Shear wave elastography characterizes passive and active mechanical properties of biceps brachii muscle in vivo

Characterization of Muscle Weakness Due to Myasthenia Gravis Using Shear Wave Elastography

“…Compared to healthy participants [ 13 ], the shear elastic modulus of BB during rest was 2.1 times higher for MG patients ( p < 0.001) and elbow angle had a significant effect ( p < 0.001) without interaction ( p > 0.05).…”

“…Eleven patients (4 males; 1 left-handed; age: 47.64 ± 15.74 years; body mass index (BMI): 26.42 ± 4.19 kg/m 2 ; body weight: 74.73 ± 13.19 kg; body height: 168.18 ± 9.51 cm; all data given as mean ± standard deviation) diagnosed with MG participated in the present study. Data collected from 14 participants (7 males; all right-handed; age: 28.07 ± 5.06 years; BMI: 24.24 ± 3.78 kg/m 2 ; body weight: 77.21 ± 17.37 kg; body height: 177.71 ± 7.53 cm) in identical conditions were used for comparing the present results with a healthy population (a comprehensive characterization of the healthy cohort can be found elsewhere [ 13 ]). Patients with different characteristics regarding antibody specificity, thymus pathology, treatment options and muscle weakness were included ( Table 1 ).…”

“…A previous study validated that the shear wave speed measured in longitudinal muscle orientation provides a measure of local muscle stiffness [ 10 ]. Furthermore, SWE was shown to represent both passive [ 11 , 12 ] and active muscle mechanics in vivo [ 13 , 14 , 15 ]. In particular, these studies revealed the potential of SWE in muscle characterization by demonstrating that shear wave speed increases with increasing muscle length in passive condition (i.e., in a relaxed state without voluntary contraction) [ 11 , 12 , 13 ] and that shear wave speed increases with contraction intensity during isometric contractions [ 13 , 14 , 15 ].…”

“…Furthermore, SWE was shown to represent both passive [ 11 , 12 ] and active muscle mechanics in vivo [ 13 , 14 , 15 ]. In particular, these studies revealed the potential of SWE in muscle characterization by demonstrating that shear wave speed increases with increasing muscle length in passive condition (i.e., in a relaxed state without voluntary contraction) [ 11 , 12 , 13 ] and that shear wave speed increases with contraction intensity during isometric contractions [ 13 , 14 , 15 ]. A recent study [ 16 ] has argued that these relationships were established assuming unloaded condition for muscles and the increase in shear wave speed is not only attributed to an increase in muscle stiffness (shear elastic modulus) but may also be more dominantly due to an increase in tensile loading conditions of the muscle.…”

“…Consequently, the purpose of this study was to characterize the mechanical properties of muscles affected by MG described by their local muscle stiffness in both passive (i.e., rest) and active conditions (i.e., contraction with different force levels). By comparing the data with the previous work on healthy muscles using the same experimental setup [ 13 ], we aimed to determine the mechanical adaptation of muscles in MG. Therefore, we hypothesized that (i) passive muscle stiffness increases with increasing muscle length, muscle stiffness in active state (ii) increases with increasing contraction intensity, (iii) shows a length-dependent characteristic for MG patients, and (iv) the muscle weakness associated with MG leads to alterations in both passive and active muscle mechanics compared to healthy muscle.…”