Herpes simplex encephalitis: diffusion MR imaging findings.

We studied five patients with herpes simplex encephalitis type 1 with diffusion-weighted MR imaging, as this sequence provides information regarding tissue integrity. Diffusion-weighted imaging was obtained using the echo-planar sequence. True diffusion images (i.e. b=1000s/mm(2) images), and the ADC (apparent diffusion coefficient) values were studied. In addition, diffusion imaging of 12 normal cases, 46 patients with acute ischemia (cytotoxic edema), and 12 patients with vasogenic edema were studied for comparison. In patients with herpes encephalitis, two distinct types of diffusion imaging findings (on b=1000s/mm(2) images, and ADC maps) were noted: lesions similar to cytotoxic edema, and lesions similar to vasogenic edema. The patients with the former type of lesions had fulminating disease, and were in severe clinical condition. Those with the latter represented early cases, and they were in fairly good clinical condition with a good outcome by prompt therapy. Diffusion imaging appears to be a promising sequence to monitor the changes in the brain tissue in herpes encephalitis, and in other infections as well with respect to restriction of movement (cytotoxic edema) or relatively high-motion (vasogenic edema) of water molecules, providing data on the severity of the disease.     

猫闭合性创伤性脑水肿扩散加权成像的实验研究

目的建立猫急性闭合性脑创伤(TBI)模型,并应用扩散加权成像(DWI)探讨伤后脑水肿类型及演变规律。方法共选取22只猫,以最大角加速度(6.43±0.15)×105rad/s2制成TBI模型,其中10只用于常规MRI及DWI扫描,连续观察伤前及伤后3、6、24、48、72 h 6个时相点,另于上述相同6个时相点,分别选取6只猫用于HE及嗜银染色、6只猫用于透射电镜观察。结果常规MRI显示蛛网膜下腔出血1例、硬膜外或硬膜下出血2例、脑挫裂伤2例、脑室内出血1例、同时显示蛛网膜下腔出血和脑挫裂伤2例、同时显示硬膜下出血和脑实质内点状出血2例。10只猫致伤前后各时点ADC值显示细胞毒性及血管源性两种类型脑水肿,其中7只(70%)猫以细胞毒性脑水肿改变为主,24 h达峰值;3只(30%)猫早期以血管源性脑水肿改变为主,6 h达峰值,而后期以细胞毒性脑水肿为主。HE、嗜银染色及透射电镜显示血管通透性增加、细胞肿胀,轴索肿胀、断裂、轴索球形成。结论猫急性闭合性创伤性脑水肿包括细胞毒性及血管源性两类,以细胞毒性水肿为主。扩散加权成像是观测脑水肿的一种可靠方法。     

A preliminary report of brain edema in patients with uremia at first hemodialysis: evaluation by diffusion-weighted MR imaging

BACKGROUND AND PURPOSE: The dynamics of brain-water content associated with hemodialysis in patients with severe azotemia remains obscure. To investigate whether either interstitial or cytotoxic edema is responsible for dialysis disequilibrium syndrome (DDS), we used diffusion-weighted MR imaging (DWI) to measure the apparent diffusion coefficient (ADC), which is sensitive for detecting tissue water dynamics. METHODS: Eight consecutive patients with end stage renal disease (ESRD) and blood urea nitrogen level of more than 100 mg/dL (160.9 +/- 53.1 mg/dL) were recruited. Conventional MR images, DWI, and clinical manifestations were obtained before and after the 1st hemodialysis. The ADC values were determined for regions of normal-appearing gray and white matter and for regions of hyperintensity of white matter on T2-weighted MR imaging. RESULTS: Foci of bright areas of white matter were found in all patients on T2-weighted images. The ADC values of the patients with ESRD, in white matter and gray matter before and after hemodialysis, were greater than those of the healthy controls (P < .005). Regarding the impact of hemodialysis, the ADC of frontal lobe white matter increased significantly after hemodialysis (1.09 +/- 0.11 versus 1.03 +/- 0.11, P = .036). We did not find the specific area of brain edema reported in posterior leukoencephalopathy and the osmotic demyelination syndrome. CONCLUSIONS: These results suggest that severe azotemia in end stage renal disease leads to interstitial brain edema reflected as increased ADC, and the further increased ADC reflects that edema associated with 1st hemodialysis is interstitial rather than cytotoxic in nature.     

