Cryptococcal choroid plexitis as a mass lesion: MR imaging and histopathologic correlation

Cryptococcosis is a relatively common mycotic infection of the CNS caused by a ubiquitous saprophytic fungus. We present an unusual case of CNS cryptococcosis in an immunocompetent patient. Florid choroid plexitis resulted in the formation of intraventricular enhancing mass lesions that filled the ventricles and were hyperintense to associated periventricular edema on T2-weighted MR images. We also noted lesions corresponding to microcystic, dilated Virchow-Robin spaces in the basal ganglia that were characteristic of cryptococcal infection.     

Intracranial cryptococcosis in immunocompromised patients: CT and MR findings in 29 cases

CT and MR scans of 29 immunocompromised patients (28 with AIDS or ARC, one with diabetes mellitus) who had documented intracranial cryptococcal infection were reviewed retrospectively. All patients had CT studies; 26 received iodinated contrast agent. CT findings included normal results in nine of 29, atrophy only in 13 of 29, nonenhancing lesions in three of 29, enhancing lesions in two of 20, and foci of leptomeningeal calcification in two of 29. Ten patients had both CT and MR studies, and four received gadopentetate dimeglumine. Among these 10 patients, five had normal CT studies and one showed moderate central atrophy. All 10, however, had abnormal MR findings. We observed four patterns: (1) parenchymal cryptococcoma (3/10); (2) numerous clustered tiny foci that were hyperintense on T2-weighted images and non-enhancing on postcontrast T1-weighted images, located relatively symmetrically in the basal ganglia bilaterally and in midbrain, representing dilated Virchow-Robin spaces (4/10); (3) multiple miliary enhancing parenchymal and leptomeningeal nodules (1/10); and (4) a mixed pattern, consisting of dilated Virchow-Robin spaces with mixed lesions such as cryptococcoma and miliary nodules (2/10). In the group of six patients with dilated Virchow-Robin spaces (patterns 2 and 4), two received gadopentetate dimeglumine, but the Virchow-Robin space lesions did not enhance; among the remaining four patients, two received gadopentetate dimeglumine (one with pattern 1 and one with pattern 3) and the lesions did enhance. Three patients in our study subsequently died and autopsies were performed. The postmortem results revealed dilated Virchow-Robin spaces filled with fungi in the basal ganglia, which correlated well with MR findings.(ABSTRACT TRUNCATED AT 250 WORDS)     

Atrophy of the basal ganglia as the initial diagnostic sign of germinoma in the basal ganglia

Germ-cell tumors of the central nervous system generally develop in the midline, but the tumors can also occur in the basal ganglia and/or thalamus. However, MR images have rarely been documented in the early stage of the tumor in these regions. We retrospectively reviewed MR images obtained on admission and approximately 3 years earlier in two patients with germinoma in the basal ganglia, and compared them with CT. In addition to hyperdensity on CT, both hyperintensity on T1-weighted images and a small hyperintense lesion on T2-weighted images were commonly seen in the basal ganglia. These findings may be early MRI signs of germinoma in this region, and the earliest and most characteristic diagnostic feature on MRI was atrophy of the basal ganglia, which was recognizable before development of hemiparesis.     

AIDS-related CNS cryptococcosis: radiologic-pathologic correlation.

PURPOSE: This study evaluates the effectiveness of cranial CT and MR in detecting autopsy findings of AIDS-related CNS cryptococcosis. METHODS: Final imaging studies compared with pathology were CT in eight patients (five with contrast) and MR in five patients (all with Gd-DTPA). RESULTS: Neither modality effectively identified cryptococcal meningitis. Punctate hyperintensities were seen in all patients with MR and corresponded pathologically to both perivascular spaces dilated by cryptococcal infection and cryptococcomas. Pathologically, cryptococcomas were more common than dilated perivascular spaces. MR detected more cryptococcomas than did CT, but both modalities underestimated the number of lesions seen at autopsy. Contrast enhancement of cryptococcomas and cryptococcal meningitis was uncommon. CONCLUSIONS: CNS cryptococcosis was more effectively demonstrated by MR than by CT, but both modalities underestimated the pathologic extent of the disease. Cryptococcal lesion contrast enhancement was unusual possibly because of the immunocompromised state of our patients and the unique characteristics of the organism itself.     

