Mapping brain changes in post-COVID-19 cognitive decline via FDG PET hypometabolism and EEG slowing

Cognitive decline is a common symptom of post-COVID-19 syndrome. However, the mechanisms underlying this deficit remain poorly understood. This study aims to investigate the relationship between brain metabolic and neurophysiological alteration patterns in patients with persistent subjective cognitive decline after mild COVID-19 using joint FDG-PET and EEG analyses. The study was conducted on 28 post-COVID-19 patients with cognitive decline, who underwent comprehensive clinical evaluation including cognitive testing, FDG-PET imaging, and EEG acquisition. Voxelwise statistical analysis of PET images was performed by comparing post-COVID-19 patients with healthy controls (p-voxel < 0.005 uncorrected, p-cluster < 0.005 FWE-corrected, K > 599 voxels). EEG spectral powers were extracted and compared with age and sex-matched controls. The results showed significant hypometabolism in the bilateral frontal, temporal, and parietal lobes, as well as in the left occipital lobe, along with predominantly frontal EEG slowing in post-COVID-19 patients compared to healthy controls. In particular, the EEG alterations were characterized by a significant increase in relative power in the delta and theta bands, accompanied by a marked reduction in alpha band power in the frontal, temporal, and central regions. The observed PET hypometabolism and EEG slowing patterns in anterior brain regions, may help to elucidate the pathophysiological mechanisms underlying cognitive decline in post-COVID-19 patients.