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Biomedical subjects

R A Bronen

Publications and source records attributed to R A Bronen.

At least 37 records · Page 2Linked to original sources
PubMed1996

Refractory epilepsy: comparison of MR imaging, CT, and histopathologic findings in 117 patients.

PURPOSE: We compared computed tomography (CT) and magnetic resonance (MR) imaging for the detection of abnormalities underlying epilepsy. MATERIALS AND METHODS: CT and MR imaging findings in 117 patients (56 female, 61 male patients; age at surgery, 12-56 years) who underwent surgery for medically refractory epilepsy were compared with histopathologic findings by using the McNemar and chi 2 statistics. RESULTS: Sensitivities for detecting abnormalities were 95% (104 of 109) for MR imaging and 32% (35 of 109) for CT; specificities were 87% (13 of 15) for MR imaging and 93% (14 of 15) for CT (P < .001 for MR versus histopathologic findings). In the subgroup of 113 patients with solitary findings, MR imaging depicted an abnormality at the surgical site in 86% (n = 97) of 113 patients compared to 28% (n = 32) for CT (P < .001). In this same subgroup, histopathologic findings were predicted by using MR imaging in 88% (n = 99) of 113 patients versus 35% (n = 40) with CT (P < .001). Multiple findings were observed in 3% of CT (three of 117) and 17% of MR (20 of 117) images. CONCLUSION: CT has no role in the diagnostic evaluation of medically refractory epilepsy. Even in patients with medically controlled epilepsy, use of less costly CT instead of MR imaging seems imprudent.

Adolescent↗
PubMed1996

Comparison of technetium-99m-HMPAO and technetium-99m-ECD cerebral SPECT images in Alzheimer's disease.

UNLABELLED: SPECT has shown increasing promise as a diagnostic tool in Alzheimer's disease (AD). Recently, a new SPECT brain perfusion agent, 99mTc-ethyl cysteinate dimer (99mTc-ECD) has emerged with purported advantages in image quality over the established tracer, 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO). This research aimed to compare cerebral images for 99mTc-HMPAO and 99mTc-ECD in discriminating patients with AD from control subjects. METHODS: Twenty-four AD patients (mean age +/- s.d. = 68.9 +/- 8.2 yr) and 13 healthy subjects (68.4 +/- 8.0 yr) were scanned sequentially with 20 mCi of each tracer using the CERASPECT system within 1 mo. Scanning began on average 11.5 +/- 2.8 min after 99mTc-HMPAO injection and 41.8 +/- 10.1 min after 99mTc-ECD. A ratio, R, was derived of count densities in "typically affected" brain structures (parietal and temporal association cortices) to "unaffected" structures (cerebellum, basal ganglia, thalamus, occipital cortex, and sensorimotor cortex). RESULTS: Analysis of variance revealed significant interaction between diagnostic group and radiopharmaceutical (F = 4.71; df = 1.35; p = 0.04), with 99mTc-ECD demonstrating better separation of R values between AD patients and control subjects than 99mTc-HMPAO. Receiver operating characteristic (ROC) analysis, revealed no significant difference in the ability of the two tracers to correctly classify AD patients and control subjects. Both tracers showed high diagnostic accuracy (99mTc-ECD: sensitivity = 100%, specificity = 92%; 99mTc-HMPAO: sensitivity = 100%, specificity = 85%). CONCLUSION: Technetium-99m-ECD shows greater contrast than 99mTc-HMPAO between affected and unaffected brain structures in AD when patients are compared to age-matched control subjects. Both tracers perform equally well in correctly classifying patients and control subjects.

Aged↗
PubMed1995

Sex differences in the functional organization of the brain for language.

A much debated question is whether sex differences exist in the functional organization of the brain for language. A long-held hypothesis posits that language functions are more likely to be highly lateralized in males and to be represented in both cerebral hemispheres in females, but attempts to demonstrate this have been inconclusive. Here we use echo-planar functional magnetic resonance imaging to study 38 right-handed subjects (19 males and 19 females) during orthographic (letter recognition), phonological (rhyme) and semantic (semantic category) tasks. During phonological tasks, brain activation in males is lateralized to the left inferior frontal gyrus regions; in females the pattern of activation is very different, engaging more diffuse neural systems that involve both the left and right inferior frontal gyrus. Our data provide clear evidence for a sex difference in the functional organization of the brain for language and indicate that these variations exist at the level of phonological processing.

Adult↗
PubMed1995

MR characteristics of neoplasms and vascular malformations associated with epilepsy.

