More Atrophy of Deep Gray Matter Structures in Frontotemporal Dementia Compared to Alzheimer's Disease

Background: The involvement of frontostriatal circuits in frontotemporal dementia (FTD) suggests that deep gray matter structures (DGM) may be affected in this disease. Objective: We investigated whether volumes of DGM structures differed between patients with behavioral variant FTD (bvFTD), Alzheimer's disease (AD), and subjective complaints (SC) and explored relationships between DGM structures, cognition, and neuropsychiatric functioning. Methods: For this cross-sectional study, we included 24 patients with FTD and matched them based on age, gender, and education at a ratio of 1: 3 to 72 AD patients and 72 patients with SC who served as controls. Volumes of hippocampus, amygdala, thalamus, caudate nucleus, putamen, globus pallidus, and nucleus accumbens were estimated by automated segmentation of 3D T1-weighted MRI. MANOVA with Bonferroni adjusted post-hoc tests was used to compare volumes between groups. Relationships between volumes, cognition, and neuropsychiatric functioning were examined using multivariate linear regression and Spearman correlations. Results: Nucleus accumbens and caudate nucleus discriminated all groups, with most severe atrophy in FTD. Globus pallidus volumes were smallest in FTD and discriminated FTD from AD and SC. Hippocampus, amygdala, thalamus, and putamen were smaller in both dementia groups compared to SC. Associations between amygdala and memory were found to be different in AD and FTD. Globus pallidus and nucleus accumbens were related to attention and executive functioning in FTD. Conclusion: Nucleus accumbens, caudate nucleus, and globus pallidus were more severely affected in FTD than in AD and SC. The associations between cognition and DGM structures varied between the diagnostic groups. The observed difference in volume of these DGM structures supports the idea that next to frontal cortical atrophy, DGM structures, as parts of the frontal circuits, are damaged in FTD rather than in AD.