The Long-Lasting Pattern of the Neuropathic Radicular Pain in An Autologous Nucleus Pulposus Model of Rat

OBJECTIVE: To observe the long-lasting changes of pain progression with time course in an autologous nucleus pulposus model of rat. METHOD: The subjects were 25 Sprague-Dawley (Sprague- Dawley, 250 gm) male rats. They were randomly assigned into either the sham or experimental group. In the experimental group (n=15), autologous nucleus pulposus was harvested from the coccygeal intervertebral disc of the rat and this was grafted on the left L5 dorsal root ganglion. In the sham group (n=10), the left L4 and L5 nerve roots were exposed by laminectomy, but the nucleus pulposus was not grafted. All the rats were evaluated for mechanical allodynia and thermal hyperalgesia at 2 days before surgery, and on days 1, 5, 10, 20, 30, 40 and 50 after surgery. The morphological changes of the spinal nerves were assessed by toluidine blue staining on days 5 after surgery. RESULTS: In the ipsilateral hindpaw of the experimental group, there was a dramatic drop of the mechanical withdrawal threshold and the thermal withdrawal latency on day 1 after surgery, which was maintained at day 50 after surgery. In morphological study, pathological findings such as swelling of the myelin sheath, demyelination, swelling and degeneration of the axoplasm were observed in the spinal nerve at day 5 after surgery. CONCLUSION: The long-lasting pattern of neuropathic radicular pain shown in a rat model of lumbar disc herniations is helpful to understand the natural history of neuropathic radicular pain due to ruptured nucleus pulposus.

Transcallosal Fibers from Corticospinal Tract in Patients with Cerebral Hemorrage

OBJECTIVE: To investigate the relationship between the transcallosal fibers (TCFs) from the corticospinal tract (CST) and the motor function of the affected extremities in patients with cerebral hemorrhage, using diffusion tensor image tractography (DTT). METHOD: 49 patients with cerebral hemorrhage and 38 controls were recruited. DTT was performed using 1.5 T magnetic resonance imaging. The DTT findings were classified into 3 groups according to targeting location: no TCF from the CST (type A), TCF ended in the corpus callosum or connected to the cortex of the opposite hemisphere (type B), and TCF that descending toward the lesion after passing through the corpus callosum (type C). RESULTS: The TCF originated from the CST of the unaffected hemisphere, and the presence of fiber descending toward the lesion after passing through the corpus callosum were significantly more prevalent in the patients who showed the worse motor function. CONCLUSION: The TCF originated from the unaffected CST toward the lesion in patients with cerebral hemorrhage might play a relevant role in compensating motor deficits in the major corticospinal disruption.