(1/3682) A genetic approach to visualization of multisynaptic neural pathways using plant lectin transgene.
The wiring patterns among various types of neurons via specific synaptic connections are the basis of functional logic employed by the brain for information processing. This study introduces a powerful method of analyzing the neuronal connectivity patterns by delivering a tracer selectively to specific types of neurons while simultaneously transsynaptically labeling their target neurons. We developed a novel genetic approach introducing cDNA for a plant lectin, wheat germ agglutinin (WGA), as a transgene under the control of specific promoter elements. Using this method, we demonstrate three examples of visualization of specific transsynaptic neural pathways: the mouse cerebellar efferent pathways, the mouse olfactory pathways, and the Drosophila visual pathways. This strategy should greatly facilitate studies on the anatomical and functional organization of the developing and mature nervous system. (+info)
(2/3682) Why and how is soft copy reading possible in clinical practice?
The properties of the human visual system (HVS) relevant to the diagnostic process are described after a brief introduction on the general problems and advantages of using soft copy for primary radiology interpretations. At various spatial and temporal frequencies the contrast sensitivity defines the spatial resolution of the eye-brain system and the sensitivity to flicker. The adaptation to the displayed radiological scene and the ambient illumination determine the dynamic range for the operation of the HVS. Although image display devices are determined mainly by state-of-the-art technology, analysis of the HVS may suggest technical characteristics for electronic displays that will help to optimize the display to the operation of the HVS. These include display size, spatial resolution, contrast resolution, luminance range, and noise, from which further consequences for the technical components of a monitor follow. It is emphasized that routine monitor quality control must be available in clinical practice. These image quality measures must be simple enough to be applied as part of the daily routine. These test instructions might also serve as elements of technical acceptance and constancy tests. (+info)
(3/3682) Rupture mechanism of a thrombosed slow-growing giant aneurysm of the vertebral artery--case report.
A 76-year-old male developed left hemiparesis in July 1991. The diagnosis was thrombosed giant vertebral artery aneurysm. He showed progressive symptoms and signs of brainstem compression, but refused surgery and was followed up without treatment. He died of rupture of the aneurysm and underwent autopsy in March 1995. Histological examination of the aneurysm revealed fresh clot in the aneurysmal lumen, old thrombus surrounding the aneurysmal lumen, and more recent hemorrhage between the old thrombus and the inner aneurysmal wall. The most important histological feature was the many clefts containing fresh blood clots in the old thrombus near the wall of the distal neck. These clefts were not lined with endothelial cells, and seemed to connect the lumen of the parent artery with the most peripheral fresh hemorrhage. However, the diameter of each of these clefts is apparently not large enough to transmit the blood pressure of the parent artery. Simple dissection of the aneurysmal wall by blood flow in the lumen through many clefts in the old thrombus of the distal neck may be involved in the growth and rupture of thrombosed giant aneurysms of the vertebral artery. (+info)
(4/3682) Secondary glioblastoma remarkably reduced by steroid administration after anaplastic transformation from gliomatosis cerebri--case report.
A 45-year-old female presented with gliomatosis cerebri manifesting as hemiballismus-like involuntary movement in the arm, motor weakness in the leg, and hypesthesia in her left side. Computed tomography showed only diffuse swelling of the right cerebral hemisphere, but T2-weighted magnetic resonance imaging revealed a diffuse lesion spreading from the right thalamus to the temporal, parietal, and occipital lobes on the same side. No abnormal enhancement was recognized. Cerebral angiography showed no specific finding. A right occipital lobectomy was performed to confirm the diagnosis of gliomatosis cerebri. Anaplastic transformation was recognized 5 months later. The disease did not resolve with radiation or interferon administration, but steroid therapy achieved remarkably effective tumor regression. The patient died due to pneumonia. Autopsy showed the features of diffuse glioblastoma. Steroid therapy may be an effective treatment for gliomatosis cerebri before the terminal stage. (+info)
(5/3682) Evaluation of "solitary" thyroid nodules in a community practice: a managed care approach.
Evaluation of thyroid nodules remains a challenge for primary care physicians. To include or exclude the presence of malignancy in a thyroid nodule, radioisotope scan, ultrasound, and fine-needle aspiration biopsy of the thyroid generally are used. The objectives of this study were to determine the utility and cost effectiveness of fine-needle aspiration biopsy of solitary thyroid nodules in a community setting; to compare the cost of fine-needle aspiration biopsy with that of radioisotope scan and ultrasound; and to determine whether the practice of obtaining radioisotope scans and ultrasound has changed in the 1990s compared with the 1980s. Patients were referred by community physicians to university-based endocrinologists for evaluation of thyroid nodules. Many of the patients had previously undergone radioisotope scans and ultrasound scans at the discretion of their primary care physicians. All patients underwent fine-needle aspiration biopsy. The biopsy results were evaluated prospectively, and the practice of community physicians' obtaining radioisotope scans and ultrasound scans was compared for the 1980s and 1990s. Eighty-three patients underwent 104 biopsies. In 20 biopsies the specimens were inadequate; the others showed 70 benign, 9 suspicious, and 4 malignant lesions. All four patients with biopsy findings read as malignant were found to have malignant growth at surgical procedures. Two benign biopsy findings were false-negative results. Malignant growth was correctly diagnosed later for one patient at a second biopsy and for the other because of growth of the nodule. The cost of 104 biopsies was $20,800. The cost of radioisotope scans was $22,400, and the cost of ultrasound scans was $10,640. The frequency of obtaining radioisotope scans (84.5% vs 77%) and ultrasound scans (65% vs 45%) was slightly higher in the 1990s compared with the 1980s. Fine-needle aspiration biopsy is a safe and cost effective initial evaluation modality for smaller community-based centers, as it is at large tertiary centers. The cost incurred ($33,040) in obtaining the radioisotope scans and ultrasound scans could have been saved if fine-needle aspiration biopsy had been used as the initial diagnostic procedure for evaluation of these nodules. Although radioisotope scan and ultrasound scan are of little diagnostic help in the evaluation of thyroid nodules, they continued to be obtained at a high frequency during the last decade. (+info)
(6/3682) Use of an intravenous contrast agent (Optison) to enhance echocardiography: efficacy and cost implications. Optison Multicenter Study Group.
