Quantifying passive muscle stiffness in children with and without cerebral palsy using ultrasound shear wave
Joline E Brandenburg1,2,3, Sarah F Eby4, Pengfei Song5
1Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine, Rochester, MN, USA.
Insights
Children with cerebral palsy (CP) exhibit greater passive muscle stiffness than typically developing children. This difference diminishes when muscle stiffness is normalized, suggesting similar stretch responses in both groups.
Area of Science:
- Biomedical Engineering
- Pediatric Physical Therapy
- Musculoskeletal Ultrasound
Background:
- Children with cerebral palsy (CP) often experience altered muscle properties.
- Accurate measurement of passive muscle stiffness is crucial for understanding CP-related motor impairments.
- Ultrasound shear wave elastography (SWE) offers a novel, non-invasive method to assess muscle stiffness.
Purpose of the Study:
- To compare passive muscle stiffness between children with CP and typically developing children.
- To utilize ultrasound shear wave elastography (SWE) for objective stiffness measurements.
- To investigate muscle stiffness at varying degrees of passive stretch.
Main Methods:
- A prospective study involving 13 children with CP and 13 typically developing children.
- Ultrasound shear wave elastography (SWE) was used to measure the shear modulus (passive muscle stiffness) of the lateral gastrocnemius.
- Measurements were taken at three plantar flexion angles: 20°, 10°, and 0°.
Main Results:
- Children with CP demonstrated significantly higher shear modulus values across all tested foot positions (p<0.050).
- When normalized to individual baseline values, no significant differences in shear modulus were observed between the CP and typically developing groups.
- This suggests that while absolute stiffness differs, the relative response to stretch may be similar.
Conclusions:
- Passive muscle stiffness, independent of spasticity, is elevated in children with CP at slack and stretched muscle states.
- Normalized shear modulus data indicate comparable muscle responses to passive stretch in both groups.
- Future research will explore the impact of treatments like botulinum toxin on passive muscle properties in CP.
Aim:
The aim of this study was to compare passive muscle stiffness in children with cerebral palsy (CP) and children with typical development using a novel ultrasound technique: ultrasound shear wave elastography (SWE).
Method:
We conducted a prospective study of 13 children with CP (six females and seven males, median age 5y 1mo [interquartile range 4y 4mo-7y 8mo]) and 13 children with typical development (six females and seven males, median age 5y 3mo [interquartile range 4y 4mo-9y 4mo]). Demographic information and physical exam measurements were obtained in addition to shear modulus measurements (passive muscle stiffness) of the lateral gastrocnemius muscle at 20° plantar flexion, 10° plantar flexion, and 0° plantar flexion using SWE.
Results:
Children with CP had significantly greater shear modulus measurements at all three foot positions (p<0.050). When the shear modulus values were normalized to the baseline value for each child, there was no significant difference between the two groups.
Interpretation:
Passive muscle stiffness, measured without the influence of spasticity, is greater in children with CP than in children with typical development when a muscle is at slack and at stretch. When shear modulus was normalized, the results indicate that muscle in children in both groups responds similarly to passive stretch. Further work includes evaluating effect of botulinum toxin on passive muscle properties.
