Relationship between postural instability and subcortical volume loss in Alzheimer's disease

Abstract

The relationship between postural instability and subcortical structure in AD has received less attention. The aims of this study were to assess whether there are differences in the ability to control balance between Alzheimer's disease (AD) and controls, and to investigate the association between subcortical gray matter volumes and postural instability in AD.We enrolled 107 consecutive AD patients and 37 controls. All participants underwent detailed neuropsychological evaluations, T1-weighted MRI at 3 T, and posture assessment using computerized dynamic posturography. We segmented the volumes of 6 subcortical structures of the amygdala, thalamus, caudate nucleus, putamen, globus pallidus and nucleus accumbens, and of hippocampus, using the FMRIBs integrated registration and segmentation tool.All subcortical structures, except for the globus pallidus, were smaller in AD compared with controls on adjusting for age and gender. Falling frequencies in unilateral stance test (UST) and composite scores in sensory organization test (SOT) were worse in AD than in controls. The motor control test did not reveal any differences between groups. On subgroup analyses in AD, the groups with poor performance in UST or SOT exhibited significantly reduced nucleus accumbens and putamen volumes, and nucleus accumbens volume, respectively. The smaller volume of the nucleus accumbens was associated with postural instability in AD (OR [95% CI] 17.847 [2.59-122.80] for UST, 42.827[6.06-302.47] for SOT, all P < .05).AD patients exhibited reduced ability to control balance compared with controls, and this postural instability was associated with nucleus accumbens volume loss. Furthermore, cognitive dysfunction was more prominent in the group with severe postural instability.

Figure 1

Example of automated segmentation of subcortical gray matter structure using FIRST in AD patient. Segmentations are shown overlaid on the 3D T1-weighted images in 3 orthogonal orientations, corresponding to the axial (left column), coronal (middle column), and sagittal (right column) planes. Colored structures—yellow: Hippocampus; Turquoise: Amygdala; Green: Thalamus; Light blue: Caudate nucleus; Pink: Putamen; Dark blue: Globus pallidus; Orange: Nucleus accumbens. AD  =  Alzheimer's disease.