We assessed the magnetic resonance (MR) imaging characteristics of two categories of epileptogenic substrates, neoplasms, and vascular malformations, to determine MR sensitivity and typical imaging features. A blinded retrospective analysis was performed on MR scans from 41 patients who had a neoplasm or vascular malformation surgically resected as treatment for medically refractory epilepsy. Abnormalities were assessed for sensitivity of MR detection, prediction of pathologic category, location, calvarial remodelling, signal intensity, and effect on adjacent tissue. Pathologic findings consisted of 33 tumors and 8 vascular malformations. We correctly localized 100% of the 41 lesions and predicted the correct pathologic category for 95% of these lesions. Neoplastic and vascular lesions (NVLs) associated with epilepsy had certain characteristic features. The temporal lobe was the most common site for NVL, involved in 68%. NVL were located in the brain periphery in 85% and remodelled the calvarium in 32%. NVL were associated with mass effect in 61%, volume loss in 1%, and no effect on adjacent tissue in 37%. NVL associated with epilepsy can be detected with high sensitivity using MR imaging. The temporal lobe location, cortical involvement, and calvarial remodelling are findings typical of NVL. MR characteristics can successfully predict the pathologic substrate of these lesions.

Brain Neoplasms↗
PubMed1995

MRI-based measurement of hippocampal volume in patients with combat-related posttraumatic stress disorder.

OBJECTIVE: Studies in nonhuman primates suggest that high levels of cortisol associated with stress have neurotoxic effects on the hippocampus, a brain structure involved in memory. The authors previously showed that patients with combat-related posttraumatic stress disorder (PTSD) had deficits in short-term memory. The purpose of this study was to compare the hippocampal volume of patients with PTSD to that of subjects without psychiatric disorder. METHOD: Magnetic resonance imaging was used to measure the volume of the hippocampus in 26 Vietnam combat veterans with PTSD and 22 comparison subjects selected to be similar to the patients in age, sex, race, years of education, socioeconomic status, body size, and years of alcohol abuse. RESULTS: The PTSD patients had a statistically significant 8% smaller right hippocampal volume relative to that of the comparison subjects, but there was no difference in the volume of other brain regions (caudate and temporal lobe). Deficits in short-term verbal memory as measured with the Wechsler Memory Scale were associated with smaller right hippocampal volume in the PTSD patients only. CONCLUSIONS: These findings are consistent with a smaller right hippocampal volume in PTSD that is associated with functional deficits in verbal memory.

Adult↗
PubMed1995

Limbic lobe embryology and anatomy: dissection and MR of the medial surface of the fetal cerebral hemisphere.

PURPOSE: To facilitate understanding of limbic lobe anatomy by showing embryologic transformations of the medial surface of the cerebral hemisphere. METHODS: Brains from fetal specimens ranging from 13 to 24 weeks of gestational age were dissected. Photographs were made of the medial surface of the cerebral hemisphere. MR images of different fetal specimens of similar age were made for comparison of MR anatomy with dissected material. RESULTS: At 13 weeks, the entire inner limbic arch of the hippocampal formation is visible on the medial surface of the cerebral hemisphere. The hippocampal sulcus extends from frontal lobe to temporal lobe. At 16 weeks, the outer neocortical limbic arch of the subcallosal area, cingulate gyrus, and parahippocampus gyrus is present. Growth of the corpus callosum is associated with reduction in size of the hippocampal formation in the frontal lobe. The sulcus of the corpus callosum is the remnant of the anterior part of the hippocampal sulcus. At 18 weeks, growth of the parahippocampal gyrus begins to conceal the hippocampal formation. The supracallosal gyrus (indusium griseum), hidden from view by the corpus callosum, and the paraterminal gyrus are remnants of the previously larger hippocampal formation. CONCLUSIONS: Analysis of fetal specimens in different developmental stages with dissection and MR provides insight into embryologic transformations responsible for the complex anatomy of the limbic lobe.

Fetus↗
PubMed1992

Quantitative magnetic resonance imaging in temporal lobe epilepsy: relationship to neuropathology and neuropsychological function.