Acquired immunodeficiency syndrome: correlation of radiologic and pathologic findings in the brain

The appearance on magnetic resonance (MR) and computed tomographic (CT) images of specific central nervous system disorders associated with acquired immunodeficiency syndrome in 12 cases was correlated with autopsy findings. There were three cases of human immunodeficiency virus (HIV) encephalopathy; three, primary lymphoma; three, toxoplasmosis; one, cryptococcosis; one, cytomegalovirus infection; and one, progressive multifocal leukoencephalopathy. MR imaging demonstrated the various cranial lesions more clearly than did CT. On the basis of MR imaging characteristics, HIV encephalopathy could be distinguished from other lesions, particularly progressive multifocal leukoencephalopathy. Basal ganglia were the most common sites of involvement in opportunistic infections and primary lymphoma. Reliable distinguishing features among lesions of the basal ganglia were not found, except for cryptococcal lesions, which had a unique appearance.     

Brain CT and MR findings in hyperphenylalaninemia due to dihydropteridine reductase deficiency (variant of phenylketonuria)

Two siblings with malignant hyperphenylalaninemia were examined by magnetic resonance (MR) imaging and CT of the brain. Both techniques demonstrated diffuse cerebral atrophy and cystic loss of parenchyma with surrounding white matter changes. T2-weighted MR images demonstrated the white matter changes better than CT. However, MR images gave no definite indication of the presence of calcification, and CT demonstrated the characteristic calcifications in the basal ganglia and subcortical region bilaterally. Both MR and CT are complementary in the evaluation of this disease.     

Gd-DTPA-enhanced MR imaging of the brain in patients with meningitis: comparison with CT

Plain and Gd-DTPA-enhanced MR images of the brain were obtained in 18 consecutive patients with meningitis (eight with tuberculous, five with bacterial, three with viral, and two with fungal infections); the MR images were compared with CT scans. MR images were obtained on a 2.0-T superconducting unit with both T1- and T2-weighted pulse sequences before injection and with a T1-weighted sequence after injection of Gd-DTPA (0.1 mmol/kg) in all patients. In tuberculous meningitis, MR imaging depicted ischemia/infarct, hemorrhagic infarct of basal ganglia, meningeal enhancement at either basal cistern or convexity surface of brain, and associated small granulomas in a few more patients than CT did. In bacterial meningitis, primary foci of extracranial inflammation (i.e., mastoid, paranasal sinuses) and adjacent intracranial lesions including localized dural inflammation, subdural fluid collection, and/or brain parenchymal lesions were demonstrated much better on MR than on CT. Otherwise, MR images generally matched the CT scan. Although the plain MR images, both T1- and T2-weighted, were the most sensitive in delineating ischemia/infarct, hemorrhage, and edema, they were not as specific as Gd-DTPA-enhanced T1-weighted images and postcontrast CT scans in defining the active inflammatory process of the meninges and focal lesions precisely. We conclude that if Gd-DTPA is used, MR imaging appears to be superior to CT in the evaluation of patients with suspected meningitis. Precontrast MR is needed to delineate ischemia/infarct, edema, and subacute hemorrhage.     

