MR imaging of CNS involvement in children affected by chronic liver disease

BACKGROUND AND PURPOSE: MR imaging sheds new light on CNS involvement in the course of acquired chronic liver disease; however, the exact pathogenetic mechanisms of hepatic encephalopathy and associated MR abnormalities remain unclear. Our purpose was to relate MR signal intensity abnormalities of the CNS to clinical, biochemical, and pathologic features of childhood-onset chronic liver disease. METHODS: Twenty-one patients (12 male and nine female patients) were included in the study; two had Crigler-Najjar disease type 2, 17 had chronic liver disease of different causes, and two had idiopathic copper toxicosis. Twelve patients had histologically proved liver cirrhosis, with a median disease duration of 175 months at the time of MR study. None had clinical symptoms of hepatic encephalopathy. MR imaging was performed using spin-echo T1- and T2-weighted sequences. RESULTS: Eleven patients had abnormal MR imaging findings of the brain revealed by T1-weighted MR sequences; two of the 11 had idiopathic copper toxicosis. The affected sites were the hypothalamus and globus pallidus, presenting symmetrical and bilateral high signal intensities, or the pituitary gland, which appeared homogeneously hyperintense, or both findings. Eight of the 12 patients with cirrhosis had abnormal MR signals of the brain. In these, the median cirrhosis duration was shorter (169 months) than in the remaining four patients with normal MR signals (177 months). A significant correlation was found between abnormal MR signals of the brain and cirrhosis (P = .008) and factor V activity (P = .008). CONCLUSION: MR imaging confirms the presence of abnormal brain signals in the globus pallidus, hypothalamus, and pituitary gland in patients with childhood-onset liver disease in the absence of clinical symptoms of encephalopathy. Signal intensity abnormalities are likely caused by an as yet unidentified metabolic process partially correlated with the severity of liver disease.     

Diffuse cerebral and leptomeningeal astrocytoma in dogs: MR features

Magnetic resonance (MR) imaging has increased sensitivity in detection of nonenhancing brain tumors and may show the extent of CNS neoplasia with greater detail than CT. Magnetic resonance images of the canine brain were acquired in two dogs with diffuse leptomeningeal and cerebral low grade astrocytoma. Abnormalities were identified with MR imaging when CT and CSF analysis were noncontributory. Changes seen with MR included decreased signal on T1-weighted images and increased signal on T2-weighted images consistent with vasogenic edema. Neither MR nor CT showed post-contrast enhancement. Magnetic resonance did not show the full extent of cellular infiltration, however. This was attributed to the diffuse submacroscopic distribution and absence of corresponding edema and contrast enhancement in certain regions of brain.     

Portal-systemic encephalopathy: presence of basal ganglia lesions with high signal intensity on MR images

Sixteen patients with cirrhosis of the liver underwent cranial magnetic resonance (MR) imaging and transarterial portography to evaluate the relationship between basal ganglia lesions and portal-systemic collateral vessels. No neuropsychiatric disturbance was observed in any of the patients at the time of the MR examination, but four patients with portal-systemic encephalopathy were included in the study. Basal ganglia lesions, characterized by increased signal intensity on T1-weighted MR images, were observed in nine of the 16 patients, including the four with portal-systemic encephalopathy. These nine patients had large portal-systemic collateral vessels that were more than 10 mm in diameter. These collateral vessels were receiving blood from the superior mesenteric vein (SMV) in all nine patients. The lesions involved the globus pallidus and portions of internal capsules in a bilateral and symmetric fashion and did not exhibit mass effect. The authors conclude that there may be a significant relationship between high-intensity basal ganglia lesions and large portal-systemic collateral vessels receiving blood from the SMV.     

