Altered Functional Connectivity in Essential Tremor. A Resting-State fMRI Study.

Abstract

Introduction: Essential tremor (ET) has been associated with a spectrum of clinical features, with both motor and non-motor elements, including cognitive deficits. We employed resting-state functional magnetic resonance imaging (fMRI) to assess whether (1) brain networks that might be involved in the pathogenesis of non-motor manifestations associated with ET are altered and (2) the relationship between abnormal connectivity and ET severity and neuropsychological function. Methods: Resting-state fMRI data in 23 ET patients (12 women and 11 men) and 22 healthy controls (HC) (12 women and 10 men) were analyzed using independent component analysis, in combination with a "dual-regression" technique, to identify the group differences of resting-state networks (RSNs) [default mode network (DMN) and executive, frontoparietal, sensorimotor, cerebellar, auditory/language, and visual networks]. All participants underwent a neuropsychological and neuroimaging session, where resting-state data was collected. Results: Relative to HC, ET patients showed increased connectivity in RSNs involved in cognitive processes (DMN and frontoparietal networks), and decreased connectivity in the cerebellum and visual networks. Changes in network integrity were associated not only with ET severity (DMN) and ET duration (DMN and left frontoparietal network), but also with cognitive ability. Moreover, in at least three networks (DMN and frontoparietal networks), increased connectivity was associated with worse performance on different cognitive domains (attention, executive function, visuospatial ability, verbal memory, visual memory, and language) and depressive symptoms. Conclusions: ET was associated with abnormal brain connectivity in major RSNs that might be involved in both motor and nonmotor symptoms. Our findings underscore the importance of examining RSNs in this population as a biomarker of disease.