Amygdala subnuclei are differentially affected in the different genetic and pathological forms of frontotemporal dementia

INTRODUCTION: Frontotemporal dementia (FTD) is a heterogeneous neurodegenerative disorder with multiple genetic and pathological causes. It is characterized by both cortical and subcortical atrophies, with previous studies showing early involvement of the amygdala. However, no prior study has specifically investigated the atrophy of different subnuclei of the amygdala. METHODS: Using an automated segmentation tool for T1-weighted volumetric magnetic resonance imaging, we investigated amygdalar subnuclei (AS) involvement in a cohort of 132 patients with genetic or pathologically confirmed FTD (age: mean = 61 years (standard deviation = 8); disease duration: 5 (3) years) compared with 107 age-matched controls. RESULTS: AS were affected in all genetic and pathological forms of FTD. MAPT mutations/FTDP-17, Pick's disease, and transactive response DNA binding protein 43 kDa type C were the forms with the smallest amygdala (35%–50% smaller than controls in the most affected hemisphere, P < .0005). In most FTD groups, medial subnuclei (particularly the superficial, accessory basal and basal/paralaminar subnuclei) tended to be affected more than the lateral subnuclei, except for the progressive supranuclear palsy group, in which the corticoamygdaloid transition area was the least-affected area. DISCUSSION: Differential involvement of the AS was seen in the different genetic and pathological forms of FTD. In general, the most affected subnuclei were the superficial, accessory basal and basal/paralaminar subnuclei, which form part of a network of regions that control reward and emotion regulation, functions known to be particularly affected in FTD.