ABSTRACT
In the course of their development, the carotid and vertebrobasilar arterial systems are temporarily anastomosed with each other by small arteries which usually disappear from the stage 4 of development (12–14 mm embryos) (Padget, 1948). These vessels (hypoglossal, proatlantal, trigeminal, otic, and cervical intersegmental arteries) may persist in adult. They often coexist with other vascular abnormalities, and may sometimes be responsible for various neurological disorders (see Bracard, 1983, for review).
