Structural Brain Volume Covariance Associated with Gait Speed in Patients with Amnestic and Non-Amnestic Mild Cognitive Impairment: A Double Dissociation

Background: Gait impairment is observed in early stages of dementia, such as mild cognitive impairment (MCI), and is associated with morphological brain volume changes like atrophy. Objective: This study aims to characterize the brain's grey matter (GM) volume covariance associated with gait speed in patients with amnestic mild cognitive impairment (aMCI) and non-amnestic MCI (naMCI). Methods: Gait speed was measured in 171 patients with MCI (age 72.0 +/- 5.1; 36.8% female; 41 with aMCI and 130 naMCI) at normal and rapid gait speeds. Brain GM covariance networks were computed using voxel-based morphometry, using the main neural correlates of gait speed in each group and for each walking condition as seed regions. Results: Normal gait speed correlated with GM volume in the left frontal cortex in patients with aMCI, and in bilateral caudate and left putamen in those with naMCI. Rapid gait speed correlated with GM volume in the bilateral caudate and right cerebellum in naMCI, but without any GM region in aMCI. For normal gait speed, the left caudate nucleus volume in naMCI covaried with subcortico-frontal regions, while the left frontal cortex covaried with cortical regions involving the frontal cortex in aMCI. For rapid gait speed, subcortico-frontal regions were similar as for normal speed in naMCI. Conclusion: Brain GM volume covariance associated with gait speed varies according to the type of MCI; it involved subcortico-frontal regions for patients with naMCI and the frontal cortex in those with aMCI.