Biomedical subjects

M J Post

Publications and source records attributed to M J Post.

At least 127 records · Page 7Linked to original sources

PubMed1978

A comparison of radiographic methods of diagnosing constrictive lesions of the spinal canal. Toshiba unit vs. CT scanner.

With the advent of computerized tomography (CT), a new method of visualizing the spinal canal in cross-section has been created. Before the introduction of CT scanning, evaluation of the cross-sectional anatomy of the spinal canal was accomplished chiefly by the Toshiba unit. This study compares these two forms of tomography and discusses their relative effectiveness in diagnosing constrictive lesions of the spinal canal.

Adult↗

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Leber congenital amaurosis in siblings with diffuse dysmyelination.

Two brothers are described with the previously unrecognized combination of Leber amaurosis and abnormal myelin detected by magnetic resonance imaging. Both have evidence of delayed psychomotor development and one has autistic features. A possible relationship with infantile autism or a peroxisomal dysfunction syndrome is explored. No peroxisomal defect was found in these patients.

Autistic Disorder↗

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Stimulation of vascular smooth muscle cell migration by macrophage migration inhibitory factor.

Macrophage migration inhibitory factor (MIF) is a well known proinflammatory factor that influences the migration and proliferation of various cell types, predominantly monocytes and macrophages. Recent evidence suggests an important role for MIF in the progression of atherosclerosis and restenosis. For this reason, we studied the effect of MIF on platelet-derived growth factor-BB (PDGF-BB)-induced migration and PDGF receptor protein expression in vascular smooth muscle cells (VSMCs). Furthermore, the possibility of MIF influencing the migration of VSMCs was investigated. Our results show that short-term incubation of MIF is able to enhance PDGF-BB-induced migration. Long-term incubation decreases PDGF-BB-induced migration, but preserves a short-term stimulatory effect. These effects are not regulated at the level of PDGF receptor protein expression. MIF also acts as a chemoattractant for VSMCs, with a maximum response at 15 ng/ml. In contrast, the proliferation of VSMCs was unaffected by MIF. We conclude that MIF has a biphasic effect on VSMC migration. It remains unclear whether this effect is direct or involves the secretion of unidentified promigratory factors. Exogenous MIF does not stimulate VSMC proliferation; however, a role for MIF in proliferation cannot be fully ruled out. In view of the known key contributions of macrophage-derived MIF and VSMCs, the observed effects may well play a role in the progression of atherosclerosis and restenosis.

Animals↗

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Metastatic disease to the cavernous sinus: clinical syndrome and CT diagnosis.

We analyzed the clinical constellation of signs and symptoms and the radiographic studies of 17 patients with histologic verification of cavernous sinus metastases. Although most patients presented with acute, unilateral, painful ophthalmoplegia, and with a rapidly progressive course, the clinical diagnosis of metastatic disease was often delayed. This was probably due to the fact that, in the majority of patients, cavernous sinus symptoms were either the first expression of an unknown malignancy or the first manifestation of metastatic disease in those with a known primary. Computed tomography was found to be an indispensable diagnostic aid. In 16 of the 17 patients CT established the presence of an enhancing mass in the cavernous sinus sometimes associated with bone erosion. Thin section, contrast enhanced high resolution CT in axial and coronal projections represents the imaging procedure of choice for metastatic disease to the cavernous sinus.

Adult↗

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Gadolinium-enhanced MR in spinal infection.

The purpose of this study was to determine what advantages the use of paramagnetic contrast material might have in evaluating patients clinically suspected of having spinal infection. To determine this we prospectively examined with noncontrast and contrast magnetic resonance (MR) 33 such patients and correlated the MR diagnoses with clinical and pathologic data. Our results showed the following advantages of gadolinium-enhanced MR: it (a) provided excellent anatomical delineation of all epidural abscesses, routinely differentiating them from the adjacent compressed thecal sac even when this was not possible by noncontrast MR; (b) increased observer confidence in the diagnosis of disk space infection and osteomyelitis in patients with equivocal noncontrast MR; (c) localized those portions of paraspinal masses most likely to yield a positive percutaneous biopsy; and (d) identified active infections from those that had responded adequately to antibiotic therapy. We conclude that contrast MR is a valuable adjunct to noncontrast MR when diagnosis, anatomical clarity, and/or lesion activity requires further elucidation.