Diffusion-weighted echo-planar MR imaging of CNS involvement in systemic lupus erythematosus

RATIONALE AND OBJECTIVES: The purpose of this study was to determine the range of findings at diffusion-weighted magnetic resonance (MR) imaging in patients with systemic lupus erythematosus (SLE) and central nervous system involvement. MATERIALS AND METHODS: Diffusion-weighted MR images were reviewed in 20 patients with SLE and correlated with clinical symptoms and findings at computed tomography, conventional MR imaging, MR angiography, or conventional angiography. RESULTS: Diffusion-weighted MR imaging showed acute or subacute lesions in nine of 20 patients (45%). In the other 11, it showed no abnormal findings or chronic lesions. In four of the nine patients with lesions, diffusion-weighted imaging primarily showed hyperintense lesions with decreased apparent diffusion coefficient (ADC), which indicates acute or subacute infarcts. In four other patients, it primarily showed iso- or slightly hyperintense lesions with increased ADC, suggesting vasogenic edema. In two of these four patients, the findings were consistent with hypertensive encephalopathy. In the other two, small hyperintense foci on diffusion-weighted images with decreased ADC were seen within the vasogenic edema. These foci presumably represent microinfarcts associated with SLE vasculopathy. In the ninth patient, diffusion-weighted imaging showed a small linear hyperintense lesion with normal ADC in the left parietooccipital region. CONCLUSION: Diffusion-weighted imaging shows primarily two patterns of acute or subacute parenchymal lesions in patients with SLE: acute or subacute infarction and vasogenic edema with or without microinfarcts.     

Alterations in diffusion and perfusion in the pathogenesis of peritumoral brain edema in meningiomas

Magnetic resonance perfusion and diffusion studies were undertaken to clarify the significance of ischemia in the pathogenesis of peritumoral brain edema in patients with meningiomas. Included in this study were 26 patients with 27 meningiomas and 5 gliomas. Perfusion-weighted imaging (PWI) was performed using a gradient-echo, echo-planar-imaging (EPI) sequence for calculation of the relative regional cerebral blood volume (rrCBV) and the relative regional cerebral blood flow index (rrCBFi). Furthermore, multi-slice spin-echo EPI sequences were applied in order to obtain anisotropic and isotropic diffusion-weighted imaging (DWI). Apparent diffusion coefficient (ADC) values were then calculated for peritumoral brain parenchyma from tumors, with and without edema, using various diffusion sensitivities. Meningiomas without edema demonstrated a minimal increase of perfusion parameters in the peritumoral brain tissue. In contrast, cases with brain edema had highly significant ( p<0.0005) lower rrCBV and rrCBFi. The edema index (EI) correlated strongly with the rrCBV. A fitting procedure resulted into the following mathematical relation: EI=0.1/rrCBV(2). The DWI showed a significantly larger ADC value within areas of brain edema, compared with the normal white matter (0.74 x 10(-3) vs 1.55 x 10(-3) mm(2)/s; p<0.0001). Increases in EI correlated with increases in ADC values. In 31% of the meningiomas associated with edema, areas with increased signal, probable ischemia, demonstrated significantly lower ADC values, in comparison with the rest of the edematous areas. These areas were confined to tissue immediately adjacent to the tumor. In general, the decrease in rrCBV in brain edema represents a consequence from, rather than a cause of, vasogenic edema. Ischemic alterations can be regarded as secondary, facultative phenomena in the pathogenesis of meningioma-related brain edema.     

Diffusion-weighted MRI in diffuse axonal injury of the brain

The goal of this study was to identify and describe the different types and patterns of tissue injury which are encountered by diffusion-weighted imaging (DWI) in diffuse axonal injury (DAI) of the brain. The DWI data sets of 98 patients who suffered from a closed-head injury were retrospectively evaluated. Medical records were reviewed to rule out pre-existing neurological diseases. Lesions were studied for their DWI signal characteristics and lesion size or extension. Traumatic lesions were classified into three categories depending on their signal characteristica on DWI and apparent diffusion coefficient (ADC) maps: type 1, DWI- and ADC-hyperintense most likely representing lesions with vasogenic edema; type 2, DWI-hyperintense, ADC-hypointense indicating cytotoxic edema; type 3, central hemorrhagic lesion surrounded by an area of increased diffusion. According to the size and extent of lesions, injury was classified into three groups: group A, focal injury; group B, regional/confluent injury; and group C, extensive/diffuse injury. Our study showed that diffusion-weighted imaging differentiates between lesions with decreased and increased diffusion in patients with DAI. Different degrees of tissue injury extent were noticed. Future prospective studies should study if this additional information can be used as a predictor of injury reversibility, final outcome and prognosis.     

