Two rare variants of the arteries in the circle of Willis.
D000328:Adult; D000368:Aged; D001766:Blindness / Q000209:etiology; D002339:Carotid Arteries / Q000000981:diagnostic imaging; D002533:Cerebral Angiography; D002941:Circle of Willis / Q000002:abnormalities* / Q000000981:diagnostic imaging; D000013:Congenital Abnormalities / Q000150:complications / Q000000981:diagnostic imaging; D004172:Diplopia / Q000209:etiology; D005260:Female; D006801:Humans; D006973:Hypertension / Q000209:etiology; D002537:Intracranial Arteriosclerosis / Q000150:complications; D014711:Vertebral Artery / Q000000981:diagnostic imaging; D014717:Vertigo / Q000209:etiology