Morphologic variation of the area drained by the basal vein.
D000328:Adult; D006801:Humans; D007031:Hypothalamus / Q000098:blood supply*; D008326:Mammillary Bodies / Q000098:blood supply; D008636:Mesencephalon / Q000098:blood supply*; D009897:Optic Chiasm / Q000098:blood supply; D014680:Veins / Q000033:anatomy & histology