Vertebrobasilar InsufficiencyVertebral ArterySubclavian Steal SyndromeBasilar ArterySubclavian ArteryVertigoCerebral AngiographyArterial Occlusive DiseasesAdrenal InsufficiencyHemodynamicsVenous InsufficiencyRenal InsufficiencyIntracranial AneurysmExocrine Pancreatic InsufficiencyVertebral Artery DissectionMagnetic Resonance AngiographyPlacental InsufficiencyAngiography, Digital SubtractionInfarction, Posterior Cerebral ArteryIschemic Attack, TransientIntracranial ArteriosclerosisPetrous BoneEchoencephalographyCerebrovascular CirculationTrigeminal Neuralgia