猫脑缺血后氢谱N-乙酰天冬氨酸在各脑区分布特点的研究

目的　通过磁共振氢谱 (1 Hmagneticresonancespectroscopy ,1 HMRS)检查 ,了解猫脑缺血后不同受累脑区N 乙酰天冬氨酸 (N acetylaspartate ,NAA)的动态变化。方法　在猫持续性局灶脑缺血模型基础上 ,以磁共振弥散加权成像 (diffusionweightedimaging,DWI)异常区作为1 HMRS检查体域的定位标准 ,在缺血前后不同时间进行 1 HMRS检查 ,动态观察缺血中心区、半暗带区及其对侧镜相区域NAA的变化特点。结果　脑缺血后NAA很快减少 ,在中心区 ,缺血后 6h减至对侧的 5 0 %左右 ,缺血后 12h减至对侧的 2 0 %左右 ,2d后完全消失 ;而在半暗带区 ,NAA减少速度较慢 ,缺血后 12h减至正常的 6 0 %左右 ,随后维持在正常的 5 0 %左右 ,差异无显著性意义。结论　在缺血中心区 ,缺血后 6h内 ,NAA的变化最为剧烈 ;而在半暗带区 ,以缺血后 12h内变化明显。因此 ,挽救缺血半暗带和缺血中心区应有不同的治疗时间窗

Study of N-acetylaspartate distribution in different cerebral regions with 1H magnetic resonance spectroscopy after cerebral ischemia in cats

Objective To investigate dynamic changes of N acetylaspartate(NAA) in different impaired cerebral regions with 1H magnetic resonance spectroscopy( 1H MRS) after cerebral ischemia in cats.Methods The permanent focal cerebral ischemia model of cat was established by electrocoagulating the terminal of left middle cerebral artery via a transorbital approach.The bright intensity regions identified by diffusion weighted imaging(DWI) were used for 1H MRS voxel localization.One day before ischemia and 1 hour,3,6,12,24 hours,2,3,5,and 7days following ischemia,DWI and 1H MRS were made.The changes of NAA in ischemic core,ischemic penumbra,and their contralateral mirror regions at different time were compared.Results NAA peak was decreased quickly.The NAA in the core was decreaesed to 50% of initial value 6 hours after ischemia(P= 0.001 ),to about 20% 12 hours after ischemia(P=0.001),and disappeared 2 days after ischemia.The decrease in NAA was relatively slow in the penumbra.60% of NAA existed 12 hours after ischemia(P=0.001) and about 50% was maintained over the whole study.Conclusions There is a drastic NAA change in the ischemic core within 6 hours following ischemia,while the change in the penumbral region is obvious within 12 hours following ischemia.So the selection of "time window"for treatment should be different for penumbral and core areas.