Ultrastructural Changes of Rat`s Sciatic Nerve after Alcohol Injection or Drip : Electron Microscopic Studies

Song, Sun Ok; Cheun, Jae Kyu

Abstract

Alcohol as a classic neurolytic agent is frequently used for the management of intractable cancer pain, but the side reactions such as motor weakness and sphincter incontinence clinically developed following their application, occasionally annoying anesthesiologists or other physicians. To observe functional changes of hind limbs and neuropathologic changes in the sciatic nerve after alcohol application, highlighting the time of nerve regeneration, we undertook this experimental study utilizing a rat. Experimental groups were injected or dripped on the right sciatic nerve, and control groups were injected normal saline on the left. The functional changes of hind limbs were observed for 6 weeks and the distal part of the alcohol injected or dripped on the sciatic nerve was severed in 3 rats of each group respectively at 10 minutes, 1 hour, 24 hours, 3 days, 1 week, 2 weeks, 4 weeks and 6 weeks. The severed nerves were prepared for electron microscopic examination and pathologic changes were observed under the electron microscope. The results were as follows: The functional changes of the rats hind limbs after alcohol or saline application were as follows. When the rats emerged from the ether anesthesia, all showed motor loss of both hind limbs, and after several minutes, normal function returned in the saline injected limbs. The alcohol injected or dripped hind limbs showed more pronounced motor weakness and gait changes were obvious. About 2 weeks after the alcohol application, gradual improvement of gait changes begun, and after 6 weeks, motor weakness and gait changes were no longer perceptible. The neuropathologie events after alcohol application were as follows. In the group with alcohol injection, at 10 minutes after injection, destructive lesions were confined to unmyelinated fibers and the myelin sheath of small myelinated fibers. At 1 hour and 24 hours, axonal fibers and Schwann cells were shrunk and separated from the myelin sheath and empty spaces respectively. On the 3rd day and at 1 week, pathologic changes on axonal fibers and Schwann cells were in progression with phagocytosis in spite of myelin restitution. From 2 to 4 weeks, axonal regeneration and remyelination appeared concurrent with myelin disintegration and axonolysis, and hlytologic findings at 6 weeks were similar to those of the control group. In the group with alcohol drip, the histologic chanaes of the sciatic nerve were very similar to the injection groups. These results suggest that histopathologic findings such as degeneration and regeneration have good correlation with functional loss and gain, and histopathologic lesions after an alcohol application on the peripheral nerves are not influenced by application methods. The progress of histopathologic changes is obvious according to the time interval following the alcohol application. Accordingly, side reactions that developed following the use of neurolytic agents may be improved around the time when the nerve regeneration occurs, between second and forth weeks after the injection.