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Muscle and fascicle excursion in children with cerebral palsy
Sigrun Matthiasdottir1, Marlee Hahn1, Megan Yaraskavitch1
1Human Performance Lab, University of Calgary, Canada.
Insights
Children with cerebral palsy have shorter medial gastrocnemius fascicles, leading to sarcomere overstretching and potential muscle weakness. This study quantizes these differences in fascicle length and excursion.
Area of Science:
- Biomechanics
- Pediatric Neurology
- Musculoskeletal Research
Background:
- Inconsistent fascicle measurements in children with cerebral palsy (CP) necessitate further investigation.
- Understanding Medial Gastrocnemius muscle properties is crucial for CP-related mobility impairments.
Purpose of the Study:
- To measure in vivo passive fascicle lengths of the Medial Gastrocnemius muscle in children with CP.
- To quantify fascicle excursions in the Medial Gastrocnemius muscle for children with CP and typically developing controls.
Main Methods:
- Ultrasound imaging was employed to measure fascicle lengths in 11 children with spastic CP and 14 controls (ages 9-16).
- Ankle range of motion was assessed using a dynamometer to analyze fascicle excursion.
Main Results:
- Medial Gastrocnemius fascicle lengths were 43% shorter in children with CP compared to controls.
- Relative fascicle excursion was 92% greater in the CP group.
- Absolute muscle excursion was greater in controls than in the CP group.
Conclusions:
- Shorter fascicles with similar excursion in CP suggest sarcomeres operate over a wider length range.
- This may lead to decreased contractile filament overlap, contributing to increased passive forces and weakness in spastic muscles.
- Findings support the hypothesis that sarcomere overstretching underlies muscle dysfunction in pediatric cerebral palsy.
Background:
Fascicle length and fascicle excursion measurements in children with cerebral palsy have yielded inconsistent results. The purpose of this study was to measure in vivo passive fascicle lengths and fascicle excursions in the Medial Gastrocnemius muscle of children with cerebral palsy and typically developing controls.
Methods:
We measured 11 children with spastic cerebral palsy and 14 controls between the ages of 9 and 16years. Ultrasound imaging was used to measure fascicle lengths while a dynamometer moved the ankle joint through the range of motion. A common range of motion for all subjects was used for analysis of fascicle excursion.
Findings:
Fascicle lengths in children with cerebral palsy were 43% smaller than those for control subjects throughout the range of motion. The relative fascicle excursion was 92% greater on average for the cerebral palsy compared to the control group children. The muscle excursion for the control group children was greater than for the cerebral palsy group children.
Interpretation:
Since the fascicles in children with spastic cerebral palsy are shorter, but they go through the same excursion as fascicles in typically developing children, sarcomeres within the medial gastrocnemius muscle must be working over a larger range of sarcomere lengths. Combined with findings of overstretched sarcomeres in spastic muscles reported in the literature, our results suggest that the increased passive forces and the weakness found in spastic muscles may be caused by a decrease in contractile filament overlap as sarcomeres are pulled to extreme lengths in children with cerebral palsy.
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