loss of blood supply to portions of the brain can occur for a variety of reasons. a blood vessel can get blocked and blood supply to a part of the brain is lost or a blood vessel leaks blood into the brain (brain hemorrhage). most commonly the blood vessel is blocked. the blockage can be caused by a blood clot that forms in the blood vessel (thrombosis) or it can be caused by a clot or debris that floats downstream (embolus). atherosclerosis or "hardening of the arteries" can cause fatty plaque formations in the blood vessel wall. the plaque can rupture and cause a small blood clot to form and occlude the blood vessel. a blockage can also occur when debris from narrowing of a carotid artery breaks off and floats downstream to cause the occlusion. sometimes in people with an irregular heartbeat called atrial fibrillation small blood clots can form and travel to the brain to cause the obstruction. brain hemorrhage or bleeding in the brain can be due to an aneurysm a weak spot in a blood vessel that ruptures and spills blood into the brain tissue or it may be due to spontaneous bleeding caused by poorly controlled hypertension (high blood pressure). such bleeding more commonly results in a true stroke as opposed to a tia.
what are the causes of transient ischemic attack or tia?