Abstract
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.
Highlights
The current prevailing view of the brain is that it is not a mixture of isolated regions but a highly organized system of interactions
We demonstrated that a focal lesion in the Vim of the thalamus induced by using minimally invasive MRgFUS could lead to changes in both the global brain network and motor circuit, and does not alter activity or connectivity changes in the target region
This study shows the usefulness of the combination of MRgFUS and connectivity analysis using rs-fMRI in exploring connectional and connectomal diaschisis identified following thalamotomy in the treatment of essential tremor
Summary
The current prevailing view of the brain is that it is not a mixture of isolated regions but a highly organized system of interactions. Analysis of network topology in the brain [1] highlights the properties of the system, such as efficient information passing, adaptability, and resilience [2]. Functional Networks after Thalamotomy Using MRgFUS and detrimental topological reorganization following damage to the neuronal hubs [3,4,5]. The network centric perspective is receiving increasing attention in understanding brain diseases and treatments, in investigating how functional networks respond immediately to insults (or treatments) in the anatomical network and reorganize afterwards. From this network perspective, we investigated changes in the brain networks of patients with essential tremor following thalamotomy. How a deliberate lesion to a focal target leads to immediate changes in the motor network and alleviates tremor remains poorly understood
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