Biomedical subjects
Publications and source records attributed to M E Jensen.
A 28-year old male patient presented for his routine dental health visit which included the above bitewing radiograph. The radiograph was taken as a follow-up nine months after the extraction of the mandibular second molar by the oral surgeon. The patient had no discomfort and was unaware of any dental problem.
We report a unique case of choroid plexus papilloma of the third ventricle in an 8-month-old girl in which preoperative embolization played a salient role in management. Initial surgery was aborted due to excessive bleeding. Cerebral angiography demonstrated enlarged posterior choroidal arteries feeding the tumor, and intense, persistent tumor staining. These vessels were effectively embolized to stasis with polyvinyl alcohol particles. The patient underwent a second craniotomy and complete resection of the tumor with minimal blood loss. Postsurgical histology showed postembolization iatrogenic intratumoral necrosis.
We studied the acoustic behaviour of bats (Eptesicus nilssonii) hunting for large (wing span 5 cm) non-hearing hepialid moths (Hepialus humuli). Groups of silvery-white male H. humuli perform a short (30 min) hovering display flight over grassland at dusk. They typically hover at, or below, the tops of grass panicles and are therefore situated in a highly acoustically cluttered habitat. Occasionally, they move to a new position by making short (1-5 s) flights at higher levels. E. nilssonii is not a clutter specialist, and yet we found that they attacked H. humuli within the 'clutter overlap zone'. The bats did not change their signal design in any marked manner for this specific task. Measurements of echoes from a moth 10 cm above or below the grass tops showed that information for detecting the moths was available to the bats. Nevertheless, the bats did not attack moths in stationary hovering display flight, only when they moved above the grass panicles. The duration of the up/down flights (movements) were almost always longer than an entire capture sequence by the bats. Apparently, the bats rely on the movement of the moth in space, monitored over successive echoes, to discriminate moth echoes from overlapping clutter echoes.
BACKGROUND AND PURPOSE: Our long-term goal is to improve intraaneurysmal fibrosis after aneurysm embolization, by implanting exogenous fibroblasts, using platinum coils. For the current project, we tested two hypotheses: 1) that exogenous, fluorescence-labeled rabbit fibroblast allografts remained viable and proliferated within rabbit carotid arteries, and 2) that these fibroblast allografts could be reliably implanted into experimental aneurysms by use of platinum coils. METHODS: Part 1. New Zealand White rabbit synovial fibroblasts obtained from a commercial vender were labeled with a fluorescent membrane marker. The common carotid arteries of New Zealand White rabbits were surgically exposed, ligated proximally and distally, and entered with 22-g angiocatheters. Through the angiocatheter we injected either phosphate-buffered saline-containing fluorescence-labeled fibroblasts (treatment vessels) or saline only (control vessels). The wounds were closed, and the subjects were kept alive for various time points up to 2 weeks. After sacrifice, the carotid artery segments were resected, processed for frozen-section histologic examination, and evaluated using epifluorescent microscopy and hematoxylin and eosin staining. Cell viability and proliferation were determined by comparing the treatment versus control vessels. Part 2. A) Fluorescence-labeled cells were grown in culture on platinum coils, which were then exposed to systemic arterial flow in the rabbit thoracic aorta for various lengths of time up to 40 minutes. The coil segments were then examined using fluorescent microscopy and the presence and relative amount of cells remaining on the coil were documented. B) Experimental aneurysms in rabbits were embolized with control platinum coils (n = 9) and platinum coils bearing rabbit synovial fibroblasts that were grown onto the coils in culture prior to implantation (n = 9). Subjects were sacrificed 3, 7, and 14 days after coil implantation. Histologic samples were studied to assess the presence or absence of nucleated cells within and around coil winds in order to determine whether fibroblasts had been successfully implanted into aneurysms. Data were evaluated using the chi-square test for statistical significance. RESULTS: Part 1. Fluorescence-labeled cells were examined in the treatment carotid artery segments and results were recorded at all time intervals. The treatment vessel segments showed evidence of progressive cellular proliferation, leading to complete vessel fibrosis at 2 weeks. Conversely, control vessel segments were filled predominately with unorganized thrombus at each time interval. Part 2. A) Numerous labeled fibroblasts remained adherent to the coil despite prolonged exposure to systemic arterial flow. B) Fibroblasts were seen adjacent to or within the central lumen of coils in eight (88%) of nine aneurysms treated with cell-bearing coils. Nucleated cells were not present in any of the nine control coil subjects. This represented a statistically significant difference (P < .001). CONCLUSION: Fibroblast allografts remain viable and proliferate in the vascular space in rabbits. Furthermore, these same fibroblasts, after seeding onto platinum coils in culture, remain protected within the lumen of the coils and are retained within the coil lumen even after prolonged exposure to arterial blood flow. Coils can be used to deliver viable fibroblasts directly into experimental aneurysms successfully. These findings indicate that coil-mediated cell implantation is feasible and may be a potential method of increasing the biological activity of embolic coils.
