Post-Covid-19 peripheral muscle weakness is not associated with muscle ultrasound echogenicity or muscle thickness

Abstract

<b>Background:</b> Peripheral muscle weakness has been observed in the post-acute phase of Covid-19 patients. However, it is unknown whether Covid-19 is associated with structural changes in skeletal muscles, like atrophy, inflammation or fibrosis. <b>Aim:</b> To examine whether peripheral muscle weakness in post-Covid-19 patients is associated with changes in muscle echogenicity and thickness. <b>Methods:</b> Post-Covid-19 patients with objectified muscle weakness (isometric quadriceps maximal voluntary contraction (MVC) &lt;lower limit of normal) at ~6 months after infection were cross-sectionally studied. Vastus lateralis (VL), rectus femoris (RF), tibialis anterior (TA) and gastrocnemius (GCM) were examined unilaterally using quantitative muscle ultrasound. Standardized scores (z-scores) of 2 were defined as limits of normal. <b>Results:</b> Fourteen post-Covid-19 patients were included (age 47±15y, 64% male, BMI 26±3 kg/m2). Median z-scores were determined for muscle thickness and echogenicity of VL (-1.0 [-1.3- -0.2], 0 [-0.2-1.1]), RF (-0.2 [-1.4-0.1], -0.2 [-1.3-0.6]), TA (0.1 [-0.8-0.6], 0.5 [-0.4-1.0]), and GCM (0.8 [0.1-1.0], -0.7 [-1.3- -0.1]), respectively. Thirteen patients had values within the limits of normal. One patient showed increased echogenicity of VL, but normal values for other muscles. There were significant moderate-to-strong correlations between MVC and muscle thickness of VL (r=0.670), RF (r=0.812), TA (r=0.593) and GCM (r=0.579), and between MVC and echogenicity of GCM (r=-0.588). <b>Conclusions:</b> In a cohort of post-Covid-19 patients with peripheral muscle weakness, standardized muscle ultrasound investigations did not show any evidence for structural abnormalities.