European journal of nuclear medicine and molecular imaging
July 15, 2026 Ā· via Europe PMC
Using CA1 rather than the whole hippocampus to capture tau-PET Braak stage II.
Aumont E, Trudel L, Hall BJ, +20 more, Rosa-Neto P.
AI summary ā for doctors, generated from the abstract only
A CA1-specific region of interest staged early Braak II tau PET more consistently than whole hippocampus.
What was studied
Cross-sectional and longitudinal analysis of TRIAD (N=456) and ADNI (N=497) tau-PET cohorts.
Key findings
- Early tau signal localized to anterior CA1
- Whole-hippocampus measures were affected by choroid plexus off-target signal
- CA1 staging gave fewer discordant classifications and stage regressions
Clinical relevance
Improves early AD staging and trial selection.
Who should care
Limitations
Limited by PET resolution.
Consider CA1-based quantification for early tau staging.
This is an AI-generated summary of the published abstract, not a clinical recommendation. It may not reflect the full text or subsequent updates ā verify against the original source before acting on it.
Abstract
Purpose
Tau-PET enables in-vivo staging of Alzheimer disease (AD) pathology, including early Braak stage II involvement of the hippocampus. Conventional whole-hippocampus definitions combine heterogeneous subfields and are susceptible to off-target signal that varies across tracers, limiting sensitivity, specificity, and longitudinal interpretability of early tau accumulation.
Methods
Cross-sectional and longitudinal analyses were conducted in the TRIAD (Nā=ā456) and the ADNI (Nā=ā497) observational cohorts with tau-PET with [18F]MK-6240 or [18F]flortaucipir and structural MRI. A CA1-specific Braak stage II region of interest was compared with a whole-hippocampus approach. Outcomes included Braak stage concordance, longitudinal stability, tau-PET progression, and biological plausibility assessed by amyloid-PET burden and extrahippocampal tau signal.
Results
Spatial analyses localised early hippocampal tau-PET signal predominantly to the anterior CA1. Whole-hippocampus measures were more frequently influenced by off-target signal consistent with choroid plexus contamination. Participants classified as CA1-based Braak stage II showed higher amyloid-PET burden, more consistent tau accumulation in the Braak stage III region, and more stable longitudinal progression. CA1-based staging yielded fewer discordant classifications and fewer stage regressions at follow-up.
Conclusion
CA1-specific tau-PET quantification improves biological plausibility and longitudinal consistency of Braak stage II classification by targeting the hippocampal subfield most vulnerable to early tau pathology and mitigating off-target contamination. CA1-based Braak stage II participants showed greater coherence with the biological framework of AD than those staged using the whole hippocampus. Applicable to available PET resolution, this approach may enhance characterisation of early AD and support participant selection in trials targeting preclinical tau accumulation.
DOI
10.1007/s00259-026-08074-z
PMID
42448890
Research metadata (titles, abstracts, authors, publication dates) is sourced from Europe PMC, which aggregates content from PubMed/MEDLINE, PubMed Central, and other providers under the U.S. National Library of Medicine (NLM/NCBI). NLM does not claim copyright on abstracts; the original journal publishers or authors may hold rights to the full articles. AI-generated summaries are derived only from the abstract, never the full text, and are always labeled as AI-generated.
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