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BACKGROUND AND PURPOSE: Among the several reports of elastase-induced aneurysm models, only the rabbit common carotid artery (CCA) model has been used for testing endovascular occlusion devices. Our purpose was to study the growth characteristics of an elastase-induced aneurysm model in rabbits for the purpose of determining whether delayed aneurysm enlargement occurs after creation. METHODS: Nine New Zealand White rabbits (3-4 kg) were used in this study. All study animals underwent surgery to isolate the right CCA. In three control animals, the lumen was incubated with saline and iodinated contrast material for 20 minutes. In six test animals, the lumen of the CCA was incubated with porcine elastase for 20 minutes. In all study animals, the distal right CCA was ligated. IV digital subtraction angiography was performed on postprocedural days 3, 5, 7, 14, 28, 35, 56, 84, and 112. Using an external sizing reference, the width and height of patent arterial segments at the right CCA origin were measured by two observers. For test animals, aneurysm dimensions were compared between early and late time points by using the Student's t test. RESULTS: In the control (no elastase) animals, slitlike cavities at the origin of the right CCA decreased in size over time to become nearly obliterated by 21 days. Conversely, a short segment of the proximal CCA remained widely patent in all six test animals. With the exception of a single time point in one test animal, all "aneurysm" cavities in the test animals were dilated as compared with the normal diameter of the CCA. On day 3 after surgery, the mean width and height of the aneurysm cavities in the test animals were 3.2 +/- 0.6 and 6.0 +/- 1.3 mm, respectively. Compared with dimensions at day 3, aneurysms in test animals were larger at day 14, with mean width and height of 4.1 +/- 1.7 and 8.3 +/- 1.9 mm, respectively (P =.02). Aneurysms in test animals had increased further at 21 days compared with 14 days (P =.01). Compared with measurements obtained at 21 days, dimensions remained essentially unchanged at 28 and 35 days. Thirty-five days after surgery, mean width and height were 5.0 +/- 0.9 and 10.0 +/- 2.2 mm, respectively. Follow-up imaging performed < or = 4 months after aneurysm creation showed no further change in aneurysm dimensions. CONCLUSION: Elastase incubation and vessel ligation results in patent aneurysmally dilated arterial segments at the origin of the right CCA in rabbits. These aneurysms show progressive increases in diameter over time, finally stabilizing at approximately 1 month. Our data, which show early progressive aneurysm enlargement, suggest that this model may be used for the study of systemic therapies aimed at diminishing aneurysm rest regrowth and also indicate that embolization of these model aneurysms should be delayed at least 21 days after aneurysm creation.
BACKGROUND AND PURPOSE: Fluid-attenuated inversion recovery (FLAIR) MR imaging sequences have been previously described in the evaluation of acute subarachnoid hemorrhage (SAH) in human subjects and have demonstrated good sensitivity. The purpose of this study was to evaluate a FLAIR sequence in an animal model of SAH and to compare the results with those obtained with non-contrast-enhanced CT. METHODS: SAH was experimentally induced in 18 New Zealand rabbits by injecting autologous arterial blood into the subarachnoid space of the foramen magnum. Nine animals had high-volume (1-2 mL) injections, and nine animals had low-volume (0.2-0.5 mL) injections. Four control animals were injected with 0.5 mL of saline. The animals were imaged with a FLAIR sequence and standard CT 2-5 hours after injection. Gross pathologic evaluation of seven of the animals was performed. Four blinded readers independently evaluated the CT and FLAIR images for SAH and graded the probability of SAH on a scale of 1 to 5 (1 = no hemorrhage, 5 = definite hemorrhage). RESULTS: Overall, the sensitivity of FLAIR was 89%, and the sensitivity of CT was 39% (P <.01). In animals with a high volume of SAH, the sensitivity of FLAIR was 100%, and the sensitivity of CT was 56%. In animals with a low volume of SAH, the sensitivity of FLAIR was 78%, and the sensitivity of CT was 22%. The specificity of FLAIR in animals without SAH was 100%, and the specificity of CT was 100%. The average reader score for FLAIR was 3.8, and that for CT was 2.2 (P <.001). Reader scores for FLAIR were higher than those for CT in 94% (P <.01) of animals with SAH and in 25% of animals without SAH (P >.05). Seven animals underwent gross pathologic examination, and all had blood in the subarachnoid space around the brain stem. CONCLUSION: FLAIR was more sensitive than CT in the evaluation of acute SAH in this model, especially when a high volume of SAH was present. This study provides a model for further experimentation with MR imaging in the evaluation of SAH. These findings are consistent with those of current clinical literature, which show FLAIR to be an accurate MR sequence in the diagnosis of SAH.
