Shear wave elastography of the brachioradialis spastic muscle and its correlations with biceps brachialis and clinical scales.

[BACKGROUND] Shear wave elastography technique estimates biological tissue shear elastic modulus (μ[kPa]), which can be used as an objective, muscle-specific indicator of stiffness increase caused by spasticity. We measured both the brachioradialis and biceps brachialis μ in hemiparetic post-stroke patients (n = 11). The spastic arm was compared with the supposedly non-affected contralateral limb and correlated with Fugl-Meyer Assessment and Modified Ashworth Scales.

[METHODS] Shear elastic modulus was estimated using an Aixplorer V.9 ultrasound device with the elbow at full extension. Average shear elastic modulus t-test, effect sizes, correlation matrix, spider plots and factor analysis were used to check for differences between spastic and nonspastic sides and explore relationships among the variables.

[FINDINGS] Spastic brachioradialis μ (22.54 ± 11.59 kPa) and biceps brachialis (26.86 ± 12.07 kPa) were significantly greater than the non-spastic counterparts (13.13 ± 2.81 kPa, p = 0.031, η = 0.3846 for brachioradialis and 15.25 ± 5.00 kPa, p = 0.007, η = 0.5345 for biceps brachialis). Significant correlations were observed between the spastic brachioradialis and biceps μ and Modified Ashworth Scales, but no correlation with Fugl-Meyer Assessment.

[INTERPRETATION] Elastography can provide muscle-specific shear elastic modulus estimations of spastic brachioradialis and biceps brachialis, which are distinct from the nonspastic side. In some patients, there was no clear correspondence of the Fugl-Meyer Assessment functional scale with Modified Ashworth Scales and μ, suggesting that spasticity is not the only determinant of arm function. Additionally, shear wave elastography of brachioradialis and biceps brachialis muscles may guide the spasticity treatment, for instance, selecting the preferable candidate for botulinum toxin therapy.