[The importance of Willis ring as valvular mechanism in cerebral circulation in patients with different degree of internal carotid artery occlusion].

Cerebrovascular deseases , cerebral vessels deseases, represents one of the greatest problems of humankind. The reasons are not just the high incidence and relatively high prevalence of letal outcomes in the acute faze of the desease, but also high level of disfunctionality caused by this disease in numerous patients who survived cerebrovascular insult and haemorraghe The onset, course and outcome of cerebrovascular diseases depends among other things on the possibility o f colateral brain circulation establishment. Willis ring onthe base of the brain is the most important anastomosis between circulation in both carotid arteries and basilar artery.