图形翻转视觉诱发电位在视神经管减压后视神经损伤不同时期的变化特征

Changes of visual evoked potentials in traumatic optic nerve injury model following optic nerve decompression

目的:观察视神经损伤动物模型在损伤后和不同时期视神经管减压后视觉诱发电位的变化,了解创伤性视神经损伤的手术时机与疗效的关系。方法:实验于2005-03/05在解放军南京军区南京总医院动物实验中心完成。①实验分组:30只新西兰白兔随机分为正常对照组、术后2d减压组、术后7d减压组、术后14d减压组、术后不减压组,每组6只。②造模:除正常对照组外,其余各组在视神经孔中塞入一细端为2mm直径的圆锥软硅胶,阻塞视神经孔,造成视神经的挤压伤。③指标检测:采用图形翻转视觉诱发电位检测损伤前、损伤后1h、减压前1h、减压后2周视功能变化,记录NPN曲线主波(P波)的绝对潜伏期、绝对波幅。正常对照组仅采集一组数据作为对照。结果:30只实验动物均进入结果分析。①正常对照组家兔图形翻转视觉诱发电位检查均引出典型NPN波型曲线,视神经挤压伤后1hNPN波形低阔扁平,P波潜伏期延长,波幅降低。②P波潜伏期:术后2d减压组减压后短于减压前[(71.25±8.51),(86.47±14.28)ms,P<0.05];术后7d减压组减压前后比较差异无显著性(P>0.05);术后14d减压组减压后明显长于减压前[(158.73±15.16),(116.35±17.13)ms,P<0.05]。术后2d减压组和术后7d减压组短于术后不减压组(P<0.01)。术后7,14d减压组和术后不减压组明显长于正常对照组(P<0.01)。③P波波幅:术后2d减压组减压后高于减压前[(5.25±0.78),(4.42±0.42)μV,P<0.05]。术后2d减压组减压后低于术后7d减压组、术后14d减压组(P<0.01),术后14d减压组低于术后7d减压组(P<0.05);术后7d减压组、术后14d减压组、术后不减压组低于正常对照组(P<0.01)。结论:神经元继发性损伤是视功能进行性下降的重要原因,视神经减压术有利于减轻视神经间接损伤,较早期(损伤后48h以内)减压可阻止轴突继发性损伤,避免视功能进一步下降,并在一定程度上逆转视功能的损害。

AIM： To observe the changes of the visual evoked potentials and find out the correlation between operation opportunity and clinical effect of traumatic optic nerve injudes in the optic neuropathy models following the optic nerve decompression. METHODS： The experiment was carded out in the Animal Experimental Center, Nanjing General Hospital of Nanjing Military Area Command of Chinese PLA from March to May in 2005.①Thirty New Zealand rabbits were randomly divided into A, B, C, D and E groups, representing normal control, decompression in 2, 7, 14 days post-trauma, and non-decompression group respectively. Each group contained 6 rabbits.②Except the normal controls, other rabbits were chose for establishing the models of traumatic optic nerve injury by optic foramen occlusion with circular silica gel, in which diameter was 2 mm. ③Before injury, 1 hours after injury, 1 hour before decompression, and 2 weeks after decompression, pattern reversal visual evoked potentials （P-VEP） was adopted to detect the optic functional change. The absolute latent period and amplitude of NPN contour P wave were recorded. Only a set of data in normal control group was selected. RESULTS： All of 30 rabbits were involved in the result analysis. ①P-VEP of normal controlled rabbits revealed typical NPN contours, while NPN waves in injured rabbits were low and fiat. The latent period of P wave was lengthened and the amplitude was reduced. ②The latent period of P wave was shorter in B group post-decompression than that pre-decompression [（71.25±8.51）, （86.47±14.28） ms, P 〈 0.05], and obviously longed in D group post-decompression than that pre-decompression [（158.73±15.16）, （116.35±17.13） ms, P 〈 0.05]. Comparison on latent period of P wave in P-VEP before and after decompression showed the insignificant differences in C group （P 〉 0.05）. The latent period of P wave was shorter in B and C groups compared with E group （P 〈 0.01）, and obviously longer in C, D, E groups compared with A group （P 〈0.01）.③Comparison on the amplitude of P wave in P-VEP before and after decompression showed the significant differences in B group [（5.25±0.78）, （4.42±0.42） μV, P 〈 0.05]. The amplitude of P wave post-decompression was lower in B group than in C and D groups （P〈 0.01）, also lower in D group than in C group （P〈 0.05）. Compared with A group, significant differences were found in C, D, E groups （P 〈 0.01 ）. CONCLUSION： The neural secondary injury is an important factor for visual impairment. The optic nerve decompression is beneficial to relieve the indirect optic nerve injuries. Visual function may be better improved by decompression within 48 hours after injury, which protect axonal secondary injury and deteriorate the damage of visual functions.