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Reflex excitability and isometric force production in cerebral palsy: the effect of serial casting
B Brouwer1, R K Wheeldon, N Stradiotto-Parker
1School of Rehabilitation Therapy, Queen's University, Kingston, Ontario, Canada. Brouwerb@post.queensu.ca
Insights
Children with spastic cerebral palsy (CP) exhibit earlier stretch-reflex onset and reduced plantar-flexor force. Serial casting improved dorsiflexion and altered muscle mechanics without strength loss in spastic cerebral palsy (CP).
Area of Science:
- Neuroscience
- Orthopedics
- Pediatric Rehabilitation
Background:
- Children with spastic cerebral palsy (CP) often present with altered muscle properties and impaired motor control.
- Understanding the biomechanical and neuromuscular characteristics of spasticity is crucial for effective therapeutic interventions.
Purpose of the Study:
- To investigate the stretch-reflex onset, plantar-flexor strength, and length-tension relationships in children with spastic cerebral palsy (CP) compared to controls.
- To evaluate the effects of serial casting on dorsiflexion range, plantar-flexor strength, reflex threshold, and muscle length-tension properties in children with CP.
Main Methods:
- Passive dorsiflexion stretch-reflex onset angle and isometric plantar-flexor force were measured in children with spastic cerebral palsy (CP) and controls.
- Length-tension curves were analyzed to assess peak force production in relation to muscle length.
- Seven children with CP underwent 3 weeks of serial casting, with reassessment of biomechanical parameters post-casting and at 6-week follow-up.
Main Results:
- Children with spastic cerebral palsy (CP) demonstrated an earlier stretch-reflex onset and reduced isometric plantar-flexor force, with peak forces occurring at greater plantar flexion.
- Serial casting significantly increased dorsiflexion range, with sustained gains at follow-up.
- Casting led to an increased reflex threshold and reduced resistance to imposed stretch, shifting the length-tension curve to generate peak tension in dorsiflexion.
Conclusions:
- Spastic cerebral palsy (CP) is associated with altered stretch reflex excitability and muscle force production characteristics.
- Serial casting is an effective intervention for improving dorsiflexion range and modifying muscle-tendon unit properties in children with spastic cerebral palsy (CP).
- The observed changes suggest that serial casting can help normalize muscle mechanics, potentially improving functional outcomes in spastic cerebral palsy (CP).
Abstract:
During passive dorsiflexion, the angle of stretch-reflex onset was earlier in the dorsiflexion range for children with spastic cerebral palsy (CP) (N=10) compared with controls (P<0.001) at comparable velocities of stretch. Isometric plantar-flexor force was lower in children with CP (P<0.0001) and a leftward shift in the length-tension curve reflected that peak forces were produced in greater plantar flexion in children with CP than in controls (P<0.0001). Seven children with CP underwent 3 weeks of serial casting resulting in increased dorsiflexion at postcasting and at 6 weeks follow-up (P<0.002). There was no associated loss in plantar-flexor strength (P>0.32), but increased reflex threshold (P<0.03) and a decline in restraint to imposed stretch (P<0.002) were evident. A rightward shift in the length-tension curve illustrated that peak tension was generated in dorsiflexion rather than plantar flexion following casting (P<0.001). The gains were still evident at follow-up although generally to a lesser extent.