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Does spasticity result from hyperactive stretch reflexes? Preliminary findings from a stretch reflex characterization
J De J Salazar-Torres1, A D Pandyan, C I M Price
1Centre for Rehabilitation and Engineering Studies (CREST), University of Newcastle upon Tyne, UK. j.d.j.salazar-torres@ncl.ac.uk
Disability and Rehabilitation
|June 19, 2004
Summary
The stretch reflex response in stroke patients with elbow spasticity showed reduced amplitude and shorter latency compared to non-impaired individuals. This suggests altered neural excitability, not necessarily hyper-excitability, following stroke.
Area of Science:
- Neuroscience
- Rehabilitation Medicine
- Motor Control
Background:
- Elbow spasticity is a common impairment following stroke.
- The stretch reflex plays a role in spasticity and resistance to passive movement.
- Understanding stretch reflex characteristics is crucial for effective rehabilitation.
Purpose of the Study:
- To quantify and compare the stretch reflex excitability of the biceps brachii in stroke patients with elbow spasticity and non-impaired volunteers.
- To identify differences in stretch reflex parameters between these groups.
Main Methods:
- A cross-sectional study design was employed.
- Stretch reflexes of the biceps brachii were elicited via controlled elbow extension.
- Surface electromyography (EMG) recorded amplitude, latency, rise time, and duration of the reflex response.
Main Results:
- Stroke patients exhibited significantly lower reflex amplitude compared to controls (p<0.05).
- Stroke patients demonstrated significantly shorter reflex latency than non-impaired volunteers (p<0.05).
- No significant differences were found in reflex rise time or duration (p>0.10).
Conclusions:
- The reduced amplitude in stroke patients challenges the assumption of universal hyper-excitability in spasticity.
- Shorter latency suggests potential decreases in presynaptic inhibition and/or increased motor neuron excitability post-stroke.
- Potential confounding effects of prior botulinum toxin treatment on amplitude warrant further investigation.