P121. Multimodal assessment of the hippocampus in patients with bilateral vestibulopathy

Introduction Bilateral vestibular loss leads to anatomical and functional changes in the hippocampal formation, which are reflected in subjective and objective behavioural deficits in spatial navigation, learning and memory ( Thomas et al., 2005 , Kremmyda et al., 2016 ). The aim of our study was to specify the seen hippocampal volume changes within grey and white matter in BVP using a novel hippocampus subfield segmentation approach ( Pipitone et al., 2014 ). Methods 50 right handed subjects (25 healthy controls (HC): aged 58 years, range 31–86 years with physiological vestibular function [head impuls test (HT) gain at 60 ms right 0.9, left 1.0] and 25 patients with bilateral vestibulopathy (BVP) with residual vestibular function (calorics warm left: −2.6°/s; right 2.8°/s) aged 61 years, range 24–87 years] were measured in a 3 T MRI (Erlangen, Siemens, Verio.After hippocampal subfield segmentation ( Pipitone et al., 2014 ) and intracranial volume correction, ANOVA was performed for both left and right hemispheres to evaluate the Bonferoni-corrected differences in the hippocampal subfield volumes between HC and BVP using FSL and R. Results Whole brain analysis did not reveal any areas of grey matter change for both contrasts (BVP > HC and HC > BVP).Within the hippocampus-subfield specific grey matter analysis volume decrease was most significant in the posterior part, more specifically in the right CA1 and subiculum ( p p p Discussion Our findings are in line with previous human and animal studies that were able to link chronic bilateral vestibulopathy to hippocampal atrophies ( Thomas et al., 2005 , Kremmyda et al., 2016 , Horii et al., 2004 ). More specifically white matter changes were laterality-unspecific and a little more localized to the anterior/middle part of the hippocampus, which is thought to represent inputs from the vestibular system (required for estimating direction during path integration). Whereas grey matter changes were right-sided and more localized to the middle/posterior part of the hippocampus, which is thought be involved in spatial navigation ( Horii et al., 2004 , Hufner et al., 2011 ).