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Introduction: Essential tremor (ET) may severely impact patient's Quality of Life. Several techniques such as radiofrequency, deep brain stimulation (DBS), gamma knife (GK) radiosurgery and high-intensity focused ultrasound may be used for the surgical treatment of ET. The aim of this paper is to summarize the most recent available literature on DBS, transcranial magnetic resonance-guided focused ultrasound (tcMRgFUS) and GK, and to compare indications, targets, and effectiveness of these surgical techniques for the treatment of ET., Evidence Acquisition: A systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The literature search was performed on the three largest medical databases (PubMed, Scopus, and Web of Science). This systematic review is focused on the effectiveness and safety of GK, DBS, and tcMRgFUS as functional neurosurgical techniques for the treatment of ET. The aim of this study was to compare these techniques by evaluating mode, target, effectiveness in improving motor outcomes, and rates of adverse effects., Evidence Synthesis: Articles meeting the predetermined criteria were included. Data for DBS, tcMRgFUS, and GK were analyzed and compared for indications, patient selection, advantages vs. disadvantages, and treatment targets for essential tremor., Conclusions: DBS, tcMRgFUS and GK are effective techniques for the treatment of ET. Despite different functioning principles, all three surgical techniques require a proper functional diagnosis to define accurate indications for patient selection. Their indication depends upon the patient's neurological condition and their effectiveness relies on proper targeting.

OBJECTIVE Transcranial magnetic resonance-guided focused ultrasound surgery (tcMRgFUS) is one of the emerging noninvasive technologies for the treatment of neurological disorders such as essential tremor (ET), idiopathic asymmetrical tremor-dominant Parkinson's disease (PD), and neuropathic pain. In this clinical series the authors present the preliminary results achieved with the world's first tcMRgFUS system integrated with a 1.5-T MRI unit. METHODS The authors describe the results of tcMRgFUS in a sample of patients with ET and with PD who underwent the procedure during the period from January 2015 to September 2017. A monolateral ventralis intermedius nucleus (VIM) thalamic ablation was performed in both ET and PD patients. In all the tcMRgFUS treatments, a 1.5-T MRI scanner was used for both planning and monitoring the procedure. RESULTS During the study period, a total of 26 patients underwent tcMRgFUS thalamic ablation for different movement disorders. Among these patients, 18 were diagnosed with ET and 4 were affected by PD. All patients with PD were treated using tcMRgFUS thalamic ablation and all completed the procedure. Among the 18 patients with ET, 13 successfully underwent tcMRgFUS, 4 aborted the procedure during ultrasound delivery, and 1 did not undergo the tcMRgFUS procedure after stereotactic frame placement. Two patients with ET were not included in the results because of the short follow-up duration at the time of this study. A monolateral VIM thalamic ablation in both ET and PD patients was performed. All the enrolled patients were evaluated before the treatment and 2 days after, with a clinical control of the treatment effectiveness using the graphic items of the Fahn-Tolosa-Marin tremor rating scale. A global reevaluation was performed 3 months (17/22 patients) and 6 months (11/22 patients) after the treatment; the reevaluation consisted of clinical questionnaires, neurological tests, and video recordings of the tests. All the ET and PD treated patients who completed the procedure showed an immediate amelioration of tremor severity, with no intra- or posttreatment severe permanent side effects. CONCLUSIONS Although this study reports on a small number of patients with a short follow-up duration, the tcMRgFUS procedure using a 1.5-T MRI unit resulted in a safe and effective treatment option for motor symptoms in patients with ET and PD. To the best of the authors' knowledge, this is the first clinical series in which thalamotomy was performed using tcMRgFUS integrated with a 1.5-T magnet.