Basilar ArteryVertebrobasilar InsufficiencyVertebral ArteryPosterior Cerebral ArteryInfarction, Posterior Cerebral ArteryCerebral AngiographyIntracranial AneurysmBrain Stem InfarctionsCerebral ArteriesDissectionMagnetic Resonance AngiographyArteriesSubarachnoid HemorrhageAneurysm, DissectingCerebrovascular CirculationVertebral Artery DissectionBrain InfarctionAneurysm, RupturedCerebral InfarctionIntracranial ArteriosclerosisEmbolization, TherapeuticMoyamoya DiseaseTomography, X-Ray ComputedStrokeCarotid Artery, InternalAnterior Cerebral ArteryBrain IschemiaMagnetic Resonance ImagingUltrasonography, Doppler, TranscranialTreatment OutcomePulmonary ArteryIschemic Attack, TransientIntracranial EmbolismAngiography, Digital SubtractionAngiographyArterial Occlusive DiseasesCarotid ArteriesRetrospective StudiesNeck DissectionCarotid Artery, Internal, DissectionCerebrovascular DisordersFollow-Up StudiesAcute DiseaseCerebral RevascularizationConstriction, PathologicVasospasm, IntracranialFemoral ArteryAortic AneurysmRenal ArteryStentsMesenteric ArteriesVasodilationBlood CirculationVasoconstrictionCranial Fossa, PosteriorBrainProspective StudiesCerebellumRisk FactorsIliac ArteryMuscle, Smooth, VascularCoronary Artery BypassRegistriesDogsSubclavian ArteryRecurrenceVasodilator AgentsRadial ArteryCarotid Artery DiseasesMammary ArteriesPredictive Value of TestsCoronary VesselsMiddle Cerebral ArteryTime FactorsAortic Aneurysm, ThoracicSerotoninDiffusion Magnetic Resonance ImagingCircle of WillisPulmonary CirculationExtracorporeal CirculationMesenteric Artery, SuperiorSplenic ArteryRabbitsBrachial ArteryCeliac ArteryCollateral CirculationVasoconstrictor AgentsCarotid Artery, CommonHepatic ArteryPapaverineMuscle ContractionRegional Blood FlowEndothelium, VascularPotassium ChlorideOphthalmic ArteryAcetylcholinePicolinesIntracranial Embolism and ThrombosisLymph Node ExcisionSumatriptan