Cerebrovascular Occlusion: A broad category of disorders characterized by impairment of blood flow in the arteries and veins which supply the brain. These include CEREBRAL INFARCTION; BRAIN ISCHEMIA; HYPOXIA, BRAIN; INTRACRANIAL EMBOLISM AND THROMBOSIS; INTRACRANIAL ARTERIOVENOUS MALFORMATIONS; and VASCULITIS, CENTRAL NERVOUS SYSTEM. In common usage, the term cerebrovascular disorders is not limited to conditions that affect the cerebrum, but refers to vascular disorders of the entire brain including the DIENCEPHALON; BRAIN STEM; and CEREBELLUM.