Thapaliya, Kiran, Marshall-Gradisnik, Sonya, Eaton-Fitch, Natalie et al. · PloS one · 2025 · DOI
Researchers used advanced brain imaging to compare a part of the brain called the hippocampus in long COVID patients, ME/CFS patients, and healthy people. They found that certain areas of the hippocampus were larger in both patient groups compared to healthy controls, and these size differences were linked to how severe symptoms like fatigue, pain, and memory problems were. This suggests that changes in brain structure might explain some of the cognitive difficulties these patients experience.
This study provides neurobiological evidence that brain structural changes in the hippocampus may underlie the cognitive and memory impairments reported by ME/CFS and long COVID patients. The findings suggest these two conditions share similar pathophysiological mechanisms, which could advance understanding of disease mechanisms and potentially inform treatment strategies targeting cognitive dysfunction.
This study does not establish causation—larger hippocampal volumes could be a consequence of illness rather than a cause of cognitive symptoms. The cross-sectional design cannot determine whether these brain changes preceded symptom onset or developed afterward. The study also cannot explain the mechanism by which volume changes produce cognitive impairment.
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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