Hippocampal subfield volumes in COVID‐19: a preliminary multicenter study using 7T MRI

Abstract Background Hippocampal formation atrophy is a well‐established imaging biomarker of several neurological diseases, including Alzheimer’s disease, temporal lobe epilepsy, and schizophrenia. The hippocampus is divided into subfields that have different functions and vary in sensitivity to different diseases. This study investigates the potential interaction between COVID‐19 and the various hippocampus subfields, which may shed light on the long‐term neurological consequences of the virus. Method We obtained high‐resolution T1‐weighted (T1w) and T2‐weighted (T2w) MRI images using 7T scanners located at three sites in two countries: Pittsburgh (n = 14) and Texas (San Antonio and Houston) (n = 40) in the USA, and Nottingham, UK (n = 33). We evaluated the hippocampus subfields using the ASHS package [1‐3]. Imaging sets of 51 subjects with minimal or no manual segmentation corrections (Figures 1 and 2) were included in the analysis. We conducted T‐tests with Bonferroni correction, adjusting for age and intracranial volume to identify the differences in hippocampus subfield volumes across groups. Result Participants who needed admission into the ICU due to Covid‐19 showed a significantly lower (p‐value = 0.0034) left CA1 volume compared to participants who did not require ICU (Figure 3). In addition, several other non‐significant trends were observed. Conclusion Our preliminary findings suggest that Covid‐19 may impact the hippocampus, particularly in patients who required intensive care. However, the study ‐ as of to date ‐ has a small sample size and lacks a comparison group with patients who were admitted into ICU for acute illnesses other than Covid‐19. Additionally, longitudinal data is needed to track the long‐term effects of the disease on the hippocampal subfields. Funding : NIH R56AG074467, R01MH111265 and R01AG063525 References : 1. Berron et al. Neuroimage 2017 2. Yushkevich et al. Human Brain Mapping 2015 3. Santini et al. Neuroimage: clinical 2021