Electromyographic findings in nucleus pulposus-induced radiculopathy in the rat.

STUDY

DESIGN

This study was conducted to investigate the electromyographic changes and their pathophysiologic background in the animal model of nucleus pulposus-induced radiculopathy.

OBJECTIVES

To observe the abnormal spontaneous activities in the electromyography (EMG) of rats with nucleus pulposus-induced radiculopathy and assess the role of nitric oxide in their development.

SUMMARY OF BACKGROUND DATA: It has been shown that application of nucleus pulposus to nerve roots induces changes consistent with radiculopathy. However, to our knowledge, electromyographic findings and their background have never been studied in this model of radiculopathy.

METHODS

Autologous nucleus pulposus was harvested from the tails of Sprague-Dawley rats, and applied to L4 and L5 nerve roots. The rats were tested for mechanical allodynia, motor paresis, and needle EMG, before and after surgery. Specimens of nerve roots were stained histochemically for nitrotyrosine.

RESULTS

The rats had mechanical allodynia after surgery, but motor paresis was absent. EMG showed abnormal spontaneous activities after surgery, but only temporarily. Immunoreactivity for nitrotyrosine was detected in the cell bodies and axons of nerve roots.

CONCLUSIONS

The data indicate that abnormal spontaneous activities can be observed in electromyographic examination of nucleus pulposus-induced radiculopathy. The development of these activities is considered related to nitric oxide-mediated protein nitration and resultant axonal dysfunction.