Focused ultrasound thalamotomy (FUS-T) is an efficacious treatment for refractory essential tremor (ET). The success of this surgery relies on creating an optimal lesion for maximizing efficacy without inducing side effects. Currently, clinical testing is the only method to determine whether sufficient lesioning is achieved. In absence of a physiological feedback, this determination can be subjective and can adversely affect the long-term tremor outcomes. We aim to develop a functional magnetic resonance imaging (fMRI) based feedback for FUS-T by studying the dysfunction in the tremor network. We hypothesize that specific thresholds of altered functional connectivity (or 'connectivity correlates of tremor' (CCT)) between the hubs of tremor network (e.g. cerebellum and motor cortex) can distinguish ET patients from controls and this abnormal pattern is reversed after FUS-T.
ET patients and controls will undergo multi-modality neuroimaging. In addition the ET cohort will also undergo imaging after FUS-T. Functional connectivity analysis will be performed using a processing pipeline based on the AFNI suite. The hubs within tremor network will be parcellated and a correlation matrix of Z-scores from the BOLD signal time-series will be created. A sensitivity analysis will be performed to identify CCT with a high sensitivity and specificity for distinguishing ET patients from controls, and pre & post-thalamotomy states.
This pilot proposal may lead to the development of real-time physiological feedback during FUS-T potentially improving patient & surgical outcomes. This framework will be critical for neurological and psychiatric disorders where immediate clinical feedback is not feasible after FUS ablation.