This study utilized volunteer subjects to examine caries-like lesions for remineralization and demineralization patterns in dentin and enamel when nine different snack foods were eaten between meals. Caries progression was observed in enamel and dentin when apple juice, a cola beverage, and sweetened (strawberry) yogurt were consumed as snacks. Remineralization of enamel was observed when cheddar cheese, skim milk, 2% milk, whole milk, chocolate milk, and orange juice were used as between meal snacks. Dairy products, with the exception of the sweetened yogurt, generally reduced the amount of demineralization produced in dentin. This study helps establish a scientific basis for appropriate between-meal snacks for patients who are concerned about their dietary habits as a part of their overall preventive oral health plan.
We report our experience with the use of the antifibrinolytic agent epsilon-aminocaproic acid (EACA), Amicar, as an adjuvant to endovascular treatment of cranial arteriovenous fistulae. We also review applications of antifibrinolytic agents to neurovascular disorders and discuss the mechanism of action, dosing strategy, contraindications, and possible complications associated with the use of EACA. We identified 13 patients with cranial arteriovenous fistulae (five direct carotid cavernous fistulae [CCF], seven dural arteriovenous fistulae [DAVF], and one vein of Galen malformation) who received EACA as an adjunct to endovascular treatment. In all cases embolic coils were the primary embolic agent. We reviewed the modes of initial endovascular therapy and angiographic findings immediately thereafter and the response to EACA. Two direct CCF and two DAVF were completely thrombosed on follow-up angiography, and two DAVF demonstrated diminished flow after EACA therapy. Seven fistulae did not respond to EACA. Four of eight tightly coiled fistulae thrombosed, while none of five loosely coiled fistulae thrombosed. None of four cases with a residual fistula separate from the coil mass underwent thrombosis with EACA, while four of nine cases without a separate fistula thrombosed. There was no morbidity related to EACA therapy. EACA may thus be useful as an adjunct to endovascular treatment of cranial arteriovenous fistulae. Loose or incomplete coil packing of the fistula predicts a poor response to EACA therapy.
PURPOSE: To study the biocompatibility of a bovine type I collagen preparation as a material for small-vessel stent-grafts in rabbits. MATERIALS AND METHODS: A composite nitinol-collagen endovascular stent-graft with a 4-mm inner diameter was deployed in the abdominal aorta in nine rabbits. Angiography was performed, and the rabbits were sacrificed at 1, 2, and 7 days and at 1 and 3 months. The portion of the aorta containing the stent-graft was excised and was histologically evaluated. RESULTS: All stent-grafts were patent at all time points. On days 1, 2, and 7 after implantation, scattered red and white blood cells adhered to the stent-graft. At 1 month, the stent-graft was endothelialized and was infiltrated with fibroblasts that deposited collagen within the interstices of the implanted collagen material. At 3 months, there was additional collagen deposition within the interstices of the stent-graft that did not narrow the lumen of the stent-grafts. CONCLUSION: Type I collagen as a intravascular stent-graft material is biocompatible for at least 3 months in rabbits. It is rapidly endothelialized and does not cause reactive stenosis. As a versatile and biocompatible polymer, collagen is potentially useful in the construction of endovascular stent-grafts for use in human arteries.
We present 4 cases of schwannomas arising from the cervical sympathetic chain. These lesions are uncommon and most often present as an asymptomatic solitary neck mass. Preoperative diagnosis can be difficult, even with the aid of computed tomography, magnetic resonance imaging, ultrasound, and angiography. While a paraganglioma can often be ruled out, exact determination of the nerve of origin is frequently elusive until the time of surgery. Operative excision remains the treatment of choice, often requiring sacrifice of a portion of the sympathetic chain. Postoperative Horner's syndrome is common, but does not appear to have an adverse effect on the patient.
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BACKGROUND AND PURPOSE: Iatrogenic dissections are an uncommon complication of cerebral angiography. We retrospectively reviewed 12 cases of arterial dissections complicating cerebral angiography and cerebrovascular interventions to evaluate the clinical course of these dissections. METHODS: Cases from a large tertiary center performing a large number of neurovascular procedures were collected retrospectively. The patients' medical records and imaging studies were reviewed, with particular attention given to the cause of the dissection, the development of ischemic events resulting from the dissection, and the treatment used. RESULTS: Each of nine dissections affected a vertebral artery, each of two affected an internal carotid artery, and one affected a common carotid artery. The prevalence of iatrogenic dissections was 0.4%. Seven of the dissections were noted at the time of contrast material injection for the filming of cerebral angiograms. The other five dissections occurred during catheter or wire manipulations for interventional neuroradiologic procedures. Five of the patients in our series were treated with IV administered heparin for 24 to 48 hours. The other seven patients had recently suffered acute intracranial hemorrhage or undergone neurosurgery and could not undergo anticoagulant therapy. None of the patients developed symptoms of ischemia, but one was later found to have an asymptomatic infarct in the territory supplied by the dissected artery. CONCLUSION: Arterial dissections are an uncommon complication of cerebral angiography and cerebrovascular interventions and usually have a benign clinical course.
