Morphological Medial Gastrocnemius Muscle Growth in Ambulant Children with Spastic Cerebral Palsy: A Prospective Longitudinal Study

Area of Science:

• Pediatric Orthopedics
• Neuromuscular Disorders
• Biomedical Engineering

Background:

• Muscle deficits are known in children with spastic cerebral palsy (SCP), but the impact of motor limitations on muscle growth is not well understood.
• Existing research relies on cross-sectional data, limiting insights into the developmental trajectory of muscle morphology in SCP.
• Longitudinal data is crucial for understanding how gross motor functional limitations influence muscle growth patterns over time.

Purpose of the Study:

• To prospectively model and compare the longitudinal muscle growth trajectories in children with spastic cerebral palsy (SCP) based on their Gross Motor Function Classification System (GMFCS) levels.
• To investigate the impact of GMFCS-level related motor limitations on muscle volume, cross-sectional area, and muscle length.
• To identify critical age periods for altered muscle growth in SCP.

Main Methods:

• A prospective longitudinal study involving 87 children with SCP (ages 6 months to 11 years, GMFCS levels I, II, III).
• Three-dimensional freehand ultrasound was used to measure medial gastrocnemius muscle volume (MV), cross-sectional area (CSA), and muscle belly length (ML) over a 2-year follow-up with at least 6-month intervals.
• Non-linear mixed-effects models were employed to compare muscle growth trajectories between GMFCS-I and GMFCS-II&III subgroups.

Main Results:

• Muscle volume and CSA growth followed a piecewise model with accelerated growth before 2 years and negative growth rates after 6-9 years.
• Children with GMFCS-II&III exhibited lower muscle growth rates than GMFCS-I before age 2.
• After age 9, normalized CSA reduction was more pronounced in GMFCS-II&III, and muscle length growth trajectories differed between GMFCS levels.

Conclusions:

• Longitudinal muscle growth in children with SCP is characterized by distinct phases and is influenced by GMFCS level, particularly before age 2 and after age 9.
• These findings underscore the importance of monitoring muscle pathology in SCP from early childhood and correlating it with motor function.
• Interventions should aim to stimulate muscle growth in children with SCP, with treatment planning tailored to motor abilities and age-specific growth patterns.