Postmortem MR imaging of the brains of patients with AIDS.

Forty-two postmortem formalin-fixed brains of known patients with AIDS were examined with T2-weighted MR imaging before brain cutting. The gross and microscopic brain findings were correlated with the T2 signal changes in the postmortem MR imaging. The brains included examples of progressive multifocal leukoencephalopathy with involvement of the central brain and cerebellum. The authors also encountered the coexistence of progressive multifocal leukoencephalopathy and HIV encephalitis, and the T2 signal changes for each were compared. The T2 signal changes of leptomeningeal and perivascular space cryptococcal infection and CMV ependymitis are documented. Several expressions of primary cerebral lymphoma, including large nodules, choroid plexus infiltration, and diffuse microscopic sites of tumor also are assessed.

Unusual pattern of enhancement in cryptococcal meningitis: in vivo findings with postmortem correlation.

Leptomeningeal enhancement on CT and MR imaging studies secondary to cryptococcal meningitis is an uncommon finding. In immunocompromised patients, this meningitis incites only a mild inflammatory reaction and abnormalities are often absent on imaging studies. We recently encountered two patients with cryptococcal meningitis in whom postcontrast MR imaging showed thick enhancing subarachnoid spaces. Both had cryptococcal meningitis at autopsy. In a different patient with cryptococcal meningitis, postmortem MR imaging and pathologic examinations showed that these areas of enhancement correspond to abundant mucoid material secreted by the yeasts.

Postmortem MR imaging of lobar cerebral infarction with pathologic and in vivo correlation.

Postmortem magnetic resonance (MR) imaging features of different types of lobar cerebral infarction are correlated with the findings in gross and histologic specimens. The postmortem findings are also correlated with in vivo findings in similar cases selected from teaching files. In acute infarction, white matter vasogenic edema leads to high signal intensity on T2-weighted images and blurring of the gray-white matter junction. Petechial hemorrhage in the cortex results in inhomogeneous signal intensity on T2-weighted images. In laminar necrosis, the hyperintense cortex on T1-weighted images is due not to hemorrhage but possibly to necrosis and the presence of lipid-laden macrophages. In subacute infarction, cortical edema and necrosis may cause the gyral pattern of enhancement. Meningeal inflammation and early fibrosis are probably responsible for meningeal enhancement. In chronic infarction, gliosis and cystic malacia are responsible for the increased signal intensity of white matter on T2-weighted images. Knowledge of the pathologic features of cerebral infarction helps in understanding the MR imaging findings.

Magnetic resonance imaging and spectroscopy of small ring-enhancing lesions using a rat glioma model.

RATIONALE AND OBJECTIVES: We sought to demonstrate the usefulness of proton and fluorine magnetic resonance spectroscopy (MRS) techniques in characterizing small ring enhancing lesions produced by experimental malignant gliomas. METHODS: The growth characteristics of a rat glioma model (RT2) were studied using contrast-enhanced magnetic resonance imaging scans of the tumors and histologic correlates obtained at various times. Changes in tumor metabolite levels were monitored on a serial basis using water-suppressed proton spectroscopy. The existence of tumor hypoxia was established using 19F MRS in combination with a fluorinated nitroimidazole and subsequently confirmed by immunohistochemical staining of tumor sections. RESULTS: Ring-enhancing lesions are produced by RT2 rat brain gliomas approximately 7 days after intracerebral implantation. Beginning at day 5, marked deviations in brain metabolite levels are observed on proton MR spectra. However, while the signal from the fluorinated nitroimidazole is first detected by 19F MRS at day 7, immunohistochemical staining of tissue sections reveals bound drug as early as day 5, when the first histologic signs of necrosis become apparent. CONCLUSIONS: Magnetic resonance imaging of RT2 rat brain glioma exhibits ring-enhancing characteristics similar to those observed in clinical studies. The appearance of the ring enhancement corresponds with the development of central necrosis and could serve as an indicator for rapid growth. Proton and fluorine MRS may be useful in confirming that a small ring-enhancing lesion represents an active tumor process early in its development.

Closed spinal dysraphism: analysis of clinical, radiological, and surgical findings in 104 consecutive patients.

We reviewed 104 consecutive cases of closed dysraphism in patients seen at one institution between December 1984 and June 1987. All patients had myelographic studies, and 43 had associated CT examinations. Clinical and surgical findings (64 patients) were correlated with myelographic information. Twenty-three patients (22%) with clinical or plain film findings compatible with dysraphism had normal-appearing cords on conventional myelography, movement between supine and prone positions, and no lesions in the spinal canal. Cerebellar tonsillar ectopia (majority of tonsils between foramen magnum and C1) was found in 17 patients (16%). Six patients (6%) exhibited varying degrees of hydromyelia. In the supine position, CT-myelography of meningoceles, meningomyeloceles, or lipomeningomyeloceles may limit demonstration of the neural placode and nerve roots because of compression of the CSF-containing sac. In the decubitus position, CT scans improved demonstration of neural tissue-CSF space relationships. CT scans were useful in demonstrating anomalous paraspinal bones, diastematomyelia spurs, and spinal and sacral bone deficiency. Axial CT-myelography of intradural lipomas showed apparent neural tissue extension into the lipomas.

