Ultrasound Elastography to Assess Botulinum Toxin A Treatment for Post-stroke Spasticity: A Feasibility Study

The aim of the study was to evaluate the feasibility of using ultrasound elastography to assess the effect of botulinum toxin A (BoNT-A) treatment on post-stroke spasticity of the upper limb. In this prospective study, we performed ultrasound elastography (strain imaging and acoustic radiation force impulse-based shear wave elastography) of the spastic biceps brachii muscle in seven patients (five men and two women, mean age: 45y) who underwent BoNT-A injection treatment for post-stroke spasticity of the upper limb. We measured ultrasound elasticity parameters including axial strain ratio (SR) (SR = muscle strain/reference strain), longitudinal SR and shear wave velocity of the biceps muscle immediately before and 17-30 d (mean: 22 d) after BoNT-A injection. Statistical analyses included a two-tailed paired t-test to examine the difference in ultrasound elasticity parameters of bilateral biceps muscles before and after BoNT-A treatment and a Spearman rank correlation coefficient (r_s) to analyze the correlation of ultrasound elasticity parameters to clinical assessment with the Modified Ashworth Scale (MAS) and Tardieu Scale (TS). The difference in ultrasound elasticity parameters before and after BoNT-A treatment was significant (p < 0.05) in the treated spastic muscle. The correlation of ultrasound elasticity parameters with MAS and the angle of catch and range of motion in TS were also significant (r_s = 0.55-0.95, p < 0.05). Our results suggest that ultrasound elastography is feasible in assessment of the effectiveness of BoNT-A treatment for post-stroke spasticity of the upper limb.