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Circle of WillisGenetic VariationCerebral ArteriesCollateral CirculationDNA, CircularMagnetic Resonance AngiographyManagement Quality CirclesNeuroendoscopyCarotid Artery, InternalCerebrovascular CirculationMoyamoya DiseaseCerebral AngiographyDoppler EffectAngiography, Digital SubtractionIntracranial ArteriosclerosisUltrasonography, Doppler, TranscranialBasilar ArteryHistory, 17th CenturyVertebral ArteryIntracranial AneurysmSphenoid BoneCarotid StenosisCarotid Artery, ExternalArachnoidEchoencephalographyMigraine with AuraOphthalmic ArteryCarotid-Cavernous Sinus FistulaIntracranial Arteriovenous MalformationsSkull BaseCranial Fossa, PosteriorBlood Flow VelocityBrainImaging, Three-DimensionalCerebral InfarctionCerebrovascular DisordersCadaverDominance, CerebralPia MaterBase SequenceMolecular Sequence DataBrain IschemiaImage Processing, Computer-AssistedSubarachnoid HemorrhageAntigenic VariationUltrasonography, Doppler, ColorCarotid ArteriesArterial Occlusive DiseasesIschemic Attack, TransientNamibiaGenotypeCarotid Artery DiseasesDNA Copy Number VariationsPolymorphism, Single NucleotideTomography, X-Ray ComputedSequence Analysis, DNAReference ValuesDNA ReplicationUltrasonographyPhylogenyPerceptual ClosureNucleic Acid Amplification TechniquesPhenotypeSpecies SpecificityAllelesSeasonsEndarterectomy, CarotidDNA, ViralPolymorphism, GeneticReproducibility of ResultsStrokeModels, GeneticRecombination, GeneticPlasmidsHaplotypesContrast MediaNucleic Acid ConformationGene Rearrangement, T-LymphocyteTime FactorsRegional Blood FlowGeographyDNA, Single-StrandedEvolution, MolecularMutationProspective StudiesGenetics, PopulationPolymerase Chain ReactionBiological EvolutionPrimed In Situ LabelingDNA, MitochondrialDNAObserver VariationGene FrequencyChromosome MappingModels, BiologicalDNA, SuperhelicalRepetitive Sequences, Nucleic AcidSensitivity and SpecificitySelection, GeneticQuantitative Trait Loci

Anatomical variationsArteriesCerebral vasculatureAnatomicAnatomy of the circlePolygonArteryArterialVesselsAneurysmMagneticAutopsySpecimensContralateralBranchesAngiographyNeurosurgical proceduresVesselPatternsComplete circleCommonStudyFoundFlowPopulationInternalLocalData

Anatomical variations9

• To analyse the impact of anatomical variations of the parent arteries on the incidence and recurrence rate following coil embolization of aneurysms of the anterior (AcoA), posterior communicating artery (PcoA) and basilar artery (BA) tip. (nih.gov)
• This may relate to a more fragile vessel disposition as it is not fully matured or to altered haemodynamics secondary to the anatomical variations. (nih.gov)
• Previous studies have indicated: (a) The variations of the structure of the CW in different populations and ethnic and (b) some correlation between those congenital anatomical variations and possible cerebrovascular diseases. (surgicalneurologyint.com)
• The frequency of such anatomical variations has not been evaluated sufficiently in the Iranian population. (surgicalneurologyint.com)
• Conclusion: The anatomical variations found in our study were not significantly different from those reported in the literature. (surgicalneurologyint.com)
• The anatomical variations of RAH are related to its presence or absence, number and the diverse origin from ACA and are of considerable clinical impact mainly from the point of view of the surgical procedures involving the anterior portion of the circle of Willis. (eurorad.org)
• Pawel Brzegowy et al, Middle cerebral artery anatomical variations and aneurysms-retrospective study based on computed tomograghy and angiographic findings, Folia Morphologica, Sep 2015. (ijmhr.org)
• anatomical variations are very common and a well-developed communication between each of its parts is identified in less than half of the population. (naqlafshk.com)
• Gen-eralizationand specificity errors for LBRP were consistentlylower than those of N-ICP-T. The first principal componentsof the SSM showed realistic anatomical variations. (kit.edu)

