dystonia: A Narrative Review

Contemporary surgical management of dystonia includes neuromodulation via deep brain stimulation (DBS) or ablative techniques such as radiofrequency (RF) ablation. MRI-guided focused ultrasound (MRgFUS) is an emerging modality that uses high-intensity ultrasound to precisely ablate targets in the brain; this is incisionless, potentially avoiding the surgical risks of a burr hole and transcortical tract to reach the anatomical target. There is some evidence of efficacy in essential tremor and Parkinson's disease (PD), but, to date, there is no study aggregating the evidence of MRgFUS in dystonia. In this narrative review, we searched Medline, Embase, CINAHL, EBSCO, and ClinicalTrials.gov for primary studies and clinical trials on MRgFUS in the treatment of dystonia. Data were analyzed concerning dystonia phenotype, reported outcomes, and complications. PD-related dystonia was also included within the scope of the review. Using our search criteria, six articles on the use of MRgFUS in adult dystonia and three articles on the use of FUS in dystonia in PD were included. Four trials on the use of FUS in dystonia were also found on ClinicalTrials.gov, one of which was completed in December 2013. All included studies showed evidence of symptomatic improvement, mostly in focal hand dystonia; improvements were also found in dystonia-associated tremor, cervicobrachial dystonia, and dystonia-associated chronic neuropathic pain as well as PD-related dystonia. Reported complications included transient neurological deficits and persistent arm pain in one study. However, the evidence is limited to level-4 case series at present. MRgFUS is an emerging modality that appears to be safe and effective, particularly in focal hand dystonia, without major adverse effects. However, the quality of evidence is low at present, and long-term outcomes are unknown. High-quality prospective studies comparing MRgFUS to other surgical techniques will be useful in determining its role in the management of dystonia.

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.