Abscess↗

PubMedDate not supplied

MRI of AIDS-related polyradiculomyelitis.

OBJECTIVE: We describe the unusual syndrome of cytomegalovirus (CMV) polyradiculomyelitis and its MR findings in two patients with AIDS. MATERIALS AND METHODS: The clinical records and MRI studies of two patients with AIDS and CMV polyradiculomyelitis were reviewed. The MR images were performed on a Picker 1.0 or 1.5 T MR unit. Axial and sagittal T1-weighted images of the lumbar spine were obtained, pre- and post-Gd-DTPA (0.1 mmol/kg) administration. Gradient echo sagittal images were also obtained. RESULTS: Precontrast images demonstrated a thickened cauda equina in both patients. In one patient the conus was ill defined on precontrast images. Post-contrast images demonstrated diffuse enhancement of the cauda equina in both patients as well as enhancement along the surface of the conus. In one patient the nerve roots were clumped and adherent to the walls of the thecal sac as well as to other nerve roots. CONCLUSION: The clinical presentation of urinary retention, flaccid paraparesis, back and/or leg pain, and "saddle anesthesia" in a patient with AIDS should suggest the diagnosis of CMV polyradiculomyelitis. Although diffuse enhancement of the cauda equina on postcontrast MRI is a nonspecific finding, it would strongly support this diagnosis in the appropriate clinical setting. The diagnosis may be easily missed without the use of a contrast agent.

AIDS-Related Opportunistic Infections↗

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CNS Nocardia in AIDS patients: CT and MRI with pathologic correlation.

OBJECTIVE: Since CNS nocardiosis is an often fatal yet potentially treatable infection in HIV patients, we sought to identify and characterize imaging features that may suggest the diagnosis in the appropriate clinical setting. MATERIALS AND METHODS: The CT scan (six), MR scans (one), or both (two) were evaluated in nine HIV patients with pathologically proven CNS Nocardia asteroides. Chest X-ray films were available in seven patients. Findings were correlated with pathologic examination. RESULTS: All nine patients had brain abscesses, and in seven that received intravenous contrast agent, all lesions demonstrated ring enhancement. Five of nine patients had hydrocephalus and four of these had clinical evidence of meningitis. Small subependymal nodules were seen in five of nine patients and four of these also had meningitis. Pathologic examination in three of nine cases demonstrated a dense inflammatory infiltrate lining the ventricles that extended through the ependymal lining, producing small subependymal abscesses. Six of seven available chest X-ray films demonstrated infiltrates due to Nocardia. CONCLUSION: Our radiologic-pathologic correlation indicates that in an HIV-positive patient with enhancing parenchymal lesions, the additional findings of subependymal nodules and/or meningitis may suggest the diagnosis of nocardiosis. An associated pulmonary infiltrate can provide a clue to the diagnosis and serve as more accessible site for biopsy or culture.

AIDS-Related Opportunistic Infections↗

PubMedDate not supplied

MR of Toxoplasma encephalitis: signal characteristics on T2-weighted images and pathologic correlation.

PURPOSE: Our goal was to determine if there are any T2-weighted MR signal characteristics of Toxoplasma encephalitis that might be useful in diagnosis and/or in gauging the effectiveness of medical therapy. METHOD: We retrospectively analyzed the MR, CT, thallium-201 SPECT brain scans, and medical records of 27 patients with medically proven (26) and biopsy proven (1) Toxoplasma encephalitis, supplemented by autopsy findings in 4 additional patients, 2 of whom had postmortem MR correlation. The neuropathologic literature was also reviewed. RESULTS: Among the 27 patients, we discovered three distinct imaging patterns. Ten (37%) patients had predominantly T2-weighted hyperintense lesions and had been on medical therapy an average of 3 days (excluding one outlier). Ten (37%) patients had T2-weighted isointense lesions and had received medical therapy an average of 61 days. Seven (26%) patients had lesions with mixed signal on T2-weighted images and had been on treatment an average of 6 days. Analysis of autopsy material from the four additional patients revealed the presence of organizing abscesses in three and necrotizing encephalitis in one, while the patient who had a brain biopsy demonstrated both types of pathologic lesions. In both cases having postmortem MRI, organizing abscesses appeared isointense to hypointense on T2-weighted images. CONCLUSION: There is a definite variation in the appearance of lesions of Toxoplasma encephalitis on T2-weighted images that precludes a definitive diagnosis based on signal characteristics alone. Pathologically, our data suggest that T2-weighted hyperintensity correlates with necrotizing encephalitis and T2-weighted isointensity with organizing abscesses. Furthermore, in patients on medical therapy the T2-weighted MR appearance may be a transition from hyperintensity to isointensity as a function of a positive response to antibiotic treatment, indicating that the signal change might be used to gauge the effectiveness of medical therapy.

