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Clinical Trial
. 2021 Aug;132(8):1974-1981.
doi: 10.1016/j.clinph.2021.04.009. Epub 2021 May 7.

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

J Agergaard  1 , S Leth  2 , T H Pedersen  3 , T Harbo  4 , J U Blicher  5 , P Karlsson  6 , L Østergaard  1 , H Andersen  4 , H Tankisi  7
Affiliations
Clinical Trial

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

J Agergaard et al. Clin Neurophysiol. 2021 Aug.

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.

Keywords: Long-term COVID-19 illness; Myopathy; Physical fatigue; Polyneuropathy; Quantitative electromyography; SARS-COV-2.

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Conflict of interest statement

Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
Quantitative electromyography of the biceps brachii muscle in a healthy control (A) and in a patient with myopathic changes (B). There are myopathic motor unit potentials with decreased amplitude and short duration in the patient and normal motor unit potentials in the healthy control.
Fig. 2
Fig. 2
Dot plots of quantitative electromyography measurements in patients compared with healthy controls. All muscles were examined in all healthy subjects. In patients, motor unit potential (MUP) analysis was performed in all patients in biceps brachii while in vastus medialis 17 and in anterior tibial muscle in 18 patients. (A) MUP duration and (B) MUP amplitude. Solid lines are the mean of the group, dashed lines are 95% confidence limits for the control group. Asterisks indicate level of significance (*** = p < 0.001, **** = p < 0.0001). MUP: Motor unit potential.
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