The utility of shear wave elastography in the evaluation of muscle stiffness in patients with cerebral palsy after botulinum toxin A injection.

[PURPOSE] The first aim of this study was to evaluate changes in the stiffness of the medial gastrocnemius muscle (GM) after a botulinum toxin A (BoNT-A) injection in children with cerebral palsy (CP) using shear wave elastography (SWE). We also wanted to investigate the usability of SWE for evaluating spasticity in a clinical setting. The second aim of this study was to show how treatment of the gastrocnemius muscle spasticity caused a change in the elasticity of the anterior tibial (TA) muscle.

[METHODS] Twenty-four pediatric patients diagnosed with a spastic type of CP, who were scheduled to receive a BoNT-A injection in the gastrocnemius muscle, were included in the study. There was a total of 43 lower extremities to evaluate, and muscle stiffness was measured before the injection and a month post injection using SWE. The physiatrist evaluated muscle spasticity using the Modified Ashworth Scale (MAS) and the Modified Tardieu Scale at about the same time.

[RESULTS] SWE values of the GM (pre-BoNT-A: 45.9 ± 6.5 kPa, post-BoNT-A: 25.0 ± 5.7 kPa) decreased significantly post BoNT-A injection (P < 0.01). SWE measurements of the GM had positive correlations with MAS, V1X, V3X, and R2-R1 (P < 0.01); and negative correlations with R2 and R1 (P < 0.05). SWE values of the TA muscle (pre: 36.9 ± 7.9 kPa, post: 28.4 ± 5.2 kPa) decreased significantly (P < 0.01).

[CONCLUSION] Quantitative measurement of muscle stiffness using SWE may provide important information for the evaluation of spasticity and treatment efficiency in pediatric CP patients.