Experimental Study Of Mechanisms Underlying Sciatica Induced By Lumbar Nucleus Pulposus Prolapse Without Mechanical Compression

Sciatica is commonly and frequently encountered diseases. Nucleus pulposus protrusion of lumbar intervertebral disc is the most important and common reason. The mechanical compression was considered the only reason of sciatica for a long time, but recent research suggested that nucleus pulposus may play an important role on the pathomechanism of nerve root injury and sciatica. There were few animal modal which had the advantage of simplicity, economy and practicability. There was little report that histology changes of nerve root had been observed consecutively. The mechanism of pathology and physiology is not clear now. In order to elucidate these problem above, the present research have put following three parts work on rats into operation.1. Autologous nucleus pulposus of coccygeal vertebral was injected to the epidural cavum of rat by lumbar puncture. The non-compressive model of experimental lumbar nucleus pulposus prolapse was build up. The caudal equine nerve conduction velocity and the histological changes were observed.2. When autologous nucleus pulposus of coccygeal vertebral was injected to the epidural cavum or circumference of sciatic nerve of rat, the mechanical withdraw threshold and the pain-related behavior were measured.3. Based on the animal model showed above, at 3,6,10,20,30,40 days after operation, we observed pathologic changes of spinal nerve roots under light microscope view.The results were described as follows:1. Motor nerve conduction velocity and sensory nerves conduction velocity observed in the nucleus pulposus group is significantly lower than that of the control group (p<0.05), especially at 6 days after operation. At 9 days after operation, nerve conduction started recovered, but there were no significant differences between the preoperative and postoperative in the control group (p>0.05).2. When autologous nucleus pulposus of coccygeal vertebral was injected to the epidural cavum or circumference of sciatic nerve of rat, the mechanical withdraw threshold were observed. The sensitivity to mechanical stimuli observed in the spinal nerve roots group is significantly hypersensitive postoperatively, mechanical withdraw threshold was significantly lower than that of the sciatic nerve group (p<0.05). Especially 5 days after operation. No changes were observed in the sciatic nerve group.3. The tissue samples were examined by light microscopy. Under light microscopic view, the nerve tissue in the control group display normal morphology. The degeneration of spinal nerve roots and Dorsal root Ganglia in nucleus pulposus group initiated on 3 days after transplantation of autologous nucleus pulposus. At 6 days after operation, the myelinated fibers in the nucleus pulposus group display edema, a few sheaths disintegrated. At 10 days after operation, a lot of sheaths disintegrated and axons display edema, the hyperemia and edema had been observed in the Dorsal root Ganglia. Nissl's body of Dorsal root Ganglia wasn't uniformity, the karyolemma was fuzziness. Disappearance of nucleolus has been found in a few DRG. Vacuoles within the Dorsal root Ganglia and the axons and the myelin sheaths were more common. At 20 days after operation, the degeneration become more seriously, most sheaths disintegrated, the axons display edema, and a few axons disappeared. There were a lot of vacuoles in the Dorsal root Ganglia cytoplasm. At 30 days after operation, the regeneration of myelin sheaths increased. Axonal swelling and marked attenuation or splitting of the myelin sheaths was reduced. At 40 days after operation, the myelinated fibers and DRG display slight changes. No significant sheath disintegration and vacuoles appeared. According to above results, the conclusions are presented as follows:1. The non-compressive animal model offered to study the mechanism of disc herniation and nerve root pain is simple, reliable and cheap.2. The Inflammatory reaction caused by autograft nucleus pulposus is an important factor in caudal equine nerve roots injury and sciatica.3. Nerve root without protection of epineurium may be one anatomy mechanism of sciatica.