Alzheimer's Imaging Consortium

Area of Science:

• Neuroimaging
• Neurology
• Infectious Diseases

Background:

• Post-COVID cognitive dysfunction is a significant extrapulmonary complication of COVID-19.
• Neuroinflammation and reduced hippocampal neurogenesis have been observed in COVID-19 cases.
• High-resolution 7T MRI offers detailed assessment of hippocampal subfields for early disease detection.

Purpose of the Study:

• To explore hippocampal subfield volumes using 7T MRI in Alzheimer's disease (AD) and post-COVID-19 conditions.
• To examine potential similarities in brain degeneration between AD and post-COVID conditions.
• To assess cognitive function using the Montreal Cognitive Assessment (MOCA) across study groups.

Main Methods:

• Analysis of hippocampal subfield volumes in four groups: AD patients (n=32), mild COVID-19 survivors (Cv, n=13), severe COVID-19 ICU survivors (ICU-Cv, n=9), and healthy controls (HC, n=29).
• Utilized high-resolution 7T MRI for detailed hippocampal subfield volumetry.
• Conducted cognitive assessments including MOCA within all participant groups.

Main Results:

• Alzheimer's disease patients showed significant atrophy in multiple hippocampal subfields (ERC, DG, Tail, CA) compared to HC and Cv.
• Severe COVID-19 survivors (ICU-Cv) exhibited reduced entorhinal cortex (ERC) volume compared to HC, while mild COVID-19 survivors (Cv) showed no differences.
• AD patients had smaller ERC and DG volumes than ICU-Cv. MOCA scores were lowest in AD, followed by ICU-Cv, then Cv and HC. ICU-Cv patients showed cognitive deficits compared to HC in specific domains.

Conclusions:

• The entorhinal cortex (ERC), crucial for memory and navigation, is susceptible in early AD and shows selective atrophy in severe COVID-19 survivors.
• Severe COVID-19 may induce targeted neurodegeneration via mechanisms like hypoperfusion, inflammation, or metabolic stress, potentially overlapping with AD.
• Findings highlight distinct yet potentially convergent neurodegenerative pathways in Alzheimer's disease and severe post-COVID-19 conditions.