Brain plasticity induced by magnetic resonance-guided focused ultrasound correlates with tremor improvement in essential tremor: a prospective cohort study.

Magnetic resonance-guided focused ultrasound (MRgFUS) is a promising and noninvasive treatment for medication-refractory essential tremor (ET). However, the mechanism of long-term postoperative brain structural remodeling remains unclear. This study aimed to investigate the changes in gray matter volume (GMV) before and after MRgFUS, as well as to explore the relationship between GMV changes and tremor control. Twenty-six ET patients who underwent MRgFUS successfully were included in this study. They received structural magnetic resonance image scanning and clinical assessment before and one year after treatment. Computational anatomy toolbox (CAT12) and Spatially Unbiased Infratentorial Template (SUIT) toolboxes were utilized to estimate changes in GMV. Then, voxel-and region of interest-wise GMV analyses were conducted. Additionally, longitudinal changes were assessed using one-way repeated measures ANOVA. Finally, Pearson correlation was used to assess the relationship between GMV changes and tremor improvement. Patients with ET showed significantly decreased GMV in the left postcentral gyrus, left thalamus and right superior temporal gyrus from baseline to one-year post-operation (cluster 1-3 respectively, voxel-level P <0.001, cluster-level PFWE <0.05). Increased GMV was found in the left Crus I, left Crus II (cluster 4), and left lobule V (cluster 5) of the cerebellum (voxel-level P < 0.001, cluster-level PFWE <0.05). ROI-wise analysis revealed that GMV reduction mainly occurred in the left external and internal globus pallidus (PFDR = 0.04). Additionally, ROI-wise analysis using the AAL3 Brain or Oxford Thalamic Connectivity Atlases identified significant GMV reductions in the lateral posterior or temporal region of the left thalamus (lateral posterior: PFDR = 0.01; temporal region: PFDR = 0.001). GMV changes in clusters 2-4 from baseline to one year postoperatively were significantly correlated with symptom improvement (P <0.05). Our findings suggest that MRgFUS may induce brain plasticity, affecting regions adjacent to the ablation lesion as well as remote brain areas. The reduction in GMV in the thalamic nuclei, which are located in non-ablated regions, may reflect neuroplastic changes and functional deafferentation induced by the MRgFUS. ET = essential tremor; MRgFUS = magnetic resonance-guided focused ultrasound; GMV = gray matter volume; VBM = voxel-based morphometry; HCs = healthy controls; VIM = ventralis intermedius; CAT12 = Computational Anatomy Toolbox; SUIT = Spatially Unbiased Infratentorial Template; CRST = Clinical Rating Scale for Tremor; FWHM = full-width at half-maximum; CTC = cerebello-thalamo-cortical; GPi = internal globus pallidus; GPe = external globus pallidus; STN = subthalamic nucleus; FWE = family-wise error; FDR = false discovery rate; DRTC = dentato-rubro-thalamo-cortical; STG = superior temporal gyrus; op-1y = one year postoperatively; DBS = deep brain stimulation; PCs = Purkinje cells.