Decrease in the volume of white matter lesions with improvement of hepatic encephalopathy

MR imaging has found abnormalities compatible with low-grade edema in the brain of patients with cirrhosis that have been related to hepatic encephalopathy. We present 3 patients with hepatic encephalopathy who exhibit supratentorial focal or diffuse white matter lesions compatible with small-vessel brain disease. The volume and number of white matter lesions reduced with the improvement of hepatic encephalopathy, suggesting the participation of the blood-brain barrier in the pathogenesis of brain edema in hepatic encephalopathy.     

Wegener granulomatosis: CT and MR findings.

PURPOSETo demonstrate the spectrum of CT and MR imaging findings in patients with Wegener granulomatosis and to determine how often these findings could be attributed to either direct extension from paranasal or orbital disease sites, remote granulomas, or central nervous system (CNS) vasculitis.METHODSWe retrospectively reviewed the CT or MR studies of 15 patients with Wegener granulomatosis.RESULTSAbnormal findings were seen in 7 patients (5 examined with MR imaging, 2 with CT). Findings included dural thickening and contrast enhancement (3 patients), infarcts (2 patients), regions of hyperintense signal on T2-weighted MR images (2 patients), and abnormal MR signal in the brain stem (2 patients). Three patients with imaging findings of dural enhancement and thickening were thought to have remote granulomatous lesions involving the dura. No patients had extension from sites external to the CNS or clinical findings suggestive of CNS vasculitis.CONCLUSIONThe spectrum of CT and MR findings in Wegener granulomatosis includes dural thickening and enhancements cerebral infarction, and MR signal abnormalities in the brain stem and white matter. Presumed remote granulomatous lesions were the most common causes of CNS findings in this study. Complications related to non-CNS disease (eg, hypertension, endocarditis) also appear to have played a role in some patients.     

West Nile virus meningoencephalitis: MR imaging findings

BACKGROUND AND PURPOSE: Reports of MR imaging in West Nile virus (WNV) meningoencephalomyelitis are few and the described findings limited. The purpose of this study was to review the spectrum of MR imaging findings for WNV meningoencephalomyelitis and investigate whether any of the findings correlates with clinical presentation of flaccid paralysis. METHODS: We reviewed the MR imaging findings of 17 patients with confirmed WNV encephalitis and/or myelitis. MR imaging brain studies were evaluated for location of signal intensity abnormalities, edema, hydrocephalus, or abnormal enhancement. MR imaging spine studies were evaluated for signal intensity abnormalities in cord and/or enhancement. RESULTS: Retrospective review of the MR imaging studies of 17 patients was performed by 2 neuroradiologists. Eleven of 16 brain MR images demonstrated abnormalities. Eight (50%) patients had abnormal studies related to meningoencephalitis. All 8 patients had abnormal findings in the deep gray matter and/or brain stem; 2 had additional white matter abnormalities. Three patients with abnormal MR studies of the spine had extremity weakness on examination. The imaging findings included abnormal signal intensity more pronounced in the ventral horns and/or enhancement around the conus medullaris and cauda equina. One patient had additional abnormalities in the pons. CONCLUSION: Abnormal MR imaging findings in patients with WNV meningoencephalomyelitis are nonspecific but not uncommon. Anatomic areas commonly affected are basal ganglia, thalami, mesial temporal structures, brain stem, and cerebellum. Extremity weakness or flaccid paralysis corresponds to spinal cord/cauda equina abnormalities.     

Sarcoidosis of the CNS: comparison of unenhanced and enhanced MR images

Sarcoidosis involving the CNS has a predilection for the leptomeninges, although parenchymal involvement occurs. We retrospectively evaluated the appearance of CNS sarcoidosis on unenhanced and enhanced MR images. MR studies were abnormal in 17 of 20 patients with CNS sarcoidosis. In all 17 patients, meningeal disease was detected on the gadopentetate-dimeglumine-enhanced T1-weighted images; the disease was detected on unenhanced images in three patients. Well-defined leptomeningeal patterns of enhancement were present in 15 patients. Other areas of involvement were the dura; brain parenchyma including hypothalamus, periventricular white matter, and ventricular ependyma; optic chiasm; and pituitary gland. Gadopentetate dimeglumine optimally evaluates meningeal disease and highlights the importance of the leptomeninges and Virchow-Robin spaces in the pathogenesis of CNS sarcoidosis. Enhanced MR is the preferred imaging technique for the evaluation of CNS sarcoidosis.     