急性闭合性创伤性脑水肿扩散加权成像的实验研究

目的：建立猫急性闭合性脑创伤（TBI）模型,并应用扩散加权成像（DWI）探讨伤后脑水肿类型及演变规律。方法：共选取22只猫,以最大角加速度（6．43±0．15）×10^5 r／s^2制成TBI模型,其中10只用于常规MRI及DWI扫描,连续观察伤前及伤后3、6、24、48和72h六个时相点,另于上述相同6个相点,分别选取6只猫用于HE及嗜银染色、6只猫用于透射电镜观察。结果：常规MRI显示蛛网膜下腔出血1例、硬膜外／硬膜下出血2例、脑挫裂伤2例、脑室内出血1例、同时显示蛛网膜下腔出血和脑挫裂伤2例、同时显示硬膜下出血和脑实质内点状出血2例。10只猫致伤前后各时间点ADC值显示细胞毒性及血管源性两种类型脑水肿,其中7只（70％）猫以细胞毒性脑水肿改变为主,24h达峰值;3只（30％）猫早期以血管源性脑水肿改变为主,6h达峰值,而后期以细胞毒性脑水肿为主。HE、嗜银染色及透射电镜显示血管通透性增加、细胞肿胀,轴索肿胀、断裂、轴索球形成。结论：猫急性闭合性创伤性脑水肿包括细胞毒性及血管源性两类,以细胞毒性水肿为主。扩散加权成像是观测脑水肿的一种可靠方法。     

Glucocorticoid treatment of brain tumor patients: changes of apparent diffusion coefficient values measured by MR diffusion imaging

Glucocorticoids (GCC) generally are administered to patients with brain tumors to relieve neurological symptoms by decreasing the water content in a peritumoral zone of edema. We hypothesized that diffusion imaging and apparent diffusion coefficient (ADC) values could detect subtle changes of water content in brain tumors and in peritumoral edema after GCC therapy. The study consisted of 13 patients with intra-axial brain tumor, and ADC was measured in the tumor, within peritumoral edema, and in normal white matter remote from the tumor before and after GCC therapy. ADC also was measured in normal white matter in four control patients with no intracranial disease who were treated with GCC for other indications. Conventional MR images showed no visually evident interval change in tumor size or the extent of peritumoral edema in any subject after GCC therapy, which nonetheless resulted in a decrease in mean ADC of 7.0% in tumors (P<0.05), 1.8% in peritumoral edema (P>0.05, not significant) and 5.8% in normal white matter (P<0.05). In patients with no intracranial disease, GCC therapy decreased mean ADC in white matter by 5.4% (P<0.05). ADC measurement can demonstrate subtle changes in the brain after GCC therapy that cannot be observed by conventional MR imaging. Measurement of ADC proved to be a sensitive means of assessing the effect of GCC therapy, even in the absence of visually discernible changes in conventional MR images.     

Apparent diffusion coefficient in vasogenic edema and reactive astrogliosis

Introduction Distinguishing between vasogenic edema and reactive astrogliosis may be difficult in some instances. This study was performed to test the hypothesis that diffusion-weighted (DW) imaging with apparent diffusion coefficient (ADC) maps can be used to differentiate these two types of changes. Methods The study population included 11 patients with perilesional vasogenic edema and 11 patients with gliosis examined with conventional MR imaging and DW imaging. The signal intensities of conventional pulse sequences and ADC values were calculated in regions of interest placed in the hyperintense edematous or gliotic regions and compared with those of normal-appearing white matter. Signal intensity ratios and ADC values in gliosis were compared with those in vasogenic edema using the Mann-Whitney U-test. Results While considerable overlap was present for signal intensity ratios on conventional MR images, areas of gliosis demonstrated significantly higher ADC values (1.76 ± 0.09 × 10⁻³ mm²/s) than areas of vasogenic edema (1.35 ± 0.06 × 10⁻³ mm²/s; P < 0.0001) without overlap. Conclusion ADC values are helpful in differentiating reactive gliosis from vasogenic edema.     

