Interesting basis of vertebrobasilar arterial territory

Vertebrobasilar arterial territory nourishes one-quarter of human brain. It constitutes some vital and strategic parts of the central nervous system. A number of keywords (vertebral, basilar, artery, and territory) were searched in MEDLINE (Ovid and PubMed) as well as Google, ProQuest, Scopus, Cochrane Library, and Science Direct online electronic search engines. Only articles containing all keywords were included. The final search was performed on October, 1, 2012. We also reviewed archives of libraries in Mashhad University of Medical Sciences (Iran) for all anatomy, embryology, neurology, and neuroscience books and journals about vertebrobasilar arterial territories. The vertebrobasilar arterial (VA) system has a high incidence of variations, anomalies, and persistent fetal vessels. Two important anatomic facts explain why VA origin lesions seldom cause chronic hemodynamically significant low flow to the vertebrobasilar system. First, the VAs are paired vessels that unite to form a single basilar artery. Second, the extracranial VA gives off numerous muscular and other branches as it ascends in the neck. Thus, in the VA system, there is much more potential for development of adequate collateral circulation. Even when there is bilateral occlusion of the VAs at their origins, patients do not often develop posterior circulation infarcts. VA origin disease is more benign than ICA origin disease from hemodynamic aspect. This important point could make influence in therapeutic interventional decisions in asymptomatic VA origin stenosis.