Bartynski W S, Boardman J F
Department of Radiology, Division of Neuroradiology, University of Pittsburgh, Presbyterian University Hospital, Pittsburgh, PA 15213, USA.
AJNR Am J Neuroradiol. 2008 Mar;29(3):447-55. doi: 10.3174/ajnr.A0839. Epub 2007 Dec 13.
The cause of posterior reversible encephalopathy syndrome (PRES) is unknown. Two primary hypotheses exist: 1) hypertension exceeding auto-regulatory limits leading to forced hyper-perfusion and 2) vasoconstriction and hypo-perfusion leading to ischemia with resultant edema. The purpose of this study was to evaluate the catheter angiography (CA), MR angiography (MRA), and MR perfusion (MRP) features in PRES in order to render further insight into its mechanism of origin.
In 47 patients with PRES, 9 CAs and 43 MRAs were evaluated for evidence of vasculopathy (vasoconstriction and vasodilation), and 15 MRP studies were evaluated for altered relative cerebral blood volume (rCBV) in PRES lesions and regions. Visualization of vessels on MRA and toxicity blood pressures were compared with the extent of hemispheric vasogenic edema.
Vasculopathy was present in 8 of 9 patients on CA (direct correlation to MRA in 3/6 patients). At MRA, moderate to severe vessel irregularity consistent with vasoconstriction and vasodilation was present in 30 of 43 patients and vessel pruning or irregularity in 7 patients, with follow-up MRA demonstrating reversal of vasoconstriction or vasodilation in 9 of 11 patients. Vasogenic edema was less in patients with hypertension compared with patients who were normotensive. Preserved normal length of the posterior cerebral artery (PCA) was commonly seen in patients with severe hypertension despite diffuse or focal vasoconstriction or vasodilation. In these patients, lengthier visualization of the distal PCA correlated with a lower grade of hemispheric edema (P = .002). Cortical rCBV was significantly reduced in 51 of 59 PRES lesions and regions compared with a healthy reference cortex (average 61% of reference cortex) with mild decrease in the remainder.
Vasculopathy was a common finding on CA and MRA in our patients with PRES, and MRP demonstrated reduced cortical rCBV in PRES lesions. Vasogenic edema was reduced in patients with hypertension, and superior distal PCA visualization correlated with reduced hemispheric edema in patients with PRES and severe hypertension.
后部可逆性脑病综合征（PRES）的病因尚不清楚。目前存在两种主要假说：1）高血压超过自动调节极限导致强制性高灌注；2）血管收缩和低灌注导致缺血并继发水肿。本研究的目的是评估PRES患者的导管血管造影（CA）、磁共振血管造影（MRA）和磁共振灌注（MRP）特征，以便进一步深入了解其发病机制。
对47例PRES患者的9次CA和43次MRA进行血管病变（血管收缩和血管扩张）证据评估，对15次MRP研究进行PRES病变及区域相对脑血容量（rCBV）变化评估。将MRA上血管的可视化情况及毒性血压与半球血管源性水肿程度进行比较。
9例接受CA检查的患者中有8例存在血管病变（3/6例与MRA直接相关）。在MRA检查中，43例患者中有30例存在与血管收缩和血管扩张一致的中度至重度血管不规则，7例患者存在血管分支减少或不规则，11例患者中的9例在随访MRA中显示血管收缩或扩张逆转。与血压正常的患者相比，高血压患者的血管源性水肿较少。尽管存在弥漫性或局灶性血管收缩或扩张，但在严重高血压患者中常见大脑后动脉（PCA）保持正常长度。在这些患者中，PCA远端更长的可视化与较低级别的半球水肿相关（P = .002）。与健康对照皮质相比，59个PRES病变及区域中有51个的皮质rCBV显著降低（平均为对照皮质的61%），其余病变及区域轻度降低。
在我们的PRES患者中，血管病变在CA和MRA检查中是常见表现，MRP显示PRES病变中皮质rCBV降低。高血压患者的血管源性水肿减轻，在PRES和严重高血压患者中，PCA远端良好的可视化与半球水肿减轻相关。