Eclamptic encephalopathy: MRI,including diffusion-weighted images

Eclampsia is a rare condition peculiar to pregnant and puerperal women. We analyse imaging features in five patients with eclampsia, and determine whether diffusion-weighted imaging (DWI) could differentiate cytotoxic and vasogenic oedema in four of them. All were imaged within 4 days of the onset of symptoms. We found lesions with a prolonged T2 in the brain of all five patients, in the basal ganglia in four, pons in three and posterior cerebral white matter in two. Isotropic DWI revealed variable intensity in these regions. The ADC was decreased in one, and increased in all the others. The lesion with reduced ADC progressed to infarction.     

Subarachnoid hemorrhage in the subacute stage: elevated apparent diffusion coefficient in normal-appearing brain tissue after treatment

PURPOSE: To prospectively evaluate whether subarachnoid hemorrhage (SAH) is associated with a change in the apparent diffusion coefficient (ADC) in normal-appearing brain parenchyma. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained for all patient and volunteer studies. One hundred patients (48 men, 52 women; mean age, 52 years +/- 12 [standard deviation]) with aneurysmal SAH underwent conventional and diffusion-weighted magnetic resonance (MR) imaging at a mean of 9 days +/- 3 after SAH to evaluate possible lesions caused by SAH, treatment of SAH, and vasospasm. Aneurysms were treated surgically (n = 70) or endovascularly (n = 30) before MR imaging. Diffusion-weighted MR imaging was performed at 1-year follow-up in 30 patients (10 men, 20 women; mean age, 51 years +/- 11). Thirty healthy age-matched volunteers (11 men, 19 women; mean age, 54 years +/- 16) underwent MR imaging with an identical protocol. ADC values were measured bilaterally in the gray and white matter (parietal, frontal, temporal, occipital lobes; cerebellum; caudate nucleus; lentiform nucleus; thalamus; and pons) that appeared normal on T2-weighted and diffusion-weighted MR images. Linear mixed model was used for comparison of ADC values of supratentorial gray matter and white matter; general linear regression analysis was used for comparison of ADC values of cerebellum and pons. RESULTS: In patients with SAH, the ADC values in normal-appearing white matter, with a single exception in the frontal lobe (P = .091), were significantly higher than they were in healthy volunteers (P /= .121). CONCLUSION: SAH and its treatment may cause global mild vasogenic edema in white matter and deep gray matter that is undetectable on T2-weighted and diffusion-weighted MR images but is detectable by measuring the ADC value in the subacute stage of SAH.     

Diffusion-weighted magnetic resonance imaging of dural sinus thrombosis

Magnetic resonance imaging (MRI) is useful to diagnose dural sinus thrombosis. However, the representative appearance of dural sinus thrombosis on diffusion-weighted MRI has not been established. This study was aimed at determining whether cytotoxic or vasogenic edema is more predominant in the affected cerebral parenchyma and assessing the time courses and prognosis of dural sinus thrombosis lesion. The studies on sixteen patients with dural sinus thrombosis who underwent diffusion-weighted MRI were retrospectively reviewed. The diagnosis was confirmed by digital subtraction angiography in 11 patients and magnetic resonance angiography in five patients. Diffusion-weighted images with echo-planar imaging were obtained using two or three b values, with the highest b value of up to 1,000 s/mm(2). A region of interest was placed on an area of abnormal signal intensity to calculate apparent diffusion coefficients (ADCs). Nine of the 16 patients had lesions with an increased ADC, whereas, three of these nine patients also had lesions with a decreased ADC. Among 11 patients who underwent initial MRI within 7 days of their last episode, eight had lesions with an increased ADC, of whom three had lesions mixed with both decreased and increased ADC areas. Follow-up studies of these three patients revealed the development of hemorrhagic infarction in two and subcortical hemorrhage in one. Vasogenic edema develops more predominantly and earlier in dural sinus thrombosis, though cytotoxic edema was also associated with the pathological changes in the early phase. Decrease of ADC value is presumed to reflect severe pathological conditions and indicate possible future development of infarction or hemorrhage.     

