Reduced TMS-evoked EEG oscillatory activity in cortical motor regions in patients with post-COVID fatigue

Abstract

ObjectivePersistent fatigue is a major symptom of the so-called ’long-COVID syndrome’, but the pathophysiological processes that cause it remain unclear.We hypothesized that fatigue after COVID-19 would be associated with altered cortical activity in premotor and motor regions. MethodsWe used transcranial magnetic stimulation combined with EEG (TMS-EEG) to explore the neural oscillatory activity of the left primary motor area (l-M1) and supplementary motor area (SMA) in a group of sixteen post-COVID patients complaining of lingering fatigue as compared to a sample of age-matched healthy controls. Perceived fatigue was assessed with the Fatigue Severity Scale (FSS) and Fatigue Rating Scale (FRS). ResultsPost-COVID patients showed a remarkable reduction of beta frequency in both areas. Correlation analysis exploring linear relation between neurophysiological and clinical measures revealed a significant inverse correlation between the individual level of beta oscillations evoked by TMS of SMA with the individual scores in the FRS (r(15) = -0.596; p = 0.012). ConclusionsPost-COVID fatigue is associated with a reduction of TMS-evoked beta oscillatory activity in SMA. SignificanceTMS-EEG could be used to identify early alterations of cortical oscillatory activity that could be related to the COVID impact in central fatigue.