(Stroke. 2000;31:128.)
© 2000 American Heart Association, Inc.
Original Contributions |
Angiographically Defined Collateral Circulation and Risk of Stroke in Patients With Severe Carotid Artery Stenosis
From the John P. Robarts Research Institute (R.D.H., M.E., H.J.M.B.) and Departments of Epidemiology and Biostatistics (M.E.), Clinical Neurological Sciences (M.E., A.J.F., H.J.M.B.), and Diagnostic Radiology (A.J.F.), University of Western Ontario, London, Ontario, Canada; and Department of Clinical Neurology, Radcliffe Infirmary, Oxford, UK (P.M.R.).
Correspondence to H.J.M. Barnett, MD, John P. Robarts Research Institute, 100 Perth Dr, PO Box 5015, London, Ontario N6A 5K8, Canada. E-mail barnett{at}rri.on.ca
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Abstract |
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Background and Purpose—Blood supply through collateral pathways improves regional cerebral blood flow and may protect against ischemic events. The effect of collaterals on the risk of stroke and transient ischemic attack (TIA), in the presence of angiographic severe internal carotid artery (ICA) stenosis, was assessed.
Methods—Angiographic collateral filling through anterior communicating and posterior communicating arteries and retrograde filling through ophthalmic arteries were determined in all patients at entry into the North American Symptomatic Carotid Endarterectomy Trial. Kaplan-Meier event-free survival analyses were performed on 339 medically treated and 342 surgically treated patients.
Results—The presence of collaterals supplying the symptomatic ICA increased with severity of stenosis. Two-year risk of hemispheric stroke in medically treated patients with severe ICA stenosis was reduced in the presence of collaterals: 27.8% to 11.3% (P=0.005). Similar reductions were observed for hemispheric TIA (36.1% versus 19.1%; P=0.008) and disabling or fatal strokes (13.3% versus 6.3%; P=0.11). For surgically treated patients, the perioperative risk of hemispheric stroke was 1.1% in the presence of collaterals versus 4.9% when absent. The 2-year stroke risks for surgical patients with and without collaterals were 5.9% versus 8.4%, respectively. Neither comparison in the surgical group was statistically significant. The observed reductions were independent of the degree of ICA stenosis and other vascular risk factors.
Conclusions—Collaterals are associated with a lower risk of hemispheric stroke and TIA, both long term and perioperatively. Angiographic identification of collaterals assists in identifying patients with severe ICA stenosis at lower risk of stroke and TIA.
Key Words: carotid stenosis • cerebral ischemia • collateral circulation • risk
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Introduction |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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Two large clinical trials have demonstrated that the risk of stroke increases with increasing degrees of angiographically defined, symptomatic internal carotid artery (ICA) stenosis.1 2 Subsequent studies have shown that the risk is further modified by other angiographic features, such as plaque ulceration, near occlusion, and intracranial atherosclerotic disease.3 4 5 6 Although the cause of stroke is primarily thromboembolic in the presence of severe ICA stenosis, changes in large-artery hemodynamics may also have a role in determining the extent of the infarction.7 8
Cerebral collateral circulation has been reported to alter the risk of stroke.9 10 11 12 The identification of collaterals depended on angiography to identify the communications that are made by the anterior communicating (ACoA) and posterior communicating (PCoA) arteries with contributions from retrograde filling of the ophthalmic artery and from leptomeningeal arteries.13 Cerebral angiography has been used as the reference modality in correlating the identification of collateral circulation by transcranial Doppler and MR studies.14 15 16 Infarcts on CT have been associated with the absence of angiographic collateral pathways.12 Unexpectedly, angiographic demonstration of collaterals, or lack of collaterals, has not been shown to correlate with cerebral perfusion studies.17
Blood supply to regions of the brain through the collateral circulation occurs with increasing severity of ICA stenosis and occlusion. To what extent collaterals modify the risk of stroke, independently of increasing stenoses, is unknown. In patients undergoing carotid endarterectomy, absent or inadequate demonstration of collateral pathways by angiography and transcranial Doppler has been shown to correlate with intraoperative electroencephalographic changes.18 19 20 Their relationship to an ischemic event is uncertain.
