Kimura, Yukio, Sato, Wakiro, Shigemoto, Yoko et al. · Frontiers in neurology · 2026 · DOI
Researchers used high-resolution brain imaging to examine a small part of the brain called the amygdala in people with long COVID, ME/CFS, and healthy controls. They observed some differences in the size of specific amygdala regions between groups and found associations between these brain measurements and certain immune markers, but these findings were preliminary and did not remain significant after statistical correction for multiple comparisons. The study is exploratory and does not yet establish why these brain differences occur or whether they are clinically meaningful.
By analogy to long COVID findings, amygdala structural variation may be relevant to understanding neurobiological features in ME/CFS, particularly given the overlapping symptom profile and evidence of limbic-system involvement in both conditions. The exploratory associations between brain structure and specific immune markers (plasmablasts, autoantibodies) suggest potential relationships that could guide future mechanistic research. However, the preliminary nature of these findings means they should inform hypothesis development rather than clinical interpretation.
This study does not establish causation, disease-specific mechanisms, or between-group neuroanatomical differences (no findings survived multiple-testing correction). The cross-sectional design does not determine whether observed amygdala variation precedes symptom onset or results from disease processes. The small sample sizes and unknown case-definition quality limit generalisability and confidence in the stability of these findings across larger, independent populations.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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Primary citation
Kimura, Yukio, Sato, Wakiro, Shigemoto, Yoko, Kagaya, Risa, Hayakawa, Akihiko, Kumazawa, Yunosuke, et al. (2026). FreeSurfer-based amygdala subfield volumetry in long COVID and ME/CFS: clinical and immunological correlations.. Frontiers in neurology. https://doi.org/10.3389/fneur.2026.1913553
BibTeX
@article{mecfsatlas-kimura-2026-freesurfer-based,
author = {Kimura, Yukio and Sato, Wakiro and Shigemoto, Yoko and Kagaya, Risa and Hayakawa, Akihiko and Kumazawa, Yunosuke and Shin, Isu and Amano, Keiko and Yamamura, Takashi and Sato, Noriko},
title = {FreeSurfer-based amygdala subfield volumetry in long COVID and ME/CFS: clinical and immunological correlations.},
journal = {Frontiers in neurology},
year = {2026},
doi = {10.3389/fneur.2026.1913553},
note = {PubMed: 42819213},
url = {https://www.mecfsatlas.com/evidence/kimura-2026-freesurfer-based},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-10-02. https://www.mecfsatlas.com/evidence/kimura-2026-freesurfer-based
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