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Biomedical subjects

R C Dawson

Publications and source records attributed to R C Dawson.

16 recordsLinked to original sources
PubMed2000

Prevention of complications resulting from endovascular carotid sacrifice: a retrospective assessment.

OBJECTIVE: To determine the protective effects of various periprocedural interventions in the prevention of cerebral ischemia as a complication of endovascular carotid sacrifice (ECS). METHODS: Thirty-two cases of ECS performed at our institution, between October 1987 and July 1998, were reviewed. Fifteen patients underwent superficial temporal artery-to-middle cerebral artery bypass surgery. In 21 patients, the carotid artery was occluded proximal to the target lesion; and in 11 patients, a lesion trapping procedure was performed. Six patients were prophylactically anticoagulated, 14 received antiplatelet agents prophylactically, and 12 received no pharmacoprophylaxis. RESULTS: Among the six patients who were anticoagulated, there were no embolic events. Embolic events affected 4 of 14 patients receiving prophylactic antiplatelet agents, 2 of 12 patients receiving no pharmacoprophylaxis, 1 of 11 patients who underwent a trapping procedure, and 5 of 21 patients whose carotid artery was occluded proximal to the target lesion. Postocclusion cerebral ischemia developed in 7 of 15 patients who underwent bypass surgery, and in 1 of the remaining 17. CONCLUSION: Superficial temporal artery-to-middle cerebral artery bypass did not protect against postocclusion cerebral ischemia after ECS in this series (P = 0.01). Although the small number of patients studied precludes statistical validity (P = 0.29), the trends suggest that antiplatelet agents provide no protection against postocclusion cerebral emboli after ECS. Prophylactic anticoagulation (P = 0.32) and lesion trapping (P = 0.12) may reduce the frequency of postocclusion embolic events after ECS; however, because of the small number of patients, statistical significance could not be demonstrated.

Aged↗
PubMed1998

Transvenous embolization as the primary therapy for arteriovenous fistulas of the lateral and sigmoid sinuses.

PURPOSE: We report on the evolution in one institution from transarterial embolization for the treatment of dural arteriovenous fistulas of the lateral and sigmoid sinuses to the safer and more durable technique of transvenous endovascular therapy for the majority of these lesions. METHODS: Arterial, venous, and combined embolizations were performed for 24 fistulas of the lateral and sigmoid sinuses between August 1991 and December 1996. The patients were followed up clinically for 2 to 63 months, with a mean follow-up period of 30 months. RESULTS: Nine patients had arterial embolization without transvenous treatment: five of the nine had angiographic and clinical obliteration of their fistulas; two of the nine, with unusual lesions, required surgery; and the remaining two had recurrences and were not retreated. Seven patients had both arterial embolization and coil embolization (packing) of the dural sinuses, four after arterial embolization had failed to cure the lesions; in all seven, the fistulas were obliterated angiographically and clinically. Eight patients had only transvenous coil embolization of the dural sinuses; all eight were cured. One patient had minimal arterial embolization during the primary venous embolization procedure. Complications occurred in two patients, both related to arterial embolization with ethanol. CONCLUSION: Our experience suggests that arterial embolization of dural arteriovenous fistulas of the lateral and sigmoid sinuses is associated with a low cure rate and high rate of recurrence, whereas transvenous endovascular packing of the involved segment of the sinus results in a high cure rate that obviates arterial embolization or surgical excision in most cases.

Adult↗
PubMed1998

Histologic and morphologic comparison of experimental aneurysms with human intracranial aneurysms.

