Quantitative assessment of muscle stiffness with acoustic radiation force impulse elastography after botulinum toxin A injection in children with cerebral palsy

Our objective in this study was to assess the changes in medial gastrocnemius muscle (GCM) stiffness after botulinum toxin A (BTA) injection in children with cerebral palsy (CP) by using acoustic radiation force impulse (ARFI) elastography and to research the usability of this technique in clinical practice. Twenty-four spastic lower extremities of 12 children with CP were assessed. BTA injection treatment was applied to the medial GCM. Muscle stiffness was measured with the ARFI technique before the procedure and a month after the procedure. The patients were assessed with the modified Ashworth scale (MAS) in the physiotherapy department at about the same time. Shear wave velocity (SWV) values and MAS scores before and after the treatment were compared. Mean SWV values were measured as 3.20 +/- 0.14 m/s before BTA and as 2.45 +/- 0.21 m/s after BTA, and the difference between them was found to be statistically significant (p < 0.001). Mean MAS score (2.33 +/- 0.70) after BTA decreased significantly when compared to the score before BTA (2.96 +/- 0.62) (p = 0.001). SWV values positively correlated with MAS scores (rho = 0.578, p = 0.003). The interobserver agreement expressed as interclass correlation coefficient (ICC) was 0.65 (95% CI 0.33-0.84, p < 0.001). ARFI elastography for identifying structural changes that occur in the spastic muscle after BTA injection in children with CP can yield more valuable information with combined use of MAS.