PubMed Health⌕ Search

Biomedical subjects

R J Sevick

Publications and source records attributed to R J Sevick.

32 records · Page 2Linked to original sources
PubMed1994

Diffuse-variant tenosynovial giant cell tumor: a rare and aggressive lesion.

The diffuse-variant tenosynovial giant cell tumor is rare. Although it shares histologic features with the exclusively intra-articular pigmented villonodular synovitis and local tenosynovial giant cell tumor, its behavior differs dramatically, being locally very aggressive. We report a case of a diffuse-variant aggressive tenosynovial giant cell tumor that, although diploid by flow cytometry, demonstrated trisomy 7 and 5 as well as clonal rearrangements involving chromosomes 1, 3, and 15. These cytogenetic abnormalities may be markers for aggressive behavior and useful for directing treatment.

Adult↗
PubMed1994

Parapharyngeal branchial cleft cyst presenting with cranial nerve palsies.

The authors report a case of branchial cleft cyst for which the location and presentation of the lesion were unusual. This abnormality should be considered in the differential diagnosis of cystic lesions of the parapharyngeal space. The presence of multiple cranial nerve palsies in association with a mass in this region does not necessarily indicate a neoplastic lesion.

Adult↗
PubMed1992

Cytotoxic brain edema: assessment with diffusion-weighted MR imaging.

To determine whether cytotoxic brain edema is associated with a decrease in diffusion, it was induced in rats, in the absence of ischemia, with an established model of acute hyponatremic encephalopathy. Cytotoxic brain edema secondary to acute hyponatremia was induced with intraperitoneal injections of 2.5% dextrose in water and subcutaneous injection of arginine-vasopressin. Coronal spin-echo magnetic resonance (MR) images were obtained with and without strong diffusion-sensitizing gradients before and after induction of acute hyponatremia. The apparent diffusion coefficient (ADC) was measured at two coronal section locations. In hyponatremic rats, the brain ADC was significantly reduced (P = .0153 and .0001) and was positively correlated with increased total brain water content (P = .0011). Plots of ADC versus total brain water showed a statistically significant inverse linear relationship between ADC and increasing brain water at the anterior coronal section location. The results indicate that the ADC may be a sensitive indicator of cytotoxic brain edema and thus may enable quantitative evaluation of such edema with diffusion-weighted MR imaging.

Animals↗
PubMed1992

Evolution of white matter lesions in neurofibromatosis type 1: MR findings.

To characterize further the evolution of white matter lesions in neurofibromatosis type 1, we reviewed 68 MR images in 43 patients (age, 1-31 years), including 25 follow-up studies (mean interval, 27 months). Lesion number, location, morphology, signal characteristics, and contrast enhancement were assessed. Lesion characteristics and changes thereof were correlated with the patients' ages. Thirty-four patients (79%) had white matter lesions. These lesions were hyperintense on T2-weighted images, were isointense on T1-weighted images, and showed no mass effect or contrast enhancement in 31 patients; in three patients, T1-prolongation was observed (one with significant mass effect). None of the lesions evolved into a glioma. The most common locations were the cerebellum (49%), brainstem (22%), and internal capsule (19%). Nineteen patients had white matter lesions and follow-up studies. Lesions decreased in size or number in seven patients (average age, 13 years), showed no change in three (average age, 12 years), increased in size or number in four (average age, 5 years), and showed a mixed pattern (increased/decreased size/number) in four (average age, 7 years). White matter lesions in neurofibromatosis type 1 frequently increase in size or number early in childhood; this did not indicate neoplasia in our study. The lesions tend to resolve with increasing age. Lesion progression in a child more than 10 years old warrants close follow-up to rule out a neoplasm.

Adolescent↗
PubMed1991

Ischemic brain damage: reduction by sodium-calcium ion channel modulator RS-87476.

A novel sodium-calcium ion channel modulator, RS-87476, reduced cerebral infarct size in cats subjected to permanent unilateral occlusion of the middle cerebral artery. Cerebral injury was assessed in vivo with a combination of magnetic resonance (MR) imaging and spectroscopy for 5-12 hours after occlusion and was compared with the area of histochemically ischemic brain tissue. Compared with infarcts in placebo-treated animals, infarcts in cats given RS-87476 were reduced by an average of 70% at the lowest dose, 75% at the intermediate dose, and 88% at the highest dose. Tissue edema, observed as areas of signal hyperintensity on diffusion- and T2-weighted spin-echo images, was confined to small regions of the parietal cortex and basal ganglia in drug-treated animals. Mean plasma levels of RS-87476 at the lowest dose were 13 ng/mL initially, falling to maintenance levels of 3-5 ng/mL; at the intermediate and highest doses, plasma levels of drug were approximately five- and 20-fold greater. The drug was only slightly hypotensive. At least part of the potent cerebroprotective effects of RS-87476 result from its ability to stabilize metabolic energy reserves, reduce lactate formation in ischemic tissues, and attenuate intracerebral edema.

Animals↗
PubMed1991

Recent advances in MR imaging/spectroscopy of cerebral ischemia.

