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MRI-guided Focused Ultrasound Thalamotomy for Patients with Medically-refractory Essential Tremor.

Authors: Meng Y, Huang Y, Solomon B, Hynynen K, Scantlebury N, Schwartz ML, Lipsman N

Essential tremor (ET) is the most common type of tremor in adults. While ET does not result in decreased life expectancy, the disabilities associated with ET can have a significant impact on quality of life, mood, functional activities, and socialization. Patients suffering from ET not sufficiently treated with first line medications may be eligible for alternative strategies such as deep brain stimulation, radiofrequency ablation, and MRI guided focused ultrasound (MRgFUS). High-intensity MRgFUS is an emerging modality to treat ET, its attraction for patients being that it is noninvasive and associated with short recovery time, as patients are home the day after treatment. While MRgFUS centers are still limited, it will become important for clinicians to consider MRgFUS as a treatment alternative, particularly in the case of a patient for whom open surgery is contraindicated. This article outlines the steps of patient selection, equipment setup, sonication, and post-treatment follow-up, as well as critical steps to be aware of when performing a MRgFUS procedure.

Introduction

Purpose thermal ablation or other (neuro ablation)
Study Objective To describe the protocol for performing MRI-guided focused ultrasound thalamotomy for the treatment of medically refractory essential tremor.
Animal model / Human subject human patients (characteristics not specified)
Disease model with essential tremor (medically refractory)
MRI or image guidance method 3T MRI guidance with real-time thermometry
Targeted brain region(s) Thalamus
Target coordinates AC-PC based indirect coordinates: ~25% anterior to PC, lateral adjusted per patient anatomy

Outcomes and Safety

Summary of Outcomes The described MRgFUS thalamotomy protocol provides a noninvasive, real-time image-guided method for creating therapeutic lesions in the Vim. Its clinical efficacy is comparable to traditional surgeries, with the unique advantages of immediate feedback, adjustability, and absence of cranial implants, though outcomes are modulated by patient-specific factors like skull density.
Duration of biological effect durable at 12 months
Safety-related matter the therapy may cause damage to surrounding tissue, with associated pain or neurologic injury if the lesions created by the MRgFUS is too superficial. In addition, the difficulty of this treatment is denpendent on patient's own physical conditions. Skull density, thickness, and shape would affect the needed acoustic energy required for the successful ablation. Skull and scalp heating can be a source of discomfort and may lead to long-term sequelae.

Brain Region

Ultrasound Parameters

Ultrasound instrument a commercially available helmet transducer with 1024 independent elements, source not specified
FUS Frequency 650kHz
FUS Mode continuous
Pulse duration 10-25s
Duration of a single FUS session 10-25s
Focal Characteristics none (not specified)
Treatment frequency 12months

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