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Open Access Research

Distinct degree of radiculopathy at different levels of peripheral nerve injury

Noboru Takiguchi1, Munehito Yoshida1, Wataru Taniguchi1, Hiroshi Hashizume1, Hiroshi Yamada1, Nobuyuki Miyazaki1, Naoko Nishio1 and Terumasa Nakatsuka2*

Author Affiliations

1 Department of Orthopaedic Surgery, Wakayama Medical University, 811-1 Kimiidera, Wakayama, 641-8509, Japan

2 Pain Research Center, Kansai University of Health Sciences, 2-11-1 Wakaba Kumatori Sennan, Osaka, 590-0482, Japan

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Molecular Pain 2012, 8:31  doi:10.1186/1744-8069-8-31

Published: 26 April 2012

Abstract

Background

Lumbar radiculopathy is a common clinical problem, characterized by dorsal root ganglion (DRG) injury and neural hyperactivity causing intense pain. However, the mechanisms involved in DRG injury have not been fully elucidated. Furthermore, little is known about the degree of radiculopathy at the various levels of nerve injury. The purpose of this study is to compare the degree of radiculopathy injury at the DRG and radiculopathy injury proximal or distal to the DRG.

Results

The lumbar radiculopathy rat model was created by ligating the L5 nerve root 2 mm proximal to the DRG or 2 mm distal to the DRG with 6.0 silk. We examined the degree of the radiculopathy using different points of mechanical sensitivity, immunohistochemistry and in vivo patch-clamp recordings, 7 days after surgery. The rats injured distal to the DRG were more sensitive than those rats injured proximal to the DRG in the behavioral study. The number of activated microglia in laminas I–II of the L5 segmental level was significantly increased in rats injured distal to the DRG when compared with rats injured proximal to the DRG. The amplitudes and frequencies of EPSC in the rats injured distal to the DRG were higher than those injured proximal to the DRG. The results indicated that there is a different degree of radiculopathy at the distal level of nerve injury.

Conclusions

Our study examined the degree of radiculopathy at different levels of nerve injury. Severe radiculopathy occurred in rats injured distal to the DRG when compared with rats injured proximal to the DRG. This finding helps to correctly diagnose a radiculopathy.

Keywords:
Radiculopathy; Microglia; Patch-clamp