• Na Wang, Liang Zhang, HuaGuang Yang, XiaoGuang Luo, and GuoGuang Fan.
• Department of Radiology, Huashan Hospital Fudan University, Shanghai, China.
• Eur Radiol. 2019 Sep 1; 29 (9): 4948-4956.

ObjectivesTo investigate the volumetric alterations of hippocampal subfields and identify which subfields contribute to mild cognitive impairment (MCI) in multiple system atrophy (MSA) and Parkinson's disease (PD).MethodsThirty MSA-MCI, 26 PD-MCI, and 30 healthy controls were administered cognitive assessment, along with hippocampal segmentation using FreeSurfer 6.0 after a 3-T MRI scan. Regression analyses were performed between the volumes of hippocampal subfields and cognitive variables.ResultsCompared with healthy controls, the volume of the hippocampal fissure was enlarged in PD-MCI patients, while left Cornu Ammonis (CA2-CA3), bilateral molecular layer, bilateral hippocampus-amygdala transition area, right subiculum, right CA1, right presubiculum, right parasubiculum, and bilateral whole hippocampus were reduced in the MSA-MCI group. Moreover, volumetric reductions of the bilateral hippocampal tail, bilateral CA1, bilateral presubiculum, bilateral molecular layer, left CA2-CA3, left hippocampus-amygdala transition area, right parasubiculum, and bilateral whole hippocampus were found in MSA-MCI relative to the PD-MCI group. The volumes of the left CA2-CA3 (B = - 11.34, p = 0.006) and left parasubiculum (B = 4.63, p = 0.01) were respectively correlated with language and abstraction functions. The volumes of the left fimbria (B = 6.99, p = 0.002) and left hippocampus-amygdala transition area (B = 2.28, p = 0.009) were correlated with visuospatial/executive function.ConclusionsThe MSA-MCI patients showed more widespread impairment of hippocampal subfields compared with the PD-MCI group, involving trisynaptic loop and amygdala-hippocampus interactions. The alteration of CA, hippocampus-amygdala transition area, and fimbria still requires further comparison between the two patient groups.Key Points• The atrophy patterns of hippocampal subfields differed between MSA and PD patients. • MSA has widespread change in trisynaptic loop and amygdala-hippocampus interactions. • The atrophy patterns may help to understand the differences of cognitive impairment in MSA and PD.

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