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Biomedical subjects

Allan J Fox

Publications and source records attributed to Allan J Fox.

At least 19 recordsLinked to original sources
PubMed2006

Carotid stenosis index revisited with direct CT angiography measurement of carotid arteries to quantify carotid stenosis.

BACKGROUND AND PURPOSE: All carotid stenosis ratio methods are based on the inability of digital subtraction angiography to measure in millimeters. Each method has potential flaws. The Carotid Stenosis Index (CSI) was designed to reduce ambiguities of NASCET and ECST ratios. We test this method's ability to correctly estimate carotid stenosis using direct computed tomography angiography millimeter measures of the carotid arteries. METHODS: Two neuroradiologists reviewed computed tomography angiographies of 268 carotids with atherosclerotic disease. Millimeter measurements were obtained at the narrowest diameter of the residual stenotic lumen, actual carotid bulb diameter (at level of greatest stenosis), and common carotid artery. Pearson correlation compared the CSI estimate of the carotid bulb to the actual carotid bulb measurement. Ratio calculations of the stenosis were performed using (1) CSI carotid bulb estimate and (2) actual carotid bulb measurement as denominator data. A paired-sample Wilcoxon signed rank test compared the results of these 2 ratio measurements per carotid. RESULTS: Interobserver variability was good to excellent (0.64 to 0.87). The CSI estimate of the carotid bulb size overestimated the measured carotid bulb by an average of 1.5 mm in a random distribution (correlation=0.39, N=151). Paired-sample Wilcoxon signed rank test demonstrated a significant difference between the 2 sets of ratios (z-value of -9.87, P<0.001). CONCLUSIONS: Direct measurement of carotid stenosis, vessel wall soft tissues, and computed tomography plaque imaging is now possible with the high-resolution anatomic data present in high-speed computed tomography angiography, alleviating the need for ratios and inaccurate mathematic estimations of carotid anatomy for carotid stenosis quantification.

Carotid Arteries↗
PubMed2006

Turning a stroke into a TIA: curative thrombolysis with combined intravenous and intra-arterial tPA.

Intravenous tissue plasminogen activator (tPA) is standard treatment for eligible patients with acute ischemic stroke, but may be less effective for very severe strokes caused by proximal intracranial artery occlusions. We report the case of a woman with a devastating stroke who recovered completely following emergency revascularization of an occluded proximal middle cerebral artery using a novel treatment approach that combines both intravenous (i.v.) and intra-arterial (IA) tPA. This case illustrates the potential value of the combined i.v.-IA thrombolytic approach, which is an emerging investigational treatment strategy for selected patients with severe acute ischemic stroke.

Female↗
PubMed2005

Diagnosis and anatomic mapping of an orbital varix by computed tomographic angiography.

PURPOSE: To report the use of computed tomographic angiography (CTA) to diagnose an orbital varix. DESIGN: Observational case report. METHODS: A 73-year-old female was investigated by CTA for carotid artery stenosis. An incidental orbital lesion was discovered. Reformations were obtained. RESULTS: CTA demonstrated a homogeneously enhancing orbital apex lesion. It provided exceptional anatomic detail of inflow and outflow veins, confirming the diagnosis of an orbital varix. CONCLUSIONS: CTA is cost effective, fast, non-invasive, and readily available. These aspects combined with the exceptional vascular detail obtained may make CTA the primary test for orbital varix diagnosis.

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PubMed2005

The hypodense artery sign.

An acute intracranial embolus may be associated with a hyperdense artery sign on CT, related to acute thrombus within the affected artery, a phenomenon that is well known and has been extensively documented. We present an unusual case of a middle cerebral artery territory acute infarct with a hypodense artery on CT. The Hounsfield unit attenuation of the embolic lesion was fat density. CT angiography and MR imaging confirmed the fatty lesion to be within the middle cerebral artery.

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PubMed2005

Identification, prognosis, and management of patients with carotid artery near occlusion.

BACKGROUND AND PURPOSE: Two large trials indicated that endarterectomy was less beneficial for symptomatic patients with internal carotid artery (ICA) near occlusion than for patients who had severe stenosis without near occlusion. Near occlusions complicate ratio calculations of ICA stenosis and require attention to detail for identification. The goal is to provide diagnostic criteria, illustrate identifying features, estimate accuracy of identification, and assess prognosis for patients with near occlusion. METHODS: We re-reviewed 1216 patients with severe (> or =70%) stenosis on angiography in the North American Symptomatic Carotid Endarterectomy Trial and European Carotid Surgery Trial. One of 5 (n = 262) had 2 or more criteria for near occlusion: (1) delayed cranial arrival of ICA contrast compared with external carotid artery (ECA); (2) intracranial collaterals seen as cross-filling of contralateral vessels or ipsilateral contrast dilution; (3) obvious diameter reduction of ICA compared with opposite ICA; or (4) ICA diameter reduction compared with ipsilateral ECA. RESULTS: Interrater agreement, sensitivity, and specificity were excellent (0.88, 90.6%, and 93.8%, respectively). By intention to treat, 3-year risks of ipsilateral stroke for medically treated patients with near occlusion was 15.1% versus 10.9% for surgically treated (absolute risk reduction [ARR] = 4.2%; P value = .33). Patients who continued to receive treatment in the medical arm for the trial's duration had a 3-year risk of 18.3% (ARR = 7.4%; P value = .13). Medically treated patients with severe stenosis but without near occlusion had a 3-year risk of 26.0% versus surgically treated of 8.2% (ARR = 17.8%; P value < .001). CONCLUSION: It is crucial to identify near occlusions on vascular imaging. Although it still is reasonable to consider endarterectomy for these patients, the benefit is muted.

