What is an ischemic stroke?
Ischemic stroke occurs most often when a blood vessel supplying blood to the brain is blocked or obstructed by a blood clot or fatty deposit or any mix thereof. The brain relies on a constant supply of blood to provide it with oxygen and nutrients and to carry away carbon dioxide. When the blood flow, and therefore this supply, becomes interrupted or blocked, brain cells can quickly begin to stop working. If the blockage lasts for more than a couple of minutes, these cells can die, leading to serious damage to the brain. Depending on the location and supply area of the affected vessel, the damage can range from mildly debilitating to severe or life-threatening.
There are two main types of stroke: the ischemic one introduced above, and the hemorrhagic one. Ischemic stroke is the most common, accounting for roughly 85 percent of all cases in the United States. If prompt treatment is received, the effects of a stroke can be managed in many cases. However, in some cases, ischemic stroke can lead to long-term disability and mortality, i.e. a person dying because of the condition.
Symptoms of ischemic stroke
In most cases, the symptoms of an ischemic stroke will appear suddenly, within seconds or minutes. Because people experiencing a stroke require immediate treatment, it is important to be aware of the immediate signs and symptoms and take action without delay.
- Face. Weakness or drooping of the face, usually limited to or more pronounced on one side.
- Arm. Numbness, weakness or strange sensations, e.g. pins and needles, in one or both arms.
- Speech. Difficulty speaking or slurred speech, mumbling or not being able to speak at all.
- Time to call the emergency services. The sooner an ambulance is called, the better the chances of a successful recovery.
Other symptoms of ischemic stroke may include:
- Weakness or numbness on one side of the body
- Difficulty walking or getting up, e.g. from a chair or out of bed
- Dropping to the floor
- Sudden, new tinnitus - a ringing, swishing or whooshing sound in the ears
- Nausea and vomiting
- Soreness in the neck or face
- Vision problems, i.e. double vision or an inability to see parts of one’s surrounding or anything at all
- Confusion, sudden sleepiness, difficulty waking up
- Sudden urinary incontinence, newly occurring with other symptoms
The symptoms that are experienced will depend on what part of the brain is affected and may vary in severity from person to person.
Causes of ischemic stroke
- Small vessel disease
- Atrial fibrillation
In rarer cases:
- Arterial dissection, e.g. due to trauma or fibromuscular dysplasia
- Certain blood clotting problems called coagulopathies, e.g. polycythemia or as a result of hormonal medications
- Inflammation of the blood vessels, known as vasculitis, e.g. giant cell arteritis
- Sickle cell disease
A condition occurring when fatty deposits – called plaques or atheromas – build up on the walls of the arteries, causing them to become narrower, harder and more easily blocked.
Small vessel disease
Small vessel disease involves the collection of deposits within the small blood vessels of the brain. As these deposits develop, the blood vessels become harder and can eventually become completely blocked. It occurs primarily as a result of high blood pressure and diabetes.
Atrial fibrillation is a type of irregular heartbeat that can cause blood clots in the heart. These then enter the bloodstream and reach other parts of the body, e.g. the brain. If this happens, ischemic stroke can result.
Arterial dissection is a rarer cause of stroke. The condition occurs when tears in the lining of the arteries develop and blood is able to get in between the different layers of the artery wall. As blood builds up, a blood clot can form and lead to a stroke.
Though uncommon, certain blood clotting problems, where the blood clots too quickly, may cause a stroke. One example is polycythemia vera, a rare condition where the body produces too many red blood cells. This causes blood clots to form more easily - potentially leading to an ischemic stroke.
This is the term for an inflammation in the blood vessels, which may develop as the result of an infection, another health condition or an adverse reaction to medication. Vasculitis may cause the blood vessels to narrow or even become blocked, potentially leading to an ischemic stroke. One type of vasculitis is giant cell arteritis, a condition that affects the arteries in the head and upper part of the body.
Sickle cell disease
This genetic condition causes the shape of red blood cells to be abnormal. These red blood cells do not last very long, leading to anemia, and they can also block blood vessels - potentially leading to a stroke.
Ischemic stroke risk factors
There are a number of factors which can increase a person’s likelihood of experiencing an ischemic stroke. These include factors which a person themselves or treatment can change over time, and factors that cannot be changed.