Recent advances in high-resolution MR imaging and multinuclear spectroscopy have stimulated studies of the functional relationships between tissue hypoperfusion, cellular energy depletion, and brain edema associated with cerebral ischemia. The very slow (microns/sec) random translational motion of water protons in various brain tissues and intracranial fluid compartments can now be assessed with MR diffusion imaging. More slowly diffusing protons in ischemic tissues can be differentiated from normal parenchyma, CSF, and flowing blood, enabling the detection and localization of ischemic regions within minutes of the onset of stroke. Perfusion imaging "snapshots," obtained in as little as 25 msec with echoplanar MR methods, permit the evaluation of tissue washin/washout kinetics of contrast agents in the microvasculature, and thus the quantification of brain perfusion on a regional basis. Also, delineation of major intra- and extracranial arterial and venous structures with MR angiography, acquired with two- or three-dimensional Fourier transformation techniques, has enabled accurate noninvasive assessments of vascular occlusive disease. Finally, improvements in MR spectroscopic techniques have facilitated investigations of metabolic regulation and bioenergetics in experimental animal models of cerebral ischemia, as well as in stroke patients. Combined MR imaging and spectroscopy will likely play an important role in differentiating reversibly from irreversibly ischemic brain tissues and in the investigation of various neuroprotective pharmaceuticals.

Animals↗
PubMed1991

Magnetic resonance imaging and computed tomography of cerebral vascular disease.

Magnetic resonance imaging has emerged as the primary modality in detection and characterization of cerebrovascular lesions. New applications of existing spin-echo and gradient-recalled echo techniques are described. Functional imaging techniques ranging from the characterization of macroscopic proton motion (diffusion-weighted MR imaging), rapid imaging of intravascular contrast transit times (perfusion MR imaging), fast-flow mapping (MR angiography), and in vivo metabolic assessment (MR spectroscopy) are discussed. CT scanning remains important as an initial screening examination, in identifying acute hemorrhage, and in demonstrating blood flow.

Cerebrovascular Disorders↗
PubMed1990

Diffusion-weighted MR imaging and T2-weighted MR imaging in acute cerebral ischaemia: comparison and correlation with histopathology.

Diffusion-weighted MR imaging is a new technique which measures the microscopic motion of water protons. Signal hyperintensity on diffusion-weighted images correlates closely with evidence of ischaemic damage on histopathologic sections. Following occlusion of the middle cerebral artery (MCA), diffusion-weighted images indicate the presence of early pathophysiologic changes occurring first in the basal ganglia and, subsequently, in cortical gray matter within the MCA vascular territory. Diffusion-weighted images also better define the anatomic locus of ischaemic tissue injury than T2-weighted images. Diffusion-weighted imaging thus appears to facilitate early detection and thereby possible therapeutic intervention in patients with acute stroke.

Acute Disease↗
PubMedDate not supplied

Three-dimensional time-of-flight MR angiography in the evaluation of cerebral aneurysms.

We review our preliminary experience with the use of three-dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiography (MRA) in the assessment of intra- and extracranial aneurysms. Six patients were examined: Five had intracranial aneurysms and one had a cervical carotid pseudoaneurysm. A 3D rephased gradient recalled echo pulse sequence and maximum intensity projection (MIP) reconstruction algorithm were used. Magnetic resonance angiography, spin echo MR, and conventional angiography were retrospectively reviewed with specific regard to individual vessel visualization, aneurysm depiction, and presence of artifact related to acquisition techniques or MIP reconstruction. All aneurysms were detected on MRA, and anatomical correlation with conventional angiography was excellent. Significant problems included loss of visualization of small vessels, intraluminal signal loss in large vessels, subacute thrombus simulating flow on MIP reconstructions, and limited projections obtainable with MIP techniques. Adequate MRA assessment of aneurysms can be obtained using a combination of T1-weighted spin echo images and 3D TOF MRA. Review of all components of the MRA is required. MRA may be useful in screening asymptomatic patients for intracranial aneurysms as well as in the follow-up of patients treated with balloon occlusion.

Adult↗
PubMedDate not supplied

Trigeminal neuropathy: Gd-DTPA enhanced MR imaging.

A review of 17 patients with Gd-DTPA enhancing lesions of the trigeminal nerve (6 patients with benign tumors, 4 with inflammatory disease, 7 with malignant tumors) was conducted to determine if contrast enhanced MR imaging is superior to nonenhanced imaging and to identify imaging characteristics that aid in separating benign and malignant disease. Contrast enhanced imaging appears to be superior to nonenhanced imaging in patients with intrinsic fifth nerve lesions. Malignant lesions are suggested by enlarged, enhancing fifth nerves with irregular margins and benign lesions by minimal or no enlargement with smooth margins. Overlap of imaging findings between benign and malignant disease strongly suggests that follow-up imaging and clinical findings are of utmost importance. Gadolinium-enhanced MR imaging of the fifth nerve is recommended in patients with trigeminal sensory or motor deficits as well as those with atypical trigeminal neuralgia.

Adolescent↗