Quantification of muscle morphology and stiffness in spastic hemiplegic cerebral palsy versus typically developing controls using magnetic resonance elastography.

[BACKGROUND] Increased muscle stiffness is common in cerebral palsy, but accurate and reliable methods for quantitative assessment are not established for cerebral palsy. Magnetic resonance elastography provides a robust approach to mapping skeletal muscle properties. This study aimed to assess muscle morphology and stiffness in the gastrocnemius-soleus complex in children with hemiplegic cerebral palsy, comparing more affected and less affected sides, and to legs of typically developing children.

[METHODS] Eleven children (age 11.5 ± 4.1 years) with spastic hemiplegic cerebral palsy (Gross Motor Function Classification System levels I/II; no botulinum toxin injections within 6 months) and fifteen typically developing children (age 13.1 ± 4.5 years) were prospectively enrolled. Magnetic resonance elastography measured both legs in participants with cerebral palsy and the dominant leg in controls. Additional imaging assessed muscle volume, cross-sectional area, and contractile to non-contractile tissue ratio. Normalized stiffness and anatomical features were compared between groups. Pearson correlations evaluated associations with age and between imaging measures.

[FINDINGS] Normalized stiffness in soleus was significantly higher in the more affected leg in unilateral cerebral palsy than the less affected leg (471 vs 328 Pa/cm, p = 0.010) and the contractile tissue ratio also differed significantly (7.44 vs 10.25, p = 0.002). Gastrocnemius and soleus cross-sectional areas were reduced in the more affected side relative to controls, more markedly in soleus. Soleus stiffness showed significant positive correlations with age.

[INTERPRETATION] Results suggest increased stiffness and reduced contractile tissue in the soleus of the more affected leg in cerebral palsy, supporting the utility of magnetic resonance elastography in characterizing muscle pathology.