Sarcoidosis of the CNS: comparison of unenhanced and enhanced MR images

Sarcoidosis involving the CNS has a predilection for the leptomeninges, although parenchymal involvement occurs. We retrospectively evaluated the appearance of CNS sarcoidosis on unenhanced and enhanced MR images. MR studies were abnormal in 17 of 20 patients with CNS sarcoidosis. In all 17 patients, meningeal disease was detected on the gadopentetate-dimeglumine-enhanced T1-weighted images; the disease was detected on unenhanced images in three patients. Well-defined leptomeningeal patterns of enhancement were present in 15 patients. Other areas of involvement were the dura; brain parenchyma including hypothalamus, periventricular white matter, and ventricular ependyma; optic chiasm; and pituitary gland. Gadopentetate dimeglumine optimally evaluates meningeal disease and highlights the importance of the leptomeninges and Virchow-Robin spaces in the pathogenesis of CNS sarcoidosis. Enhanced MR is the preferred imaging technique for the evaluation of CNS sarcoidosis.     

Analysis of central nervous system vasculitis with diffusion-weighted imaging and apparent diffusion coefficient mapping of the normal-appearing brain

BACKGROUND AND PURPOSE: Diffusion-weighted imaging (DWI) is a novel method of studying the brain that creates tissue contrast secondary to water diffusion. Central nervous system (CNS) vasculitis is a rare inflammatory disease that continues to be difficult to diagnose and evaluate with MR imaging. DWI with apparent diffusion coefficient (ADC) analysis may demonstrate abnormalities within the brain that would otherwise be undetected by conventional imaging, thus aiding in the diagnosis and evaluation of patients with CNS vasculitis. MATERIALS AND METHODS: A retrospective analysis was performed of patients who were diagnosed with CNS vasculitis and had undergone DWI. A total of 15 patients who had DWI with b = 1000 were analyzed. Regions of interest were drawn in the anterior, central, and posterior regions of white matter (WM) at 3 levels. Regions of interest were also drawn bilaterally in the caudate heads, putamina, thalami, posterior internal capsules, and the cerebellar WM. ADC values were measured and compared with 15 healthy controls who were matched for age, sex, and MR imaging scanner. RESULTS: There was a significant increase in the ADC values (P<.00625) for the anterior WM, central WM, thalami, and posterior internal capsules in patients with CNS vasculitis. CONCLUSION: Diffuse increase in water diffusion was present in the normal-appearing brain in patients with CNS vasculitis, and these abnormalities were not demonstrated by conventional MR imaging sequences. The detection and quantification of ADC abnormalities may provide useful diagnostic information for patients with CNS vasculitis.     

Hip pain in three children accompanied by transient abnormal findings on MR images

In a study of three children experiencing hip pain, low-signal-intensity patterns in the femoral head on T1-weighted magnetic resonance (MR) images eventually resolved, reverting to the normal signal patterns. These findings occurred in conjunction with documented clinical improvement of the patients' condition. T2-weighted images revealed isointense signals initially at the abnormal sites. Isointense signals prevailed on follow-up T2-weighted images. These MR imaging findings are likely due to transient bone marrow edema. These findings support the apparent sensitivity of MR imaging in the evaluation of marrow-based pathologic processes. Some pediatric patients with hip pain may have signs of transient bone marrow edema, rather than avascular necrosis, on MR images. Conservative management should be considered in such cases.     

