颅内动脉瘤影像诊断的价值
一.概述
动脉瘤是动脉壁的某一部分因病变而向外突出,形成永久性的局限性扩张,可由于管壁的先天性缺陷所致,也可以是获得性的。脑动脉瘤发生率为1.5%~8%,是引起蛛网膜下腔出血最常见的原因,死亡率高达50%。动脉瘤的外形不一,可呈囊状、梭形、柱状和蜿蜒状等。囊状动脉瘤是由血管起源处或分叉部先天性缺陷造成的,血管内压力高,使管壁缺陷部分向外局限性膨出。囊状动脉瘤占颅内动脉瘤的80%—90%,颅内囊状动脉瘤好发于Willis动脉环及脑动脉分叉、分支和弯曲部,约30%~37%发生在大脑前动脉系统,91%位于前交通动脉。
二.动脉瘤模型的制备
由于在人体研究颅内动脉瘤受到很多因素的制约,因此采用模型的方法研究动脉瘤的血流动力学、动脉瘤的生成、生长、血栓形成与破裂之间的关系,以及评价血管内栓塞治疗的效果成为主要手段。
动脉瘤动物模型的制作方法分为两大类:一类是诱发的颅内动脉瘤。毒力因素如高渗盐水、透明质酸酶、氮芥类物质不能形成一致性、可重复的动脉瘤。Hashimoto和Hazama等,结扎猴子一侧或双侧颈总动脉造成高血压,并饲含β-氨基丙腈的饲料,使动脉自身形成动脉瘤,其发病机制和发病部位都与人类颅内囊状动脉瘤十分相似。但动脉瘤的部位和发生频率均难以预测,且需要几年时间才能形成。Cawley等用微导管向结扎的颈外动脉分支囊腔内注射弹性蛋白酶建立兔动脉瘤模型,其特点是动脉瘤的狭颈和总体结构类似于人类颅内囊状动脉瘤,但该模型不仅制作困难,而且动脉瘤三层结构在组织学上与人类颅内动脉瘤不同,动脉分支结扎后,形成反常的血流动力学改变。另一类是静脉移植法,即人为地制作一个动脉瘤,方法是用静脉制成一个静脉囊,将它镶嵌在颈总动脉的不同部位,制成单侧型、分叉型和未梢型动脉瘤,分别类似于人临床上颅内囊状动脉瘤的三种类型。此模型的优点是成功率高,重复性好,造型时间短,一般两周后就可用于观察。由于静脉的平滑肌层远少于动脉肌层,只起到支撑管腔的作用,没有运动功能,而类似人类颅内囊状动脉瘤囊壁的内弹力层和平滑肌层缺如或显著减少,或仅由纤维结缔组织构成的这种形态结构。Miskolczi等认为动脉瘤颈部的手术斑痕可减弱血流对动脉瘤壁的切应力,静脉囊壁与自动形成的动脉瘤壁组织学上的差异,限制了它对动脉瘤治疗效果的评价,也不宜进行动脉瘤发展过程的血流动力学研究。而Strothet等研究表明三种类型犬颈总动脉静脉囊动脉瘤模型对血流动力学的改变类似于人类颅内囊状动脉瘤。(全文见PDF)……
参考文献:
[1]宋继海,主编.病理学.北京:科学出版社,1999,28-50.
[2]尚京伟,戴建平,王忠诚,等.颅内动脉瘤的介入放射治疗.中华放射学杂志, 1996,1:33.
[3]Hashimoto N, Kim C, Kikuchi H, et al. Experimental induction of cerebral aneurysms in monkeys. J neurosurg, 1987,67:903-905.
[4]Hazama F, Hashimoto N. An animal model of cerebral aneurysms.Neuropathol Appl neurobiol, 1987,13:77-90.
[5]Cawley CM, Dawson RC, Shengelaia G, et al. Arterial saccular aneurysm model in the rabbit. AJNR Am J neuroradiol, 1996,17:1761-1766.
[6]Miskolczi L, Guterman IR, Flaherty JD, et al. Rapid saccular aneurysm induction by elastase application in vitro. neurosurgery, 1997,41: 220-229.
[7]Strother CM, Graves VB, Rappe A. Aneurysm hemodynamics: an experimental study. Am jNeuroradiol, 1992,13:1089-1095.
[8]Bowen Bc, Quencer RM, Margosian P, et al. MR angiography of ocelusive disease of the arteries in the head neck: current concepts. aJR, 1994,162(1):9-18.
[9]Korogi Y,Takahashi M,Mabuchi N,et al. Intracranial aneurysms:diagnostic accuracy of three-dimensional, fourier transform,time-flight MR angiography. Radiology, 1994,193:181-186.
[10]Schuierer G, WJ, Laub G. Magnetic resonance angiography of intracranial aneurysms: comparison with intra-arterial digital subtraction angiography. Neuroradiology, 1992,35:50.
[11]Horikoshi T, Fukamachi A, Nishi H, et al. Detection of intracranial aneurysms by three-dimentional time of flight magnetic angiography.Neuroradiology, 1994,36:203.
[12]张宗军,许建,李苏健,等.磁共振血管造影在脑动脉瘤诊断中的应用价值.中华放射学杂志, 1996,30:139.
[13]Bosmans H,Wilms G,Marchal G, et al. Characterisation of intracranial aneurysms with MR angiography. Neuroradiology, 1995,37:262.
[14]Snidow,JJ,Johnson MS,Harris VJ,et al.Three-dimentional gadolinium-enhanced MR angiography for anrtoiliae inflow assessment plus renal artery screening in a single breath hold. Radiology, 1996, 198: 725-732.
[15]Anderson GB,Findlay JM,Steinke DE,et al. Experience with computed tomographic angiography for the detection of intracranial aneuysms in the setting of acute subarchnoid hemorrhage. neurosurgery, 1997,41: 522-528.
[16]Ogawa T, Okudera T, Noguchi K, et al.Cerebral aneurysms:evaluation with three-dimensional CT angiography. AJNR, 1996,17:447-454.
[17]Brown JH, Lustrin ES, Lev MH, et al. Characterization d intracrnial aneurysms using CT angiography. AIR, 1997,169:889-893.
[18]Viceo PT, Maurin EE, Cross CE, et al. Vertebrobasilar delichoectasia: evaluation with CT angiography. AJNR, 1997,18:1385-1388.
[19]John NKH, Eison YL, Joseph MKL, et al. The role of computed tomographic angiography in the diagnosis of intracranial aneurysms and emergent aneurysms clipping. neurosurgery, 1996,28:481.
[20]Korogi Y,Takahashi M, Katada K, et al.Intracranial aneurysms:detection with three-dimensional CT angiography with volume renderingcomparison with conventional angiographic and surgical finding.Radiology, 1999,211:497-506.