Percutaneous vertebroplasty is an innovative and successful approach to the treatment of painful osteoporotic compression fractures refractory to medical therapy. We encourage all neuroradiologists to take an active interest in bringing this exciting technology to their patients and their practices.
Answering the telephone is an important first contact with the dental office. The voice tone, inflection and other non-verbal aspects of the person answering all have a profound impact on how the caller perceives the dental office. Suggestions are presented which are designed to avoid communication problems and to project a positive professional image to a caller. Audio clips are included to demonstrate variations in telephone technique to assist the reader in the development of a telephone answering protocol that reflects a desirable image for the office staff and for the dental practice.
Esophageal variceal hemorrhage (EVH) is a serious and expensive sequela of chronic liver disease, leading to increased utilization of resources. Today, endoscopic sclerotherapy (ES) and endoscopic ligation (EL) are the accepted, community standards of endoscopic treatment of patients with EVH. However, there are no published studies comparing the economic costs of treating EVH using these interventions. As part of a prospective, randomized trial comparing ES and EL for the treatment of EVH, we estimated the direct costs of health care utilization and cost-effectiveness for the prevention of variceal rebleeding and patient survival at 1-year follow-up. Treatment groups were similar in incidence of variceal rebleeding (41.9% vs. 42.9%), variceal obliteration (41.9% vs. 40.0%), hospital days, blood transfusions, shunt requirements, and survival (71.0% vs. 60.0%). There were significantly more treatment failures for active bleeding using EL (42% vs. 0%; P =.027) and esophageal stricture formation in the ES-treated patients (19.4% vs. 2.9%; P = 0.03). Median total direct cost outcomes were similar between groups (EL = $9,696 and ES = $13,197; P =.46). EL and ES had similar cost/variceal rebleeding prevented ($28,678 vs. $29,093) and cost/survival ($27,313 vs. $23,804). In the subgroup of active bleeders, ES had a substantially lower cost/survival ($28,523 vs. $51,696). We conclude that resource utilization was similar between treatment groups and that the choice of endoscopic therapy for EVH must still rely on clinical grounds. Further studies comparing costs and resource utilization in this patient population are needed.
We studied the natural history of canine side-wall experimental aneurysms to determine the incidence of spontaneous aneurysm thrombosis, to serve as control data for future studies focusing on development of aneurysm occlusion devices. Bilateral common carotid artery vein patch aneurysms were surgically created in eight mongrel dogs (20-25 kg). Duplex Doppler sonography was performed at 14 days and angiography between 30 and 210 days following aneurysm creation. Sonography demonstrated patency of 13 (81%) of 16 aneurysms. Patent aneurysms ranged in size from 8 x 10 mm to 14 x 16 mm. Conventional angiography was performed in four dogs approximately 30 days following aneurysm creation; in these four, all of 7 initially patent on sonography remained fully patent. One dog underwent conventional angiography at approximately 60 days following aneurysm creation; both aneurysms in this case remained widely patent. Three dogs underwent conventional angiography at approximately 200 days following aneurysm creation; all 4 aneurysms initially patent on sonography remained fully patent. None of the three aneurysms found to be occluded on sonographs demonstrated spontaneous recanalization. The canine side-wall aneurysm model is a valid tool for testing some aneurysm-occlusion devices, because control aneurysms remain patent indefinitely.
We report a series of American adults with idiopathic steno-occlusive disease of the supraclinoid internal carotid artery and its bifurcation. We reviewed the clinical records and imaging of 18 patients, 16 women and 2 men, aged 20-53 years (mean 35 years). There were no predominating risk factors for vascular occlusive disease, such as oral contraceptive use, hypertension, diabetes mellitus, or smoking. Four patients had irregularity of their cervical internal carotid arteries in a pattern not classic but suspicious of fibromuscular dysplasia. Eleven patients met the criteria for moyamoya disease, having both bilateral disease and moyamoya collateral lenticulostriate arteries. Necropsy in one case showed intimal thickening with duplication of the internal elastic lamina involving the internal carotid artery bifurcation bilaterally. We found a marked predominance of young and middle-aged females in our American adults, but our findings do not support the association with birth-control pills previously reported.