• S Yabuki, T Igarashi, and S Kikuchi.
• Department of Orthopaedic Surgery, Fukushima Medical University, School of Medicine, Japan. yabuki@fmu.ac.jp
• Spine. 2000 Jun 15;25(12):1471-6.

Study DesignAn experimental study to clarify the effects of nucleus pulposus on blood flow in the dorsal root ganglion and hindpaws.ObjectivesTo investigate the effects of application of nucleus pulposus to nerve root on blood flow in the dorsal root ganglion and the corresponding hindpaw.Summary Of Background DataIt has been reported experimentally that application of nucleus pulposus into the epidural space induces morphologic and functional changes in the nerve roots and induces compartment syndrome in the dorsal root ganglia. However, it has not been clarified which of these changes induces symptoms in the lower limbs.MethodsSixteen adult, female Sprague-Dawley rats had the left L5 nerve root and associated dorsal root ganglions exposed. Autologous nucleus pulposus was applied to the L5 nerve root, just proximal to the dorsal root ganglion (NP group). For control, the same volume of muscle tissue was applied similarly to the neural tissue (control group). Blood flow in the dorsal root ganglion, corresponding hindpaw, and the contralateral hindpaw was continuously monitored by two-channel laser Doppler flowmeter for 3 hours. After measurement of blood flow, the nerve root and dorsal root ganglion were processed for histology and evaluated by light microscope.ResultsBlood flow in the NP group was reduced, not only in the dorsal root ganglion, but also in the corresponding hindpaw. These reductions were statistically significant compared with the control group (P < 0.01). Edema was the principal pathologic finding seen consistently in the nerve roots and in many of the associated dorsal root ganglia from nucleus pulposus-treated animals.ConclusionApplication of nucleus pulposus to nerve root decreased blood flow in the dorsal root ganglion and corresponding hindpaw. These basic pathophysiologic changes are associated with compression injuries caused by herniated discs and are accepted neuropathologic mechanisms of injury associated with painful neuropathies. These acute observations in the dorsal root ganglion and the hindpaw may be important initial factors in the pathogenesis of radicular leg pain (sciatica) due to disc herniation.

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