The Intersection Between Vestibular Function and Spatial Memory in Adults with Chronic Moderate-Severe Traumatic Brain Injury

Traumatic Brain Injury (TBI) is a leading cause of disability among adults. There is evidence to suggest the peripheral vestibular system is vulnerable to damage in individuals with TBI. However, there are limited prospective studies that describe the type and frequency of vestibular impairment in individuals with chronic moderate-severe TBI. Furthermore, several lines of evidence show anatomical connections between the vestibular system and brain areas involved in spatial cognition. However, it is unclear what influence vestibular impairments have on spatial cognitive deficits commonly observed in adults with TBI. Vestibular evoked myogenic potentials (VEMPs) and video head impulse test (vHIT) were used to assess the function of otolith organ and horizontal semicircular canal (hSCC) pathways in adults with chronic moderate-severe TBI and in non-injured comparison (NC) participants. Self-report questionnaires were administered to participants with TBI to determine prevalence of vestibular symptoms and quality-of-life associated with those symptoms. A triplet binding task (TBT) was used to assess spatial and non-spatial memory. About 63% of participants with TBI had evidence of peripheral vestibular impairment, compared to ~7% of NC participants. TBI was associated with a greater degree of impairment in otolith organ rather than hSCC pathways. As many as 80% of participants with TBI reported vestibular symptoms, and up to 36% reported that these symptoms affected their quality of life. The NC group had the highest spatial and non-spatial memory scores, followed by the group with TBI but no peripheral vestibular impairment (TBI-No VI) with intermediate scores, and the group with TBI and peripheral vestibular impairment (TBI-VI; all with otolith organ impairment) with the lowest scores. Significant differences between the NC group and the TBI-VI group were found for spatial memory, but not for non-spatial memory. Results suggest vestibular testing for adults with chronic moderate-severe TBI who report persistent dizziness and imbalance may lead to more appropriate triage and comprehensive rehabilitation programs for this TBI population. Additionally, examining the relationship between peripheral vestibular function and spatial memory may have further implications for treatment and rehabilitation plans for patients with vestibular and/or primary neurological disorders, such as TBI.