Electrophysiologic analysis of the motor system after stroke: the "suppressive" effect of vibration.

The "suppressive" effect of vibration on the H-reflex was studied in 18 patients with motor system deficits due to cerebrovascular lesions of less than 3 weeks duration. No meaningful difference was found in the degree of H-reflex suppression between clinically involved and uninvolved sides in the patients, several of whom had increased deep tendon reflexes at the time of examination. It is concluded that hyperreflexia of "spasticity" cannot be explained purely on the basis of lack of presynaptic inhibition, even if it were one of the underlying mechanisms responsible for the suppression of the H-reflex by vibration, as previously claimed. Not only specific lesions themselves but also changes with the passage of time after CNS damage are important for understanding and treatment of motor system abnormalities.