Quantifying Effect of Onabotulinum Toxin A on Passive Muscle Stiffness in Children with Cerebral Palsy Using Ultrasound Shear Wave Elastography

Objective A pilot study was conducted to longitudinally quantify effect of onabotulinum toxin A (BoNT-A) on passive muscle properties in children with cerebral palsy using ultrasound shear wave elastography. Design This was a prospective longitudinal cohort study. Results Between 1 and 3 mos post-BoNT-A, a significant improvement in the shear modulus of the lateral gastrocnemius was found at 10-degrees plantar flexion (PF) (-7.57 [-10.98, -5.07], P = 0.02) and 0-degrees PF (-14.74 [-18.21, -9.38], P = 0.03). There was a notable, but nonsignificant, difference in shear modulus at 20-degrees PF, 10-degrees PF, and 0-degrees PF between pre-BoNT-A and 1 mo post-BoNT-A. Pre-BoNT-A shear modulus was not significantly different from 3 mos post-BoNT-A at all foot positions. No significant differences in ankle passive range of motion or spasticity were found. Conclusion Despite no significant change in ankle range of motion or spasticity, shear wave elastography was able to detect a difference in lateral gastrocnemius passive muscle properties in children with cerebral palsy after BoNT-A injections. The difference in passive muscle properties resolved by 3 mos post-BoNT-A.