Soleus H-reflex recruitment is not altered in persons with chronic spinal cord injury.

Abstract

To determine whether spasticity in persons with spinal cord injury (SCI) is associated with elevated monosynaptic reflex excitability. One-way experimental. Research laboratory. Convenience sample of 9 subjects (8 men, 1 woman) with chronic and complete SCI and 20 persons (14 men, 6 women) with no neurologic impairment. Subjects with SCI exhibited lower-extremity spasticity as indicated by velocity-dependent increased resistance to passive muscle stretch, abnormally brisk deep tendon reflexes, involuntary lower-extremity flexion and/or extension spasms, and clonus. Soleus H-reflex recruitment curves were elicited in all subjects. Soleus H-reflex threshold (HTH), gain (HGN), and amplitude (HPP). There was no difference between subjects with and without SCI in HTH, HGN, or HPP. Spasticity in people with chronic and complete SCI was not associated with increased excitability of the connections between Ia afferent projections and motoneurons. Factors extrinsic to these connections may have a role in spasticity caused by SCI.