Prevention of compartment syndrome in dorsal root ganglia caused by exposure to nucleus pulposus

Study Design. An experimental study to clarify the effects of pentoxifylline, as an anti-tumor necrosis factor-alpha therapy on endoneurial fluid pressure in the dorsal root ganglion using an animal model of herniated nucleus pulposus. Objectives. To investigate the effects of anti-tumor necrosis factor-alpha therapy to nucleus pulposus-induced nerve root/dorsal root ganglion changes, Summary of Background Data. It has been reported experimentally that application of nucleus pulposus into epidural space induces morphologic and functional changes in the nerve roots and induces compartment syndrome in the dorsal root ganglia, Tumor necrosis factor-alpha has been considered a key pathogenic factor in the initiation and maintenance of neuropathic pain states. Methods. A total of 11 adult, female Sprague-Dawley rats had their left L5 nerve roots and associated dorsal root ganglions exposed. Autologous nucleus pulposus was applied to the L5 nerve root just proximal to the dorsal root ganglion. A piece of Spongel (Yamanouchi Pharmaceutical Co., Tokyo) containing 20 muL of 1000 mug/m L pentoxifylline was applied with the nucleus pulposus (NP+PTX group). In control animals nucleus pulposus was applied with a piece of Spongel containing 20 muL of physiologic saline solution in a similar fashion (NP+PS group). Endoneurial fluid pressure was recorded with a servo-null micropipette system using glass micropipettes with tip diameters of 4 mum. Endoneurial fluid pressure in the dorsal root ganglion was measured before and 3 hours after application of test substances. After measurement of endoneurial fluid pressure, the nerve root and dorsal root ganglion were processed for histology and evaluated by light microscope. Results. Values of endoneurial fluid pressure before application of test substances were as follows: 2.4 +/- 1.2 cmH(2)O in the NP+PS (control) group and 1.8 +/- 0.4 cmH(2)O in the NP+PTX group. There was no statistically significant difference between these two pretreatment measurements. However, values of endoneurial fluid pressure after application were as follows: 8.6 +/- 1.8 cmH(2)O in the NP+PS group and 2.9 +/- 0.8 cmH(2)O in the NP+PTX group. Values of endoneurial fluid pressure in the NP+PTX group were significantly lower compared with the NP+PS group. Histologic examination consistently showed only a slight degree of edema evident in the NP+PTX group compared with the NP+PS group. Conclusion. Pentoxifylline, an anti-tumor necrosis factor-alpha drug, prevented the dorsal root ganglion compartment syndrome caused by topical application of nucleus pulposus. Anti-inflammatory cytokine therapy may become an effective treatment of sciatica due to disc herniation.