Factors that can be changed over time (modifiable factors) include:
- High blood pressure - this is the strongest single risk factor for the development of both ischemic and hemorrhagic stroke
- Atherosclerosis (fatty deposits in the arteries)
- Hypercholesterolemia (high cholesterol levels in the blood)
- Obesity and physical inactivity
- High alcohol consumption
- Tobacco use
- Illicit (illegal) drug use
- Cardiovascular (heart and heart vessel) diseases
- Blood clotting disorders
- Oral contraceptives (birth control pills)
- Postmenopausal hormone intake
Factors that cannot be changed over time (non-modifiable factors) include:
- Being over the age of 40
- Being male
- Ethnicity - African Americans, Native Americans, Alaska Natives, and Hispanic people are at higher risk
- Family history of stroke, heart or heart vessel conditions
- Genetic disorders, e.g. sickle cell disease
Recent childbirth also leads to a somewhat increased risk of stroke, due to an increased risk of blood clotting problems.
Although the above factors may make a stroke more likely, people who do not possess any risk factors may also experience a stroke.
Diagnosing ischemic stroke
Anyone displaying any signs of stroke should immediately be taken to a hospital emergency room for diagnosis. Typically, this will first involve a physical examination, that may include an ECG to rule out atrial fibrillation and a review of the person’s medical history, before a number of other scans and tests.
Brain scans can help establish whether a stroke is ischemic or hemorrhagic, as well as its severity and the part of the brain affected. CT and MRI scans are the most commonly used types of scans for people suspected of having a stroke.
- CT scans allow doctors to create a 3D image of the brain, enabling them to see what section of the brain is being affected and whether a stroke is ischemic or hemorrhagic. A CT scan is, in general, the best option (gold standard) and is quicker than an MRI scan. However, it may not be able to detect blood vessel blockages in the very early stages. Within the first 30 minutes of the blockage, an MRI will most likely produce more reliable results.
- MRI scans use radio waves and a strong magnetic field to build a detailed image of the interior of the body. In the first 30 minutes from the onset of stroke symptoms, an MRI may be able to detect blood vessel blockages and stroke damage more accurately than a CT scan.
Brain scans should be carried out as quickly as humanly possible when the person reaches the hospital, allowing for prompt and appropriate treatment to be received.
Heart and blood vessel tests
Various heart and blood vessel tests can be used to establish the cause of a stroke. Two of the most common are carotid ultrasound and echocardiography.
- Carotid ultrasound is able to identify any blockages or clots in the arteries running along the neck and leading to the brain.
- Echocardiography is a kind of ultrasound that can produce a detailed picture and provide certain measurements of the heart, enabling doctors to locate any issues that may have contributed to the stroke.
Ischemic stroke treatment
The aim of treatment for ischemic stroke is to restore blood flow as quickly as possible to the affected area of the brain. This will usually involve a combination of different medications while the person is being treated in the hospital and possibly others, once they are at home or at a rehabilitation facility. Some of these will only need to be taken for a short period of time, while others may be used to prevent future recurrences of stroke and will require long-term use.
Some of the most commonly prescribed medications for treating an ischemic stroke include:
- Alteplase: A type of medication used to dissolve clots and restore blood flow to the brain. Alteplase is most effective when administered as soon as possible after the stroke has taken place. It will most often be given through a drip into a person’s veins, from where it will spread through the entire blood vessel system. Sometimes, the medication has to be given directly into an artery, close to the obstruction - this procedure is then called intra-arterial thrombolysis. Alteplase can only be used for ischemic strokes, not if there is bleeding into the brain - as in the case of a hemorrhagic stroke. To confirm that the stroke is indeed ischemic in nature, alteplase can only be prescribed following a brain scan.
- Antiplatelets: This type of medication helps to prevent further clots from forming. Aspirin is the most common antiplatelet, as well as a painkiller, though others, such as clopidogrel and dipyridamole, are also sometimes used.
- Anticoagulants: This type of medication, sometimes called blood thinners, includes drugs like warfarin or heparin and can be used to help reduce the chances of a stroke recurring by preventing blood clots from forming. Anticoagulants are sometimes also used in the acute treatment of a stroke.
In some cases, usually those involving a blood clot in one of the brain’s larger arteries, a procedure known as a mechanical thrombectomy may be used. During a thrombectomy, a catheter is inserted into the affected artery, through which a device, known as a stent retriever, is able to remove the clot in the artery in the brain. The procedure can be done under general or local anesthetic and is most effective when carried out shortly after the stroke has taken place. The procedure will usually be carried out in addition to IV thrombolytic therapy, e.g. with alteplase.
UpToDate. “Patient education: Stroke symptoms and diagnosis.” July 7, 2017. Accessed December 18, 2017. ↩ ↩ ↩
Southern Cross Medical Library. “Giant cell arteritis - symptoms, diagnosis, treatment.” December, 2017. Accessed March 13, 2018. ↩
The Internet Stroke Center. “Stroke as a Complication of Sickle Cell Disease.” Accessed March 13, 2018. ↩