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Abnormal spontaneous activities on needle electromyography and their relation with pain behavior and nerve fiber pathology in a rat model of lumbar disc herniation.

Abstract：

STUDY DESIGN:This longitudinal experimental study was conducted to investigate electrophysiologic characteristics, pain behavior, and histological changes in a rat model of lumbar disc herniation. OBJECTIVE:To observe abnormal spontaneous activity (ASA) on needle electromyography (EMG) and to determine its relation with neuropathic pain behavior and histological changes longitudinally in a rat model of lumbar disc herniation. SUMMARY OF BACKGROUND DATA:Needle EMG is generally performed to determine the existence and the degree of radiculopathy caused by disc herniation. The local application of autologous nucleus pulposus to the spinal nerve has been shown to induce neuropathic pain. However, little is known about the relations between neuropathic pain and abnormal EMG findings and the manner in which they change with time in rat models of lumbar disc herniation. METHODS:Twenty-five Sprague-Dawley rats were randomly assigned to either sham or experimental groups. In the experimental group, autologous nucleus pulposus was grafted on the left L5 dorsal root ganglion. All rats were evaluated for mechanical allodynia and thermal hyperalgesia and underwent needle EMG examinations before and on days 1, 5, 10, 20, 30, 40, and 50 after surgery. Morphologic changes of L5 spinal nerves and of sciatic nerves were assessed by toluidine blue staining on days 1, 5, and 50 after surgery. RESULTS:A dramatic decrease in mechanical withdrawal threshold and in thermal withdrawal latency was observed on day 1 after surgery, and these changes persisted until day 50 after surgery. ASAs on needle EMG were observed on day 1 (33%), peaked on day 5 (93%), and gradually decreased from day 10 (69%) to day 40 (18%) after surgery. Pathologic findings of nerve fibers, such as swelling of myelin sheaths, demyelination, and degeneration of axoplasms were observed from day 1. These findings were exaggerated on day 5 and then diminished but were still evident on day 50. CONCLUSION:Neuropathic pain and pathologic changes in spinal nerve fibers probably remain even after ASAs in EMG have disappeared in our rat model of lumbar disc herniation. These results provide baseline data concerning the natural courses of electrophysiologic findings and of radicular pain in patients with intervertebral disc herniation.

journal_name

Spine (Phila Pa 1976)

journal_title

Spine

authors

Kim SJ,Kim WR,Kim HS,Park HW,Cho YW,Jang SH,Hwang SJ,Ahn SH

doi

10.1097/BRS.0b013e318210aa10

subject

Has Abstract

pub_date

2011-11-15 00:00:00

pages

E1562-7

issue

eissn

0362-2436

issn

1528-1159

journal_volume

pub_type

杂志文章

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Abnormal spontaneous activities on needle electromyography and their relation with pain behavior and nerve fiber pathology in a rat model of lumbar disc herniation.