PURPOSE: Vein pouch aneurysms are the most commonly created experimental lesions in neuroendovascular research. We sought to determine whether an experimental aneurysm that is derived from a pancreatic elastase-digested arterial sac (EDASA) models the histology and morphology of human cerebral aneurysms more accurately than the vein pouch aneurysm does. METHODS: EDASAs were created in the common carotid arteries of four rabbits, and vein pouch aneurysms were created in the common carotid arteries of four pigs. Five recently ruptured human cerebral aneurysms were obtained at autopsy. Identical histologic preparations were made for all specimens, and a vascular pathologist performed blinded histologic analyses. Morphologic dimensions were measured with a micrometer at 40-fold magnification. RESULTS: In each human cerebral aneurysm, there was complete absence of internal elastic lamina and tunica media, and none showed evidence of mural inflammation or neointimal proliferation. Average wall thickness was 51 microm. All vein pouch aneurysms had a well-developed internal elastic lamina and tunica media, and all exhibited profound inflammation and neointimal proliferation. Average wall thickness was 290 microm. EDASAs were devoid of internal elastic lamina, their tunica medias were mildly atrophic, and the sac walls contained only mild inflammation and neointimal proliferation. Average wall thickness was 46 microm. CONCLUSIONS: EDASAs model the morphologic and histologic characteristics of human cerebral aneurysms more accurately than vein pouch aneurysms do.

Aneurysm↗
PubMed1997

Initial experience with collagen-filled Guglielmi detachable coils for endovascular treatment of experimental aneurysms.

PURPOSE: To evaluate the effectiveness of Guglielmi detachable coils (GDCs) filled with collagen threads in the permanent treatment of experimental aneurysms. METHODS: Seventeen side-wall aneurysms were surgically constructed in the canine common carotid artery; six were treated with conventional GDCs and 11 with collagen-filled GDCs. One aneurysms was removed at 1 week, the others were studied by digital subtraction angiography for a period of 8 to 12 weeks. Longitudinal sections of all aneurysms were examined by light microscopy. RESULTS: Angiograms obtained throughout the follow-up period showed no significant difference between aneurysms treated with conventional GDCs and those treated with collagen-filled GDCs. Light microscopy revealed a dense meshwork of newly formed collagen and fibroblasts near the collagen-filled GDCs, whereas a loose cellular meshwork surrounded the conventional GDCs at 8 and 12 weeks after treatment. CONCLUSION: Collagen threads within GDCs do not noticeably improve angiographic treatment of experimental aneurysms; however, these threads did induce local proliferation of fibroblasts and production of collagen within the aneurysmal cavities.

Aneurysm↗
PubMed1996

Histologic effects of collagen-filled interlocking detachable coils in the ablation of experimental aneurysms in swine.

PURPOSE: To assess the histologic changes produced by platinum microcoils with an inner core of cross-linked bovine collagen in experimentally induced aneurysms in swine, and to assess the feasibility of the system for the delivery of the collagen. METHODS: Bilateral pouch aneurysms were created in the side wall of the common carotid artery in seven barnyard pigs. Eight aneurysms were treated with coils designed with an interlocking detachment mechanism: in four of these, the coils had an inner core of collagen; in the other four, the platinum microcoils had a similar design but without the collagen mandrel. The packing density of the coils within the aneurysm was approximately the same for both types of coils. The other six aneurysms were left untreated and served as controls. Angiograms were obtained at the time of treatment (2 weeks after the aneurysms were created) and at 1, 4, and 8 weeks after treatment. All animals were killed 8 weeks after the treatment (10 weeks after the aneurysms were created). Arteries and aneurysms were resected en bloc and fixed for histopathologic study. RESULTS: The interlocking detachment mechanism worked well. Little difference was noted between the two types of coils in their ability to effect complete aneurysmal thrombosis (three of four aneurysms treated with collagen-core coils and two of four aneurysms treated with conventional coils). The collagen-core coils stimulated new collagen formation in areas proximal to the coils, and more fibroblasts were noted near the collagen-core coils than near the conventional coils. CONCLUSION: Local fibroblast proliferation and collagen production were stimulated by heterologous cross-linked collagen embedded in micro-coils in this experimental model. Such biologic stimulation holds promise for improving the endovascular cure rate of aneurysms in humans.

Aneurysm↗
PubMed1996

Arterial saccular aneurysm model in the rabbit.

Saccular aneurysms arising from the common carotid artery in the neck at the origin of the internal carotid artery were created in male rabbits using the stump of a ligated external carotid artery. These stumps were intraluminally perfused with varying concentrations of porcine pancreatic elastase for 45 minutes via a microcatheter introduced into the femoral artery. The aneurysms were allowed to mature for 2 to 12 weeks. Gross examination and histologic studies confirmed the presence of an aneurysm in all 15 experiments. Ninety-two percent (12 of 13) of the aneurysms studied by postoperative angiography were shown to be angiographically patent: 40% of all aneurysms were noted to be patent at harvest; and the remainder showed evidence of intraluminal thrombus. On histologic examination, all aneurysms showed complete loss of elastic lamina without evidence of fibrosis or scarring.

