Immediate and Longitudinal Alterations of Functional Networks after Thalamotomy in Essential Tremor

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.

Cerebello-thalamo-cortical network is intrinsically altered in essential tremor: evidence from a resting state functional MRI study

“…Recently the rise of MRI-guided high-intensity focused ultrasound (MRgFUS) thermal ablation technique to produce a thalamotomy allowed the chance to use fMRI to study the changes in the brain network caused by a focal lesion. Two rs-fMRI studies performed in drug-resistant ET patients treated with MRgFUS, confirmed connectivity changes in the motor tremor network and not only in the target region 49,50 .…”

Right Brodmann area 18 predicts tremor arrest after Vim radiosurgery: a voxel-based morphometry study

“…The authors concluded that these areas, involved in higher order visuospatial processing and control, might exhibit an adaptive reorganization, and compensate skilled movements in case of tremor. In a recent functional resting-state MRI study, Jang et al [22] evaluated the effect on brain networks of Vim HIFU in 10 patients, using graph analysis. Interestingly, the authors observed changes in functional connectivity in right lateral inferior occipital cortex.…”

Graph theory analysis of resting‐state functional magnetic resonance imaging in essential tremor

“…Unlike previous techniques, graph theory approach permits one to not only visualize the overall connectivity pattern among all the brain regions, but also to quantitatively characterize the global organization (Medaglia, 2017; providing a novel insight into the biological mechanisms of many neurological diseases, such as mild cognitive impairment and Alzheimer's disease (Khazaee, Ebrahimzadeh, & Babajani-Feremi, 2016), epilepsy (Chiang, Stern, Engel Jr., Levin, & Haneef, 2014), Huntington's disease (Gargouri et al, 2016), and Parkinson's disease (Gottlich et al, 2013;Sreenivasan et al, 2019;Zhang, Liu, Chen, Liu, & Wang, 2015), among others. (Jang, Park, Chang, Pae, & Chang, 2016) Thalamotomy led to changes in both the global brain network and motor circuit (Jang et al, 2016). (Jang, Park, Chang, Pae, & Chang, 2016) Thalamotomy led to changes in both the global brain network and motor circuit (Jang et al, 2016).…”

“…Only one previous study applied graph theory analysis to longitudinal rs-fMRI data in eight ET patients before and after a focal lesion in the ventralis intermedius nucleus of the thalamus, using MRI-guided high-intensity focused ultrasound. (Jang, Park, Chang, Pae, & Chang, 2016) Thalamotomy led to changes in both the global brain network and motor circuit (Jang et al, 2016). However, the fact that the sample size was small (N = 8) as well as selection factors (e.g., as surgical patients, the ET patients included in the study had a more severe form of the disease) does not permit one to draw reliable conclusions.…”