The aim of the present study is to examine and quantify the effect of angiographically visualized collateral pathways that supply the hemisphere distal to a severe ICA stenosis on the risk of hemispheric stroke and transient ischemic attack (TIA). Data for this study are taken from the North American Symptomatic Carotid Endarterectomy Trial (NASCET).
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Subjects and Methods |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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NASCET was a multicenter, randomized, controlled trial of carotid endarterectomy in patients with symptomatic ICA stenosis. A total of 2885 patients were enrolled who had a TIA or nondisabling ischemic stroke in the territory of a carotid bifurcation stenosis within 180 days of randomization. Patients were excluded if they had a probable cardiac source of embolism, serious disease likely to cause death within 5 years, or intracranial disease that was judged to be more significant than the surgically accessible carotid bifurcation lesion. Patient baseline characteristics and final results have been reported.1 21
Selective angiography, including intracranial views, was performed as part of the entry assessment into NASCET. The principal neuroradiologist (A.J.F.) reviewed the angiograms blinded to all clinical information. All carotid bifurcation stenoses, except those recognized as having angiographic features of near occlusion, were measured at the site of the minimal residual lumen and compared with the diameter of the distal lumen at the point at which the walls become parallel.22 To assess the absence or presence of collateral pathways, biplane (anterior-posterior, lateral, and/or oblique) views were examined. Collaterals were recognized on the angiogram by the contrast filling the ACoA, PCoA, or ophthalmic arteries following a carotid or vertebral injection. The appearance of the collaterals was then graded on a 3-point scale: 1, slight collateral distribution, often with dilution (eg, just to anterior cerebral artery); 2, small but definite collateral supply (eg, to anterior cerebral and some to middle cerebral arteries); and 3, full collateral filling (eg, to the middle cerebral artery). For the purpose of the present study, grades 2 and 3 were combined to indicate the presence of collateral pathways. Collaterals were considered absent if they were not visualized on the angiogram or were assigned a grade of 1.
The method of assessing the degree of ICA stenosis used in NASCET begins with the recognition of the near-occlusion state, which is characterized by the physiological reduction in pressure and overall flow through the distal ICA.6 22 Since the resulting poststenotic reduction in luminal diameter would lead to a misleading calculation of stenosis by the ratio formula for comparing the diameter at the point of greatest narrowing with that of the distal ICA well beyond the bulb where the walls are parallel, NASCET opted not to assign a calculated degree of stenosis for recognized near-occlusion cases.6 22 Instead, these cases were grouped into a separate category with an arbitrarily assigned value of 95%, representing a very severe stenosis. Clinically, patients with a reduced distal ICA lumen have been reported to have a lower risk of stroke.5 6 23
A method to quantify distal ICA luminal diameter reduction has been
proposed.5 This calculation consists of taking the ratio
of the distal ICA lumen diameter at the point at which the walls become
parallel, to the disease-free portion of the common carotid artery
(CCA) lumen diameter. The term "collapse" has been used to
designate an ICA/CCA ratio <0.42, an indication of severe
poststenotic reduction in lumen diameter beyond the normal
range of observed ICA/CCA ratios in patients with minimal carotid
stenosis.5 In the present study the degree of
ICA stenosis was calculated only when the ICA/CCA ratio was
0.42 and was otherwise designated as "severe distal
reduction."
The primary outcome was the risk of hemispheric stroke at 2 years,
ipsilateral to the symptomatic ICA stenosis. The
risk of a hemispheric TIA and of a disabling stroke was also
calculated. Disabling strokes were defined as having Rankin grades
3.24 The risks were derived from Kaplan-Meier event-free
survival curves. Cox proportional hazards regression modeling was used
to assess the extent to which the presence of collaterals can predict
the risk of stroke, independent of other vascular risk factors.