Gd-DTPA-enhanced MR imaging of the brain in patients with meningitis: comparison with CT

Plain and Gd-DTPA-enhanced MR images of the brain were obtained in 18 consecutive patients with meningitis (eight with tuberculous, five with bacterial, three with viral, and two with fungal infections); the MR images were compared with CT scans. MR images were obtained on a 2.0-T superconducting unit with both T1- and T2-weighted pulse sequences before injection and with a T1-weighted sequence after injection of Gd-DTPA (0.1 mmol/kg) in all patients. In tuberculous meningitis, MR imaging depicted ischemia/infarct, hemorrhagic infarct of basal ganglia, meningeal enhancement at either basal cistern or convexity surface of brain, and associated small granulomas in a few more patients than CT did. In bacterial meningitis, primary foci of extracranial inflammation (i.e., mastoid, paranasal sinuses) and adjacent intracranial lesions including localized dural inflammation, subdural fluid collection, and/or brain parenchymal lesions were demonstrated much better on MR than on CT. Otherwise, MR images generally matched the CT scan. Although the plain MR images, both T1- and T2-weighted, were the most sensitive in delineating ischemia/infarct, hemorrhage, and edema, they were not as specific as Gd-DTPA-enhanced T1-weighted images and postcontrast CT scans in defining the active inflammatory process of the meninges and focal lesions precisely. We conclude that if Gd-DTPA is used, MR imaging appears to be superior to CT in the evaluation of patients with suspected meningitis. Precontrast MR is needed to delineate ischemia/infarct, edema, and subacute hemorrhage.     

Similarities and differences of MR findings between Japanese encephalitis and Wilson's disease

Although Japanese Encephalitis (JE) and Wilson's disease (WD) are different entities, MR findings in both these conditions are quite similar. The purpose of this retrospective study was to find out the similarities and differences between JE and WD on MR imaging. The study group comprised 25 proven cases of JE and 10 cases of WD. Spin echo (SE) TI- and T2-weighted imaging was performed on a 1.5-T MR system. Fourteen of these 35 cases (10 JE, 4 WD) were also examined using T1-weighted magnetization transfer (MT) SE sequence before and after contrast administration. Although both JE and WD showed similar topographical distribution of lesions, predominant involvement of the basal ganglia and thalami, there were some differences. Brain stem lesion was more frequent for WD than for JE, and posteromedial part of the thalami was spared in WD. The lesion characteristics were also different between both; in WD mixed intensity in the basal ganglia and hyperintense linear rim at the peripheral putamen was observed frequently, whereas hyperintense basal ganglia on T2-weighted images, subacute hemorrhage in the thalami and meningeal enhancement were seen only in the patients with JE. These characteristic lesion criteria may help in differentiation of JE from WD on MR imaging.     

Primary intracranial CNS lymphoma: MR manifestations

We reviewed MR scans of 10 patients with biopsy-proved primary CNS lymphoma. Twenty-five lesions were identified in 10 patients (four with AIDS and six without AIDS). In general, the typical lesion of CNS lymphoma was found to have the following MR characteristics: they were slightly hypointense on T1-weighted images and slightly hyperintense on proton density and T2-weighted images relative to gray matter; they induced mild edema and mild to moderate mass effect. In AIDS patients, 82% of the lesions were smaller than 2 cm in diameter, and were frequently located in the temporal lobes and basal ganglia; they were often multiple. In non-AIDS patients, 75% of the lesions were larger than 2 cm in diameter and were primarily found in the deep parietal lobe; most were solitary.     

Germinoma originating in the basal ganglia and thalamus: MR and CT evaluation.

PURPOSETo describe MR and CT features of germinoma originating in the basal ganglia and thalamus and to discuss the roles of each modality for its diagnosis.METHODSMR and CT studies of six cases of germinomas, five of which were histologically proved, were retrospectively reviewed. T1-weighted, T2-weighted, and contrast-enhanced T1-weighted conventional spin-echo images, and unenhanced and contrast-enhanced CT images were evaluated.RESULTSTypically, the tumor consisted of an irregular solid area with contrast enhancement and various-size cysts. Cystic components were found in five cases and calcification in four. Intratumoral hemorrhage was noted in one. Ipsilateral cerebral hemiatrophy and brain stem hemiatrophy were noted in three cases each. MR was superior to CT in evaluating precise tumor extension, cystic components, and intratumoral hemorrhage, although in one case, extension of the tumor was better defined on CT in its early stage. Calcification was difficult to identify by MR alone. The solid components of the tumors generally showed slightly high density on CT, which seemed to be characteristic compared with nonspecific intensity pattern on MR.CONCLUSIONThe combination of CT and MR findings allows early detection and appropriate diagnosis of the mass in the basal ganglia and/or thalamus.     

