The iatrogenically produced drug injection injury of a peripheral nerve is of particular concern. Because of both its clinical and medicolegal implications. Among the numerous agents, local anesthetic solutions are most frequently injected near the main nerve trunks. In spite of low incidence of nerve fiber injury associated with these local anesthetic agents, there are several clinical reports of injuries. The author performed experimentally injection injury into the rat sciatic nerve with 1% lidocaine HCI, and observed the neurotoxicity of the lidocaine HCI to the peripheral nerve by light and election microscope.
The followings are the results :
1. Some inflammatory round cells and vasodilation were observed at the surrounding loose areolar tissues from the immediate after the injection. No fibroblast or fibrosis was observed on light and electron microscopic examinations.
2. Immediate after the injection, the axons were separated by the splitting of the collagen fibers between axons- But within one week, collagen fibers were reunited and compact between axons.
3. Most cytoplasmic organelles of axon. Including microtubules and microfilaments, were quite normal and were not changed by injection injury. But the shape of axon was changed and shrinked to make a large space from the myelin sheath. The above changes were recovered to normal withii, one wtek.
4. Schwanu cell, itself, maintained normal structure in its cvtcnlasm and in its nucleus. But some Schwann cells were separated from the axons, and floated in the collagen tissue. But they were reunited to axons within one week.
5. Above changes were reversible easily and not so severe to interfere the nerve function permanently. As a conclusion, local injection of 1 % lidocaine Hci is ´very safe to the peripheral nerve.
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