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Results |
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Among the 2885 patients entered into NASCET, 280 (9.7%) were identified by angiography to have collateral pathways toward the randomized, symptomatic ICA: 195 through the ACoA only, 25 through the PCoA only, 5 retrograde through the ophthalmic arteries only, and 55 with multiple collateral pathways. Figure 1
shows that the percentage of patients
with collaterals increases with the degree of ICA stenosis,
from next to nil at moderate degrees of stenosis to >50% at
the highest degrees of stenosis (P<0.001). Since
collaterals were largely a feature of severe ICA stenosis and
the number of patients with collaterals in the moderate
stenosis categories was small, further analyses were
restricted to the 681 patients (339 medically treated and 342
surgically treated) with either 70% to 99% stenosis or severe
distal reduction.
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Baseline characteristics of the patients are shown in the
Table. In general, patients with
collaterals were less likely to harbor the risk factors that are
associated with stroke. Patients with collaterals were also less likely
to have intracranial atherosclerotic disease in comparison to those
without collaterals (24.3% versus 42.2%; P<0.001).
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The risks of a disabling or fatal ipsilateral hemispheric stroke, any
ipsilateral hemispheric stroke, and ipsilateral hemispheric TIA are
shown in Figure 2 for medically treated
and surgically treated patients with and without collaterals. In all
analyses, the presence of collaterals was associated with a
reduced risk of a hemispheric event in medically treated patients
(13.3% versus 6.3%, P=0.11 for disabling or fatal stroke;
27.8% versus 11.3%, P=0.005 for any hemispheric stroke;
and 36.1% versus 19.1%, P=0.008 for hemispheric TIA).
Correction for the patient characteristics listed in the Table
in a Cox proportional hazards regression did not appreciably
alter this association. Reductions in risk were also observed in the
surgically treated patients but were not statistically significant. The
above analyses were repeated when the ACoA was considered
alone, with no substantive changes in results.
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In a secondary analysis, the 2-year risk of an ipsilateral
hemispheric stroke in medically treated patients was ascertained for
different ICA stenosis categories (Figure 3). The risk of stroke approximately
doubled for patients with 85% to 99% stenosis in comparison
to those with 70% to 84% stenosis. Nevertheless, the presence
of collaterals reduced the risk by approximately two thirds in both ICA
stenosis categories. Patients in the severe distal reduction
group had a lower risk of stroke in comparison to those in the 85% to
99% stenosis category, which was relatively unaffected by the
presence of collaterals.
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The effect of collaterals on stroke risk was also assessed in patients
who underwent carotid endarterectomy (Figure 3). The 2-year risk of stroke was lowest among the surgical
patients who had collateral pathways visualized on their preoperative
angiogram and 70% to 99% stenosis. This reduced risk was
primarily due to a low 30-day hemispheric stroke risk of 1.1%, in
comparison to a 4.9% risk for patients without collaterals. In all
cases, surgically treated patients with 70% to 99% stenosis
had a lower risk of stroke in comparison to their medical counterparts.
In contrast, surgical patients in the severe distal reduction group did
not appear to have their 2-year stroke risk reduced beyond what was
achieved by best medical care alone.
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Discussion |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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The results from the present study suggest that collateral circulation is important in reducing the risk of hemispheric stroke and TIA in patients with symptomatic severe ICA stenosis. This effect is observed across all degrees of severe ICA stenosis except in the case of severe distal reduction. These results confirm the collateral circulation observations of other studies9 10 11 12 13 17 25 26 in a larger number of patients with symptomatic ICA stenosis, of whom one half underwent carotid endarterectomy. The reduction in stroke risk in the perioperative period suggests that the observations from the intraoperative electroencephalographic studies are of clinical relevance.18 19 20
The beneficial effect of collateral circulation in patients with a severe ICA stenosis may be due to improved cerebral perfusion in the presence of collaterals and protection of the brain from small thromboemboli that cause stroke and TIA.8 9 Patients were also less likely to have a disabling or fatal stroke, suggesting that the underlying cerebral hemodynamics9 25 27 may have a role in determining the severity of the stroke and/or the extent of recovery.
When severe distal reduction of the ICA luminal diameter occurred, no beneficial effect of collaterals was observed. Since the primary cause of stroke in the presence of severe ICA stenosis is likely to be thromboembolism,7 8 28 it is postulated that the potential for thromboembolism is greatly reduced when the distal artery is severely narrowed.5 6 23 Collaterals present beyond this poststenotic reduction would then be expected to have little or no effect.
