Enhanced stretch reflex excitability of the soleus muscle in persons with incomplete rather than complete chronic spinal cord injury.
OBJECTIVE
To compare excitabilities of spinal stretch reflex among clinically complete spinal cord injury (SCI), incomplete SCI, elderly healthy, and young healthy subjects.


METHODS
Case comparison.


METHODS
Research laboratory.


METHODS
Volunteer sample of 12 complete SCI, 10 incomplete SCI, 10 elderly, and 11 young subjects.


METHODS
Mechanically induced stretch reflex, H-reflex, and M response in electromyographic activity of the soleus muscle were recorded in all subjects.


METHODS
Absolute peak-to-peak stretch reflex amplitude and maximum H-reflex (Hmax), and those values relative to the maximum M response (Mmax) amplitude (relative peak-to-peak stretch reflex amplitude) and H/M ratio.


RESULTS
Both the absolute and relative peak-to-peak stretch reflex amplitudes showed the greatest values in incomplete SCI among the 4 groups. Although absolute and relative peak-to-peak stretch reflex amplitudes of the incomplete SCI group were greater than those of the complete SCI group, the H/M ratios of both groups were comparable, and were greater than those of the younger and elderly groups.


CONCLUSIONS
The results suggest that the greater absolute and relative peak-to-peak stretch reflex amplitudes of incomplete SCI were mostly due to the greater maximum motor potential (Mmax), while the elevated spinal motoneuronal excitability shown by the increased H/M ratio was maintained in the chronic stage after both complete and incomplete SCIs.
Nakazawa
Kimitaka
K
Department of Movement Functions, Research Institute, National Rehabilitation Center for Persons with Disabilities, Saitama, Japan. nakazawa@rehab.go.jp
Kawashima
Noritaka
N
Akai
Masami
M
D000367:Age Factors; D016022:Case-Control Studies; D002908:Chronic Disease; D004558:Electric Stimulation / Q000379:methods*; D004576:Electromyography; D005260:Female; D005500:Follow-Up Studies; D006181:H-Reflex / Q000502:physiology; D006801:Humans; D015601:Injury Severity Score; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D009048:Motor Skills / Q000502:physiology*; D009460:Neurologic Examination / Q000379:methods; D010264:Paraplegia / Q000503:physiopathology / Q000534:rehabilitation; D026741:Physical Therapy Modalities; D011782:Quadriplegia / Q000503:physiopathology / Q000534:rehabilitation; D011930:Reaction Time; D012016:Reference Values; D012026:Reflex, Stretch / Q000502:physiology*; D018570:Risk Assessment; D012494:Sampling Studies; D012737:Sex Factors; D013119:Spinal Cord Injuries / Q000175:diagnosis* / Q000534:rehabilitation*