Stroke A sudden loss of brain function caused by a blockage or rupture of a blood vessel of the brain, resulting in necrosis of brain tissue and characterized by loss of muscular control, weakening or loss of sensation or consciousness, dizziness, slurred speech, or other symptoms that vary with the extent and severity of brain damage. Also called cerebrovascular accident or cerebral infarction .
Ischemic strokes are those that are caused by interruption of the blood supply, while hemorrhagic strokes are the ones which result from rupture of a blood vessel. Strokes can be classified into two major categories: Ischemic and Hemorrhagic About 87% of strokes are caused by ischemia, and the remainder by hemorrhage.
Ischemic Strokes Brain ischemia followed by cerebral infarction In an ischemic stroke , blood supply to part of the brain is decreased, leading to dysfunction of the brain tissue in that area. There are four reasons why this might happen: <ul><li>Thrombosis </li></ul><ul><li>Embolism </li></ul><ul><li>Systemic hypoperfusion </li></ul><ul><li>Venous thrombosis. </li></ul>
In thrombotic stroke a thrombus ( blood clot ) usually forms around atherosclerotic plaques. Since blockage of the artery is gradual, onset of symptomatic thrombotic strokes is slower. Cerebral Thrombosis - blood flow is blocked by a narrow or closed artery.
Two types of thrombosis can cause stroke: Small vessel disease involves the smaller arteries inside the brain such as branches of the circle of Willis, middle cerebral artery, stem, and arteries arising from the distal vertebral and basilar artery. Diseases that may form thrombi in the small vessels include atherosclerosis, arteriosclerosis, and hypertension. Large vessel disease involves the common and internal carotids, vertebral, and the Circle of Willis arteries. The most common causes of thrombi in the large vessels include atherosclerosis and vasoconstriction.
Cerebral Embolism - small part of an artery wall or a small blood clot from a diseased artery or heart travels to the brain. An embolic stroke refers to the blockage of an artery by an arterial embolus. The embolus is most frequently a thrombus, but it can also be a number of other substances including fat, air, cancer cells or clumps of bacteria.
Because an embolus arises from elsewhere, local therapy solves the problem only temporarily. Thus, the source of the embolus must be identified. Because the embolic blockage is sudden in onset, symptoms usually are maximal at start. Also, symptoms may be transient as the embolus is partially resorbed and moves to a different location or dissipates altogether. Emboli most commonly arise from the heart, especially from atrial fibrillation, but may originate from elsewhere.
Transient Ischemic Attack (T.I.A.) A temporary blockage of the blood supply to the brain, typically caused by an embolus and usually lasting ten minutes or less, during which dizziness, blurring of vision, numbness on one side of the body, and other symptoms of a stroke may occur. Also called ministroke .
Hemorrhagic strokes The result of an intracranial hemorrhage which is the accumulation of blood anywhere within the skull vault due to the rupture of a blood vessel. A distinction is made between intra-axial hemorrhage (blood inside the brain) and extra-axial hemorrhage (blood inside the skull but outside the brain). The two most commonly used terms to describe these events are: Cerebral Hemorrhage Subarachnoid Hemorrhage
Cerebral Hemorrhage – blood vessel to the brain ruptures and bleeds into surrounding brain tissue ( intra-axial ). Hypertension and associated arteriosclerosis are the main causes.
Subarachnoid Hemorrhage (SAH) – rupture of a cerebral aneurysm on the surface of the brain ( extra-axial ). This is often a hereditary condition.
An aneurysm is a localized, blood-filled dilation of an artery caused by disease or weakening of the vessel wall. In 85% of cases of spontaneous SAH, the cause is rupture of a cerebral aneurysm . Most cases of SAH are due to bleeding from small aneurysms, larger aneurysms (which are less common) are more likely to rupture. 
<ul><li>Symptoms for an aneurysm that has not ruptured: </li></ul><ul><li>Fatigue </li></ul><ul><li>Loss of perception </li></ul><ul><li>Loss of balance </li></ul><ul><li>Speech problems </li></ul><ul><li>Symptoms for a ruptured aneurysm: </li></ul><ul><li>Severe headaches </li></ul><ul><li>Loss of vision </li></ul><ul><li>Double vision </li></ul><ul><li>Neck pain and/or stiffness </li></ul><ul><li>Pain above and/or behind the eyes </li></ul>
Cranial aneurysms At the current time, there are two treatment options for brain aneurysms: surgical clipping or endovascular coiling .
Surgical clipping was introduced by Walter Dandy of the Johns Hopkins Hospital in 1937. It consists of performing a craniotomy, exposing the aneurysm, and closing the base of the aneurysm with a clip. The surgical technique has been modified and improved over the years. Surgical clipping remains the best method to permanently eliminate aneurysms.
Endovascular coiling was introduced by Guido Guglielmi at UCLA in 1991. It consists of passing a catheter into the femoral artery in the groin, through the aorta, into the brain arteries, and finally into the aneurysm itself. Once the catheter is in the aneurysm, platinum coils are pushed into the aneurysm and released. These coils initiate a clotting or thrombotic reaction within the aneurysm that, if successful, will eliminate the aneurysm.