OBJECTIVE: To compare the overall diagnostic costs associated with non-contrast and contrast echocardiography. STUDY DESIGN: Phase III clinical trial. PATIENTS AND METHODS: In a secondary analysis of data from a phase III clinical trial of the intravenous contrast agent Optison, we compared the costs associated with obtaining a diagnosis in 203 patients who underwent non-contrast and contrast echocardiography. Costs for the initial test and any follow-up tests were derived from adjusted Medicare charges and a transition-1 microcost accounting system. RESULTS: Diagnostic yield from echocardiograms was 87% with the use of Optison (3 mL) and 49% when no contrast agent was used (P < 0.001). Because technically inadequate echocardiograms were more common in the non-contrast group, follow-up testing was recommended for 42% of patients in this group compared with 12% of those who had undergone a contrast-enhanced echocardiogram (P < 0.001). Although use of Optison increased the initial diagnostic cost by $125, overall costs were 17% lower when Optison was used (P < 0.0001). Use of Optison also resulted in a 17% to 70% decrease in confirmatory transesophageal echocardiography, catheterization, and nuclear studies. Optison improved diagnostic accuracy by 2.7-fold in patients with an initial non-diagnostic echocardiogram, resulting in a substantial cost savings of $269 per patient. (+info)
(7/3682) Reversible congestive heart failure caused by myocardial hibernation.
Myocardial hibernation is reversible contractile dysfunction of cardiac myocytes caused by chronic ischemia. Animal studies and observations in human beings suggest that the term hibernation is a misnomer. Repetitive ischemic insult that does not produce necrosis results in functional and histologic tissue deterioration, which culminates in myocyte apoptosis. Revascularization of "hibernating" myocardium results in partial or complete recovery of function, depending upon the duration of ischemia and the severity of cellular degeneration. Improvement in global left ventricular function is proportional to the quantity of hibernating tissue that is revascularized, but this threshold quantity has not been determined with certainty. Diagnostic methods used to detect viable tissue within akinetic left ventricular segments depend upon the recognition of recruitable contractile function or the active concentration of a radioactive tracer. No diagnostic method has shown clear superiority. The most sensitive methods appear to be single-photon emission computed tomographic imaging after reinjection of thallium-201 at 24 hours and positron-emission tomographic imaging with 18F-fluorodeoxyglucose. The most specific diagnostic method appears to be measurement of dobutamine-stimulated contractile function, using either echocardiography or gated magnetic resonance imaging. We present a review of the pathophysiology, diagnosis, and treatment of myocardial hibernation, and include an illustrative case report involving a 57-year-old man with myocardial hibernation. (+info)
(8/3682) Segmental spinal dysgenesis: neuroradiologic findings with clinical and embryologic correlation.
BACKGROUND AND PURPOSE: Segmental spinal dysgenesis (SSD) is a rare congenital abnormality in which a segment of the spine and spinal cord fails to develop properly. Our goal was to investigate the neuroradiologic features of this condition in order to correlate our findings with the degree of residual spinal cord function, and to provide insight into the embryologic origin of this disorder. We also aimed to clarify the relationship between SSD and other entities, such as multiple vertebral segmentation defects, congenital vertebral displacement, and caudal regression syndrome (CRS). METHODS: The records of patients treated at our institutions for congenital spinal anomalies were reviewed, and 10 cases were found to satisfy the inclusion criteria for SSD. Plain radiographs were available for review in all cases. MR imaging was performed in eight patients, one of whom also underwent conventional myelography. Two other patients underwent only conventional myelography. RESULTS: Segmental vertebral anomalies involved the thoracolumbar, lumbar, or lumbosacral spine. The spinal cord at the level of the abnormality was thinned or even indiscernible, and a bulky, low-lying cord segment was present caudad to the focal abnormality in most cases. Closed spinal dysraphisms were associated in five cases, and partial sacrococcygeal agenesis in three. Renal anomalies were detected in four cases, and dextrocardia in one; all patients had a neurogenic bladder. CONCLUSION: SSD is an autonomous entity with characteristic clinical and neuroradiologic features; however, SSD and CRS probably represent two faces of a single spectrum of segmental malformations of the spine and spinal cord. The neuroradiologic picture depends on the severity of the malformation and on its segmental level along the longitudinal embryonic axis. The severity of the morphologic derangement correlates with residual spinal cord function and with severity of the clinical deficit. (+info)