Fast MR imaging of fetal CNS anomalies in utero

BACKGROUND AND PURPOSE: Although sonography is the primary imaging technique for evaluating the developing fetus, significant limitations exist in the sonographic prenatal diagnosis of many brain disorders. Fast MR imaging is increasingly being used to determine the underlying cause of nonspecific fetal CNS abnormalities detected sonographically and to confirm or provide further support for such anomalies. Our goal was to determine the value of MR imaging in establishing the diagnosis of fetal CNS anomalies, to ascertain how this information might be used for patient counseling, and to assess its impact on pregnancy management. METHODS: We prospectively performed MR examinations of 73 fetuses (66 pregnancies) with suspected CNS abnormalities and compared these with available fetal sonograms, postnatal images, and clinical examinations. Retrospectively, the impact on patient counseling and pregnancy management was analyzed. RESULTS: Images of diagnostic quality were routinely obtained with in utero MR imaging, which was particularly valuable in detecting heterotopia, callosal anomalies, and posterior fossa malformations, and for providing excellent anatomic information. We believe that 24 (46%) of 52 clinical cases were managed differently from the way they would have been on the basis of sonographic findings alone. In every case, the referring physicians thought that MR imaging provided a measure of confidence that was not previously available and that was valuable for counseling patients and for making more informed decisions. CONCLUSION: Sonography is the leading technique for fetal assessment and provides reliable, inexpensive diagnostic images. Fast MR imaging is an important adjunctive tool for prenatal imaging in those instances in which a complex anomaly is suspected by sonography, when fetal surgery is contemplated, or when a definitive diagnosis cannot be determined.     

Bone marrow edema pattern in osteoarthritic knees: correlation between MR imaging and histologic findings

PURPOSE: To correlate magnetic resonance (MR) images of a bone marrow edema pattern with histologic findings in osteoarthritic knees. MATERIALS AND METHODS: Sixteen consecutive patients (age range, 43-79 years; mean, 67 years) referred for total knee replacement were examined with sagittal short inversion time inversion-recovery (STIR) and T1- and T2-weighted turbo spin-echo MR imaging 1-4 days before surgery. Tibial plateau abnormalities on MR images were compared quantitatively with those on histologic maps. RESULTS: The bone marrow edema pattern zone (ill-defined and hyperintense on STIR images and hypointense on T1-weighted MR images) mainly consisted of normal tissue (53% of the area was fatty marrow, 16% was intact trabeculae, and 2% was blood vessels) and a smaller proportion of several abnormalities (bone marrow necrosis [11% of area], abnormal [necrotic or remodeled] trabeculae [8%], bone marrow fibrosis [4%], bone marrow edema [4%], and bone marrow bleeding [2%]). The bone marrow edema pattern zone and the zone with a normal MR imaging appearance differed significantly in the presence of bone marrow necrosis (P =.021), bone marrow fibrosis (P =.014), and abnormal trabeculae (P =.011) but not in the prevalence of bone marrow edema (P =.069). Bone marrow edema also was found in zones with an unremarkable MR appearance (perifocal zone, 5% edema; control zone, 2% edema). CONCLUSION: A bone marrow edema pattern in osteoarthritic knees represents a number of noncharacteristic histologic abnormalities. Edema is not a major constituent of MR imaging signal intensity abnormalities in such knees.     

Neuroimaging of scuba diving injuries to the CNS

Diving accidents related to barotrauma constitute a unique subset of ischemic insults to the CNS. Victims may demonstrate components of arterial gas embolism, which has a propensity for cerebral involvement, and/or decompression sickness, with primarily spinal cord involvement. Fourteen patients with diving-related barotrauma were studied with MR imaging of the brain and spinal cord and with CT of the brain. In four patients with presumed cerebral gas embolism, cranial MR was abnormal in three patients while CT was abnormal in only one. Twelve patients had decompression sickness and spinal cord symptoms. MR documented spinal cord abnormalities in three patients. However, scans obtained early in our study were frequently limited by technical constraints. MR of the brain is more sensitive than conventional CT scanning techniques in detecting and characterizing foci of cerebral ischemia caused by embolic barotrauma to the CNS. Although spinal MR may be less successful in the localization of spinal cord lesions related to decompression sickness, these lesions were previously undetectable by other neuroimaging methods.     

