Altered resting state – functional connectivity in patients with bilateral vestibular failure

Background: Patients with bilateral vestibular failure (BVF) suffer from gait unsteadiness and oscillopsia. Brain imaging studies applying vestibular stimulation in patients with BVF have shown altered neural activity of cortical visual-vestibular interaction: decreased bilateral neural activity in the posterior insula and parietal operculum and decreased deactivations in the visual cortex. It is unknown how this affects functional connectivity in the resting brain.

Methods: We applied a novel data driven approach based on graph theory to investigate altered whole-brain resting-state functional connectivity in BVF patients (n = 22) compared to age- and gender-matched healthy controls (n = 25) using resting-state fMRI. BVF patients were examined by a battery of neuro-otological tests. BVF was defined by bilateral severe caloric hyporesponsiveness (< 5 °/s) and severely reduced gain (< 0.6) of the vestibulo-ocular reflex.

Results: Patients with BVF showed lower connectivity in the posterior insula and parietal operculum (bilateral) compared to controls. These regions were also identified in stimulus-related activation studies employing vestibular stimuli in healthy subjects and they showed reduced neural activity in BVF.

Conclusions: Here we showed that enduring deficient or missing vestibular input leads to long lasting changes in resting-state connectivity of the brain. Importantly, these changes in the resting brain were task-independent and robust and gain significance as they were found in the absence of sensory stimulation and without a region-related a priori hypothesis. Further studies can now investigate the relation between decreased connectivity to levels of functional impairments in BVF. Seed-based functional and effective connectivity analyses may identify affected brain networks which can be helpful for vestibular rehabilitation.