Acute bilateral basal ganglia lesions in diabetic uraemia: diffusion-weighted MRI

Methods We studied four patients with diabetes mellitus and chronic renal failure who developed sudden choreic movement disorders. The clinical manifestations, laboratory findings, MR imaging findings, and clinical outcome in each patient were evaluated. Results All four patients had long-term diabetes mellitus and severe azotaemia. Brain MR findings consisted of bilateral symmetric basal ganglia lesions, with decreased signal intensity on T1-weighted images and increased signal intensity on T2-weighted images. All three patients who underwent diffusion-weighted MR imaging (DWI) showed signal intensities similar to those of the surroundings in regions corresponding to increased signal intensity on T2-weighted images, with slightly increased apparent diffusion coefficient (ADC) values. Two of the patients showed small focal areas of restricted diffusion within the basal ganglia lesions. After haemodialysis, follow-up MR imaging in all patients demonstrated that the basal ganglia lesions had regressed markedly, with some residual changes. The movement disorders also improved in all patients. Conclusion A syndrome associated with acute bilateral basal ganglia lesions in diabetic uraemic patients is rare, with reversible changes demonstrated by clinical and imaging findings. DWI showed that the bilateral basal ganglia lesions in this syndrome were primarily vasogenic in origin, although there were small foci of cytotoxic oedema within the lesions.     

High-intensity basal ganglia lesions on T1-weighted MR images in neurofibromatosis

Basal ganglia lesions, characterized on MR by increased signal intensity on T1-weighted images, were observed in seven patients with documented neurofibromatosis. These lesions most often involved the globus pallidus and internal capsules in a bilateral and symmetric fashion, and extended across the anterior commissure resulting in a "dumbbell" configuration. Smaller and less prominent foci of increased signal also were present on corresponding T2-weighted images. These lesions did not exhibit mass effect, edema, or enhancement with gadolinium-DTPA. They were not visible on CT (performed in two patients) and demonstrated no progression during a 2-year interval in three patients. Their signal characteristics and morphology suggest that they represent heterotopias containing Schwann cells and/or melanin deposits. Migrational abnormalities of these neural crest derivatives are known to occur in neurofibromatosis, and the presence of such heterotopias has been documented pathologically in patients with this disorder. While recent reports discuss foci of increased signal intensity on T2-weighted MR images in patients with neurofibromatosis, signal abnormalities on T1-weighted images have not yet been described. When lesions characterized by similar signal as well as morphologic characteristics are encountered on MR, the diagnosis of neurofibromatosis should be considered.     

High-intensity basal ganglia lesions on T1-weighted MR images in neurofibromatosis

Basal ganglia lesions, characterized on MR by increased signal intensity on T1-weighted images, were observed in seven patients with documented neurofibromatosis. These lesions most often involved the globus pallidus and internal capsules in a bilateral and symmetric fashion, and extended across the anterior commissure resulting in a "dumbbell" configuration. Smaller and less prominent foci of increased signal also were present on corresponding T2-weighted images. These lesions did not exhibit mass effect, edema, or enhancement with gadolinium-DTPA. They were not visible on CT (performed in two patients) and demonstrated no progression during a 2-year interval in three patients. Their signal characteristics and morphology suggest that they represent heterotopias containing Schwann cells and/or melanin deposits. Migrational abnormalities of these neural crest derivatives are known to occur in neurofibromatosis, and the presence of such heterotopias has been documented pathologically in patients with this disorder. While recent reports discuss foci of increased signal intensity on T2-weighted MR images in patients with neurofibromatosis, signal abnormalities on T1-weighted images have not yet been described. When lesions characterized by similar signal as well as morphologic characteristics are encountered on MR, the diagnosis of neurofibromatosis should be considered.     

