Spatial orientation and postural control under vestibular guidance in patients with central dysfunction of the nervous system

Abstract

The brain processing of the vestibular signals of self-motion is used for guiding spatial orientation as well as postural control, two faculties simultaneously engaged in ecological behaviour such as foraging. It follows that brain disease affecting the processing of vestibular signals will manifest with spatial disorientation and postural imbalance. Research investigating the neural control of these two vestibular-dependent functions is sparse, particularly in patients with central dysfunction of the nervous system. This thesis attempts to assess how the spatial and postural modalities are affected in patients with brain disease by using clinical and non-clinical behavioural tests and linking these with neuro-imaging data, where available.

I investigated vestibular-guided spatial and postural control in:

(1) acute traumatic brain injury - linking behavioural tests of vestibular-spatial orientation and posture with structural brain imaging, I found that (1) postural imbalance is linked to widespread bi-hemispheric WM microstructural abnormalities, whereas spatial impairment is not as widespread and predominantly but not exclusively right-hemispheric including also some left-hemispheric regions, as assessed by whole-brain and ROI DTI, (2) imbalanced patients’ right inferior longitudinal fasciculus correlates with vestibular perceptual thresholds and represents a circuit whose damage might be linked to loss of vestibular motion perception and imbalance.

(2) patients with memory and (balance) complaints – using vestibular-based posturography and specifically designed vestibular system-based spatial tests of self-motion perception, egocentric and allocentric (egocentric+) performance, I found that (1) patients with worse cognition show impaired balance and abnormal performance for all three vestibular spatial tasks, (2) the allocentric (egocentric+) task discriminated better between patients and controls than the pure egocentric task, and (3) cognitive tests correlate better with the allocentric than egocentric navigation.

These findings suggest that vestibular-dependent spatial orientation and postural control are deficient in brain disease patients, some of whom with cognitive impairment. Understanding how posture, navigation, and cognition are linked from a vestibular system perspective and how they are affected during disease may allow the development of targeted treatment of these ecologically important functions.