Patients with collaterals had fewer of the risk factors associated with
stroke than those without collaterals. A previous study has shown that
patients with 2 collateral pathways were less likely to have a
history of hypertension than those with 1 or no collateral
pathway.29 The lower prevalence of hypertension among
patients with collaterals in the present study supports this
observation.
Several items regarding the generalizability of the present results
deserve comment. First, the reduction in stroke risk for both medically
and surgically treated patients was demonstrated when the presence of
collaterals was defined as the angiographic visualization of 1 ACoA,
PCoA, or ophthalmic arteries. Other collateral pathways that may be
important, such as the leptomeningeal collaterals over the hemispheres,
were not considered in the present study because there were too few
images over the brain surfaces submitted to the NASCET data office. In
addition, there were too few patients and outcome events to consider
the PCoA and ophthalmic arteries alone. These limitations may not
affect the generalizability of the present results to any great
extent, since others have shown that the ACoA may be the functionally
most important collateral pathway.13 25 30 The results of
the present study support this since the findings were similar when
the ACoA was considered alone in the analyses.
Second, it was not possible to fully assess anatomic variability in this study because only selected films from the angiographic sequence were submitted to the NASCET data office. This meant that distinction between some anatomic variation of the circle of Willis and a true collateral pathway often needed to be judged from 1 angiographic film instead of a serial study. Nevertheless, it is believed that the collaterals visualized during angiography after contrast injection were functional pathways in patients with severe ICA stenosis.
Finally, only one quarter of the patients in NASCET had the vertebral studies that were needed for the assessment of PCoA collaterals. The decision regarding vertebral studies was made by the patient’s local treating team. It is unlikely that a systematic bias in deciding which patients had vertebral studies occurred at the treating center, but rather the visualization of collateral pathways may have represented the local practice of cerebral angiography. When the analyses were repeated on the subset of patients who had full bilateral carotid and vertebral studies, the results for the primary outcome of stroke were similar to those reported in the whole group.
In conclusion, patients with collaterals that supply the hemisphere distal to a severe ICA stenosis have a lower risk of stroke and TIA, both disabling and nondisabling, than patients without collaterals. Patients with collaterals supplying the operative side were less likely to have a perioperative stroke. These results applied when the ACoA, PCoA, and ophthalmic sources were considered as a group or when the ACoA was considered alone. Assessing collateral pathways may be helpful in identifying patients with a severe ICA stenosis at a lower risk of stroke and TIA.
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Acknowledgments |
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This study was supported by grant RO1-NS-24456 from the National Institute of Neurological Disorders and Stroke. The authors acknowledge the support of all participants in NASCET and are grateful to SmithKline Beecham for providing Ecotrin for all NASCET patients.
Received August 27, 1999; revision received October 1, 1999; accepted October 1, 1999.
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References |
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|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
1. Barnett HJM, Taylor DW, Eliasziw M, Fox AJ, Ferguson GG, Haynes RB, Rankin RN, Clagett GP, Hachinski VC, Sackett DL, Thorpe KE, Meldrum HE, for the North American Symptomatic Carotid Endarterectomy Trial Collaborators. Benefit of carotid endarterectomy in patients with symptomatic moderate or severe stenosis. N Engl J Med. 1998;339:1415–1425.
2. The European Carotid Surgery Trialists’ Collaborative Group. Randomized trial of endarterectomy for recently symptomatic carotid stenosis: final results of the MRC European Carotid Surgery Trial (ECST). Lancet. 1998;351:1379–1387.[Medline] [Order article via Infotrieve]
3. Eliasziw M, Streifler JY, Fox AJ, Hachinski VC, Ferguson GG, Barnett HJM, for the North American Symptomatic Carotid Endarterectomy Trial. Significance of plaque ulceration in symptomatic patients with high-grade carotid stenosis. Stroke. 1994;25:304–308.[Abstract]
4.
