Associated reaction and spasticity among patients with stroke

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Clinical Electrophysiology

Background:

• Spasticity is a common motor disorder following stroke, significantly impacting upper limb function.
• Associated reaction (AR) is an involuntary movement observed in the affected limb during exertion or sensory stimulation.
• The relationship between AR and spasticity in the paretic arm remains incompletely understood.

Purpose of the Study:

• To investigate the correlation between associated reaction (AR) and clinical spasticity in the paretic arm of stroke survivors.
• To compare the AR ratio with monosynaptic reflex measures (H- and T-waves) in relation to spasticity.
• To examine the effect of median nerve block on these relationships.

Main Methods:

• Surface electromyography (EMG) was used to analyze AR and calculate the AR ratio in ten hemiparetic stroke patients.
• M-, H-, and T-wave amplitudes were measured, and H/M and T/M ratios were calculated.
• Spasticity was assessed using the modified Ashworth scale (MAS); measurements were repeated after median nerve block.

Main Results:

• The AR ratio showed a significant positive correlation with the modified Ashworth scale (MAS) scores (P < 0.01).
• H/M and T/M ratios did not significantly correlate with spasticity.
• Median nerve block did not alter the observed relationships between AR ratio and spasticity.

Conclusions:

• Associated reaction (AR) is strongly correlated with clinical spasticity in hemiparetic stroke patients.
• Monosynaptic reflexes (H- and T-reflexes) do not show a significant correlation with spasticity.
• These findings suggest that AR and spasticity share common neural pathways, providing potential targets for therapeutic interventions.