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Acute Ischemic Stroke

A. JABBAR DENTAL CLINIC KARACHI

Sadia Khan

Overview

An ischemic stroke is characterized by a blockage of blood supply to the brain, resulting in cell death in the region.&nbsp; 
Stroke is a major cause of disability worldwide and the fifth most common cause of death in the United States.

According to the CDC, 795,000 Americans experience a stroke every year<a href="#accordion">[4] [9]</a>. Moreover, every 40 seconds, a person in the United States suffers a stroke<a href="#accordion">[9]</a>. And every 3.5 minutes, a person loses their life due to the condition<a href="#accordion">[9]</a>. Around 610,000 of these cases occur in people with a history of stroke<a href="#">[9]</a>.

In Pakistan, the exact incidence and prevalence of stroke remain unknown. A recent review found an incidence of 95 per 100,000 persons per year between 2000 and 2016<a href="#accordion">[10]</a>. Another study, conducted among people in Khyber Pakhtunkhwa, Pakistan, reported a 1.2% prevalence of stroke<a href="#accordion">[11]</a>.&nbsp;

The prevalence of stroke typically increases with age. Furthermore, women are at a greater risk compared to men<a href="#accordion">[1]</a>.

Strokes can be classified into ischemic, subarachnoid, or hemorrhagic. Ischemic stroke is the most common type, accounting for 87% of all stroke cases<a href="#accordion">[5]</a>. An acute ischemic stroke is a medical emergency and is caused by reduced blood flow to a part of the brain. <a href="https://merisehat.pk/disease/hypertension-57">Hypertension</a>, <a href="https://merisehat.pk/disease/diabetes-type-1-and-2">diabetes</a>, hypercholesterolemia, and cardiovascular disease are the most common modifiable risk factors of ischemic stroke. People experiencing an acute ischemic stroke will typically present with a facial droop, weakness or numbness in the arm, confusion, and difficulty speaking.

A transient ischemic attack (TIA) may sometimes precede an acute ischemic stroke. Also called a &lsquo;mini-stroke&rsquo;, it is a temporary blockage of blood vessels in the brain. Symptoms are similar to that of an ischemic stroke and include vision problems, severe headaches, loss of balance, and numbness or weakness in one side of the body. These symptoms last a few minutes and typically resolve in 24 hours. However, TIA increases the risk of a stroke occurring later. 
&nbsp;

Note: Acute ischemic stroke is a medical emergency. If someone is experiencing symptoms, a healthcare professional should be contacted immediately. 
&nbsp;

There are essentially two main types of ischemic stroke: 
&nbsp;

<ul>
	<li>Thrombotic Stroke: Also called an atherosclerotic stroke, it results from a blood clot forming in the cerebral arteries and causing an obstruction. 
	&nbsp;</li>
	<li>Embolic Stroke: An embolic stroke is a condition in which a clot travels from somewhere else in the body to the brain. This in turn disrupts blood flow to the brain cells. Atrial fibrillation can cause blood clots in the heart, which can then result in an embolic stroke. 
	&nbsp;</li>
</ul>

Signs and Symptoms

In an acute ischemic stroke, signs and symptoms typically develop rapidly and evolve over hours. The symptoms typically depend on the cerebral artery that is affected. Common signs and symptoms include: 
&nbsp;

<ul>
	<li>Trouble Speaking&nbsp;And Understanding: Confusion, slurring of words, and an impaired understanding of speech are common among stroke patients. 
	&nbsp;</li>
	<li>Paralysis Or Numbness Of The Face, Arm, Or Leg: People may present with a facial droop and sudden weakness or paralysis in the arm or leg. Paralysis mostly affects one side of the body but in rare cases can affect both sides or all four limbs. 
	&nbsp;</li>
	<li>Visual Impairment: Individuals may also experience a sudden onset of blurred or blackened vision, in one or both eyes. Double vision, or diplopia, is also common. 
	&nbsp;</li>
	<li>Headache: People who are going through a stroke may suddenly get a severe headache, which can be associated with vomiting, dizziness, or altered consciousness. 
	&nbsp;</li>
	<li>Trouble Walking: People may present with loss of balance and coordination and sudden dizziness. 
	&nbsp;</li>
</ul>