Whole-brain histogram and voxel-based analyses of apparent diffusion coefficient and magnetization transfer ratio in celiac disease, epilepsy, and cerebral calcifications syndrome

BACKGROUND AND PURPOSE: Diffusion and magnetization transfer (MT) techniques have been applied to the investigation with MR of epilepsy and have revealed changes in patients with or without abnormalities on MR imaging. We hypothesized that also in the coeliac disease (CD), epilepsy and cerebral calcifications (CEC) syndrome diffusion and MT techniques could reveal brain abnormalities undetected by MR imaging and tentatively correlated to epilepsy. MATERIALS AND METHODS: Diffusion and MT weighted images were obtained in 10 patients with CEC, 8 patients with CD without epilepsy and 17 healthy volunteers. The whole brain apparent diffusion coefficient (ADC) and MT ratio (MTR) maps were analyzed with histograms and the Statistical Parametric Mapping 2 (SPM2) software. We employed the non-parametric Mann-Whitney U test to assess differences for ADC and MTR histogram metrics. Voxel by voxel comparison of the ADC and MTR maps was performed with 2 tails t-test corrected for multiple comparison. RESULTS: A significantly higher whole brain ADC value as compared to healthy controls was observed in CEC (P = 0.006) and CD (P = 0.01) patients. SPM2 showed bilateral areas of significantly decreased MTR in the parietal and temporal subcortical white matter (WM) in the CEC patients. CONCLUSION: Our study indicates that diffusion and MT techniques are also capable of revealing abnormalities undetected by MR imaging. In particular patients with CEC syndrome show an increase of the whole brain ADC histogram which is more pronounced than in patients with gluten intolerance. IN CEC patients, voxel-based analysis demonstrates a localized decrease of the MTR in the parieto-temporal subcortical WM.     

Role of MR cholangiopancreatography in patients with failed or inadequate ERCP

OBJECTIVE: The purpose of this study was to evaluate the spectrum of MR imaging features of primary sclerosing cholangitis. MATERIALS AND METHODS: A retrospective review was performed of MR imaging findings including MR cholangiography and multiphasic contrast-enhanced dynamic sequences in 22 patients with primary sclerosing cholangitis. MR imaging analysis included abnormalities of intra- and extrahepatic bile ducts, abnormalities of liver parenchyma, changes in liver morphology, and lymphadenopathy. RESULTS: Abnormal findings of bile ducts were seen in all 22 patients; the most common finding was intrahepatic bile duct dilatation (77%), followed by intrahepatic bile duct stenosis (64%), extrahepatic bile duct wall enhancement (67%), extrahepatic bile duct wall thickening (50%), extrahepatic bile duct stenosis (50%), and intrahepatic bile duct beading (36%). Increased enhancement of the liver parenchyma on dynamic arterial-phase images, predominantly in the peripheral areas of the liver, was identified in 56% of patients. Other findings included periportal lymphadenopathy (77%), periportal high signal intensity on T2-weighted images (68%), hypertrophy of the caudate lobe (68%), and abnormal hyperintensity of the liver parenchyma on T1-weighted images (23%). CONCLUSION: On MR imaging, primary sclerosing cholangitis showed several characteristic features, including bile duct abnormalities and increased enhancement of the liver parenchyma. MR cholangiography and contrast-enhanced dynamic MR techniques are useful for revealing intra- and extrahepatic signs of primary sclerosing cholangitis.     