AIDS-Related Opportunistic Infections↗

PubMedDate not supplied

Dentate nuclei involvement in AIDS patients with CNS cryptococcosis: imaging findings with pathologic correlation.

PURPOSE: Our goal was to describe the involvement of the dentate nuclei in AIDS patients with CNS cryptococcosis since this finding has not been emphasized in previous radiological literature. METHOD: Plain and contrast-enhanced CT of the brain (10 and 10), MR studies (1 premortem and 1 postmortem), and autopsy findings in 11 AIDS patients with CNS cryptococcosis were reviewed. The imaging studies and pathological specimens were analyzed for signs of meningitis, presence of dilated Virchow-Robin spaces, gelatinous pseudocysts, cryptococcoma, ventriculomegaly, choroid plexus, and ependymal lesions. RESULTS: Five of 11 patients were found at autopsy to have macroscopically visible "cystic" lesions in the dentate nuclei that were not detected on CT (10 patients), but were seen on premortem MR (1 patient). Macroscopic supratentorial (basal ganglia, thalamic, midbrain) lesions were detected by CT in 5 of 11 patients and by MR in 2 of 2 patients. Enhancement of the leptomeninges was seen in only 1 patient by CT despite pathological evidence of cryptococcal meningitis in all 11 patients. Dilated Virchow-Robin spaces were seen in all 11 pathologic specimens and in the 2 MR studies but not on CT. Communicating hydrocephalus was detected by CT in two patients. CONCLUSION: CT scans of the brain underestimate infratentorial parenchymal cryptococcal disease. MR is a more sensitive procedure to evaluate cerebellar and brainstem cryptococcosis, including the dentate nuclei, which in our autopsy series was not an uncommon site to be infected with cryptococcal gelatinous pseudocysts.

AIDS-Related Opportunistic Infections↗

PubMedDate not supplied

Serial motion assessment by reference tracking (SMART): application to detection of local functional impact of chronic myocardial ischemia.

PURPOSE: To compare measurements of wall motion and thickening with and without correcting for cardiac twisting and shortening. METHOD: Inversion recovery Gd-DPTA perfusion and cine motion MRI were performed on 12 pigs with chronic ischemia induced by ameroid occluder. Analyses were based on conventional fixed plane imaging and serial motion assessment by reference tracking (SMART). RESULTS: Normal motion was 31.3 +/- 1.9%, and normal wall thickening was 41.4 +/- 2.2%. At the maximum perfusion defect, SMART wall motion was 10.5 +/- 2.4% and fixed wall motion was 20.6 +/- 1.7% (p < 0.004), SMART wall thickening was 20.1 +/- 4.4%, and fixed wall thickening was 32 +/- 1.9% (p < 0.03). CONCLUSION: SMART measurements of wall thickening and motion detect much smaller thickening and motion in ischemic myocardium than fixed radial metrics. SMART data, covering the entire heart, should prove twice as sensitive to abnormalities in motion and thickening, such as any produced by ischemic heart disease or improved by treatment.

Animals↗

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The value of computed tomography in spinal trauma.

Computed tomography (CT) is recommended for routine use in the evaluation of patients with spinal trauma. An evaluation of the CT scans and complementary radiographic studies of 117 patients with spinal trauma was performed. CT provides critical information often not afforded by conventional radiographs concerning fractures, bullet fragments, surgical devices, and paraspinal pathology. Furthermore, in contrast to myelography, it can demonstrate directly certain soft-tissue abnormalities within the spinal canal, such as intramedullary hematomas, herniated discs, and posttraumatic syrinxes. CT can also determine the etiology of myelographic defects, including those causing total myelographic blocks. Further, aided by intrathecal metrizamide, it can differentiate cord swelling from extrinsic cord pressure and thereby demonstrate the need for medical or surgical therapy.

