The experimental study was conducted in order to observe the change and degree of the sciatic nerve damage following direct injection and dripping of physiological normal saline solution, sulpyrine and gentamysin sciatic nerve.

Twenty-four normal adult Wistar rats were divided into three groups depending on the injected materials. The sciatic nerves of the rat were surgically exposed and injected into the right sciatic nerve intraneurally and dripped around the left sciatic nerve perineurally.

The nerve conduction study, needle electromyography were performed before experimental injury and were performed at 3, 7, 10, 14 days after experimental injury and the pathologic study was also performed at 7, 14 days after experimental injury.

In the nerve conduction study, there was no decrement of the amplitude of compound muscle action potentials after injection and dripping in normal saline group. There was significant decrement (P<0.05) of the amplitude at 3 days after injection and remained same at 7, 10, 14 days after injection but no significant decrement of the amplitude after dripping in sulpyrine and gentamycin group.

In the needle EMG, the abnormal spontaneous acitivies (ASA) were noted at 3 days after injection and the amount of ASA remained same at 7, 10, 14 days after injection and no ASA was observed after dripping in normal saline group. The ASA were noted at 3 days after injection and the amount of ASA were increased at 7, 10, 14 days after injection in sulpyrine and gentamycin group.

Histologic studies showed splitting of myelin sheath at 14 days after saline injection and showed decreased numbers of myelinated fibers, hydropic change of axon, disruption and collapse of myelin sheath at 14 days after sulpyrine and gentamycin injection.

With the above findings, it is suggested that the main cause of the injection injury of the peripheral nerve is chemical reaction rather than mechanical problem.