H reflex study in upper motoneuron diseases

Abstract

The H reflex was studied by meansof paired stimulation in 9 normal subjects, 5 parkinsonian patients, 4 patients with spasticity, and 8 patients with hyperkinetic-dystonic syndromes. The excitability recovery curve expressed by this method showed the long-lasting depression of motoneurons following the conditioning afferent volley in normal subjects. All of the diseased groups showed early recovery followed by facilitation in their excitability recovery curve of motoneurons. The excitability recovery curves of both normal and diseased.groups remained unaltered under procaine nerve bloekat a time when there was a block predominantly of fusimotor nerve fibers. This supports the idea that in parkinsonism, spastictty, and hyperkinetic-dystonic syndromes there exists an abnormal excitation of spinal alpha motoneurons independent, at least in part, of the fusimotor system.