Adolescent↗

PubMedDate not supplied

Thrombogenicity and intimal hyperplasia after conventional and thermal balloon dilation in normal rabbit iliac arteries.

Acute occlusion and restenosis are the major complications of percutaneous transluminal coronary balloon angioplasty. Application of heat during balloon dilation was postulated to reduce these complications. We evaluated thrombogenicity and intimal hyperplasia of normal rabbit iliac arteries after conventional (37 degrees C) and thermal balloon dilation. Thermal dilation was performed with a radio-frequency-heated balloon, provided with three thermocouples attached to the inside of the balloon skin. In a previous in vitro study, thrombogenicity of human subendothelium was increased at 55 degrees C and greatly decreased at temperatures over 70 degrees C. Thermal balloon dilation was therefore performed at 55 and 90 degrees C in vivo. Rabbits survived 2 h for evaluation of platelet adhesion or either 3 or 8 weeks for intimal hyperplasia. Angiograms revealed no occlusions or thrombi after any procedure. Platelet adhesion was quantified on 20 scanning electron microscopic pictures per balloon dilation site and was expressed as the percentage of the luminal surface covered by platelets. Platelet adhesion was similar in all groups, although large thrombi were present in the 90 degrees C group. Intimal hyperplasia was measured morphometrically at regular intervals over the balloon site. After 3 weeks, the average intimal hyperplasia was significantly reduced in the 90 degrees C balloon dilation group, which was mainly due to the absence of intimal hyperplasia in the midpart of these segments. After 8 weeks, intimal hyperplasia was equal in all groups. Thus, in the applied model, platelet coverage was equal after conventional balloon angioplasty and after 55 and 90 degrees C balloon angioplasty.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

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In the normal rabbit femoral artery increasing arterial wall injury does not lead to increased intimal hyperplasia.

Angioplasty inflicts damage to the arterial wall. We studied whether augmented medial smooth muscle cell necrosis leads to augmented intimal hyperplasia and thus aggravates restenosis. Sixty-three normal femoral arteries of New Zealand White rabbits were overstretched with an angioplasty balloon during either maximal vasoconstriction with phenylephrine (32 arteries) or maximal vasodilation with nitroprusside (31 arteries). After 3 days' survival, medial necrosis was determined as percentage of cross-sectional medial area. In the 3 weeks' survival group, intimal hyperplasia was quantified as its average thickness. The dilation ratios, i.e. balloon diameter divided by arterial diameter at the time of dilation, were significantly higher in the 3 days' and 3 weeks' vasoconstriction groups (VC groups), respectively: 1.96 +/- 0.10 (mean +/- SD) and 2.14 +/- 0.08 in the VC groups versus 1.27 +/- 0.03 and 1.32 +/- 0.05, respectively, in the vasodilation groups (VD groups) (both p < 0.001). Medial necrosis was more extensive in the VC group (64 +/- 5%) than in the VD group (23 +/- 7%, p < 0.001) and proportional to the dilation ratio (r = 0.69, p < 0.01). Intimal hyperplasia, however, was equal in the VC (59 +/- 8 microns) and VD (57 +/- 6 microns, NS) groups and not dependent on dilation ratio (r = 0.10). Thus, extensive medial necrosis produced during balloon dilation in maximally vasoconstricted arteries did not lead to more intimal hyperplasia than when less medial necrosis was induced by balloon dilation during vasodilation.

Angioplasty, Balloon↗

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Endothelial cell recoverage and intimal hyperplasia after endothelium removal with or without smooth muscle cell necrosis in the rabbit carotid artery.

