P13. Dendato-thalamo-cortical pathways in association with otolith dysfunction

Abstract

Introduction The processing of otolith information within the human cortex is still poorly understood (Lopez and Blanke, 2011). Two distinct anatomical otolith pathways within the thalamo-cortical vestibular network were proposed in patients with thalamic infarctions who presented with contra- or ipsiversive tilts of the subjective visual vertical (SVV) (Dieterich and Brandt, 1993; Baier et al., submitted for publication). Aim of this study was to investigate the dendato-thalamo-cortical pathways in association with otolith dysfunction by means of DTI (diffusion tensor imaging) based on the regions found in a recent patient study using statistical lesion-behavior mapping (Baier et al., submitted for publication). Methods Twenty-four healthy volunteers (11 females; aged 20–4years, mean age 28.2±6.3years) were measured in a 3Tesla MRI (Erlangen, Siemens, Verio). The data was analyzed with FSL. For the examination of the dendato-thalamo-cortical pathways we calculated voxelbased DTI tractography between the dendate nuclei, vestibular nuclei, the thalamic regions defined in the patients with thalamic infarctions (Baier et al., submitted for publication) and the cortex. Results At group level the data-driven DTI tractography showed that the dendato-thalamo-cortical pathways connected to ipsiversive SVV tilts projected ipsilaterally from the dendate and vestibular nuclei to the cortex via the caudate nucleus. Thalamus regions connected to contraversive SVV tilts received input from the contralateral cerebellar hemispheres, the dendate and vestibular nucleus crossing either in the pons or mesencephalon and reaching the cortex via the putamen. Discussion These data verify that there are two distinct anatomical otolith signal-processing pathways within a dendato-thalamo-cortical vestibular network. This supports results of earlier PET- and fMRI-studies with caloric and galvanic stimulation in humans (Dieterich and Brandt, 2008). Therefore, our data support the existence of two functionally distinct dendato-thalamo-cortical vestibular pathways leading - when damaged - either to a vestibular tone imbalance to the ipsiversive or to the contraversive side. Acknowledgements Supported by the Support Program for Research and Teaching (FoFoLe LMU ), Graduate School of Systemic Neuroscience (GSN), the German Foundation for Neurology (Deutsche Stiftung Neurologie) and the German Federal Ministry of Education and Research (German Center for Vertigo and Balance Disorders -IFB LMU , Grant code 01 EO 0901).