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Biomedical subjects

A J Fox

Publications and source records attributed to A J Fox.

At least 289 records · Page 16Linked to original sources
PubMedDate not supplied

Clinico-topographic correlation of small vertebrobasilar infarct using magnetic resonance imaging.

Neurological, CT and high-field (1.5T) magnetic resonance imaging (MRI) data were correlated in 6 patients previously clinically diagnosed as having suffered small vertebrobasilar infarct. MRI demonstrated infarcts in areas where CT was nearly always negative. MRI allowed very precise clinico-topographic correlations and appears to be the preferred imaging technique in vertebrobasilar infarcts.

Aged↗
PubMedDate not supplied

Bilateral occlusion of the trunk of the middle cerebral artery. Results of an international randomized trial. The EC/IC Bypass Study Group.

Bilateral occlusion of the middle cerebral artery (MCA) trunk theoretically should be a very severe condition, but its actual prognosis has never been studied. Nine of 1,377 patients (7 Asians, 1 Black, 1 Caucasian) from the Cooperative Study of Extracranial/Intracranial Arterial Anastomosis were found to have atherosclerotic bilateral occlusion of the middle cerebral artery (MCA) trunk before entering the trial. Three presented with a stroke followed by a contralateral stroke, two experienced a unilateral stroke, two had a unilateral stroke preceded by ipsilateral TIAs, one had a unilateral stroke preceded by TIAs on both sides and one experienced isolated unilateral TIAs. Retrograde filling to the distal MCA was universally present. During follow-up (mean: 45 months), only one (non-operated) patient had further cerebrovascular events, and ultimately a fatal stroke. One additional patient died of sepsis and one had a silent myocardial infarct. All survivors resumed their previous activities. This study shows that in bilateral MCA trunk occlusion, the long-term prognosis is reasonable in the patients who do not present with a devastating stroke.

Adult↗
PubMedDate not supplied

Atherosclerotic disease of the middle cerebral artery.

Three hundred and fifty-two patients with atherosclerotic middle cerebral artery stenosis (MCAS, 53%) or occlusion (MCAO, 47%) have been systematically studied. The study involved all patients entered into the EC/IC Bypass Study with isolated MCA disease or a tandem lesion predominating in the MCA ipsilateral to the ischemic events (18 patients with a tandem lesion of greater magnitude in the internal carotid artery were not included). The Asian patients represented 58% of all Asians entered into the EC/IC Bypass Study, whereas the white patients represented 18% of all whites and the black patients 34% of all blacks. Isolated TIAs were less frequent in MCAO (12%) than in MCAS (34%). Warning TIAs before a stroke occurred in one third of the cases. Presentation with stroke or isolated TIA was not influenced by sex, age, level of MCA obstruction, collateral circulation nor associated carotid disease. In MCAS, no major difference in presentation was found between severe and moderate stenosis. Pure motor hemiparesis occurred in 15% and pure sensory stroke in 2% of the patients with stroke and 30% of the MCA territory infarcts were small and limited to the lenticulocapsular area, confirming that so-called lacunar infarcts may be due to large vessel disease. During follow-up (42 months) of 164 medically-treated patients, further cerebrovascular events (TIA and stroke) occurred in 11.7% of the patients per year. In MCAO the stroke rate was 10.1% per patient-year and the ipsilateral infarct rate was 7.1% per patient-year. In MCAS, the stroke rate was 9.5% per patient-year and the ipsilateral stroke rate was 7.8% per patient-year.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral Arteries↗
PubMedDate not supplied

Clinical events following neuroangiography: a prospective study.

Clinical events following cerebral angiography were prospectively evaluated in 1,002 procedures. The ischemic event rate between 0 and 24 hours was 1.3% (0.1% permanent). This incidence was higher (2.5%) in patients investigated for cerebrovascular disease, but the difference was not significant. In addition, 1.8% of the patients suffered ischemia (0.3% permanent) between 24 and 72 hours after angiography. Cerebral ischemic events occurred as a recurrence or worsening of a preexisting phenomenon. twice as often as de novo. All permanent ischemia was a worsening of a preexisting phenomenon. There was a significant increase in the incidence of neurologic events between 0 and 24 hours when the procedure lasted longer than 60 minutes and when there was systolic hypertension. Trends toward higher incidence were noted with the use of increased volume of contrast, with increased serum creatinine, when transient ischemic attacks or stroke were the indications, and when 3 or more catheters were used. The incidence of neurologic events between 24 and 72 hours increased significantly with the increase in the amount of contrast used, with age, and with diabetes. The occurrence of nonneurologic events (mostly hematomas) was significantly increased by multiple factors. This study shows that events can and do occur beyond the usual observation period of 24 hours but confirms the low risk of cerebral angiography when performed judiciously.