Interventional-injury-induced intimal hyperplasia involves smooth muscle cell proliferation that may be limited by endothelial cell coverage. We hypothesized that endothelial cell coverage modulates intimal hyperplasia. Therefore rabbit carotid arteries were injured with (2-french Fogarty balloon) and without media necrosis (Prolene loop). After termination at 3, 7, 21, or 42 days, endothelial cell coverage was assessed with an antibody to CD31 and cross-sectional intimal hyperplasia area was measured morphometrically. At 21 and 42 days, maximal intimal hyperplasia thickness was measured at a site where endothelium was present and where endothelium was absent. Proliferating cells were identified with an antibody to the nuclear antigen Ki-67. From 3 to 42 days, endothelial cell coverage progressed from the caudal and cranial ends of the lesion towards the center and was slower in balloon- versus loop-injured arteries (p<0.001, Anova). At 21 and 42 days, intimal hyperplasia area was larger after balloon than after loop injury (21 days: 0.20 +/- 0.01 vs. 0.09 +/- 0.04 mm2, p<0.05; 42 days: 0.26 +/- 0.03 vs. 0.08 +/- 0.02 mm2, p<0.01). At 21 days, the intimal hyperplasia was maximal at the center of the lesion and diminished towards the edges in both balloon- and loop-injured arteries. Surprisingly, at 21 and 42 days, maximal intimal hyperplasia thickness was larger in CD31-positive compared to CD31-negative regions (104 +/- 8 vs. 72 +/- 12 micron, p<0.01, paired t test). At 3 and 7 days, more medial proliferation was found after balloon than after loop injury (3 days: 46.2 +/- 8.8 vs. 0.2 +/- 0.1%, p<0.01; 7 days: 18.5 +/- 6.4 vs. 1.0 +/- 0.4%, p<0.01). In the same period, abundant adventitial proliferation was found after balloon injury that was entirely absent after loop injury. We conclude, first, that endothelial cell recoverage proceeded at a lower rate over damaged than over normal media. This retarded endothelial cell recoverage may contribute to enhanced intimal hyperplasia. Second, at a late stage of vascular healing, when intimal hyperplasia had already been formed, reendothelialization seems to have been enhanced over areas with thick intimal hyperplasia. Third, dilation-induced medial damage was accompanied with massive adventitial cell proliferation.

Animals↗

PubMedDate not supplied

Thrombogenicity of the human arterial wall after interventional thermal injury.

Thermal injury has been shown to reduce platelet adhesion (PA) in vitro but not in vivo. The controversy may be based on the mode of thermal injury, the anticoagulation regimen, or species differences. Human and rabbit arteries were dilated by a radio-frequency (RF)-heated balloon (RF dilation) or by immersion in heated buffer. The artery segments were perfused in an annular perfusion chamber with blood anticoagulant by citrate or heparin (37 degrees C, 5 min, shear rate: 1,300 s-1). To determine PA to deep wall layers, 6-micron cross-sections of heated arteries were perfused in a rectangular perfusion chamber (37 degrees C, 5 min, 1,300 s-1). After RF dilation of human arteries at 55 and 90 degrees C, subendothelical PA (citrated blood) decreased from 28.9% at 37 degrees C to 6.8%, and increased to 39.6%, respectively (in both cases p<0.05). Heparin anticoagulation resulted in subendothelial fibrin deposition that was equal after 37 and 90 degrees C, and decreased after 55 degrees C. Heating of cross-sections of atherosclerotic coronary arteries to 55 and 90 degrees C, showed increased and decreased PA, respectively, to the intima and media. No effect was observed on the highly reactive adventitia and atherosclerotic plaque. We conclude that thermal balloon angioplasty at 90 degrees C reduces PA to the arterial subendothelium, but not to the adventitia or the atherosclerotic plaque. As thermal balloon angioplasty in patients will always produce a region with increased PA at 55 degrees C and as heparin anticoagulation permits fibrin deposition that is not affected by heat, it is unlikely that thermal balloon angioplasty alone will reduce thrombotic complications.

Angioplasty, Balloon↗

PubMedDate not supplied

The influence of lesion length on intimal hyperplasia after Fogarty balloon injury in the rabbit carotid artery: role of endothelium.

