Non-Hospitalized Patients With Post-COVID Condition and Myopathic Electromyography Findings Show no Difference in Symptom Severity and Clinical Manifestations Compared to Those Without Myopathic Findings.

Abstract

Introduction: The COVID-19 pandemic has resulted in a post-infectious syndrome designated as long-COVID or post-COVID condition (PCC) that presents with numerous symptoms including fatigue and myalgias. This study evaluated myopathic electromyography (EMG) findings in non-hospitalized PCC patients in relation to symptom severity, quality of life (QoL), and physical function.

Methods: Twenty-nine PCC patients with persistent symptoms ≥ 3 months after laboratory-confirmed SARS-CoV-2 infection, without hospitalization or comorbidities, were included. EMG, nerve conduction studies (NCS), and quantitative sensory testing (QST) were performed. Symptom severity was measured with visual analog scales, QoL with validated questionnaires, and physical function with the 6-min walk test, cardiopulmonary exercise testing, handgrip strength, and isokinetic dynamometry.

Results: Myopathic findings on EMG were present in 62% of PCC patients (n = 18). Symptom severity (muscle pain and fatigue) and QoL (physical function and fatigue) were similar between patients with and without myopathic EMG findings. The 6-min walk test (457 ± 81 vs. 459 ± 86 m) and peak VO₂ (29 ± 9 vs. 28 ± 6 mL/kg/min) were similar between patients with and without myopathic EMG findings. Handgrip strength (32 [29-43] vs. 33 [29-50] kg) and quadriceps muscle strength (136 [111-191] vs. 136 [114-184] Nm) were comparable between the groups. NCS and QST results were normal in all patients.

Discussion: Myopathic findings on EMG are common in PCC patients, but no significant differences in symptom severity, QoL, or physical function were found between those with and without myopathic EMG findings. Myopathic EMG changes in PCC patients should be interpreted with caution, considering the overall clinical context.