Magnetic resonance images (MRIs) were obtained from 25 patients with medically refractory epilepsy of temporal lobe origin (12 on the left, 13 on the right) and 14 right-handed control subjects. The hippocampi and temporal lobes were traced by computer on successive coronal images and the resulting measurements of area were summed for each region. The left and right hippocampi were symmetrical in the control subjects; however, for patients the hippocampus was smaller on the side of the seizure focus. Moreover, the left-right hippocampal ratio significantly differentiated the control subjects from each patient group. The left temporal lobe was significantly smaller than the right in control subjects. The epileptics' temporal lobes were smaller on the side of the seizure focus, compared to the temporal lobes in the control subjects. MRI hippocampal measurements were compared to hippocampal neuronal densities obtained postoperatively. Significant correlations were obtained between the ratio (side ipsilateral to focus/side contralateral to focus) of MRI hippocampal measurements and neuronal densities in all hippocampal subfields except CA2. Prior to surgery, patients were administered the Wechsler Memory Scale and the verbal Selective Reminding Test. Significant correlations existed between MRI measurements of the left hippocampus and the Wechsler logical memory percent retention scores and between the left temporal lobe measurements and the verbal Selective Reminding Test scores for patients with seizure foci in the left temporal lobe.

Adolescent↗
PubMed1992

Epilepsy: the role of MR imaging.

MR is the imaging technique of choice when examining a patient who is having seizures. Detection, localization, and differentiation of structural epileptogenic abnormalities are much better with MR imaging than with CT. MR imaging has a high success rate in identifying hippocampal sclerosis, a common cause of surgically treatable temporal lobe epilepsy. The affected hippocampus is atrophic and hyperintense on long TR images. Functional imaging with single-photon emission computed tomography and positron emission tomography is complementary to MR imaging but is not as widely available. In summary, MR imaging has dramatically changed the workup of epilepsy, especially for the patient with medically uncontrollable seizures. As surgical treatment of epilepsy becomes more available, the need for preoperative evaluation with MR imaging will increase.

Brain↗
PubMed1992

Efficacy of gadoteridol for magnetic resonance imaging of the brain and spine.

RATIONALE AND OBJECTIVES: The efficacy of gadoteridol for contrast enhancement of central nervous system pathology was assessed in a multicenter clinical trial involving 411 patients suspected of having intracranial or spinal pathology. METHODS: Magnetic resonance imaging was performed before and after intravenous administration of 0.10 mmol/kg gadoteridol. Two groups of images were interpreted by one of two neuroradiologists blinded to patient history. The results were analyzed separately. RESULTS: Patients with radiologic evidence of disease demonstrated enhancement of intracranial pathologic lesions in 44 of 63 (70%) and in 91 of 111 (82%) cases, respectively, whereas enhancement of spinal lesions was observed in 36 of 58 (62%) and in 65 of 78 (83%) cases, respectively. Subjectively, postcontrast scans provided more information than precontrast images in 37 of 63 (59%) and 84 of 111 (76%) intracranial cases, respectively, and in 25 of 58 (43%) and 55 of 78 (71%) spinal cases, respectively. Additional information included the subjective sense that there was improved visualization of pathology and definition of lesion borders. CONCLUSIONS: Subjective assessment of magnetic resonance scans suggest gadoteridol is an effective intravenous contrast agent for magnetic resonance imaging.

Adolescent↗
PubMed1991

MRI of the normal hippocampus.

Before it is possible to use MR imaging to investigate changes in the hippocampus in disease processes such as epilepsy and memory disorders, it is imperative that normal variations are defined. Using specific anatomic locations, we evaluated the hippocampi of 29 normal volunteers with coronal MR studies. Mild variations occur with regard to hippocampal size and shape, and hippocampal fissure visualization. Hippocampal signal intensity is isointense to cortical gray matter. Recognition of normally occurring variations should help prevent over-interpretation of hippocampal changes in pathologic disorders.

Amygdala↗
PubMed1991

MRI of the temporal lobe: normal variations, with special reference toward epilepsy.

Recent investigations of epilepsy, Alzheimer's disease, amnesia, and schizophrenia have used magnetic resonance imaging (MRI) to evaluate changes in temporal lobe structures. Normal variations in these structures need to be defined before one can use these structures to describe abnormal conditions. Twenty-nine normal volunteers were studied by coronal MRI. Frequent findings include notching of the uncus by the tentorium or adjacent vessels (22/29) and asymmetry of the temporal horns (20/29). This finding of uncal notching strengthens the evidence against "incisural sclerosis" as the basis for hippocampal sclerosis. Temporal horn dilatation occurred in four. However, mild asymmetry of the temporal horn was seen frequently at its anterior tip (16/29) and may be related to head rotation. Asymmetry of the choroidal fissure was never marked. Mild asymmetry was common at the hippocampal head (pes). Mild enlargement of the right temporal lobe by visual inspection is not uncommon. Subtle asymmetry of the white matter between the hippocampus and the collateral sulcus occurred in six. The collateral sulcus does not always point to the temporal horn. The occipitotemporal sulcus may point to the temporal horn. Asymmetric uncal protrusion (0/29) and Sylvian fissure dilatation (4/29) occur rarely.

