Vestibular Agnosia: Toward a Better Understanding of Its Mechanisms.

Background/Objectives: Vestibular agnosia is characterized by a reduced or absent self-motion perception while demonstrating the presence of normal peripheral vestibular function following stimulation. This condition has previously been reported by previous authors in different populations and more recently in traumatic brain injury patients. However, the underlying mechanisms responsible for vestibular agnosia remain a matter of debate. The objective of this manuscript is to review and compare the behavioral and neuroanatomical findings in populations where vestibular agnosia has been demonstrated to better understand the underlying mechanism. Methods: A review of the literature was conducted using four databases: Medline, Embase, Google Scholar, and PubMed. A normal vestibulo-ocular reflex function with an impaired self-motion perception following vestibular stimulation represented the inclusion criteria used. Results: Behavioral data reviewed in the studies revealed a clear association with postural instability. However, no consensus can be drawn from neuroanatomical data due to variability in brain impairments in those populations even though impairments in the parietal cortex are often reported. Conclusions: In general, behavioral data and neuroanatomical data regarding vestibular agnosia have been poorly documented throughout the literature. However, vestibular agnosia can be observed in different populations and is present in concomitant postural control deficits, an important predictor of falls. Finally, even though the parietal cortex has been associated with vestibular agnosia, future studies are required to adequately identify the underlying mechanism. Indeed, the parietal cortex could be part of a larger network mediating vestibular agnosia. This review proposes various methods that future studies should use to overcome the present limitations.