Age Factors↗
PubMedDate not supplied

Ribosomal RNA gene restriction fragment diversity amongst Penner serotypes of Campylobacter jejuni and Campylobacter coli.

Diversity based on ribosomal RNA gene-restriction endonuclease digest patterns was detected amongst forty-seven strains of Campylobacter made up of 38 strains of Campylobacter jejuni and 9 strains of Campylobacter coli. Restriction digests of chromosomal DNA prepared by treating with Hae III were probed with an oligonucleotide specific for Campylobacter 16S ribosomal RNA genes. Seventeen distinct hybridization patterns, each indicating the presence of 2-4 copies of the 16S rRNA gene are encoded in Campylobacter DNA. Differences in fragment patterns were observed not only between members of two species, but also between individual strains of the same species. Ribopattern fragments of 8.71, 7.56, 2.81 and 1.0 kb were characteristic of the majority of C. jejuni, whereas 7.59 and 4.68 kb fragments were commonly present in C. coli. In conclusion, Hae III ribotyping was even more discriminatory than the Penner serotyping of C. jejuni and C. coli, as strains of the same serotype were distinguished.

Blotting, Southern↗
PubMedDate not supplied

MR imaging after surgery for vertebrobasilar aneurysm.

We examined the safety and utility of high-field MR in patients who had surgery for cerebral aneurysms of the vertebrobasilar system. Eighteen posterior (and three coincidental anterior) circulation aneurysms were treated. Twenty-one MR scans were obtained at a mean postoperative interval of 7.2 days. The mean size of the preoperative vertebrobasilar aneurysm was 2.2 cm; six were giant (greater than 2.5 cm) and eight were large (greater than 1.5, less than or equal to 2.5 cm). In 17 patients, Sugita nonmagnetic clips were used. In one other, a Drake tourniquet was used. No ill effects occurred from scanning with a high-field imaging unit at 1.5 T. The MR clip artifact was much less obtrusive than that on CT. In 11 cases, the aneurysm could be partially imaged postoperatively, mainly in very large aneurysms or in those treated by clipping the parent vessel. Of these, two revealed residual lumina on MR and nine looked completely thrombosed. Postoperative angiography showed that in four of the thrombosed-appearing aneurysms a residual lumen with a mean diameter of 1.0 cm had been missed. In the patient imaged after application of a Drake tourniquet, no artifact was seen, and a good assessment of progressive partial thrombosis was obtained. Evolution of the signal intensity of new aneurysm thrombus, in those minimally or not obscured by artifact, coincides with patterns previously described for hemoglobin in intracerebral hematomas. The earliest hyperintensity could be seen in either the periphery or the center of the new thrombus. All 15 patients examined with new postoperative deficits showed appropriate lesions, mainly small brainstem ischemic foci. Postoperative CT (performed in all but four of these patients) missed over 80% of these lesions, mainly owing to artifact from clip or bone. We conclude that MR is better than CT in the postoperative assessment of aneurysm patients, particularly in demonstrating small zones of ischemia. High-field MR scanning is safe if nonmagnetic surgical clips are used. MR is not accurate in assessing residual lumina.

Adolescent↗
PubMedDate not supplied

Evaluation of three embolic agents in pig rete.

In ongoing research into potential embolic agents, three substances were evaluated for their effectiveness in occluding the pig rete. Selective injection of these agents produced varying degrees of occlusion, with the most effective a microfibrillar collagen hemostat in a 33% ethanol solution. Angiostat, a collagen particulate, did not produce rete occlusion, and all pigs injected with it developed adverse effects, including coma and apnea. Tisseel, a tissue sealant, produced partial rete occlusion, but was uniformly difficult to manage through long catheters, and its use was discontinued. Microfibrillar collagen hemostat with ethanol appears to have the greatest potential as an embolic agent in low-flow structures.

Animals↗
PubMedDate not supplied

n-Butyl 2-cyanoacrylate--substitute for IBCA in interventional neuroradiology: histopathologic and polymerization time studies.

