백서 모델에서 신경 견인 손상에 의한 기능적 회복 및 전자현미경적 변화에 대한 고찰

Abstract

Introduction Postoperative peripheral nerve damage or paralysis usually occurs during oral and maxillofacial surgery. Traction injury is the most common type of peripheral nerve dysfunction in civilian populations. The sciatic nerve has an almost identical capacity for regeneration in rats and subhuman primates. It is the approximate size of the intra-parotid facial nerve of human. The purpose of this study is to evaluate the relation between amount of traction force to nerve and its functional damage.

Material & Methods Eighteen male Sprague-Dawley rats weighing 250 gram were divided into three groups; A, B and C (n=6 in each group). In the sham operation (group A), after skin incision and complete dissection of the sciatic nerve, no further injury or tension was applied. Group B was given tension injury of 150g for a minute. Group C was subjected to 300g of tension injury for a minute. Functional change of motor action was evaluated by gait analysis with sciatic function index. And histological changes were evaluated by H&E staining and average myelin thickness and relative sheath thickness (G-ratio) were measured by transmission electron microscopic (TEM) examination at 2 and 4 weeks after operation.

Results The sciatic function index (SFI) was -6.59±5.14 for group A, -20.89±5.26 for group B, -48.85±12.58 for group C respectively at 2 week after surgery. After 4 weeks, the SFI was -6.45±4.47 for group A, -20.60±5.71 for group B, -23.80±7.81 for group C. Transmission electron microscopic results showed partial demyelination and decreased diameter of nerve fiber in both Group B and C at postoperative 2 and 4 weeks. The myelin thicknesses of Group A, B, C were 1298.36±246.45, 1061.06±245.46, 801.64±435.71 nm after 2 weeks and 1293.84±207.81, 735.94±280.48, 493.38±98.45 nm after 4 weeks. The G-ratio of the myelinated fiber was 0.60±0.09 for Group A, 0.64±0.07 for Group B and 0.67±0.10 for Group C after 2 weeks. G-ratio of Group A, B, C was 0.62±0.08, 0.71±0.09 and 0.75±0.06 respectively at 4 weeks.

Conclusion The functional loss of the rat sciatic nerve had positive relation with the extent of traction injury in the first 2 weeks. However, damage due to the 300g of traction injury was temporary and it tends to recover following next 2 weeks. Both 150g and 300g of traction injury group showed degenerating pattern in the TEM examination during 4 weeks after operation.