Kappelle LJ, Eliasziw M, Fox AJ, Sharpe BL, Barnett
HJM, for the North American Symptomatic Carotid
Endarterectomy Trial (NASCET) Group. Importance of
intracranial atherosclerotic disease in patients with
symptomatic stenosis of the internal carotid
artery. Stroke. 1999;30:282–286.
5. Rothwell P, Warlow C, for the ECST Trialists’ Collaborative Group. Low risk of ischemic stroke in patients with symptomatic carotid near-occlusion: implications for imaging and treatment. Cerebrovasc Dis. 1999;9(suppl 1):1–66.
6.
Morgenstern LB, Fox AJ, Sharpe BL, Eliasziw M, Barnett
HJM, Grotta JC, for the North American Symptomatic Carotid
Endarterectomy Trial (NASCET) Group. The risks and
benefits of carotid endarterectomy in patients with
near occlusion of the carotid artery. Neurology. 1997;48:911–915.
7. Schroeder T. Hemodynamic significance of internal carotid artery disease. Acta Neurol Scand. 1988;77:353–372.[Medline] [Order article via Infotrieve]
8.
Caplan LR, Hennerici M. Impaired clearance of emboli
(washout) is an important link between hypoperfusion, embolism, and
ischemic stroke. Arch Neurol. 1998;55:1475–1482.
9. Powers WJ, Press GA, Grubb RL, Gado M, Raichle ME. The effect of hemodynamically significant carotid artery disease on the hemodynamic status of the cerebral circulation. Ann Intern Med. 1987;106:27–35.
10. Norris JW, Krajewski A, Bornstein NM. The clinical role of the cerebral collateral circulation in carotid occlusion. J Vasc Surg. 1990;12:113–118.[Medline] [Order article via Infotrieve]
11.
Schomer DF, Marks MP, Steinberg GK, Johnstone IM,
Boothroyd DB, Ross MR, Pelc NJ, Enzmann DR. The anatomy of the
posterior communicating artery as a risk factor for ischemic
cerebral infarction. N Engl J Med. 1994;330:1565–1570.
12.
Harrison MJ, Marshall J. The variable clinical and
CT findings after carotid occlusion: the role of collateral blood
supply. J Neurol Neurosurg Psychiatry. 1988;51:269–272.
13. Mount LA, Taveras JM. Arteriographic demonstration of the collateral circulation of the cerebral hemispheres. AMA Arch Neurol Psychiatry. 1957;78:235–253.[Medline] [Order article via Infotrieve]
14. Baumgartner RW, Baumgartner I, Mattle HP, Schroth G. Transcranial color-coded duplex sonography in the evaluation of collateral flow through the circle of Willis. AJNR Am J Neuroradiol. 1997;18:127–133.[Abstract]
15. Müller M, Hermes M, Brückmann H, Schimrigk K. Transcranial Doppler ultrasound in the evaluation of collateral blood flow in patients with internal carotid artery occlusion: correlation with cerebral angiography. AJNR Am J Neuroradiol. 1995;16:195–202.[Abstract]
16. Furst G, Steinmetz H, Fischer H, Skutta B, Sitzer M, Aulich A, Kahn T, Modder U. Selective MR angiography and intracranial collateral blood flow. J Comput Assist Tomogr. 1993;17:178–183.[Medline] [Order article via Infotrieve]
17.
Derdeyn CP, Shaibani A, Moran CJ, Cross DT, Grubb RL,
Powers WJ. Lack of correlation between pattern of collateralization and
misery perfusion in patients with carotid occlusion. Stroke. 1999;30:1025–1032.
18. Lopez-Bresnahan MV, Kearse LA Jr, Yanez P, Young TI. Anterior communicating artery collateral flow protection against ischemic change during carotid endarterectomy. J Neurosurg. 1993;79:379–382.[Medline] [Order article via Infotrieve]
19.
Schneider PA, Ringelstein EB, Rossman ME, Dilley RB,
Sobel DF, Otis SM, Bernstein EF. Importance of cerebral collateral
pathways during carotid endarterectomy.
Stroke. 1988;19:1328–1334.
20.
