Vestibular Loss Predicts Poorer Spatial Cognition in Patients with Alzheimer’s Disease

Abstract

The vestibular system is an important contributor to balance control, spatial orientation, and falls risk. Recent evidence has shown that Alzheimer's disease (AD) patients have a higher prevalence of vestibular impairment relative to healthy controls. We sought to evaluate whether vestibular loss is specifically associated with poor spatial cognitive skills among patients with mild cognitive impairment (MCI) and AD. We enrolled 50 patients (22 MCI and 28 AD) from an interdisciplinary Memory Clinic and measured vestibular physiologic function in all patients. Spatial cognitive function was assessed using the Money Road Map Test (MRMT) and the Trail Making Test Part B (TMT-B). General cognitive function was assessed with the Mini-Mental Status Examination (MMSE). In multivariable linear regression analyses adjusted for age, gender, education level, and MMSE, MCI and AD patients with vestibular loss made significantly more errors on the MRMT relative to patients with normal vestibular function (β= 7.3, 95% CI 2.4, 12.1 for unilateral vestibular loss and β= 6.4, 95% CI 1.9, 10.9 for bilateral vestibular loss). We further stratified AD patients into "spatially normal" and "spatially impaired" groups based on MRMT performance, and found that the prevalence of vestibular loss was significantly higher in the spatially impaired AD group relative to the spatially normal AD group. These findings support the hypothesis that vestibular loss contributes specifically to a decline in spatial cognitive ability in MCI and AD patients, independently of general cognitive decline, and may predict a "spatially impaired" subtype of AD.

Altered Regional Cerebral Blood Perfusion in Mild Cognitive Impairment Patients with Dizziness

“…In particular, vestibular dysfunction and impaired vestibular balance control were more frequently reported in patients with MCI or Alzheimer’s dementia. In this study, we found that MCI patients with dizziness performed significantly worse on the COWAT, one of the tests assessing verbal fluency and executive function, than MCI patients without dizziness, which is consistent with previous studies that showed executive function impairment among patients with dizziness [ 10 , 31 ]. Notably, frontal areas, especially the lateral pars orbitalis, were found to be associated with the letter-based phonemic COWAT among AD patients [ 34 ].…”

“…Previous studies have suggested that having dizziness is related to subjective memory complaints or cognitive dysfunction in various domains including visuospatial, memory, and executive function [ 4 , 6 , 13 , 31 , 32 ]. This phenomenon was also observed in patients with AD-related cognitive impairment [ 10 , 33 ]. In particular, vestibular dysfunction and impaired vestibular balance control were more frequently reported in patients with MCI or Alzheimer’s dementia.…”

“…In addition to spatial cognition, non-spatial functions such as executive function, memory, and attention were affected by bilateral vestibulopathy [ 8 , 9 ]. Likewise, it was reported that patients with cognitive impairment, such as Alzheimer’s disease (AD) and mild cognitive impairment (MCI), have a higher prevalence of vestibular impairment [ 10 ]. Poor balance performance was found among patients with subjective cognitive decline, MCI, and dementia and the worst performance was found in patients with the most severe cognitive impairment [ 11 ].…”

“…Poor balance performance was found among patients with subjective cognitive decline, MCI, and dementia and the worst performance was found in patients with the most severe cognitive impairment [ 11 ]. Moreover, vestibular deficit was associated with greater decline in spatial cognition in patients with AD [ 10 ]. Interestingly, vestibular rehabilitation improved both dizziness severity and cognitive function in patients with intractable dizziness [ 12 ].…”

Spatial Navigation Is Distinctively Impaired in Persistent Postural Perceptual Dizziness

“…Subjects with impaired memory or spatial navigation abilities (such as hippocampal lesions) fail to locate the platform and wander erratically around for a long period of time, even after having found the platform in previous trials. For human testing, virtual versions of the MWM paradigm have been validated and proved for use in identifying memory impairments, such as those found in individuals with Alzheimer's disease (15)(16)(17)(18).…”