Carotid Stenosis↗
PubMed2004

Internal carotid artery stenosis measurement: comparison of 3D computed rotational angiography and conventional digital subtraction angiography.

BACKGROUND AND PURPOSE: Clinical trials have shown that carotid endarterectomy reduces stroke risk in symptomatic individuals with severe internal carotid artery (ICA) stenosis. As a result of these trials, digital subtraction angiography (DSA) became a standard of reference for ICA stenosis diagnosis. Newer 3D techniques provide a larger number of views than DSA, which may influence the estimated degree of stenosis. We evaluate this possibility by directly comparing stenosis grades from 3D computed rotational angiography (CRA) and DSA. METHODS: As a prospective diagnostic study, we performed CRA and DSA on 26 consecutive symptomatic patients. Only 1 angiographic procedure was performed on normal asymptomatic arteries, yielding 42 arteries for comparison. Four neuroradiologists graded the CRA maximum intensity projections (MIPs) and DSA images, according to the North American Symptomatic Carotid Endarterectomy Trial guidelines. CRA studies included a search for the narrowest view by evaluating 60 MIPs generated at 3 degrees intervals and measurement of actual artery diameters. Artery diameters and stenosis grades were analyzed graphically; statistical significance was determined using a paired t test. RESULTS: The mean difference of 1.2% (CI, -18%, 21%) between CRA and DSA stenosis grades was not statistically significant (P=0.55). Agreement of the optimal CRA viewing angle was limited, with an interobserver variability of 24+/-13 degrees . The interobserver variability of DSA and CRA stenosis grades, 9.1% (CI, 0%, 21%) and 9.4% (CI, 0%, 22%), respectively, was not significantly different (P=0.79). CONCLUSIONS: CRA provides stenosis grades equivalent to DSA, as well as absolute measurements, providing a comparison for newer 3D techniques.

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PubMed2003

Side of brain infarction and long-term risk of sudden death in patients with symptomatic carotid disease.

BACKGROUND AND PURPOSE: Current publications suggest increased risk of sudden death in experimental animals with acute right insular lesions and in patients with recent right-sided brain infarction, particularly if the insula is involved. METHODS: Using 3 different time definitions, we related long-term risk of sudden death to presence and side of brain infarction on the baseline brain scan and handedness in 2885 patients with symptomatic carotid disease. RESULTS: In 1295 patients without brain infarction, 5-year risk of sudden death was 5.3% (24-hour definition); in those with left-sided infarction (n=471), 8.8%; in those with right-sided infarction (n=477), 6.0%; and in those with bilateral infarction (n=535), 9.7%. After accounting for differences of other risk factors (eg, previous myocardial infarction) in Cox regression, adjusted hazard ratios (HRs) compared with no infarction were as follows: left-sided HR, 1.45 (95% confidence interval [CI], 1.00 to 2.10); right-sided HR, 0.96 (95% CI, 0.62 to 1.47); and bilateral HR, 1.40 (95% CI, 0.98 to 2.00). Insular infarction occurred in 41 patients; none died suddenly. Left-handed or ambidextrous patients (n=183) had a lower risk of sudden death than right-handers; the adjusted HR for left-handed or ambidextrous patients was 0.24 (95% Cl, 0.07 to 0.70). These results were essentially the same for the 10- and 60-minute definitions of sudden death. CONCLUSIONS: In the long-term, left-sided, not right-sided, brain infarction is associated with increased risk of sudden death. Left-handed or ambidextrous patients have a lower risk of sudden death than right-handed patients, suggesting a role for the brain.

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PubMed2003

Development and progression of leukoaraiosis in patients with brain ischemia and carotid artery disease.