Schwartz RB, Jones KM, LeClercq GT, Ahn SS, Chabot R,
Whittemore A, Mannick JA, Donaldson MC, Gugino LD. The value of
cerebral angiography in predicting cerebral ischemia during
carotid endarterectomy. AJR Am J
Roentgenol. 1992;159:1057–1061.
21. North American Symptomatic Carotid Endarterectomy Trial Collaborators. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. N Engl J Med. 1991;325:445–453.[Abstract]
22.
Fox AJ. How to measure carotid stenosis.
Radiology. 1993;186:316–318.
23.
Norris JW, Zhu CZ. Stroke risk and critical carotid
stenosis. J Neurol Neurosurg Psychiatry. 1990;53:235–237.
24.
De Haan R, Limburg M, Bossuyt P, van der Meulen J,
Aaronson N. The clinical meaning of Rankin "handicap" grades after
stroke. Stroke. 1995;26:2027–2030.
25.
Kluytmans M, van der Grond J, van Everdingen KJ, Klijn
CJM, Kapelle LJ, Viergever MA. Cerebral hemodynamics in
relation to patterns of collateral flow. Stroke. 1999;30:1432–1439.
26. Van Everdingen KJ, Visser GH, Klijn CJM, Kapelle LJ, van der Grond J. Role of collateral flow on cerebral hemodynamics in patients with unilateral internal carotid artery occlusion. Ann Neurol. 1998;44:167–176.[Medline] [Order article via Infotrieve]
27. Powers WJ. Cerebral hemodynamics in ischemic cerebrovascular disease. Ann Neurol. 1991;29:231–240.[Medline] [Order article via Infotrieve]
28. Barnett HJM. Hemodynamic cerebral ischemia: an appeal for systematic data gathering prior to a new EC/IC trial. Stroke. 1997;28:1857–1860.
29. Hedera P, Bujdáková J, Traubner P, Pancák J. Stroke risk factors and development of collateral flow in carotid occlusive disease. Acta Neurol Scand. 1998;98:182–186.[Medline] [Order article via Infotrieve]
30. Doblar DD, Plyushcheva NV, Jordan W, McDowell H. Predicting the effect of carotid artery occlusion during carotid endarterectomy: comparing transcranial Doppler measurements and cerebral angiography. Stroke. 1998;28:2038–2042.
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T. G. Phan, G. A. Donnan, P. M. Wright, and D. C. Reutens A Digital Map of Middle Cerebral Artery Infarcts Associated With Middle Cerebral Artery Trunk and Branch Occlusion Stroke, May 1, 2005; 36(5): 986 - 991. [Abstract] [Full Text] [PDF]
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N. U. Ko, A. S. Achrol, M. Chopra, M. Saha, D. Gupta, W. S. Smith, R. T. Higashida, and W. L. Young Cerebral Blood Flow Changes after Endovascular Treatment of Cerebrovascular Stenoses AJNR Am. J. Neuroradiol., March 1, 2005; 26(3): 538 - 542. [Abstract] [Full Text] [PDF]
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M. Kamouchi, K. Kishikawa, Y. Okada, T. Inoue, S. Ibayashi, and M. Iida Poststenotic Flow and Intracranial Hemodynamics in Patients with Carotid Stenosis: Transoral Carotid Ultrasonography Study AJNR Am. J. Neuroradiol., January 1, 2005; 26(1): 76 - 81. [Abstract] [Full Text] [PDF]
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J. J. Kim, N. J. Fischbein, Y. Lu, D. Pham, and W. P. Dillon Regional Angiographic Grading System for Collateral Flow: Correlation With Cerebral Infarction in Patients With Middle Cerebral Artery Occlusion Stroke, June 1, 2004; 35(6): 1340 - 1344. [Abstract] [Full Text] [PDF]
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D.R. Rutgers, C.J.M. Klijn, L.J. Kappelle, and J. van der Grond Recurrent Stroke in Patients With Symptomatic Carotid Artery Occlusion Is Associated With High-Volume Flow to the Brain and Increased Collateral Circulation Stroke, June 1, 2004; 35(6): 1345 - 1349. [Abstract] [Full Text] [PDF]
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J. Hendrikse, J. van der Grond, H. Lu, P. C.M. van Zijl, and X. Golay Flow Territory Mapping of the Cerebral Arteries With Regional Perfusion MRI Stroke, April 1, 2004; 35(4): 882 - 887. [Abstract] [Full Text] [PDF]