急性有机磷中毒后脑水肿MRI表现和病理改变的实验研究

目的建立有机磷农药皮下染毒急性猫中毒模型，观察急性有机磷中毒脑损害MR影像学表现的发生发展规律，比较影像学表现与脑组织病理改变的关系。方法将25只健康猫分为3组，对照组、染毒治疗组、染毒未治疗组。对照组(5只)：腹部皮下4点等量注射生理盐水0．3mE／ks。染毒治疗组(简称染毒组)(15只)：腹部皮下4点等量注射40％N-甲基氨基甲酰甲基硫代磷酸酯(氧化乐果)0．3ml／kg。染毒后2min肌内注射0．5mg／kg硫酸阿托品，然后视动物流涎、流泪情况酌情肌内注射阿托品。染毒未治疗组(5只)：腹部皮下4点等量注射40％氧化乐果0．3ml／kg。对染毒后3、6、24h脑MRI表现与相应时间点脑组织病理检查结果进行对照研究。结果氧化乐果皮下染毒制作猫急性中毒模型，染毒后6、24hMR图像出现脑水肿。HE染色光学显微镜(简称光镜)和透射电子显微镜(简称电镜)观察，3h开始即出现广泛水肿表现，同时存在细胞毒性水肿和血管源性水肿，三者形态学表现相一致。电镜观察显示血脑屏障出现形态学变化，延髓6、24h电镜切片中观察到神经元细胞质近三角形类晶体样物质。结论氧化乐果染毒急性脑水肿模型成功建立，中毒后脑水肿为混合性水肿，MRI出现异常表现稍晚于病理改变。     

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.     

Neonatal citrullinemia: comparison of conventional MR, diffusion-weighted, and diffusion tensor findings

Conventional MR, diffusion-weighted, and diffusion tensor imaging were performed in an 8-day-old girl with citrullinemia. She had severe hyperammonemia for several days. On conventional T2-weighted MR images, symmetric, confluent high signal intensity was found in the bilateral thalami, basal ganglia, cortex, and subcortical white matter. Diffusion-weighted imaging demonstrated decreased apparent diffusion coefficient in these areas, reflecting cytotoxic edema. Follow-up MR imaging at the age of 4 months revealed subcortical cysts, ulegyric changes, and atrophy, which were most prominent in the occipital lobes. Diffusion tensor imaging revealed decreased anisotropy throughout the brain, consistent with diffuse injury to the oligodendro-axonal unit. Diffusion-weighted and diffusion tensor imaging are valuable techniques for the detection of irreversible brain damage and for the characterization of hyperintense lesions on T2-weighted MR images in patients with the neonatal form of citrullinemia.     

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.     

Posterior reversible encephalopathy syndrome: utility of fluid-attenuated inversion recovery MR imaging in the detection of cortical and subcortical lesions

BACKGROUND AND PURPOSE: Posterior reversible encephalopathy syndrome (PRES) is typically characterized by headache, altered mental functioning, seizures, and visual loss associated with imaging findings of bilateral subcortical and cortical edema with a predominantly posterior distribution. Our goal was to determine whether fluid-attenuated inversion recovery (FLAIR) imaging improves the ability to detect subtle peripheral lesions of PRES, as compared with conventional MR techniques. METHODS: Sixteen patients with clinical and imaging findings consistent with PRES were studied. Thirteen patients had undergone transplantation and had cyclosporin A neurotoxicity. Fast-FLAIR images were compared with spin-echo proton density- and T2-weighted images. RESULTS: FLAIR imaging improved diagnostic confidence and conspicuity of the T2 hyperintense lesions of PRES, typically in the subcortical white matter of the parietooccipital regions bilaterally. On all 23 abnormal MR studies, FLAIR was judged superior to proton density- and T2-weighted images for the detection of PRES in the supratentorial brain. In a mean of 6.7 of 23 studies, FLAIR findings prompted a raise in the grade of disease severity. FLAIR also showed cortical involvement in 94% of patients with PRES and in a mean of 46% of the total lesion burden. In four cases, subtle lesions were virtually undetectable without FLAIR. Brain stem or cerebellar disease was encountered in 56% of patients. CONCLUSION: FLAIR improves the ability to diagnose and detect subcortical and cortical lesions in PRES as compared with proton density- and T2-weighted spin-echo images. We therefore believe that FLAIR should be performed in patients with suspected PRES to allow more confident recognition of the often subtle imaging abnormalities.