Myopathic changes in patients with long-term fatigue after COVID-19.

Abstract Objective To investigate the peripheral nerve and muscle function electrophysiologically in patients with persistent neuromuscular symptoms following Coronavirus disease 2019 (COVID-19). Methods Twenty consecutive patients from a Long-term COVID-19 Clinic referred to electrophysiological examination with the suspicion of mono- or polyneuropathy were included. Examinations were performed from 77 to 255 (median: 216) days after acute COVID-19. None of the patients had received treatment at the intensive care unit. Of these, 10 patients were not even hospitalized. Conventional nerve conduction studies (NCS) and quantitative electromyography (qEMG) findings from three muscles were compared with 20 age- and sex-matched healthy controls. Results qEMG showed myopathic changes in one or more muscles in 11 patients (55%). Motor unit potential duration was shorter in patients compared to healthy controls in biceps brachii (10.02±0.28 vs 11.75 ± 0.21), vastus medialis (10.86±0.37 vs 12.52±0.19) and anterior tibial (11.76±0.31 vs 13.26±0.21) muscles. All patients with myopathic qEMG reported about physical fatigue and 8 patients about myalgia while 3 patients without myopathic changes complained about physical fatigue. Conclusions Long-term COVID-19 does not cause large fibre neuropathy, but myopathic changes are seen. Significance Myopathy may be an important cause of physical fatigue in long-term COVID-19 even in non-hospitalized patients.