Objective: To assess whether changes in hippocampal subfield volumes are associated with cognition or CSF β-amyloid 1–42 (Aβ42) levels in Parkinson’s Disease (PD).

Background: Hippocampal structures are atrophic in people with PD, even in early disease stages. Cross-sectional data showed that cognitive, but not Aβ42, status was associated with volumes of the CA1 and hippocampal-amygdaloid-transition-area (HATA) [1]. To the best of our knowledge, nothing is known about the longitudinal course of these associations.

Method: Twenty-nine non-demented patients with PD underwent imaging and neuropsychological assessments at an interval of 2.02±0.09 years. CSF was collected at baseline; pathological Aβ42 levels were defined as <600 pg/mL. Cognitive status was classified using the Montreal Cognitive Assessment [<26=mild cognitive impairment (PD-MCI)]. Hippocampal volumes were segmented into 12 subfields using FreeSurfer 6.0 and corrected for intracranial volume at each visit. Repeated measures analyses of covariance examined the relationship between each corrected hippocampal subfield, time, and either baseline cognitive or Aβ42 status as predictors, covarying for baseline disease duration. Change in corrected hippocampal volumes was correlated with neuropsychological change scores (Repeatable Battery for the Assessment of Neuropsychological Status, RBANS, cognitive index scores) between visits (follow-up–baseline).

Results: Of all patients, 11 (37.9%) were classified as PD-MCI. Regarding Aβ42 status, 16 (55.2%) patients had pathological levels. Only the CA3 region showed a significant interaction where patients with normal baseline Aβ42 levels (n=8) had reductions in CA3 volumes over time [F(1,27)=4.24, p=.045, partial η²=.15]; no other interactions or main effects were observed. Worsening of RBANS immediate memory performance was significantly correlated with volumetric decline in the granule cell layer of the dentate gyrus (GC-DG) and CA4 (.46≤r≤.56, p<0.01). Improvements in the visuospatial index were associated with volumetric reductions in GC-DG, CA4, and HATA (-.52≤r≤-.39, p<0.04), and the attention index with CA3 regions (r=-.39 p=.034).

Conclusion: Normal baseline Aβ42 levels were associated with more pronounced degeneration of the CA3 region. However, we could not detect an association of Aβ42 levels and volumes of CA1 or HATA, as hypothesized. Memory and certain hippocampal subfields may decline in parallel.

References: [1] Becker S, Granert O, Timmers M, et al. Association of Hippocampal Subfields, CSF Biomarkers, and Cognition in Patients With Parkinson Disease Without Dementia. Neurology. 2021;96(6):e904-e915. doi:10.1212/WNL.0000000000011224

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MDS Abstracts - https://www.mdsabstracts.org/abstract/association-between-changes-in-hippocampal-volumes-cognition-and-csf-markers-in-parkinsons-disease/