Brain & Nervous System Stroke Overview of Ischemic Stroke By Jose Vega MD, PhD Updated on April 17, 2024 Medically reviewed by Brigid Dwyer, MD Fact checked by Khara Scheppmann Print An ischemic stroke occurs when a blood clot blocks blood flow in a vessel that carries blood to the brain. A common risk factor for this type of stroke is high blood pressure. Approximately 87% of all strokes are ischemic strokes. Encyclopaedia Britannica / UIG / Getty Images Types There are two types of ischemic stroke: embolic stroke and thrombotic stroke. Embolic Stroke An embolic stroke occurs when an embolus, or a clot forms in either the heart or neck arteries and moves through the bloodstream. It is then carried in the bloodstream, blocking a blood vessel leading to or in the brain. Thrombotic Stroke A thrombotic stroke occurs when a blood clot, or thrombus, forms in an artery supplying blood to the brain. The blood clot blocks the flow of oxygen-rich blood to a portion of the brain. A thrombotic stroke may be preceded by one or more transient ischemic attacks (TIAs), also known as “mini-strokes.” A TIA is an "almost" or a "near" stroke. However, the area affected by the TIA is at risk of a more permanent blockage. Causes Ischemic strokes are most often caused by arteries becoming narrowed by fatty deposits, a condition known as atherosclerosis. Embolic strokes are largely due to atrial fibrillation. Diagnosis When a person shows symptoms of a stroke or has a TIA (transient ischemic attack), the doctor will examine the patient in order to make a diagnosis. After obtaining a medical history, the following diagnostic tests may be performed: Neurological examinationBlood tests including complete blood count, hemoglobin A1c, cholesterol panelComputed tomography (CT) scanMagnetic resonance imaging (MRI)Blood vessel imaging, which may include CT angiography, magnetic resonance angiography, carotid ultrasound, or transthoracic echocardiogram (TTE) Symptoms A person who is having a stroke may not notice that they are experiencing symptoms. If you think you are having stroke symptoms, or if you believe someone else is, a simple test is to think “FAST” and do the following: Face: Ask the person to smile. Does one side of their face droop?Arms: Ask the person to raise both arms. Does one of the arms drift downward or can they raise either of their arms?Speech: Ask the person to repeat a simple phrase. Is their speech slurred?Time: Seek immediate medical attention if you observe any of these signs. Other symptoms of an ischemic stroke include: Trouble understanding or speakingNumbness of the arm, face, or legBlurred or blackened vision in one or both eyesDouble visionSudden, severe headacheVomitingDizzinessDifficulty walkingLoss of balance or coordination Treatment Immediate treatment is required to limit the level of brain damage that results from the blockage in blood flow. Treatment with tissue plasminogen activator, or tPA, has been effective for patients with an ischemic stroke as long as the patient has received it intravenously within three hours of the onset of symptoms. Reducing Risk Factors While certain risk factors as age, gender, heredity, and ethnicity are uncontrollable, a patient can reduce their risk of stroke by beginning treatment that controls their risk factors and adjusts their lifestyle choices. Ways to control risk factors for a stroke include: Quitting smokingLosing weightIncreasing physical activityReducing alcohol intakeEliminating illegal drug use 6 Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. American Stroke Association. Ischemic stroke (clots). Johns Hopkins Medicine. Types of stroke. National Heart, Lung, and Blood Institute. Stroke diagnosis. American Stroke Association. Stroke symptoms. National Institute of Neurological Disorders and Stroke. Tissue plasminogen activator for acute ischemic stroke (Alteplase, Activase®). Centers for Disease Control and Prevention. Prevent stroke: what you can do. By Jose Vega MD, PhD Jose Vega MD, PhD, is a board-certified neurologist and published researcher specializing in stroke. See Our Editorial Process Meet Our Medical Expert Board Share Feedback Was this page helpful? Thanks for your feedback! What is your feedback? Other Helpful Report an Error Submit