MRgFUS thalamotomy for the treatment of tremor: evaluation of learning curve and operator's experience impact on the procedural and clinical outcome.

BACKGROUND: MRgFUS Vim ablation is increasingly used for the treatment of tremor in ET e PD patients but there is little published research on the importance of operator experience in this procedure. This study aims to evaluate the learning curve and the influence of the operator experience on the procedural and clinical outcomes. METHODS: We retrospectively evaluated 90 patients (38 ET, 52 PD) submitted to MRgFUS unilateral thalamotomy in the period between February 2018 and July 2020. Clinical endpoints, procedural times, and technical parameters were recorded in all procedures. Based on the time of treatment, patients were divided into three groups of 30 units each, comparing all variables between each time period group. RESULTS: In Group A, the average patient preparation time was 120.6 min, the treatment time was 105.2 min, the number of was sonications 14.1, and the mean target shifts 3.1. In Group B, the mean preparation time was 105.5 min, the treatment time was 89.5 min, the number of sonications was 13.2, and the target shifts 3.0. Group C showed inferior values of preparation time (101.9 min), treatment time (71.7 min), numbers of sonications (10.6), and shifts (1.7). Thalamotomy-related complications occurred in 9 patients of Group A, 2 of Group B, and 5 of Group C. Tremor relapse occurred in 7 patients of Group A, 3 of Group B, and 2 of Group C. The days of hospitalization were comparable in the three groups. CONCLUSIONS: The operators experience is associated with the improvement of clinical and procedural outcome in MRgFUS thalatomy for the treatment of ET and PD tremor.

Prognostic value of brain tissues' volumes in patients with essential tremor treated with MRgFUS thalamotomy.

MRgFUS Vim thalamotomy is a novel, effective, minimally invasive therapeutic option for patients with essential tremor (ET). Among the selection criteria, some parameters related to the patient's anatomy, such as the skull density ratio (SDR), are well recognized. The role of brain tissue interposed between the target and the ultrasound transducers has never been explored. Therefore, the purpose of our study was to evaluate the correlation and the possible predictive value between brain tissue volumes (grey matter - GM, white matter - WM, and cerebrospinal fluid - CSF) and several treatment-related variables (periprocedural parameters, MRI imaging findings, and the clinical outcome). We analysed data from thirty ET patients previously submitted to MRgFUS thalamotomy. Pre-treatment images were automatically segmented in sopra-tentorial (ST) WM, GM, and CSF using SPM 12. The most significant findings were a positive correlation of the ST-GM with the Accumulated Thermal Dose (ATD) (p < 0,001) and a negative correlation of the ATD temperature with ST-CSF and ST-TIV (p < 0,001). Ultrasound propagation speed is lower in fluids than brain tissues. Also, WM has an attenuation rate of 1.5 higher than the GM. Therefore, the difference in the ATD may be explained by the different acoustic properties of normal brain tissues interposed between the transducers and the VIM.