title: Associations of hippocampal subfields in the progression of cognitive decline related to Parkinson's disease.
abstract: Hippocampal atrophy has been associated with mild cognitive impairment (MCI) in Parkinson's disease (PD). However, literature on how hippocampal atrophy affects the pathophysiology of cognitive impairment in PD has been limited. Previous studies assessed the hippocampus as an entire entity instead of their individual subregions. We studied the progression of cognitive status in PD subjects over 18 in relation to hippocampal subfields atrophy.
  
  
  
  65 PD subjects were included. Using the MDS task force criteria, PD subjects were classified as either having no cognitive impairment (PD-NCI) or PD-MCI. We extended the study by investigating the hippocampal subfields atrophy patterns in those who converted from PD-NCI to PD-MCI (PD-converters) compared to those who remained cognitively stable (PD-stable) over 18 months. Freesurfer 6.0 was used to perform the automated segmentation of the hippocampus into thirteen subregions.
  
  
  
  PD-MCI showed lower baseline volumes in the left fimbria, right CA1, and right HATA; and lower global cognition scores compared to PD-NCI. Baseline right CA1 was also correlated with baseline attention. Over 18 months, decline in volumes of CA2-3 and episodic memory were also seen in PD-converters compared to PD-stable. Baseline volumes of GC-DG, right CA4, left parasubiculum, and left HATA were predictive of the conversion from PD-NCI to PD-MCI.
  
  
  
  The findings from this study add to the anatomical knowledge of hippocampal subregions in PD, allowing us to understand the unique functional contribution of each subfield. Structural changes in the hippocampus subfields could be early biomarkers to detect cognitive impairment in PD.
authors.affiliation: Department of Neurology, National Neuroscience Institute, Singapore.
authors.forename: Heidi
authors.initials: H
authors.lastname: Foo
authors.affiliation: Department of Psychiatry, University of Cambridge, United Kingdom.
authors.forename: Elijah
authors.initials: E
authors.lastname: Mak
authors.affiliation: Department of Neurology, National Neuroscience Institute, Singapore.
authors.forename: Russell Jude
authors.initials: RJ
authors.lastname: Chander
authors.affiliation: Department of Neurology, National Neuroscience Institute, Singapore; Department of Medicine, University of Sydney, Australia.
authors.forename: Aloysius
authors.initials: A
authors.lastname: Ng
authors.affiliation: Department of Neurology, National Neuroscience Institute, Singapore; Duke-NUS, Graduate Medical School, Singapore.
authors.forename: Wing Lok
authors.initials: WL
authors.lastname: Au
authors.affiliation: Duke-NUS, Graduate Medical School, Singapore; Department of Neuroradiology, National Neuroscience Institute, Singapore.
authors.forename: Yih Yian
authors.initials: YY
authors.lastname: Sitoh
authors.affiliation: Department of Neurology, National Neuroscience Institute, Singapore; Duke-NUS, Graduate Medical School, Singapore.
authors.forename: Louis C S
authors.initials: LC
authors.lastname: Tan
authors.affiliation: Department of Neurology, National Neuroscience Institute, Singapore; Duke-NUS, Graduate Medical School, Singapore.
authors.forename: Nagaendran
authors.initials: N
authors.lastname: Kandiah
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003072:Cognition Disorders / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology*; D005260:Female; D007839:Functional Laterality; D006624:Hippocampus / Q000000981:diagnostic imaging / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D008609:Mental Status Schedule; D008875:Middle Aged; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000150:complications*
keywords: CA, cornu ammonis; Cognitive impairment; HATA, hippocampal-amygdaloid transition region; Hippocampal atrophy; Parkinson's disease; Volumetry