| Objective This experiment is proposed to irradiate the trigeminal nerve root of normal animals through gamma knife radiosurgery in different doses of radiation. At different time period, the results are observed in pathology and monitored in electrophysiology. The aim is to predict possible effect mechanism of gamma knife treating trigeminal neuralgia and recurrence, and relationship of complications and dose, and therefor provide a theoretical basis of the mechanism of the cranial nerve damage caused by gamma knife in clinical research.Methods Thirty New Zealand rabbits,which were randomly divided one group for pathological observation in three months and the other group for pathological observation in six months with fifteen in each, were used as the experiment of pathological study. Fifteen New Zealand rabbits for pathological observation in three and six months were randomly divided into the experimental group with twelve and the control group with three. According to different radiation dose, the experimental groups were randomly divided into four groups, which included60Gy group,80Gy group,100Gy group and120Gy group with three rabbits in each. Bilateral trigeminal nerves of all New Zealand rabbits in the experimental group were irradiated, and a4-mm isocenter was placed at trigeminal nerver root entry zone. All New Zealand rabbits for pathological observation in three months were sacrificed after three months. The roots were examined by light microscopy, immunohistochemistry, and electron microscopy. The experimental method of the group for pathological observation in six months was the same with that of the group for pathological observation in three months. All New Zealand rabbits for pathological observation in six months were sacrificed after six months. The roots were examined by light microscopy, immunohistochemistry, and electron microscopy. The results of the group for pathological observation in six months were compared with the results of the group for pathological observation in three months. Integrated optical density of the myelin staining and immunohistochemistry pathology results of experimental group and control group was examined by Image-pro plus6.0image processing system, and was analyzed using method of statistics. Fifteen New Zealand rabbits,which were randomly divided experimental group with twelve and the control group with three. According to different radiation dose, the experimental groups were randomly divided into four groups, which included60Gy group,80Gy group,100Gy group and120Gy group with three rabbits in each. Bilateral trigeminal nerves of all New Zealand rabbits in the experimental group were irradiated, and a4-mm isocenter was placed at trigeminal nerver root entry zone. Trigeminal somatosensory evoked potential of the experimental groups and the control group was examined before irradiation, and was examined at nine different time points of7,14,30,60,90,120,150,180days after irradiation. The data of every group was recorded in detail at different time points, and was analyzed using method of statistics.Results The results of group for pathological observation in three months showed the result of60Gy group after irradiation did not differ significantly compared with the result of control group. In80Gy group, there was part nerve fiber fragmentation, degeneration, and demyelination. In100Gy group, there was most nerve fiber fragmentation, degeneration, demyelination, and part of nervous necrosis. In120Gy group, there was almost nerve fiberdissolution, disappearance, demyelination, and most of nervous necrosis. Compared with the results of group for pathological observation in three months, the result of60Gy group for pathological observation in six months was not aggravated, while the results of80Gy,100Gy and120Gy group for pathological observation in six months were aggravated. Integrated optical density of the myelin staining and immunohistochemistry pathology results was analyzed using method of statistics. The result of60Gy group in three months did not differ significantly compared with that in six months (P>0.05). The result of80Gy,100Gy and120Gy group in three months differed significantly compared with that in six months (P<0.05). The results of trigeminal somatosensory evoked potential in this experiment suggested that the data of P1latency, N1latency, P2latency, P1-N1inter peak latency and N1-P2inter peak latency extended transiently at early7days and14days. Since30days after irradiation, the data did not differ significantly between the experimental group and control group (P>0.05), which was reversible change. After irradiation, the data of P1latency, N1latency, P2latency, P1-N1inter peak latency and N1-P2inter peak latency of trigeminal somatosensory evoked potential in80Gy group,100Gy group, and120Gy group extended over time and differed significantly between the experimental group and control group (P<0.05). After irradiation, the data of amplitude in60Gy group without any change did not differ significantly between the experimental group and control group (P>0.05). The data of amplitude in80Gy group,100Gy group, and120Gy group reduced over time and differed significantly between the experimental group and control group (P<0.05).Conclusions By choosing New Zealand rabbit as experiment object, this experiment successfully establishes the trigeminal nerve gamma knife radiation injury model which had many advantages of stable, economy, accurate, simple. The histopathological changes of the trigeminal nerve irradiated by gamma knife have a significant correlation with irradiation dose. The result of60Gy group after irradiation did not change significantly. The radiation injury of80Gy-120Gy group aggravated with increase of dose, and radiation injury in six months aggravated than radiation injury in three months.The changes of trigeminal nerve evoked potential are closely are closely related with gamma knife irradiation dose, and time. The data of peak latency and inter peak latency of trigeminal somatosensory evoked potential in60Gy group extended transiently differed in the early days, which was reversible change. The data of amplitude in60Gy group did have any change. The data of peak latency, inter peak latency in80Gy group,100Gy group, and120Gy group increased and the date of amplitude reduced over time, which was irreversible change. |
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