可逆性后部白质脑病 POSTERIOR REVERSIBLE ENCEPHALOPATHY SYNDROME (PRES)

病史：

59 year old female  Altered mental status. History of bone marrow transplant 59岁女性,精神状态异常,有骨髓移植病史.

影像改变：

Head CT (with and without IV contrast): Bilateral temporal/occipital, bilateral parietal, and right frontal hypodensities with extension across the splenium of the corpus callosum. Hypodensities do not enhance post contrast administration. There is no mass-effect associated with these hypodensities.

头部CT(平扫与增强)显示:双侧颞/枕叶,双侧顶叶和右侧额叶可见低密度影,并通过胼胝体压部延伸扩展,低密度影无强化,无占位效应.

MR Brain: Areas of high signal throughout the white matter particularly involving the parietal regions with some extension on the right to the frontal lobe and inferiorly bilaterally to involve the occipital and right temporal lobes. No mass-effect is present. High signal on diffusion is appreciated only focally in the parietal regions at the gray-white junction. There is mild mass-effect, without hemorrhage or midline shift.

颅脑MR:主要累及双侧顶叶白质区的高信号影,右侧扩展至额叶,下方层面累及到双侧枕叶及右侧颞叶,无明显占位效应,弥散成像表现为双侧顶叶灰白质交界区的高信号影,无出血及中线移位.

诊断：

POSTERIOR REVERSIBLE ENCEPHALOPATHY SYNDROME (PRES) secondary to cyclosporin 继发于环孢菌素的可逆性后部白质脑病

要点：

• Consider the diagnosis when you see patchy cortical/subcortical posterior territory lesions in a patient with acute severely elevated BP 当病人出现急性严重的高血压,影像上表现为大脑后部皮质及皮质下补丁状异常病变时,需要考虑PRES
• 95% will have parietal occipital subcortical/cortical lesions that are hyper intense on T2/FLAIR sequences 95%的病人有顶枕叶的皮质或皮质下病变,T2/Flair序列上呈高信号影.
• Additional common locations include the cerebellum, junctions of vascular watershed zones. Can less commonly be seen in the basal ganglia; rarely in the brainstem or deep white matter 其他常见部位包括:小脑,分水岭区.很少一部分可以出现在基底节区,极少见于脑干与深部脑白质.
• Usually bilateral 通常是双侧
• Extent of findings is highly variable 病变的范围高度可变的
• Usually has a patchy morphology as opposed to a confluent one 通常表现为补丁状形态而不是融合
• Patchy, bilateral hypo dense foci with a predilection for the posterior circulation on CT 在CT上表现为补丁状/双侧低密度影,主要位于后循环区域.
• The most important differential diagnosis is cerebral ischemia. Acutely, diffusion will be decreased in cerebral ischemia, but increased in PRES. Diffusion, can, however, be increased if PRES is untreated and results in irreversible ischemia. 最重要的鉴别诊断为脑缺血症,急性期脑缺血弥散受限,PRES弥散增加.然而弥散也可以受限,假如PRES未得到处理而转变为不可逆的缺血.
• Usually reverses with control of BP but can occasionally result in death or permanent neurologic disability 通常在控制血压后是可逆的,但偶尔会导致死亡或永久性神经功能障碍.

讨论：

Posterior Reversible Encephalopathy Syndrome (PRES) or Reversible Posterior leukoencephalopathy syndrome (RPLS) is an increasingly recognized neurologic disorder with characteristic computed tomographic (CT) and magnetic resonance (MR) imaging findings, and it is associated with a multitude of diverse clinical entities. These include acute glomerulonephritis, preeclampsia and eclampsia, systemic lupus erythematosus, and thrombotic thrombocytopenic purpura and hemolytic-uremic syndrome, as well as drug toxicity from agents such as cyclosporine, tacrolimus, cisplatin, and erythropoietin. Most, but not all, cases manifest with acute to subacute hypertension, and seizures are also frequent. Classic CT findings are those of bilaterally symmetric low attenuation in the posterior parietal and occipital lobes, whereas MR imaging demonstrates hyperintensity on T2-weighted images in the same distribution. Since PRES is often unsuspected by clinicians, radiologists may be the first to suggest the diagnosis. As this diagnosis has important therapeutic and prognostic implications, radiologists should be aware of the spectrum of imaging findings in PRES.

PRES或RPLS是一种逐步为临床所认识的具有特征性的CT和MRI表现的神经系统病症,可有多种临床病因,包括急性的肾小球肾炎,先兆子痫和子痫,系统性红斑狼疮,血栓性血小板减少紫癜和溶血性尿毒症综合征,以及药物毒性如环孢菌素,他罗利姆,顺铂,红细胞生成素等.大多数,并不是所有,出现急性或亚急性高血压,癫痫发作也比较常见,典型的CT表现为双侧后顶叶及放射冠区对称性低密度影,MRI T2序列上表现为同样区域的高信号影,PRES经常为临床所忽视,放射人员可能首先诊断者,由于早期诊断对于预后有重要意义,放射医师应掌握PRES的各种影像改变.

Two pathophysiologic mechanisms for RPLS have been proposed. One postulates cerebral vasospasm with resulting ischemia within the involved territories, whereas the other posits a breakdown in cerebrovascular autoregulation with ensuing interstitial extravasation of fluid. Diffusion MR imaging can be used to discriminate between these two possibilities, as the cytotoxic edema of cerebral ischemia demonstrates decreased water mobility, whereas vasogenic edema due to cerebrovascular autoregulatory dysfunction results in increased water mobility.

对于PRES的病理生理有两种机制被推测,一种是考虑受累区域的脑血管痉挛导致脑缺血,而另一种推测考虑脑血管自身调节功能的故障导致细胞间隙内液体渗出,弥散成像可以用于鉴别两种情况.

病例来源：MYPACS.net