Atherosclerosis

The most common cause of thrombotic occlusion, atherosclerosis typically effects large arterial vessels at the base of the brain as well as the internal carotid artery in its extracranial portion. The incidence of central nervous system atherosclerosis parallels that of systemic atherosclerosis and CNS atherosclerosis historically is identical to that elsewhere in the body. The long-term presence of atherosclerosis will influence the development of collateral circulation providing some "back-up" to total occlusion.

A second cause of thrombotic occlusion is a group of diseases collectively termed the arteritidies -- caused by several diseases each of which produces a similar pathologic picture. Unlike an acute atherosclerotic occlusion which typically involves a single medium-large sized artery, arteritis usually effects multiple, small-medium sized arteries and causes focal hemorrhages. Some of the causes of arteritis are: collagen vascular disease, fungal infections, tuberculosis, syphilis, sarcoid, and meningitis.

Systemic diseases can also cause central nervous system arterial thrombic occlusion.  Diseases such as sickle cell anemia and polycythemia may produce hyperviscosity and result in vascular occlusion.

Various coagulopathies such as thrombotic thrombocytopenic purpura and diffuse intravascular coagulation may also produce arterial occlusions.