Objective: We compared quantitative susceptibility mapping (QSM) values in the hippocampi among patients with Parkinson disease (PD) and PD with dementia (PDD)/ Lewy body dementia (DLB) and healthy controls (HC).

Background: The PDD/DLB is pathologically characterized by the occurrence of Lewy bodies and neurodegeneration in various brain regions including the hippocampus, especially in the cornu ammonis (CA) 2-3.¹ A previous postmortem study showed that the iron-containing microglia associated with neurodegeneration was present in hippocampi. The signal intensity in QSM is thought to be reflective of underlying iron deposition in patients with neurodegenerative diseases.^2-5 Therefore, we hypothesized that hippocampal iron deposition may also relate to developing neurodegeneration in patients with PDD/DLB.

Methods: All studies were performed on a 3T MR imaging system. Coronal QSM was obtained with a 3D multi-echo spoiled gradient echo sequence, and reconstructed using the morphology enabled dipole inversion (MEDI). For 41 PD, 17 PDD/DLB, and 28 age/sex-matched HC, we first evaluated hippocampal appearances on coronal QSM images according to the previous MRI and histological reports, and found continuous layer of intra-hippocampal grey matter (GM) layer as high SI striation (figures A and B). Then we measured the mean QSM values in the GM layer, which were subdivided into three parts: external, middle, and internal part. The QSM values in each part were compared among three groups (figures C and D).

Results: The QSM values in the middle and internal parts of hippocampi were significantly higher in PDD/DLB than in PD (p<.005) and HC (p<.001), whereas there were no significant differences between PD and HC for the QSM values in any parts.

Conclusions: Our study is the first to show hippocampal iron deposition in PD and PDD/DLB on QSM. The internal part of the hippocampi in PDD / DLB showed higher QSM values than those in PD and HC, which may be due to increased iron-containing microglia associated with neurodegeneration.

References: 1.           Iseki E, Takayama N, Marui W, Uéda K, Kosaka K. Relationship in the formation process between neurofibrillary tangles and Lewy bodies in the hippocampus of dementia with Lewy bodies brains. Journal of the neurological sciences 2002;195(1):85-91.

2.           de Rochefort L, Liu T, Kressler B, et al. Quantitative susceptibility map reconstruction from MR phase data using bayesian regularization: validation and application to brain imaging. Magnetic Resonance in Medicine 2010;63(1):194-206.

3.           Liu J, Liu T, de Rochefort L, et al. Morphology enabled dipole inversion for quantitative susceptibility mapping using structural consistency between the magnitude image and the susceptibility map. Neuroimage 2012;59(3):2560-2568.

4.           Liu T, Wisnieff C, Lou M, Chen W, Spincemaille P, Wang Y. Nonlinear formulation of the magnetic field to source relationship for robust quantitative susceptibility mapping. Magnetic resonance in medicine 2013;69(2):467-476.

5.           Murakami Y, Kakeda S, Watanabe K, et al. Usefulness of quantitative susceptibility mapping for the diagnosis of Parkinson disease. American Journal of Neuroradiology 2015;36(6):1102-1108.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/hippocampal-iron-deposition-in-parkinson-disease-and-parkinson-disease-with-dementialewy-body-dementia-quantitative-susceptibility-mapping-assessments/