Objective: Our primary endpoint was to verify whether rs-FC between tremor-related areas was effectively modulated by MRgFUS at 1 and 3 months post-operatively.  Alongside, we explore whether rs-FC between tremor-related regions was effectively modulated by MRgFUS at 1,3,6 and 12 months after surgery and whether such changes are associated longitudinally with individual clinical outcome assessed by TETRAS sub-items for motor performance.

Background: Magnetic Resonance-guided high-intensity Focused Ultrasound (MRgFUS) has increasingly gained interest as a new non-invasive method alternative to standard neurosurgery to treat tremor. Functional connectivity (FC) correlates of MRgFUS treatment of Essential Tremor (ET) have been only partially investigated.

Method: We conducted a hypothesis-driven ROI-to-ROI resting state-FC MRI analysis, exclusively focusing on brain regions expected to be relevant for tremor pathogenesis in a group of 30 consecutive ET patients who underwent MRgFUS.

Results: FC increased significantly in bilateral Lobe IV/V and the supplementary motor area of the treated side. The bilateral anterior cingulate, bilateral paracingulate gyrus and the Lobe IV/V of both cerebral hemispheres showed a correlation between disease duration and FC decrease at 1-mo and 3-months.
The dentate nucleus of the treated side and bilateral supplementary motor areas exhibited a positive correlation between post-treatment tremor improvement and TETRAS drop points. As a percentage of intra-subject TETRAS, we calculated the potential relationship between FC and tremor improvement at 3 months between the thalamic ventral intermediate nucleus and bilateral occipital fusiform gyrus. By using 50% tremor improvement as response threshold, responders showed reduced FC between the postcentral gyrus of the untreated side and the occipital fusiform gyrus of both hemispheres, and between the superior parietal lobe of the treated side and the bilateral occipital fusiform gyrus. Hypoconnectivity within Lobe VI of the treated side and the contralateral SMA was retrospectively detected in responders at baseline.

Conclusion: MRgFUS can successfully modulate brain FC within the tremor network in ET. Such changes are associated with good clinical outcome. The shifting mode of cooperation among the constituents of this network is therefore susceptible to external redirection despite the chronic nature of ET.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/reconfiguration-of-functional-motor-connectome-after-mrgfus-vim-thalamotomy-in-essential-tremors/