Neurophysiology and muscle histopathology in ICU-acquired muscle weakness: Lessons learned from COVID-19.

Objective: To describe different electrophysiological, histopathological, and ultrastructural patterns of muscle pathology in COVID-19-associated intensive care unit acquired weakness (ICUAW) and raise the question of whether COVID-19-associated critical illness myopathy (CIM) is a distinct entity or is similar to CIM of other causes. Methods: A series of three patients with COVID-19-associated ICUAW were presented.Clinical examination, electrophysiological testing, and muscle pathology with light and electron microscopy were reported systematically. Results: All three patients were clinically affected with severe proximal and distal weakness of upper and lower extremities, increased plasma levels of muscle enzymes, and had myopathic electromyography. Furthermore, in two patients, electrophysiological signs of inflammatory myopathy with profuse denervation activity were present. Muscle pathologies were prominent but very diverse. One patient had signs of CIM, another showed severe inflammatory myopathy, and the main finding in the third patient was mitochondrial changes. Conclusion: Although the three cases showed similar clinical and electrophysiological patterns, muscle pathology revealed distinct underlying features. This spectrum of muscle disease among patients with severe COVID-19 includes CIM, autoimmune response to the COVID-19 infection, and mitochondrial dysfunction. Significance: Electrophysiology and histopathology complement each other and are important for determining the etiology, as well as guiding treatment and prognosis.