MR of Leigh's disease (subacute necrotizing encephalomyelopathy)

MR images of three patients with Leigh's disease (subacute necrotizing encephalomyelopathy) were compared with CT findings. In all patients typical lesions in the basal ganglia were identified with both MR and CT. In two patients MR permitted identification of additional lesions not detected with CT. In one patient progression of MR abnormalities over a 4-month period correlated well with clinical deterioration in neurologic status. T2-weighted images with a repetition time (TR) greater than 1950 msec and an echo time (TE) greater than or equal to 60 msec or inversion-recovery images with a 50-msec TE, 1213-msec inversion time, and 3000-msec TR were advantageous in identifying multiple necrotic lesions in the brainstem, deep gray matter, periventricular white matter, and cerebral cortex. In this series MR was more sensitive in detecting and localizing multifocal necrotic lesions of Leigh's disease than CT was, and thus may be a useful diagnostic tool for patients with the appropriate clinical and laboratory abnormalities.     

MR appearance of Virchow-Robin spaces along lenticulostriate arteries: spin-echo and two-dimensional fast low-angle shot imaging.

PURPOSETo delineate the appearance of normal Virchow-Robin spaces on routine spin-echo images and demonstrate the lenticulostriate arteries within them with a flow-sensitive fast low-angle shot (FLASH) pulse sequence.METHODSSeventy subjects, free of cerebrovascular diseases and other neurologic disorders, ranging in age from 1 to 75 years, were examined. On a 1.5-T MR system, axial spin-echo images of 5 mm thickness were obtained in all subjects. In 45 of 70 subjects axial two-dimensional FLASH images of 3 mm thickness were continuously imaged.RESULTSOn T1- and spin density-weighted images Virchow-Robin spaces were detected as small foci of cerebrospinal fluid intensity around the anterior commissure in all subjects (100%), and in the basal ganglia at the level of the foramen of Monro in 40 (57%). T2-weighted images equally showed Virchow-Robin spaces around the anterior commissure but were less sensitive than T1- and spin-density weighted images at the level of the foramen of Monro (14%). Virchow-Robin spaces identified on T2-weighted images should be isointense with cerebrospinal fluid. However, one or two spaces in 11 younger subjects were hypointense relative to adjacent brain tissue. On FLASH images most Virchow-Robin spaces identified on spin-echo images were delineated as high-intensity foci, corresponding to lenticulostriate arteries.CONCLUSIONSNormal Virchow-Robin spaces along the lenticulostriate arteries are frequently detected on spin-echo images. Their appearance, affected by the flow of associated lenticulostriate arteries, varies from hyper- to hypointensity to brain tissue on T2-weighted images. The two-dimensional FLASH sequence can demonstrate the flow of the arteries, thereby helping confirm that these are truly Virchow-Robin spaces.     

Magnetic resonance imaging of the brain in glutaric acidemia type I: a review of the literature and a report of four new cases with attention to the basal ganglia and imaging technique

RATIONALE AND OBJECTIVES: In glutaric acidemia type I (GA I), a pediatric neurometabolic disease that may be mistaken for nonaccidental trauma, expeditious detection is critical as early treatment may substantially improve psychomotor dysfunction. In this study, we examine in depth the magnetic resonance (MR) findings, with special attention to the basal ganglia, in 4 new cases and compare the findings with those described in the literature. METHODS: MR studies of 4 children, diagnosed to have GA I via cultured fibroblast enzyme studies or urine metabolite assays, were performed on a 1.5 T system in the axial plane using spin echo T(1)-weighted, fast spin echo T(2)-weighted, and fluid-attenuated inversion recovery (FLAIR) technique. Three of 4 patients were followed with serial exams to document temporal evolution of the disease. RESULTS: On T(2)-weighted images, abnormal increased signal intensity was seen in both the putamen and globus pallidus in all cases. However, in contradistinction to cases reported in the literature, involvement of the caudate nucleus was minimal or absent even on serial MR exams. In children 15 months and older, FLAIR improved recognition of basal ganglia and white matter abnormalities. The previously described widened cerebrospinal fluid spaces anterior to the temporal lobes, increased T(2)-weighted signal intensity in the periventricular white matter, and widened sylvian fissures characteristic of GA I were noted in all patients. CONCLUSIONS: Abnormalities of the caudate nucleus are not a prominent presentation of these patients and the absence of this finding should not exclude a diagnosis of GA I. FLAIR scans, as an adjunct to more conventional T(1)- and T(2)-weighted sequences, can play an important role in children 15 months or older despite immature myelination in these patients.     