围产期脑后部可逆性脑病综合征的临床影像分析

目的：分析研究围产期脑后部可逆性脑病综合征的影像特征,提高诊治水平。方法：回顾性分析我院30例围产期脑后部可逆性脑病综合征患者的临床及影像学资料。结果：所有患者均急性起病,8例产前发病,22例产后发病（其中20例发生于自然阴道分娩后,2例为剖宫产术后发病）;16例发生于产后48h后。产前发病者6例具有子痫前期表现,而产后发病者仅1例具有子痫前期表现。首发症状以头痛为主,主要表现头痛（23例）、抽搐（22例）、视觉异常（19例）、意识障碍（8例）。影像表现为双侧对称性可逆性以大脑后部皮质下白质为主的病变,包括枕叶（27例）、顶叶（23例）、颞叶（10例）、额叶（7例）等。MR扩散成像显示血管源性脑水肿。治疗以降血压和控制癫痫为主,所有患者的临床症状和影像改变在1天～6个月有明显改善或消退,其中25例在2周内缓解。结论：围产期脑后部可逆性脑病综合征具有特征性的临床和影像表现,好发于产后,特别是产后48h后,且发病前多无子痫前期;MR扩散成像有助于鉴别病灶性质;治疗及时病灶完全可逆,预后良好。     

低氧致脑水肿的磁共振扩散加权成像和病理观察

目的 通过对模拟高原低氧致脑水肿的磁共振扩散加权成像和病理改变的研究,探讨高原脑水肿的病理基础.方法 选320～380 g的雄性Wistar大鼠32只,按体重随机分为常氧组、4 000 m组、6 000 m组和8 000 m组各8只.后3组动物置于低压舱中模拟海拔4 000 m、6 000 m、8 000 m高原低氧环境持续8 h后,对所有大鼠进行扩散加权成像检查及脑组织的光镜和电镜观察.结果 低氧处理的各组扩散加权成像均出现低强度信号,表观扩散常数值升高.与常氧组比较,4 000 m组表观扩散常数值的升高无明显差异,6 000 m组和8 000 m组表观扩散常数值升高有显著性差异.病理检查显示,4 000 m组脑组织呈现混合性脑水肿,血脑屏障轻度损伤;6 000 m组以血管源性脑水肿为主,血脑屏障损伤加重;8 000 m组重度血管源性脑水肿,血脑屏障破坏解体.结论 低氧所致的脑水肿主要是血管源性脑水肿,其病理基础是低氧导致的血脑屏障损害.     

Atypical manifestations of reversible posterior leukoencephalopathy syndrome: findings on diffusion imaging and ADC mapping

Typically, reversible posterior leukoencephalopathy syndrome (RPLS) involves the parieto-occipital lobes. When regions of the brain other than the parieto-occipital lobes are predominantly involved, the syndrome can be called atypical RPLS. The purpose of this study is to find radiological and pathophysiological features of atypical RPLS by using diffusion-weighted imaging (D-WI). We retrospectively reviewed seven patients (two with eclampsia, one with cyclosporine neurotoxicity, and four with hypertensive encephalopathy) with atypical MR manifestations of RPLS. Changes in signal intensity on T2-weighted imaging (T2-WI) and D-WI, and ADC ratio, were analyzed. In patients with atypical manifestation of RPLS, high signal intensities on T2-WI were noted in the frontal lobe, basal ganglia, thalamus, brainstem, and subcortical white matter in regions other than the parieto-occipital lobes. These areas of increased signal intensities on T2-WI showed increased ADC values, representing vasogenic edema in all seven patients. This result should be very useful in differentiating atypical RPLS from other metabolic brain disorders that affect the same sites with cytotoxic edema.     

Diffusion-weighted imaging shows cytotoxic and vasogenic edema in eclampsia.

In eclampsia, MR imaging shows reversible T2 hyperintensities in a parietal and occipital distribution. Findings on diffusion-weighted images suggest that these abnormalities are areas of vasogenic edema. We describe the presence of both cytotoxic and vasogenic edema, as detected by diffusion-weighted imaging, in a woman with eclampsia. Follow-up MR imaging showed that the regions of cytotoxic edema progressed to cerebral infarction. This case suggests that diffusion-weighted imaging allows the early detection of ischemic infarcts in patients with eclampsia.     