Arteries7

• The arrangement of the brain's arteries into the circle of Willis is believed to create redundancy (analogous to engineered redundancy) for collateral circulation in the cerebral circulation. (wikipedia.org)
• If one part of the circle becomes blocked or narrowed (stenosed) or one of the arteries supplying the circle is blocked or narrowed, blood flow from the other blood vessels can often preserve the cerebral perfusion well enough to avoid the symptoms of ischemia. (wikipedia.org)
• Fetal ultrasound image at the level of circle of Willis, showing PCA, MCA and ACA Cerebral angiogram showing an anterior/posterior projection of the vertebrobasilar and posterior cerebral circulation, the posterior aspect of the circle of Willis, and one of its feeding vessels An anterior view of major cerebral and cerebellar arteries. (wikipedia.org)
• Knowledge of the collateral ability of the circle of Willis is important for neurosurgeons, vascular surgeons, and interventional radiologists when a procedure in the intracranial or extracranial cerebral arteries is to be attempted. (ajnr.org)
• Hypoplasia of the posterior communicating arteries was the most common variation in our study. (surgicalneurologyint.com)
• Middle cerebral artery variations: Duplicated and Accessory arteries. (ijmhr.org)
• The PCAs complete the circle of Willis by joining the anterior circulation formed by the ICAs via the posterior communicating (PCOM) arteries. (naqlafshk.com)

Cerebral vasculature2

• We present the clinical and diagnostic features of this presentation and attempt to ascertain, by reviewing existent medical literature, the frequency and patterns of structural variations in cerebral vasculature. (biomedcentral.com)
• Schematic of the circle of Willis and cerebral vasculature in relation to local anatomy. (naqlafshk.com)

Anatomic1

• Considerable anatomic variation exists in the circle of Willis, with classic anatomy seen only in about one-third of people. (wikipedia.org)

Anatomy of the circle1

• MR angiography is an attractive, noninvasive technique for assessing the anatomy of the circle of Willis ( 3 ). (ajnr.org)

Polygon2

• The circle of Willis (also called Willis' circle, loop of Willis, cerebral arterial circle, and Willis polygon) is a circulatory anastomosis that supplies blood to the brain and surrounding structures in reptiles, birds and mammals, including humans. (wikipedia.org)
• The Circle of Willis is an arterial polygon formed as the internal carotid and vertebral systems anastomose around the optic chiasm and infundibulum of the pituitary stalk in the suprasellar cistern. (neurologyneeds.com)

Artery5

• The anterior cerebral artery forms the anterolateral portion of the circle of Willis, while the middle cerebral artery does not contribute to the circle. (wikipedia.org)
• Visible collaterals of the circle of Willis on MR angiograms are able to supply collateral flow in the presence of carotid artery obstruction. (ajnr.org)
• The circle of Willis, located at the base of the brain, provides the main route for collateral blood flow in severe occlusive disease of the internal carotid artery (ICA). (ajnr.org)
• Another type of the precerebral blood flow distribution was observed in patients with multiple ICA and vertebral artery stenoses or variation the circle of Willis. (oatext.com)
• The circle of Willis begins to form when the right and left internal carotid artery (ICA) enters the cranial cavity and each one divides into two main branches: the anterior cerebral artery (ACA) and middle cerebral artery (MCA). (naqlafshk.com)

Arterial3

• However, considering that the circle of Willis is present in many non-human species (reptiles, birds and mammals), and that arterial narrowing is mostly associated with old age and the human lifestyle, more generally applicable explanations of its functions have been suggested, such as dampening of pulse pressure waves within the brain and involvement in forebrain sensing of water loss. (wikipedia.org)
• Patient groups were compared regarding gender, age, arterial vasculature side, anatomical location, diameter, preoperative DSA appearance, aneurysmal and anatomical Circle of Willis variations (CWV) co-existence. (hippokratia.gr)
• Normal cerebral arterial development and variations. (ijmhr.org)

