H-reflexes are less depressed following muscle stretch in spastic spinal cord injured patients than in healthy subjects.
The size of the soleus H-reflex was measured after a slow (17 deg/s) passive stretch of ankle plantarflexors and compared to its control size without muscle stretch in ten neurologically healthy subjects and in six spastic spinal-cord-injured patients. Two seconds after the end of the stretch, the size of the H-reflex was reduced to about 30% of its pre-stretch size in the healthy subjects. The depression remained for 10-15 s. In the spastic, spinal-cord-injured patients, stretch caused significantly less reduction in the size of the H-reflex. The H-reflex also regained its pre-stretch size much faster than in healthy subjects. We suggest that the smaller depression of the H-reflex observed in spastic patients may be involved in the pathophysiology of spasticity.
Nielsen
J
J
Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark.
Petersen
N
N
Ballegaard
M
M
Biering-Sørensen
F
F
Kiehn
O
O
D000328:Adult; D000843:Ankle Joint / Q000502:physiology; D004576:Electromyography; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D009128:Muscle Spasticity / Q000209:etiology / Q000503:physiopathology*; D009132:Muscles / Q000294:innervation / Q000503:physiopathology*; D009475:Neurons, Afferent / Q000502:physiology; D013119:Spinal Cord Injuries / Q000150:complications / Q000503:physiopathology*