Thalamotomy at the ventralis intermedius nucleus has been an effective treatment 
method for essential tremor, but how the brain network changes immediately 
responding to this deliberate lesion and then reorganizes afterwards are not 
clear. Taking advantage of a non-cranium-opening MRI-guided focused ultrasound 
ablation technique, we investigated functional network changes due to a focal 
lesion. To classify the diverse time courses of those network changes with 
respect to symptom-related long-lasting treatment effects and symptom-unrelated 
transient effects, we applied graph-theoretic analyses to longitudinal 
resting-state functional magnetic resonance imaging data before and 1 day, 
7 days, and 3 months after thalamotomy with essential tremor. We found reduced 
average connections among the motor-related areas, reduced connectivity between 
substantia nigra and external globus pallidum and reduced total connection in 
the thalamus after thalamotomy, which are all associated with clinical rating 
scales. The average connectivity among whole brain regions and inter-hemispheric 
network asymmetry show symptom-unrelated transient increases, indicating 
temporary reconfiguration of the whole brain network. In summary, thalamotomy 
regulates interactions over the motor network via symptom-related connectivity 
changes but accompanies transient, symptom-unrelated diaschisis in the global 
brain network. This study suggests the significance of longitudinal network 
analysis, combined with minimal-invasive treatment techniques, in understanding 
time-dependent diaschisis in the brain network due to a focal lesion.