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Stretch reflexes in the upper limb of spastic man
Journal of Neurology, Neurosurgery, and Psychiatry
|December 1, 1971
Summary
The reflex response to stretch in spastic patients is velocity-dependent, not caused by autogenic inhibition. This explains the pseudo-clasp-knife reaction in the upper limb, differing from the quadriceps mechanism.
Area of Science:
- Neuroscience
- Physiology
- Biomedical Engineering
Background:
- Spasticity, a condition characterized by increased muscle tone, affects motor control.
- The clasp-knife phenomenon is a hallmark of spasticity, but its underlying mechanisms are not fully understood.
Purpose of the Study:
- To investigate the reflex response to stretch in the upper limbs of spastic patients.
- To elucidate the neurophysiological mechanisms underlying the clasp-knife sensation in the upper limb.
Main Methods:
- Studied the reflex electromyographic (EMG) response to stretch in the upper limbs of 20 spastic patients.
- Analyzed the relationship between stretch velocity and reflex EMG amplitude.
- Investigated the effect of muscle length on reflex EMG.
Main Results:
- Reflex EMG amplitude was strongly correlated with the velocity of stretch.
- Increasing muscle length augmented reflex EMG in biceps and triceps.
- Minimal inhibition was observed in only two patients with extreme stretch.
Conclusions:
- The upper limb clasp-knife sensation is likely a velocity-dependent reflex, not autogenic inhibition.
- This reflex mechanism, termed pseudo-clasp-knife reaction, differs neurophysiologically from the quadriceps clasp-knife phenomenon.
- Understanding this velocity-dependent reflex is crucial for managing spasticity.