The Effect Of ～(125)I Radioactive Seeds Implantation Upon Peripheral Nerves

Objective To evaluate the effect of 125I seeds permanent implantation upon peripheral nerves by animal experiment, to histologically evaluate its impairment to peripheral nerves.Methods (1) Modeling: select 32 healthy New Zealand rabbits; implant 2 radioactive 125I seeds with the intensity of radioactivity 0.9mCi to both sides of the left sciatic nerves of the operating healthy New Zealand rabbits by operation; implant 2 125I seeds without radiation to both sides of the right sciatic nerves of the same rabbits. Regard as experimental group and control group separately, feeding routinely. (2) Measurement and analysis of action potential: measure the mixed nerve action potential, afferent nerve action potential and efferent nerve action potential of both sides of the experimental rabbits'sciatic nerves near the location where 125I seeds has been implanted at the time of fifth day, seventh day, tenth day and twentieth day. The indexes of measurement are amplitude and conduction velocity. Analyze and compare the difference of three action potentials of both experiment group and control group among points of time and the difference of every point of time between experimental group and control group. Evaluate the effect of 125I seeds to peripheral nerve fiber action potential.Result At all points of time after 125I seeds implantation, there is no effect on operating legs'movement of both experiment group and control group. From the time of fifth day, the amplitude and conduction velocity of mixed nerve action potential, afferent nerve action potential of experiment group descent obviously while that of efferent nerve action potential shows no difference statistically. Under electron microscope, the impairment of myelin sheath of nervous tissue aggravates gradually along with the passing of timeConclusion By releasingγ-ray and x-ray, 125I seeds irradiate nervous tissue in a short distance with low dose persistently. The myelin sheath of irradiated nerve fiber is distorted and ruptured, which lead to reduction of action potential's amplitude and conduction velocity of both afferent nerve fibers and mixed nerve fibers, nerve impulse blocked without effect upon amplitude and conduction velocity of peripheral efferent nerve fibers. These indicate that 125I radioactive seeds implantation for tumor's therapy may not only repress the growth of tumor, minify the volume of tumor but also relieve the pain accompanying with tumor, improve the patients'quality of life.