An ischemic stroke is a blockage of a blood vessel that deprives the brain of oxygen-rich blood. It is the most common type of stroke, accounting for approximately 80 to 85 percent of all strokes. An ischemic stroke can be caused by 1) an embolism, a sudden obstruction by a particle in a blood vessel; or 2) a thrombosis, a blood clot that has formed in a blood vessel over time.
Stroke Overview »
An ischemic stroke is caused by a clot or other blockage within an artery leading to the brain. Like the rest of the body, the brain relies on its arteries to bring fresh blood, with oxygen and nutrients, from the heart and lungs. A blocked artery means neurons (cells in the brain) will not receive enough oxygen and glucose to continue to function. If the artery remains blocked for more than a few minutes, the brain cells may die. This is why immediate medical treatment is crucial. A stroke can be classified as embolic or thrombotic.
In an embolic stroke, a blood clot forms somewhere in the body (usually the heart or carotid artery) and travels through the bloodstream to the brain. Once in the brain, the clot eventually travels to a blood vessel small enough to block its passage. The clot lodges there, blocking the blood vessel and causing a stroke. The medical word for this type of blood clot is embolus.
In a thrombotic stroke, blood flow is impaired because of a primary blockage to one or more of the arteries supplying blood to the brain. The process leading to this blockage is known as thrombosis. Strokes caused in this way are called thrombotic strokes.
Signs and Symptoms
Signs and symptoms of an ischemic stroke include: Sudden weakness or numbness of the face, arm or leg, usually on one side of the body, difficulty speaking or understanding others, decreased or blurred vision in one or both eyes, sudden, severe headaches and/or unexplained loss of balance or dizziness.
Transient Ischemic Attack (TIA)
Transient ischemic attacks, or TIAs, are brief episodes of stroke symptoms. TIAs are caused by the temporary interruption of blood flow to the brain. A TIA can last for just a few seconds, but its symptoms can persist for as long as 24 hours.
Treatment for Acute Stroke
Tissue Plasminogen Activator (tPA) is a clot-busting drug and is the only drug approved by the U.S. Federal Drug Administration to treat acute ischemic stoke. It works by restoring blood flow in the brain by dissolving brain clots that are causing decreased blood flow (ischemia).
TPA is proven to improve patient outcomes when administered for an acute ischemic stoke, one major risk associated with tPA is bleeding. Therefore, patients who have bleeding disorders, recent surgery, traumatic injury, or patients with intracerebral hemorrhage may not receive tPA.
TPA can be delivered either intravenously through an IV or intra-arterially. IV tPA is time-specific and works best when given within 90 minutes of symptoms onset, but can be administered up to four and a half hours after symptom onset. TPA is given intravenously as a one-time dose over a period of 60 minutes.
Intra-arterial tPA is administered directly into the brain where the blood clot is located via a catheter that is threaded up from the groin into the brain. The procedure takes place in the neuron-radiology department and is performed by a neuro-interventionalist, a physician who specializes in endovascular techniques and stroke treatments.
Other mechanical devices may also be used to retrieve the blood clot such as the MERCI retrieval device. The device is attached to a long guide wire that is threaded up from the groin into the brain and attaches to the blood clot. The physician is then able to pull the clot out of the affected artery thus restoring blood flow. When using intra-arterial tPA or mechanical clot retrieval devices, the treatment time window can be extended up to six hours or more from time of symptom onset.
Patients who receive tPA are admitted to the Neuroscience Intensive Care Unit (NSICU) for close monitoring of vital signs and symptoms of bleeding. They also undergo frequent neurological exams.