Note: If you notice a sudden onset of facial droop, inability to raise both arms or difficulty speaking, contact a healthcare professional immediately. 
&nbsp;&nbsp;

Causes

An acute ischemic stroke is the result of a thrombotic or an embolic event which in turn leads to a diminished blood supply in the brain. A thrombotic event is essentially an obstructed blood vessel because of an abnormality in the vessel itself. This is usually due to <a href="https://merisehat.pk/disease/atherosclerosis">atherosclerosis </a>where fatty deposits called plaque narrow the arteries. Thus, reducing the flow of oxygen and nutrients to the brain cell.

Whereas, in an embolic event, a blood clot from elsewhere in the body travels via the vessels to the brain. 
&nbsp;

In the past, doctors have used the acronym F.A.S.T. for assessing if someone is having a stroke. The letters stand for Face, Arms, Speech, and Time. But, research carried out by physicians at the University of Kentucky Stroke Center reported that F.A.S.T. can miss around 14% of stroke diagnoses<a href="#accordion">[7]</a>. This is because there are a lot more common symptoms of an acute stroke except face drooping, arm weakness, or slurred speech. Hence, another acronym was formulated to improve accuracy.

The new acronym, B.E. F.A.S.T. has led to the number of missed cases going down to 4%<a href="#accordion">[7]</a>. 
&nbsp;

<h5>B:&nbsp;BALANCE</h5>

Someone going through a stroke may have unexplained, sudden balance or coordination problems. 
&nbsp;

<h5>E: EYES</h5>

A person going through a stroke will be noticing a blurred, double, or complete loss of vision. Vision problems may appear in one or both eyes. 
&nbsp;

<h5>F: FACE</h5>

A facial droop is a common sign of a stroke. Doctors may ask the person to smile and notice one side of the face drooping. Depending on which brain hemisphere is affected, facial weakness will occur on the opposite side. 
&nbsp;

<h5>A: ARMS</h5>

People may experience muscle weakness. Doctors will ask the patient to raise both arms and in a stroke, the individual will have difficulty doing so. One may drift down.&nbsp; 
&nbsp;

<h5>S: SPEECH</h5>

People experiencing a stroke have trouble speaking or understanding speech. The doctor may ask the person to repeat a sentence and assess whether they are repeating it correctly. 
&nbsp;

<h5>T: TIME TO GET HELP</h5>

Acute ischemic stroke is a medical emergency. If a person presents with any of the above symptoms, a healthcare professional should be contacted immediately. 
&nbsp;

Diagnosis

To reach a diagnosis of acute ischemic stroke, the doctor will rely on a physical exam, history, and various tests. Based on the findings of the physical exam and the patient&rsquo;s symptoms, the doctor will order brain scans. 
&nbsp;

CT Scan - A non-contrast computed tomography (CT) scan is the first imaging study used for detecting strokes. It helps differentiate ischemic stroke from tumors or bleeding in the brain. 
&nbsp;

MRI Scan - This imaging scan provides a detailed view of the brain and can also assess for early cerebral edema. However, it is not used in emergencies as many patients have contraindications, such as pacemakers and implants. 
&nbsp;

Carotid Ultrasound - Using sound waves, the test provides a detailed image of the carotid arteries. It can help detect plaque formation in the vessels. 
&nbsp;

Cerebral Angiogram - This uncommon test involves inserting a catheter through an incision near the groin and guiding it through the major arteries into the carotid or vertebral artery. A dye is then injected to visualize the vessels under X-ray imaging. Thus, providing a detailed view of the neck and brain vessels. 
&nbsp;

Echocardiogram - This can help detect the source of blood clots in the heart that may have resulted in an embolic stroke. 
&nbsp;

Lumbar Puncture - If a CT scan fails to show any findings, doctors may perform a lumbar puncture to rule out meningitis or subarachnoid hemorrhage. 
&nbsp;

Laboratory tests are also carried out to aid in the diagnosis and assessment of ischemic stroke. These include the following: 
&nbsp;