Parenchymal abnormalities associated with cerebral venous sinus thrombosis: assessment with diffusion-weighted MR imaging

BACKGROUND AND PURPOSE: The common entity cerebral venous sinus thrombosis is associated with the poorly characterized imaging finding of parenchymal abnormalities; diffusion-weighted imaging has offered some insight into these manifestations. We assessed the relationship between the diffusion constant from apparent diffusion coefficient (ADC) maps in patients with cerebral venous thrombosis (CVT) with follow-up imaging findings and clinical outcome. METHODS: We evaluated the medical records and T2-weighted MR images of 13 patients with CVT complicated by intraparenchymal abnormality. Diffusion-weighted (DW) images and ADC maps were evaluated for increased, decreased, or unchanged signal intensity and were compared with signal intensity of contralateral, normal-appearing brain. In addition, ADCs were obtained in nine pixel regions of interest in abnormal regions in eight of the 13 patients. RESULTS: Eight patients had superficial CVT, and five had superficial and deep CVT. CVT of deep veins was associated with deep gray nucleus and deep white matter abnormalities, whereas superficial CVT was associated with cortical and subcortical abnormalities. Twenty-four nonhemorrhagic lesions were identified in 10 of 13 patients on the basis of follow-up imaging findings. Four patients without seizures had lesions with decreased diffusion that appeared hyperintense on follow-up T2-weighted images, three patients with seizures had lesions with decreased diffusion that resolved, and seven patients had lesions with increased diffusion that resolved. Three of 10 patients had more than one lesion type. No difference was noted in mean ADCs for lesions with decreased diffusion that resolved compared with lesions with decreased diffusion that persisted. CONCLUSION: DW imaging in these patients disclosed three lesion types: lesions with elevated diffusion that resolved, consistent with vasogenic edema; lesions with low diffusion that persisted, consistent with cytotoxic edema in patients without seizure activity; and lesions with low diffusion that resolved in patients with seizure activity. This information may be important in prospectively determining severity of irreversible injury and in patient treatment.     

MR imaging with quantitative diffusion mapping of tacrolimus-induced neurotoxicity in organ transplant patients

Our objective was to investigate brain MR imaging findings and the utility of diffusion-weighted (DW) imaging in organ transplant patients who developed neurologic symptoms during tacrolimus therapy. Brain MR studies, including DW imaging, were prospectively performed in 14 organ transplant patients receiving tacrolimus who developed neurologic complications. In each patient who had abnormalities on the initial MR study, a follow-up MR study was performed 1 month later. Apparent diffusion coefficient (ADC) values on the initial MR study were correlated with reversibility of the lesions. Of the 14 patients, 5 (35.7%) had white matter abnormalities, 1 (7.1%) had putaminal hemorrhage, and 8 (57.1%) had normal findings on initial MR images. Among the 5 patients with white matter abnormalities, 4 patients (80.0%) showed higher than normal ADC values on initial MR images, and all showed complete resolution on follow-up images. The remaining 1 patient (20.0%) showed lower than normal ADC value and showed incomplete resolution with cortical laminar necrosis. Diffusion-weighted imaging may be useful in predicting the outcomes of the lesions of tacrolimus-induced neurotoxicity. Electronic Publication     

A case of MELAS showing both cytotoxic and vasogenic edema on serial diffusion-weighted imaging

In patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), T2-, FLAIR, and diffusion-weighted imaging reveal lesions as hyperintense areas after stroke-like episodes. It has been speculated that the lesions occur by vasogenic edema. However, we describe a case of MELAS which presented both normal and restricted water diffusion after stroke-like episodes, as detected by apparent diffusion coefficient map and values. Both cytotoxic and vasogenic edema can occur at acute stage after stroke-like episodes.     

MRI imaging of posterior reversible encephalopathy syndrome associated with pregnancy

Purpose

Our purpose is to characterize MRI, and diffusion-weighted imaging (DWI) findings in pregnant patients who were identified clinically to have PRES. We study the conversion of reversible vasogenic edema to irreversible cytotoxic edema and predict the progression to infarction.

Patients and methods

Twenty two pregnant females, aged between 20 and 46 years with gestational age between 20 and 40 weeks of gestation and with neurological manifestations had undergone conventional MRI, diffusion weighted image study, and ADC map.

Results

Lesions were mainly affecting the parieto-occipital regions, symmetrical or slightly asymmetrical distribution of the lesions in both cerebral hemispheres was found in most cases. The MRI findings in all the twenty two patients were: abnormal low SI in T1 WI, abnormal high SI on T2 and FLAIR WI. In DWI, hyperintensity with hyperintensity in ADC map was seen in 15 patients, hyperintensity with hypointensity in ADC map in 4 patients, normotensive in DWI with hyperintensity in ADC map in 3 patients.

Conclusion

The diagnosis of PRES has important therapeutic and prognostic value. The use of diffusion-weighted imaging and ADC maps allows an earlier and clearer differentiation of cytotoxic and vasogenic edema, which can predict the development of infarction.