CT of intracranial cryptococcosis

CT scans of 35 patients with intracranial cryptococcal infection were reviewed retrospectively. Studies were normal in 43% of the patients. Positive findings in others included diffuse atrophy in 34%, mass lesions (cryptococcoma) in 11%, hydrocephalus in 9%, and diffuse cerebral edema in 3%. Two unusual types of cryptococcoma were encountered, namely gelatinous pseudocysts and an intraventricular cryptococcal cyst. All findings were nonspecific for CNS cryptococcosis. The results suggest that CNS cryptococcosis should be considered in all patients at risk for the disease who have these abnormal CT findings, no matter what their initial clinical presentation. In addition, MR demonstration of gelatinous pseudocysts in one patient indicates that this technique may be helpful in locating cryptococcal mass lesions not visualized on CT.     

CT of intracranial cryptococcosis

CT scans of 35 patients with intracranial cryptococcal infection were reviewed retrospectively. Studies were normal in 43% of the patients. Positive findings in others included diffuse atrophy in 34%, mass lesions (cryptococcoma) in 11%, hydrocephalus in 9%, and diffuse cerebral edema in 3%. Two unusual types of cryptococcoma were encountered, namely gelatinous pseudocysts and an intraventricular cryptococcal cyst. All findings were nonspecific for CNS cryptococcosis. The results suggest that CNS cryptococcosis should be considered in all patients at risk for the disease who have these abnormal CT findings, no matter what their initial clinical presentation. In addition, MR demonstration of gelatinous pseudocysts in one patient indicates that this technique may be helpful in locating cryptococcal mass lesions not visualized on CT.     

Islet cell tumor of the pancreas: biphasic CT versus MR imaging in tumor detection

PURPOSE: To compare the effectiveness of biphasic computed tomography (CT) and magnetic resonance (MR) imaging in the detection of pancreatic islet cell tumors. MATERIALS AND METHODS: Retrospective quantitative, qualitative, and receiver operating characteristic analyses of biphasic CT and MR imaging were performed in 19 patients with 26 histopathologically proved islet cell tumors. Delayed arterial dominant-phase (AP) and portal venous-phase (PVP) biphasic CT was performed after the administration of contrast material. MR imaging included T1-weighted spin-echo (SE) and T2-weighted SE or fast SE imaging, fat-saturated T1-weighted SE imaging, dynamic contrast material-enhanced T1-weighted gradient-echo imaging, and delayed enhanced T1-weighted SE imaging with or without fat saturation. RESULTS: PVP CT and delayed enhanced T1-weighted MR imaging had the highest A(z) values (0.98 and 0.97, respectively; P <.05). Delayed enhanced T1-weighted MR imaging had the highest relative sensitivity (14-15 [74%-79%] of 19 lesions), followed by PVP CT (18-19 [69%-73%] of 26 lesions), AP CT (17-19 [65%-73%] of 26 lesions), fat-saturated T1-weighted MR imaging (eight to 10 [57%-71%] of 14 lesions), T2-weighted (16-17 [62%-65%] of 26 lesions), T1-weighted (15-18 [58%-69%] of 26 lesions) MR imaging, and dynamic MR imaging (nine [56%] of 16 lesions). CONCLUSION: Biphasic (especially PVP) CT and MR imaging have similar effectiveness in the detection of islet cell tumors if fat-saturated T1-weighted and delayed enhanced T1-weighted MR imaging are included.