Local amygdala structural differences with 3T MRI in patients with Alzheimer disease

Abstract

Objective: Histologic studies show that the amygdala is affected by Alzheimer disease (AD) pathology, and its medial aspect is the most involved. We aimed to assess in vivo local structural differences in the amygdala of patients with AD using high-field MRI.Methods: A total of 19 patients with AD (mean age 76, SD 6 years, mean Mini-Mental State Examination score [MMSE] 13, SD 4) and 19 healthy elderly controls (age 74, SD 5, MMSE 29, SD 1) were enrolled. The radial atrophy mapping technique was used to reconstruct the 3-dimensional surface of the amygdala. Maps of surface tissue loss in patients with AD vs controls were computed and statistically tested with permutation tests thresholded at p Ͻ 0.05, to correct for multiple comparisons. A digital atlas of the amygdalar nuclei was used to infer which nuclei were involved.Results: Both amygdalar volumes were significantly smaller in patients with AD (right 1,508 mm 3 , SD 418; left 1,646, SD 419) than controls (right 2,129 mm 3 , SD 316; left 2,077, SD 376; p Ͻ 0.002). In the dorsomedial part, significant local tissue loss (20%-30%) was mapped in the medial and central nuclei. Ventrally, the lateral nucleus (La) and the basolateral ventral medial nucleus (BLVM) were also involved (20%-30% loss). Conclusions:We found in vivo local structural differences in the amygdala of patients with AD.The nuclei involved have known connections to the hippocampus (BLVM, La) and olfactory system (medial nucleus) and with cholinergic pathways (central nucleus). This pattern is consistent with the known pathophysiology of neural systems affected by AD. Neurology Declarative memory is the main cognitive function affected by Alzheimer disease (AD). While the role of the hippocampus and hippocampal pathology in AD are widely known, the role of the amygdala is much less studied. The amygdala plays a key role in enhancing explicit memory both for pleasant and unpleasant emotional stimuli, by modulating of the encoding and consolidation processes. 1 It also has abundant neural connections with the hippocampus. 2 The amygdala is also among the brain structures where tau deposition occurs in the earliest stages of Alzheimer pathology, 3,4 with more marked tau and A␤ deposition in the medial than lateral nuclei. 5Amygdalar volumetric studies using MRI techniques repeatedly find differences in patients with AD relative to healthy controls. [6][7][8] However, none has focused on mapping local structural changes in the amygdala, although the amygdala is known to be made of a heterogeneous From the LENITEM

Regional Analysis of the Magnetization Transfer Ratio of the Brain in Mild Alzheimer Disease and Amnestic Mild Cognitive Impairment

“…35 Moreover, volumetry MRI data in vivo indicate that both the hippocampus and amygdala show global or local atrophy in AD. [5][6][7][8] The automatic VOI analysis in our study showed that the decrease of the MT ratio in the hippocampus and amygdala was prominent in the left side but was also significant in the right side.…”

“…4 T1WI shows global and local volume loss in structures typically affected by the disease such as the temporal lobe, including the hippocampus, amygdala, and enthorinal cortex. [5][6][7][8] DTI and magnetization transfer (MT) imaging allow assessment of the microstructure of the residual WM and GM in the same structures. [9][10][11][12][13][14][15][16] In particular, MT is a peculiar MR contrast that is based on the exchange of magnetization between free protons and protons bound to macromolecules and is influenced by the direct saturation of free protons by the radiofrequency pulse.…”

Revolution of Alzheimer Precision Neurology. Passageway of Systems Biology and Neurophysiology

“…The most widely studied and accepted structural MRI marker of AD is atrophy of the medial temporal lobe [142, 143]. Assessment of medial temporal atrophy can be performed in clinical routine using visual scales [144].…”

Shape and diffusion tensor imaging based integrative analysis of the hippocampus and the amygdala in Alzheimer's disease

“…5 and 6), the localized surface area atrophy in the right amygdala is more wide spread than that in the left amygdala, with the main subregions affected being the basolateral and basomedial components. A thorough survey of the AD literature would suggest that there have been very few published amygdalar subfield morphometric analyses, with [69] being the sole example outside of previous studies by the current authors' research groups [20,23,24]. A direct comparison with the findings reported in [69] is challenging given that the subdivision criteria of the amygdalas were rather different.…”