Cerebral Ventricles↗
PubMed1991

Relationship of hippocampus and amygdala to coronal MRI landmarks.

Magnetic resonance imaging is playing an increasingly important role in the evaluation of the hippocampus, particularly in epilepsy, schizophrenia, and Alzheimer's dementia. Because of the complex configuration of the hippocampus, it is difficult to compare from patient to patient. We developed a system to allow comparison of the hippocampus on coronal images. We performed 34 magnetic resonance studies on 29 normal subjects. Ten anatomic landmarks were identified. These landmarks have a consistent 5-mm periodicity regardless of usual head flexion. In the second phase of our investigation, we showed that the amygdala, hippocampal head, hippocampal body, and hippocampal tail have a consistent relationship to the coronal magnetic resonance imaging landmarks.

Adolescent↗
PubMed1990

Magnetic resonance imaging contrast agents: theory and application to the central nervous system.

The theoretical aspects of magnetic resonance (MR) imaging contrast agents are reviewed, and their current applications to the central nervous system (CNS) and their future applications are discussed. Profound differences exist between contrast agents used for MR imaging and computerized tomography (CT). In MR imaging, the contrast agents are not imaged directly but rather act on adjacent protons to shorten T1 and T2 relaxation times. This in turn results in signal intensity changes. The lanthanide metal, gadolinium, in the form of gadopentetate dimeglumine, has been found to be both safe and efficacious as the only currently approved contrast agent for MR imaging. Magnetic resonance imaging revolutionized the detection and treatment of disease affecting the brain and spine. Initially, it was thought that signal characteristics on MR imaging would allow differentiation of specific pathology. It was soon found that MR studies were able to detect more abnormalities but were less able to characterize them. The recent development of contrast agents for MR imaging has allowed this modality to surpass CT for the evaluation of most CNS lesions. At present, contrast-enhanced MR imaging is generally accepted as the study of choice for evaluating acoustic neurinomas, pituitary lesions, meningeal disease, primary and secondary brain tumors, active multiple sclerosis, intradural spinal neoplasms, intramedullary spinal disease, and postoperative states in both the spine and brain. Even when contrast-enhanced CT can detect the same abnormalities, evaluation of the lesions in multiple planes on MR imaging can sometimes yield invaluable information, especially prior to surgery. Future developments of contrast material for MR imaging include non-gadolinium compounds, intrathecal contrast media, cerebral blood flow and volume evaluation, and, possibly, antibody-labeled contrast agents.

Animals↗
PubMed1984

Diffuse lymphoid follicles of the colon associated with colonic carcinoma.

In four patients aged 59-75 years, colonic carcinoma was associated with diffuse lymphoid follicles in the colon. In one case, the prominence and distribution of the lymphoid follicles corresponded to the progression and regression of the tumor bulk. It is extremely unusual to demonstrate lymphoid follicles, particularly diffuse, on barium enema in patients in this age range. The colonic carcinomas and lymphoid follicles are directly related, possibly representing an immune response.

Aged↗
PubMed1984

Meckel's diverticulum: axial volvulus mimicking emphysematous cholecystitis.

A 48-year-old man presented with symptoms of acute cholecystitis. Abdominal roentgenograms suggested emphysematous cholecystitis. Axial volvulus of a Meckel's diverticulum was discovered at surgery. We discuss this unusual complication of Meckel's diverticula as well as the roentgenographic differential diagnosis of air in the gallbladder.

Cholecystitis↗
PubMedDate not supplied

CT-guided percutaneous insertion of interstitial radiotherapy catheters in head and neck tumors.

We describe a new method of placing interstitial radiation therapy catheters in patients with head and neck tumors. In three patients with recurrent inoperable head and neck tumors CT guidance was utilized to insert interstitial radiation therapy catheters percutaneously. This method enabled palliative radiation therapy to be administered without the need for surgical placement of seeds or catheters. The detailed anatomical localization of tumor and vascular structures provided by CT enabled precise percutaneous placement of afterloading catheters while ensuring safety. Pain was reduced and tumor size was decreased in all three patients. The CT-guided percutaneous insertion of afterloading catheters is a simple yet effective method of providing interstitial radiation therapy for head and neck tumors.

Aged↗