Vessels1

• The aim of this study is to find the variations of the anatomy of the vessels in the CW in sample population of Iranian people and compare it with other available studies in the literature, providing a new grouping for variations. (surgicalneurologyint.com)

Aneurysm1

• Two of these variations were also associated with aneurysm recurrence following coil embolization: asymmetrical A1 segment (p=0.01), and asymmetrical BA tip (p=0.02). (nih.gov)

Magnetic1

• Magnetic resonance arteriography illustrating the circle of Willis and its branches. (naqlafshk.com)

Autopsy1

• autopsy series, only 18% of specimens of the circle of Willis were found to be anatomically normal [ 1 ] and Krabbe-Hartkamp et al. (biomedcentral.com)

Specimens1

• In the remaining 65.5% of the specimens, there were variations in the CW. (surgicalneurologyint.com)

Contralateral1

• These patients had either bilateral ICA stenosis greater than 90% or the contralateral ICA occlusion, or a variation the circle of Willis. (oatext.com)

Branches2

• The central branches supply the interior of the circle of Willis, more specifically, the Interpeduncular fossa. (wikipedia.org)
• The cortical branches are named for the area they supply and do not directly affect the circle of Willis. (wikipedia.org)

Angiography3

• We investigated the usefulness of MR angiography in identifying functional collaterals of the circle of Willis. (ajnr.org)
• MR angiography of the circle of Willis was performed in 50 healthy volunteers. (ajnr.org)
• We performed MR angiography of the circle of Willis in healthy subjects, and the results were compared with those of transcranial color duplex sonography (TCCD). (ajnr.org)

Neurosurgical procedures1

• The awareness of the various anatomical and morphometric variations of the RAH is essential in planning neurosurgical procedures to avoid neurological complications such as an ischaemic infarct. (eurorad.org)

Vessel2

• Unfortunately, hypoplasia of vessel segments frequently hampers the collateral function of the circle of Willis ( Fig 1 ). (ajnr.org)
• The current vessel model is the circle of Willis (CW) of the brain. (nau.edu)

Patterns1

• Variations in the elastic behavior confirmed that different layering patterns yield adjustable anisotropic material properties within the scaffolds. (nau.edu)

Complete circle1

• A complete circle of Willis (in which no component is absent or hypoplastic) is only seen in 20-25% of individuals. (neurologyneeds.com)

Common1

• What are the common variations of this position? (renalandurologynews.com)

Study1

• Variations in the Anatomy of the Willis' circle: A 3-year cross-sectional study from Iran (2006-2009). (surgicalneurologyint.com)

Found1

• Although people associate mandalas primarily with the civilizations of South Asia, variations of them can be found across time, cultures, and religious and philosophical systems - just look at the windows of European cathedrals or the dream catchers of American Indians. (ceskamincovna.sk)

Flow2

• The adaptive flow that the circle of Willis introduces can also lead to reduced cerebral perfusion. (wikipedia.org)
• Subclavian steal syndrome has potential to affect flow in the circle of Willis. (wikipedia.org)

Population1

• The southern hemisphere climate faces limited anthropogenic emissions, because only 10 percent of the world population can contribute with less pollutant providing activities, and hasn't changed, but that could well be because it is equally influenced and driven, like the northern hemisphere, by the variation of sun activity in diverse cycles. (scirp.org)

Internal1

• The circle of Willis encircles the stalk of the pituitary gland and provides important communications between the blood supply of the forebrain and hindbrain (ie, between the internal carotid and vertebro-basilar systems following obliteration of primitive embryonic connections). (naqlafshk.com)

Local1

• tially determined by spatial variations in local packing density. (lu.se)

Data1

• The preliminary data gathered from the bone scaffolds indicate that variations in stiffness properties can be altered to match physiological conditions such as bone tissue. (nau.edu)