After balloon angioplasty, retarded endothelial cell recoverage of the injured segment may lead to enhanced intimal hyperplasia. We tested the hypothesis that long lesions result in more intimal hyperplasia than short lesions due to a prolonged time to complete endothelial cell recoverage. A 2-french Fogarty balloon was used to create 2.5- and 5-cm-long lesions in the rabbit carotid artery. After termination, the injured arteries (n = 9 for all groups) were serially processed for histochemistry. Endothelial cell coverage was assessed with an antibody to CD31 and cell proliferation with a monoclonal antibody to Ki-67 nuclear antigen. The intimal hyperplasia cross-sectional area was measured morphometrically. All data are mean +/- SEM. At 21 days, endothelial cell recoverage was almost complete in the 2.5-cm lesions. In the 5-cm lesions, endothelial cell recoverage was 66 +/- 6% in the middle segments (p = 0.04, 2.5 vs. 5 cm) and 100% at the cranial and caudal ends of the lesion. At 42 days, endothelial cell coverage had increased to 81 +/- 7% in the middle segments of the 5-cm lesions. The intimal hyperplasia area was similar in the 2.5- and the 5-cm lesions both at 21 days (0.19 +/- 0.02 and 0.20 +/- 0.01 mm2, respectively) and 42 days (0.27 +/- 0.02 and 0.26 +/- 0.03 mm2, respectively). The increase in intimal hyperplasia from 21 to 42 days was significant for both lesion lengths (p = 0.004). At 21 days, intimal proliferation was similar for the 2.5- and 5-cm lesions. After 42 days postinjury, intimal proliferation had decreased (p < 0.001) equally for both lesion lengths. Earlier recoverage by endothelium in the 2.5-cm lesions did not inhibit intimal hyperplasia compared to the 5-cm lesions which were still incompletely reendothelialized. We conclude that in the rabbit, rapid endothelial cell recoverage of Fogarty balloon-injured arteries may not limit intimal hyperplasia in the center of the lesion. It is conceivable that the inability of regenerated endothelium to inhibit intimal hyperplasia is due to its initially dedifferentiated and possibly dysfunctional phenotype.

Angioplasty, Balloon↗

PubMedDate not supplied

Cerebrovascular disease in sickle cell anemia: a clinical, pathological and radiological correlation.

An opportunity to study cerebrovascular changes in sickle cell anemia (SCA) presented itself when a black child with this disorder died of bihemispheric strokes. Angiography demonstrated severe occlusive vascular disease involving primarily the circle of Willis and major bifurcations of both internal carotid arteries. Collateral circulation to the distal branches of the internal carotid arteries occurred through transdural anastomoses from the external carotid system and via the leptomeningeal route. Perfusion of the basal ganglia was accomplished by vessels arising from the proximal internal carotid arteries. These changes resembled those of Moyamoya disease. Autopsy showed old and recent cerebral infarcts. Two vascular processes were responsible for the arterial occlusions: (1) exuberant intimal hyperplasia, and (2) old and recent thrombi with partial recanalization. The former has been described only once before in SCA. Small vessels in the basal ganglia were exceptionally numerous and dilated. We conclude that intimal hyperplasia within large cerebral arteries may be responsible for infarction and small vessel prliferation in basal ganglia in patients with SCA.

Anemia, Sickle Cell↗

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Progressive multifocal leukoencephalopathy in AIDS: are there any MR findings useful to patient management and predictive of patient survival? AIDS Clinical Trials Group, 243 Team.

BACKGROUND AND PURPOSE: While MR findings in progressive multifocal leukoencephalopathy (PML) have been described previously, usually in retrospective studies with limited sample size, what has not been well addressed is whether any are predictive of longer survival. Our participation in a large prospective clinical trial of AIDS patients with biopsy-proved PML and MR correlation allowed us to test our hypothesis that certain MR features could be found favorable to patient survival. METHODS: The patient cohort derived from a randomized multicenter clinical trial of cytosine arabinoside for PML. Pretreatment T1- and T2-weighted noncontrast images (n = 48) and T1-weighted contrast-enhanced images (n = 45) of 48 HIV-positive patients with a PML tissue diagnosis as well as the follow-up images in 15 patients were reviewed to determine signal abnormalities, lesion location and size, and the presence or absence of mass effect, contrast enhancement, and atrophy, and to ascertain the frequency of these findings. A statistical analysis was performed to determine if any MR abnormalities, either at baseline or at follow-up, were predictive of patient survival. RESULTS: No MR abnormalities either on univariate or multivariate analysis significantly correlated with patient survival, with the exception of mass effect, which was significantly associated with shorter survival. The mass effect, however, always minimal, was infrequent (five of 48). More severe degrees of cortical atrophy and ventricular dilatation, lesion location and size, and other MR variables were not predictive of outcome. CONCLUSION: Except for mass effect, we found no MR findings predictive of the risk of death in patients with PML. The mass effect, however, was so infrequent and minimal that it was not a useful MR prognostic sign.

AIDS Dementia Complex↗