Background: Differentiating Alzheimer's disease (AD) and dementia with Lewy bodies (DLB), two of the commonest forms of dementia in older age, remains a diagnostic challenge. To assist with better understanding of the differences between the conditions during life, we assessed limbic and subcortical brain volumes in AD, DLB, and healthy older individuals using magnetic resonance imaging (MRI), with the hypothesis that when compared with controls, subcortical volumes would be reduced to a greater extent in DLB than in AD.
Methods: One hundred participants (35 healthy controls, 32 AD, and 33 DLB) underwent 3 Tesla T1 weighted MR scanning. Volumes were automatically segmented for each participant using FreeSurfer, then expressed as a percentage of their total intracranial volumes. Group effects were assessed using multivariate analysis of covariance, controlling for age and gender.
Results: Significant group effects were apparent among subcortical brain volumes (F28,162 = 4.8, p < 0.001; Wilk's Λ = 0.30, partial η2 = 0.45), while univariate tests showed differences in all volumetric measures (p < 0.03) except in right caudate (p = 0.08). Post-hoc analyses indicated that while not significantly different from AD, changes compared to healthy subjects in left caudate, bilateral putamen, left thalamus, brainstem and total subcortical grey volume were more pronounced in DLB. Significant differences between AD and DLB were confined to the bilateral hippocampus (DLB > AD, p < 0.008).
Conclusions: For similar levels of dementia severity, DLB appears to have greater involvement of subcortical brain atrophy than AD. Further investigation of the subcortical brain structures in DLB is warranted to fully understand their neurobiological role in this disease.