Objective
To investigate and compare the vibratory inhibition of H-reflex in the subjects with and without brain injury.

Method
H-reflex and the vibratory inhibition of H-reflexes were evaluated in thirty two limbs in subjects without brain injury and twenty two limbs in the brain injury patients. The maximal amplitudes of H-reflexes were recorded before and while vibrating the Achilles tendon. The ratio of the two trials (vibratory maximal H-reflex amplitude / previbratory maximal H-reflex amplitude) was defined as 'H-reflex vibratory inhibition'. H-reflex vibratory inhibition was correlated to the spasticity (Asworth scale).

Results
The mean values of H-reflex vibratory inhibition were 0.5361⁑0.0373 in the control group and 0.7539⁑0.0543 in the brain injured group. There was a significant difference between two groups. H-reflex vibratory inhibition tends to increase as the spasticity increases.

Conclusion
The vibratory inhibition of H-reflex was significantly decreased in the brain injured patients than in the controls. We conclude that the H-reflex vibratory inhibition can be used in the evaluation of the spasticity.