Neurophysiologic changes in hemiplegia. Possible explanation for the initial disparity between muscle tone and tendon reflexes.

In an attempt to clarify the neurophysiologic changes that may follow a cerebral lesion in man, we have studied patients with recent and with long-standing hemiplegia from cerebral infarction. In patients with recent cerebral lesions, inhibition of the monosynaptic reflex by vibration is enhanced. In patients with long-standing cerebral lesions, this inhibitory mechanism is less effective and a comparison of the electrically and mechanically induced monosynaptic reflexes suggests that fusimotor drive may be increased. Related clinical findings are reduced muscle "tone" immediately after the lesion and increased muscle "tone" and exaggerated tendon jerks in patients with long-standing hemiplegia.