ABSTRACT
Background: 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. Aim(s): To examine whether peripheral muscle weakness in post-Covid-19 patients is associated with changes in muscle echogenicity and thickness. Method(s): Post-Covid-19 patients with objectified muscle weakness (isometric quadriceps maximal voluntary contraction (MVC) <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. Result(s): 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). Conclusion(s): In a cohort of post-Covid-19 patients with peripheral muscle weakness, standardized muscle ultrasound investigations did not show any evidence for structural abnormalities.
ABSTRACT
Background: Muscle weakness is prevalent among post-Covid-19 patients, but longitudinal studies quantifying muscle strength following Covid-19 are lacking. Aim(s): To describe the course of quadriceps muscle strength over ~1,5 year following Covid-19. Method(s): A prospective analysis of 63 hospitalized (age 60+/-9y, 68% male) and 31 non-hospitalized (age 52+/-15y, 36% male) post-Covid-19 patients with persisting symptoms ('long covid') was performed. Isometric quadriceps maximal voluntary contraction (MVC) was evaluated using a computerized dynamometer at a knee angle of 60degree during 3 visits in hospitalized (89 [80-104], 215 [198-233], 434 [416-478] days after Covid-19) and non-hospitalized (138 [114-176], 282 [249-347], 540 [486-596] days after Covid-19) patients. MVC was expressed as percentage predicted and muscle weakness was defined as MVC <lower limits of normal. Result(s): Over the 3 visits, hospitalized patients had a MVC of 65+/-18, 70+/-17, and 68+/-16 %pred, and muscle weakness was present in 54, 49, 51% of cases, respectively. Similarly, non-hospitalized patients had a MVC of 70+/-16, 76+/-17, and 74+/-19 %pred, and a muscle weakness prevalence of 65, 52, and 52% was found. In both groups, MVC improved between visit 1 and 2 (p<0,05) whereas no change was observed between visit 2 and 3. The prevalence of muscle weakness in both groups did not change significantly. Conclusion(s): Quadriceps muscle strength modestly improves during the first 7-9 months following acute Covid-19 in both hospitalized and non-hospitalized 'long covid' patients. However, still half of the patients in both groups had long-term muscle weakness. Further investigation is needed into the aetiology of muscle weakness in post-Covid-19 patients.