Despite the development of new alternative embolic agents, the endovascular treatment of brain arteriovenous malformations continues to frequently require the use of cyanoacrylic glue, especially in situations where particulate or sclerosing agents are ineffective, such as when flow is very rapid or fistulous. Because isobutyl 2-cyanoacrylate (IBCA), the most commonly used embolic glue, is no longer available or manufactured, a real need exists for an alternative fast polymerizing agent. In vivo and in vitro studies were performed to compare IBCA with n-butyl 2-cyanoacrylate (NBCA, supplied as Histoacryl Blue), a tissue adhesive approved for surgical use in some countries. Polymerization times in static plasma were compared, and the effect of the addition of iophendylate oil or glacial acetic acid on polymerization was assessed. Polymerization times in vivo were compared after intraarterial injection into the internal carotid artery in pigs using a standardized technique. The histopathologic reactions to each glue in the embolized pig rete were assessed and compared over a period of 0-60 days after embolization. Our results show that while NBCA polymerization is demonstrably faster than IBCA in vitro, intraarterial injections of each glue show no significant difference in polymerization times. Like IBCA, NBCA polymerization can be predictably prolonged by the addition of oil or glacial acetic acid, though the effect is less for NBCA. Histopathologic reactions were similar, with acute vasculitis observed, becoming chronic and granulomatous after about 1 month. Both glues showed frequent foci of extravascular extrusion through the embolized rete and recanalization of previously occluded embolized vessels. We conclude that NBCA has clinical and biologic behaviors similar to IBCA, and therefore should be an acceptable alternative to IBCA for intravascular use.

Animals↗
PubMedDate not supplied

Adjusting the polymerization time of isobutyl-2 cyanoacrylate.

Isobutyl-2 cyanoacrylate (IBCA) polymerizes by an anionic mechanism. The initiation of polymerization depends on an alkaline medium and can be inhibited with the addition of small amounts of acid. Using small amounts of glacial acetic acid (3.7%-7.1% by volume), the polymerization time was prolonged from 2.3 sec to 7.8 sec. In vivo experiments in dogs demonstrated no additional inflammatory reactions to the mixture of IBCA, iophendylate, and tantalum powder when acetic acid was added. Glacial acetic acid offers a safe and effective way, without increase in viscosity, to manipulate the polymerization time of IBCA.

Acetates↗
PubMedDate not supplied

Magnetic resonance imaging of small medullary infarctions.

Small infarctions of the medulla produce typical neurologic deficits and can be clinically recognized fairly reliably. High-field magnetic resonance imaging with a 1.5 T prototype scanner successfully demonstrated very tiny medulla infarctions in three of five patients. These lesions were imaged readily by a fairly rapid (approximately 1-2 min scan time) partial-saturation technique and confirmed on multiple spin-echo images. In addition, in two cases vertebral occlusion ipsilateral to the infarction was suggested by high signal on T2 weighted spin-echo images.

Aged↗
PubMedDate not supplied

Angiographic follow-up of large cerebral AVMs incompletely embolized with isobutyl-2-cyanoacrylate.

This study evaluated the long-term angiographic results in large cerebral arteriovenous malformations (AVMs) partially embolized with isobutyl-2-cyanoacrylate. Preembolization, immediate postembolization, and long-term follow-up angiograms were performed in 30 large, partially embolized brain AVMs. Particular attention was paid to the relative size of the residual AVM nidus and the embolized arterial feeders, to recruitment of new feeders, to the size of residual draining veins, and to the speed of arteriovenous shunt. Nine cases with less than 50% AVM nidus obliteration showed no significant morphologic changes. In 18 cases with 50-75% obliteration of the AVM nidus, 11 (61.1%) showed no significant changes, six (33.3%) showed enlargement of the AVM nidus, and one (5.5%) evolved to complete angiographic obliteration. In three cases with 75-99% AVM nidus obliteration, one remained unchanged, one showed an increase in the size of the AVM nidus, and one evolved to complete obliteration. Evaluation by plain film, CT, and cerebral angiography of the isobutyl-2-cyanoacrylate deposits showed that when the polymer was positioned predominantly in arterial feeders there was invariably reconstitution of the AVM nidus through leptomeningeal, deep medullary, and/or dural collaterals. This phenomenon did not occur when the isobutyl-2-cyanoacrylate was deposited mainly in the AVM nidus.

Arteriovenous Malformations↗
PubMedDate not supplied

Saccular aneurysms in basilar artery fenestration.

Of 59 cases of vertebrobasilar junction aneurysms diagnosed and treated from January 1977 to April 1986, 21 (35.5%) saccular aneurysms arose in a fenestration of the proximal basilar artery. Defects of the media at the junctures of the fenestrated segments, as well as the possible presence of turbulent flow at the vertebrobasilar junction, may explain the high incidence of vertebrobasilar aneurysms associated with proximal basilar artery fenestration.

Adult↗