Altered Static and Dynamic Functional Motor Networks in Essential Tremor After Magnetic Resonance-Guided Focused Ultrasound: A Resting-State Functional MRI Study.

Abstract

Rationale and objectivesMR-guided focused ultrasound (MRgFUS) thalamotomy is an emerging treatment for medication-refractory essential tremor (ET), but its effects on the motor network remain unclear. This study investigated static and dynamic functional connectivity (FC) within the motor network following MRgFUS in ET and explored correlations between changes in network properties and tremor improvement.Materials and methodsTwenty-six ET patients who successfully underwent MRgFUS were included, with resting-state fMRI acquired before and one year post-procedure. Additionally, 26 healthy controls were recruited. Tremor severity was assessed using the clinical rating scale for tremor. Thirty ROIs related to the motor network were selected to construct FC matrices. Graph-theoretical analysis was used to assess topological properties, and network-based statistics were applied to evaluate FC. Dynamic FC was estimated using a sliding-window approach. Pearson correlation analysis was performed to assess the relationship between changes in network properties and tremor improvement.ResultsET patients showed a significant decrease in characteristic path length and significant increases in small-worldness (σ) and global efficiency within the motor network following MRgFUS. K-means clustering of the dFC matrices identified two distinct connectivity states: State 1 (weak connectivity) and State 2 (strong connectivity). In State 2, strong connectivity was mainly within the sensorimotor cortex and motor-related cerebellar regions. The occurrence of State 1 significantly decreased, while that of State 2 significantly increased in ET patients after MRgFUS. Changes in σ and state occurrence rates were associated with tremor improvement.ConclusionThese findings suggest MRgFUS may alter both static network topology and dynamic connectivity in the motor network, reflecting changes in information transfer efficiency and functional integration.