Ultrasound strain elastography in assessment of chronic post-stroke spasticity of biceps brachii muscle

The assessment of post-stroke muscle spasticity is challenging due to lack of a gold standard. The Modified Ashworth Scale (MAS), commonly used in evaluating spasticity is neither quantitative or reliable. We have reported the use of ultrasound strain imaging (USI) to assess rigid biceps brachii muscle (BBM) in Parkinson's disease [1]. We have now extended the application of USI to determining spastic BBM in stroke survivors. We performed USI in 8 healthy volunteers and 8 subjects with chronic post-stroke spasticity of the upper limb. BBM axial deformation was produced by external compression using a sandbag (1.0 kg) tied transducer [2]. Lengthening and shortening of BBM was generated by manual passive elbow extension (from 90° to 0°) and flexion (from 0° to 90°), respectively. We used offline 2-D speckle tracking to estimate axial strain (representing BBM stiffness) as well as lateral strain and tissue velocity (representing BBM dynamic displacement). ANOVA was used to assess statistically significant differences in USI between healthy controls and both non-spastic and spastic BBMs in stroke survivors. The Bonferroni correction was then applied to test the difference in the paired groups (healthy vs non-spastic; non-spastic vs spastic; and healthy vs non-spastic). We observed significant differences in USI parameters between healthy and spastic BBM, and between non-spastic and spastic BBM (all p <;0.01). Our results suggest that USI seems to be feasible in determining chronic post-stroke spasticity of the BBM (MSA>1
⁺
).