Animals↗
PubMed1996

Superior oblique myokymia associated with a dural arteriovenous fistula.

Superior oblique myokymia (SOM) is an uncommon ocular motility disorder characterized by intermittent uniocular vertical or torsional oscillations with periodic remissions and exacerbations. Although generally idiopathic in origin, isolated case reports have documented its association with intracranial pathology. We present a case of superior oblique myokymia associated with a dural arteriovenous fistula.

Adult↗
PubMed1995

Treatment of experimental aneurysms using collagen-coated microcoils.

Endovascular treatment of certain surgically difficult aneurysms is currently performed using fibered microcoils or electrolytically detachable microcoils to obliterate these lesions by forming an intra-aneurysmal thrombus. Unfortunately, this treatment option results in a significant incidence of incomplete obliteration of treated aneurysms. A thrombus can recanalize, resulting in further aneurysm growth and subsequent rupture. Nineteen aneurysms were surgically created in 10 pigs using jugular venous pouches. The aneurysms were allowed to mature for periods of 7 days to as long as 11 weeks prior to embolization. Fourteen remained patent for embolization. The aneurysms were then embolized (9 with collagen-coated microcoils, 5 with dacron-fibered platinum microcoils). Follow-up angiograms were obtained prior to sacrifice at 1, 3, 6, 9, and 12 weeks postembolization, and the embolized aneurysms and parent vessels were harvested for histopathological studies. The current study was designed to evaluate the potential efficacy of collagen-coated microcoils in providing an enduring therapy for aneurysms by comparing this new embolic device with the standard dacron-fibered platinum microcoils in a swine common carotid artery side wall aneurysm model. The aneurysms treated with collagen microcoils were completely obliterated with a collagen-rich fibrous scar with no histological evidence of residual thrombus or recanalization. Additionally, after treatment of experimental aneurysms with collagen microcoils, re-endothelialization across the former aneurysm neck was seen. In contrast, aneurysms embolized with dacron-fibered microcoils contained persistent thrombus surrounded by a relatively immature scar with residual aneurysmal lumen and lack of endothelium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Interventional neuroradiology in the community hospital.

The active participation of the neuroradiologist in the therapy of neurosurgical patients is a concept with which many neurosurgeons as well as many radiologists are uneasy. Interventionally oriented radiologists have much to offer the neurosurgeon who accepts the radiologist as a partner in the management of patients with difficult problems. Technological advances in imaging, in guidewire and catheter design, and experience gained by radiologists and neurosurgeons have led to a number of therapeutic advances. We present several illustrative examples.

Aneurysm↗
PubMedDate not supplied

Treatment of arteriovenous malformations of the brain with combined embolization and stereotactic radiosurgery: results after 1 and 2 years.

Seven patients with large arteriovenous malformations (AVMs) of the brain were selected for combined therapy with particulate embolization, followed by radiosurgery of the residual nidus. The goal of embolization was to reduce the patient nidus to a size that facilitated successful stereotactic radiosurgery. Angiograms obtained 1 and 2 years after radiosurgery were evaluated for changes in nidus size, flow rate, and feeding and draining vessels. One year after stereotactic radiosurgery, one AVM was angiographically undetectable. Three other AVMs demonstrated a volume reduction of greater than 50%, in addition to decreased shunt speed and altered angioarchitecture at 1-year follow-up. At 2-year follow-ups, two of seven AVMs were cured, and an additional two of seven had a greater than 98% reduction in nidus volume. Although one patient experienced a transient deficit from embolotherapy, none of our patients suffered a new neurologic deficit or a hemorrhage during the follow-up period. Our data support the efficacy of combined embolotherapy and radiosurgery for definitive therapy of selected large AVMs of the brain.

Adult↗
PubMedDate not supplied

Retinal Wada test.

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Amobarbital↗