Regular Research Article
Differential Atrophy of Hippocampal Subfields: A Comparative Study of Dementia with Lewy Bodies and Alzheimer Disease

https://doi.org/10.1016/j.jagp.2015.06.006Get rights and content

Objectives

Dementia with Lewy bodies (DLB) is characterized by relative preservation of the medial temporal lobe compared with Alzheimer disease (AD). The differential involvement of the hippocampal subfields in both diseases has not been clearly established, however. We aim to investigate hippocampal subfield differences in vivo in a clinical cohort of DLB and AD subjects.

Methods

104 participants (35 DLBs, 36 ADs, and 35 healthy comparison [HC] subjects) underwent clinical assessment and 3T T1-weighted imaging. A Bayesian model implemented in Freesurfer was used to automatically segment the hippocampus and its subfields. We also examined associations between hippocampal subfields and tests of memory function.

Results

Both the AD and DLB groups demonstrated significant atrophy of the total hippocampus relative to HC but the DLB group was characterized by preservation of the cornu ammonis 1 (CA1), fimbria, and fissure. In contrast, all the hippocampal subfields except the fissure were significantly atrophied in AD compared with both DLB and HC groups. Among DLB subjects, CA1 was correlated with the Recent Memory score of the CAMCOG and Delayed Recall subscores of the HVLT.

Conclusions

DLB is characterized by milder hippocampal atrophy that was accompanied by preservation of the CA1. The CA1 was also associated with memory function in DLB. Our findings highlight the promising role of hippocampal subfield volumetry, particularly that of the CA1, as a biomarker for the distinction between AD and DLB.

Section snippets

Subjects, Assessment, and Diagnosis

Seventy-one individuals over the age of 60 years (36 subjects with probable AD13 and 35 with probable DLB1) were recruited from a community-dwelling population of patients referred to local Old Age Psychiatry, Geriatric Medicine, or Neurology Services. Thirty-five similarly aged HC subjects were recruited from relatives and friends of subjects with dementia or volunteered via advertisements in local community newsletters. The research was approved by the local ethics committee. All subjects or,

Subject Characteristics

The demographic and clinical data for patients and HC subjects are summarized in Table 1. Subject groups were well matched for age (F(2,101) = 0.74; p = 0.479), sex (χ2(2) = 4.27; p = 0.118), and years of education (χ2(2) = 5.62; p = 0.060). As expected, the DLB group had significantly higher UPDRS scores than the AD group (Z = −6.817, p <0.001) DLB subjects also scored significantly higher on the Cognitive Fluctuations Scale (Z = −3.915, p <0.001), although there were no significant

Discussion

The main findings of the study were a) DLB was associated with significantly milder hippocampal atrophy than AD; b) AD showed a global pattern of hippocampal atrophy affecting all the subfields with the exception of the fissure; c) the CA1 region was relatively preserved in DLB compared with HC and AD groups; and d) the CA1 region is associated with memory functions in DLB.

Neuropathological studies have shown that the hippocampus is one of the earliest sites of pathology in the disease course

Conclusions

To date, very few studies have compared atrophy patterns of the hippocampal subfields in DLB and AD. The main findings of CA1 preservation and milder global hippocampal atrophy in clinically diagnosed DLB subjects are largely consistent with the topography of neuronal loss described in histopathological studies as well as with previous imaging studies. The distinct involvement of the CA1 in DLB and AD suggests that hippocampal subfield volumetry could be a promising biomarker to aid in the

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