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L. B. Goldstein Extracranial Carotid Artery Stenosis Stroke, November 1, 2003; 34(11): 2767 - 2773. [Abstract] [Full Text] [PDF]
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D. S. Liebeskind Collateral Circulation Stroke, September 1, 2003; 34(9): 2279 - 2284. [Abstract] [Full Text] [PDF]
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J. Hendrikse, D. R. Rutgers, C. J.M. Klijn, B. C. Eikelboom, and J. van der Grond Effect of Carotid Endarterectomy on Primary Collateral Blood Flow in Patients With Severe Carotid Artery Lesions Stroke, July 1, 2003; 34(7): 1650 - 1654. [Abstract] [Full Text] [PDF]
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P. M. Rothwell For Severe Carotid Stenosis Found on Ultrasound, Further Arterial Evaluation Prior to Carotid Endarterectomy Is Unnecessary: The Argument Against Stroke, July 1, 2003; 34(7): 1817 - 1819. [Full Text] [PDF]
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 R. H.C. Bisschops, C. J.M. Klijn, L. J. Kappelle, A. C. van Huffelen, and J. van der Grond Collateral flow and ischemic brain lesions in patients with unilateral carotid artery occlusion Neurology, May 13, 2003; 60(9): 1435 - 1441. [Abstract] [Full Text] [PDF]
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A. W.J. Hoksbergen, C. B.L. Majoie, F.-J. H. Hulsmans, and D. A. Legemate Assessment of the Collateral Function of the Circle of Willis: Three-Dimensional Time-of-Flight MR Angiography Compared with Transcranial Color-Coded Duplex Sonography AJNR Am. J. Neuroradiol., March 1, 2003; 24(3): 456 - 462. [Abstract] [Full Text] [PDF]
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P. M. Rothwell, S. A. Gutnikov, and C. P. Warlow Reanalysis of the Final Results of the European Carotid Surgery Trial Stroke, February 1, 2003; 34(2): 514 - 523. [Abstract] [Full Text] [PDF]
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S.S.Y. Ho, C. Metreweli, and C.H. Yu Color Velocity Imaging Quantification in the Detection of Intracranial Collateral Flow Stroke, July 1, 2002; 33(7): 1795 - 1798. [Abstract] [Full Text] [PDF]
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 H. J.M. Barnett, H. E. Meldrum, and M. Eliasziw The appropriate use of carotid endarterectomy Can. Med. Assoc. J., April 1, 2002; 166(9): 1169 - 1179. [Abstract] [Full Text] [PDF]
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 O. Benavente, M. Eliasziw, J. Y. Streifler, A. J. Fox, H. J.M. Barnett, H. Meldrum, and the North American Symptomatic Carotid Endarterect Prognosis after Transient Monocular Blindness Associated with Carotid-Artery Stenosis N. Engl. J. Med., October 11, 2001; 345(15): 1084 - 1090. [Abstract] [Full Text] [PDF]
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R. L. Sacco Extracranial Carotid Stenosis N. Engl. J. Med., October 11, 2001; 345(15): 1113 - 1118. [Full Text] [PDF]
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G. L. Bernardini, R. C. Darling III, D. M. Shah, R. Berguer, and H. J. M. Barnett Results of carotid endarterectomy with prospective neurologist follow-up Neurology, April 24, 2001; 56(8): 1119 - 1121. [Full Text] [PDF]
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J. S. Jeret, H. J. M. Barnett, and J. P. Broderick Carotid endarterectomy: Another wake-up call Neurology, April 24, 2001; 56(8): 1118 - 1118. [Full Text] [PDF]
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 Do Collaterals Lower Stroke Risk in Severe ICA Stenosis? Journal Watch Neurology, June 1, 2000; 2000(601): 5 - 5. [Full Text]
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