Ventilator-induced pulmonary pseudocysts in preterm neonates.

Twenty-three pulmonary pseudocysts were identified in 20 preterm neonates undergoing mechanically assisted ventilation. Most of the pseudocysts occurred in a right parahilar location; cysts were either single (13) or multiple/multilocular (10). The pseudocysts persisted from less than 2 days to longer than 3 months (modal duration, 7 days), and they were commonly associated with generalized pulmonary interstitial emphysema (18 of 20), pneumothorax (18 of 20), bronchopulmonary dysplasia (16 of 20), and pneumomediastinum (six of 20). The reason for the predominantly right parahilar location of these pseudocysts remains uncertain. Pulmonary pseudocysts are almost always right-sided and are associated with pulmonary interstitial emphysema and pneumothoraces; complete resolution usually occurs.

Computerized tomography and ultrasonographic findings in massive thymic hyperplasia. Case discussion and review of current concepts.

Massive thymic hyperplasia in the neonate and young infant can be difficult to diagnose. Differentiation from neoplastic lesions may require thoracotomy for a pathologic specimen. We review a case in a 15-month-old child referred to our institution and discuss the radiographic, ultrasound, and computerized tomographic features of hyperplastic thymic tissue. We review current concepts of the hyperplastic thymus as an anterior mediastinal mass in infancy.

Neonatal intestinal obstruction from omphalomesenteric duct remnants.

Three cases of omphalomesenteric band obstruction in early infancy with various radiographic presentations, including intermittent obstruction in one, are reported. Small-bowel volvulus was found in all three patients at surgery. One case progressed to bowel necrosis with portal venous gas. A survey of the mode of presentation, surgical findings, and pathology of 135 published cases of intestinal obstruction in children demonstrates that a closed loop, with or without volvulus, is the most common complication of remnant bands.

Metastatic renal cell carcinoma mimicking a meningioma.

We report a patient with renal cell carcinoma metastatic to the left trigone, which mimicked an intraventricular meningioma. The metastasis was recognized 1.3 years after removal of the primary tumor, a longer disease-free interval than any previously reported cases with brain metastases of renal cell carcinoma. The patient is now free of disease of years after resection and 17 years after the discovery of the primary tumor. Metastatic disease should be considered in all patients with prior resection of renal cell carcinoma who experience the onset of neurological disease, even after a prolonged disease-free interval. Long term survival is observed after the resection of solitary metastases, particularly if these appear after a prolonged disease-free interval.

The failed transhepatic cholangiogram.

A study of percutaneous transhepatic cholangiograms in 94 consecutive patients revealed that success is largely determined by the number of passes attempted. Two of 43 patients with dilated intrahepatic ducts had unsuccessful cholangiograms, but in these patients only two and three passes were attempted. In the remaining 41 patients fewer than seven passes were required. In patients with nondilated ducts, the success rate bears an almost linear relationship to the number of attempted passes beyond the fourth pass. Since patient tolerance often limits the number of passes, careful technique is important; one such technique is described. In the cholangiogram failures with nondilated ducts, subsequent liver biopsy had a high diagnostic yield.

Cerebral venous angioma: correlation of radionuclide brain scan, transmission computed tomography, and angiography.

Three cases of intracerebral venous angioma, a rare vascular malformation, were studied by radionuclide brain scan, transmission computed tomography (TCT) and angiography. In each case, the radionuclide flow study demonstrated a typical area of abnormal increase in activity during the venous phase; in two of the cases the arterial phase was also abnormal. Each contrast angiogram demonstrated a normal arterial distribution and a characteristic network of abnormal veins that converged to a large transcerebral draining vein. The TCT scans showed enhancing, curvilinear densities; while not specific, this finding should suggest the possibility of venous angioma in the brain.

Computed tomography and spinal dysraphism: clinical and phantom studies.

Two cases illustrating the value of CT in the assessment of spinal dysraphic tissue are presented. In one case, the configuration and origins of two osseous diastematomyelic spurs were shown well; in the second case, the CT recognition of a sacral lipoma led to air myelographic confirmation of the tumor and tethered cord. CT phantom studies indicated that dysraphic tissues, such as fat, cartilage, and fibrous tissue, are better identified and quantitated in the spinal canal when surrounded by air. Varying degrees of image degradation occur with water (simulating CSF) or metrizamide.