Enlarged Brain Structure May Be Behind Long COVID Brain Fog

A new study published in Molecular Psychiatry has found that people with long COVID may have an enlarged choroid plexus — a small but important structure in the brain that helps produce cerebrospinal fluid and regulate immune activity. Researchers observed that patients with post-COVID condition (PCC) had significantly larger choroid plexus (ChP) volumes compared to healthy individuals, more than a year after infection.

Crucially, those with the greatest ChP enlargement also showed the most severe cognitive problems, especially in areas like attention, memory, and executive function.

The findings suggest that inflammation or immune dysregulation in this brain region may contribute to the lingering neurological symptoms many long COVID patients report. This structural change was also linked to alterations in brain connectivity and white matter integrity, pointing to a possible mechanism behind persistent brain fog. As more studies explore immune-brain interactions in long COVID, the choroid plexus may emerge as a key target for future diagnostics and treatments, especially for those with overlapping neuroimmune or autoimmune conditions.

Citation

Diez-Cirarda, M., Yus-Fuertes, M., Delgado-Alonso, C. et al. Choroid plexus volume is enlarged in long COVID and associated with cognitive and brain changes. Mol Psychiatry 30, 2821–2830 (2025). https://doi.org/10.1038/s41380-024-02886-x