BACKGROUND AND PURPOSE: Leukoaraiosis (LA) or the presence of white matter changes, a frequent finding on brain CT scans of elderly individuals, is a risk factor for stroke and vascular death. The aim of the study was to seek development and progression of LA and associated risk factors in patients with symptomatic carotid artery disease. METHODS: Presence and extent of LA were determined on entry and follow-up CT scans from 685 patients in the North American Symptomatic Carotid Endarterectomy Trial. RESULTS: Among 596 patients without LA at entry, 107 (18.0%) developed restricted LA and 18 (3.0%) developed widespread LA during a mean follow-up of 6.1 years (range, 3.0 to 9.6 years). Older age was associated significantly with LA development (P<0.001). History of hypertension, diabetes mellitus, ischemic heart disease, and intermittent claudication had weak associations with LA development. During follow-up, 36.0% of patients who developed LA had 1 or more strokes, particularly of the lacunar type, in comparison to 23.5% of patients who did not develop LA (P=0.01). In patients who developed LA, the percentage with small deep infarcts (diameter < or =1.5 cm) increased from 34.4% on entry to 45.6% on follow-up CT scans compared with no increase (20.4% and 20.4%, respectively) in patients who did not develop LA. Among 89 patients who had restricted LA at entry, 28 (31.5%) progressed to widespread LA. Progression was associated with occurrence of strokes. CONCLUSIONS: LA is common in elderly patients with symptomatic cerebrovascular disease. Its development and progression are associated with higher occurrence of strokes, mainly of the lacunar type.

Age Factors↗
PubMed2003

Risk, types, and severity of intracranial hemorrhage in patients with symptomatic carotid artery stenosis.

BACKGROUND AND PURPOSE: We sought to report the occurrence and risk factors of intracranial hemorrhage during long-term follow-up of patients with internal carotid artery stenosis, with and without carotid endarterectomy. METHODS: From the prospective data of the North American Symptomatic Carotid Endarterectomy Trial, 3 types of intracranial hemorrhage were recognized: petechiae within infarction (PTI), intracerebral hematoma (ICH), and subarachnoid hemorrhage (SAH). The 30-day and 5-year risks of intracranial hemorrhage (PTI or ICH) were estimated from Kaplan-Meier event-free survival curves. Cox proportional-hazards regression modeling was used to identify risk factors. RESULTS: Of 1039 strokes that occurred in 749 of 2885 patients during an average follow-up of 5 years, there were 24 PTIs, 14 ICHs, and 1 SAH. The 5-year risk of intracranial hemorrhage was 1.7% in both medically and surgically treated patients, but the 30-day risk of 0.64% in surgically treated patients was 10 times higher than the risk of 0.07% in medically treated patients (P=0.01). Approximately 50% of all intracranial hemorrhages were either disabling or fatal, and ICHs were more likely to be fatal than PTIs. Old age, a history of hypertension, intermittent claudication and smoking, and infarct on brain images were risk factors for intracranial hemorrhage in medically treated patients, whereas diabetes mellitus was the sole risk factor in surgically treated patients. CONCLUSIONS: Intracranial hemorrhages are uncommon in patients with internal carotid artery stenosis but are associated with high mortality and morbidity. The risk factors for intracranial hemorrhage are different between medically and surgically treated patients.

Carotid Stenosis↗
PubMed2003

Assessment of the patient with hyperacute stroke: imaging and therapy.

Neuroimaging is an important part of the assessment of patients with hyperacute stroke. As new treatments that may reverse cerebral ischemia have been developed, the role of neuroimaging has changed from simply anatomic depiction of early infarction to identification, by means of physiologic (rather than simply anatomic) information, of regions that are at risk for infarction. The goal of such imaging techniques is to monitor successes and complications of recently developed treatments such as thrombolysis.

Acute Disease↗
PubMed2002

Prognostic importance of leukoaraiosis in patients with symptomatic internal carotid artery stenosis.

BACKGROUND AND PURPOSE: Leukoaraiosis (LA) is a frequent finding on brain CT scans. This study examined patients with LA and symptomatic internal carotid artery disease. METHODS: Patients in the North American Symptomatic Carotid Endarterectomy Trial were evaluated for the extent of LA. Long-term prognosis and perioperative risk associated with carotid endarterectomy were assessed. RESULTS: Among 2618 patients, 493 had LA: 354 restricted and 139 widespread. Patients with LA were older, had a history of hypertension, had more hemispheric ischemic events (particularly stroke), and had small, deep brain infarcts. The 3-year risks of stroke for medically treated patients were 20.2% (no LA), 27.3% (restricted LA), and 37.2% (widespread LA) (P=0.01). For surgically treated patients, the risks were 14.2%, 25.4%, and 33.6%, respectively (P<0.001). With widespread LA, occurrence of disabling strokes doubled in medical patients and tripled in surgical patients. The 30-day perioperative risks of any stroke or death for surgical patients with 50% to 99% internal carotid artery stenosis were 5.3% (no LA), 10.6% (restricted LA), and 13.9% (widespread LA). Despite higher perioperative risk, endarterectomy reduced the absolute 3-year risk of stroke ipsilateral to the symptomatic 50% to 99% stenosed artery by 11.6% (P=0.46) for patients with widespread LA, 7.6% (P=0.39) with those with restricted LA, and 10.9% (P<0.001) for those with no LA. CONCLUSIONS: In patients with a transient ischemic attack or nondisabling stroke associated with internal carotid artery disease, presence of LA was associated with an increased risk of any stroke and of disabling or fatal stroke. Patients with widespread LA had the worst prognosis. Despite the higher perioperative risk, endarterectomy reduced the risk of stroke.

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