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Assessment of spasticity in hemiplegic cerebral palsy. I. Proximal lower-limb reflex excitability
J P Lin1, J K Brown, R Brotherstone
1Department of Paediatric Neurology, R. Brotherstone, E.P.T.A., Royal Hospital for Sick Children, Edinburgh, UK.
Insights
Children with hemiplegic cerebral palsy showed altered hamstring muscle responses. Hamstrings, especially hemiparetic ones, had lower reflex thresholds near full knee extension, indicating greater velocity sensitivity.
Area of Science:
- Neurology
- Biomedical Engineering
- Kinesiology
Background:
- Cerebral palsy (CP) often leads to muscle spasticity and altered motor control.
- Understanding muscle reflex responses in children with hemiplegic CP is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate the stretch reflex properties of quadriceps and hamstring muscles in children with hemiplegic cerebral palsy.
- To compare the velocity sensitivity and reflex thresholds between hemiparetic and non-paretic limbs.
Main Methods:
- Ramp and sinusoidal stretches were applied to quadriceps and hamstring muscles at three different knee joint angles in 13 children with hemiplegic CP.
- Reflex responses were analyzed to determine velocity sensitivity and reflex thresholds.
Main Results:
- Hamstring muscles exhibited greater velocity sensitivity than quadriceps muscles.
- Lowest reflex velocity and frequency thresholds were observed in hamstrings near maximum knee extension.
- Hemiparetic hamstrings showed a weakly significant reduced reflex frequency threshold compared to non-paretic hamstrings at this specific joint angle.
- Similar reflex thresholds were found for hemiparetic and non-paretic muscles at other lengths and with different stretch types.
- The ability to elicit a reflex response decreased as knee flexion increased towards 90 degrees.
Conclusions:
- Hamstring muscles in hemiplegic CP demonstrate distinct stretch reflex characteristics, particularly at near-full knee extension.
- Velocity sensitivity and reflex thresholds are influenced by muscle group, limb involvement (hemiparetic vs. non-paretic), and joint angle.
- These findings highlight the complex neuromuscular adaptations in hemiplegic cerebral palsy and inform potential therapeutic interventions.
Abstract:
The quadriceps and hamstring muscles of 13 children with hemiplegic cerebral palsy were studied using ramp and sinusoidal stretches at three different muscle lengths. Overall, the hamstring muscles showed greater velocity sensitivity than the quadriceps, with the hamstrings having the lowest reflex velocity and frequency thresholds close to maximum knee extension. At this position, the hemiparetic hamstrings alone showed a weakly significant reduced reflex frequency threshold compared with non-paretic muscles. For all other muscle lengths, non-paretic and hemiparetic muscles displayed similar reflex thresholds when subjected to sudden, discontinuous or repetitive rhythmical, sinusoidal stretches. The number of muscles for which a reflex threshold could be established declined progressively as the angle at the knee joint approached 90 degrees of flexion. Muscles for which no reflex threshold could be demonstrated had similar velocities and frequencies of stretch as those in which a reflex was obtained.