<ul>
	<li>Complete Blood Count (CBC): A CBC is a baseline evaluation that is used to find a cause for the stroke which may include polycythemia, thrombocytosis, and leukemia. It also provides information on any illness and confirms the absence of thrombocytopenia when the healthcare provider is considering fibrinolytic therapy. 
	&nbsp;</li>
	<li>Biochemistry: It is also a baseline study that may provide information if the patient has a condition that can mimic a stroke. These conditions include hypoglycemia (low glucose level), hyponatremia (low sodium levels), or even comorbidity, such as diabetes and renal insufficiency. 
	&nbsp;</li>
	<li>Coagulation Studies: Doctors typically advise coagulation studies when planning to treat patients using fibrinolytics or anticoagulants. 
	&nbsp;</li>
	<li>Cardiac Biomarkers: This is crucial as it is associated with cerebral vascular disease and coronary artery disease. 
	&nbsp;</li>
	<li>Toxicology Screening: Many toxic substances have the ability to resemble states that may look much like a stroke. While this may seem an unimportant part of history, it should be noted that treatment in such cases is usually an antidote and not the typical treatment of stroke.</li>
</ul>

<ul>
	<li>Pregnancy Testing: It is extremely important to know if the patient who has a stroke is pregnant or not as it may alter the treatment agents as well. A urine pregnancy test is sufficient to make the confirmation. Recombinant tissue-type plasminogen activator (rt-PA) is typically avoided in pregnancy as it is a pregnancy class C agent. 
	&nbsp;</li>
</ul>

Imaging scans such as CT and MRI scans can help determine how old the stroke is<a href="#accordion">[3]</a>.

<ul>
	<li>Early Hyperacute: 0 to 6 hours after the onset</li>
	<li>Late Hyperacute: 6 to 24 hours after the onset</li>
	<li>Acute: 24 hours to 1 week after the onset</li>
	<li>Subacute: 1 to 3 weeks after the onset</li>
	<li>Chronic: More than 3 weeks after the onset 
	&nbsp;</li>
</ul>

Treatment

<h5>Emergency IV Medication </h5>

The mainstay treatment for an ischemic stroke is intravenous tissue plasminogen activator (tPA), which has the ability to dismantle clots. According to the 2018 guidelines laid out by the American Heart Association (AHA) and the American Stroke Association (ASA), it is stated that tPA works most efficiently when it is administered within four and a half hours from the initiation of a stroke<a href="#accordion">[5]</a>. It should be ensured that the drug is administered no later than five hours after the onset of the stroke. 
&nbsp;

As tPA may cause bleeding, people with the following factors are not eligible:

<ul>
	<li>Hemorrhagic stroke</li>
	<li>Previous bleeding in the brain</li>
	<li>A much recent and major surgery</li>
	<li>Head injury</li>
	<li>Usage of anticoagulants 
	&nbsp;</li>
</ul>

<h5>Emergency Endovascular Procedures</h5>

Endovascular therapy treats ischemic stroke directly inside the blood vessel. In some cases, a catheter may be inserted via an artery in the groin to the brain. tPA is then delivered directly to the area of the stroke.

If tPA fails to work, a surgical approach is taken to remove the clots mechanically using a stent retriever. However, this treatment modality also comes with a designated window and that is up to 24 hours of the stroke&rsquo;s onset. The procedure is mostly reserved for people with large clots that cannot be completely dissolved with tPA.&nbsp;

Long-term treatment for an ischemic stroke will include aspirin or an anticoagulant which can avoid the production of clots. Furthermore, if the ischemic stroke is secondary to a condition like high blood pressure or atherosclerosis, treatment of these conditions will also be required. These treatments may include a stent to open a clogged artery or medicines like statins to reduce blood pressure. 
&nbsp;

Once an ischemic stroke has taken place, hospitalization may be required for further assessments, at least for a couple of days. This is because a stroke has the potential to cause paralysis or extreme weakness. Lastly, sometimes rehabilitation may also be needed after the treatment has been administered to improve functionality 
&nbsp;

An acute ischemic stroke is a medical emergency. If left untreated or treatment is delayed, it can lead to several complications. These include: 
&nbsp;

<ul>
	<li>Permanent weakness or numbness</li>
	<li>Difficulty talking or swallowing</li>
	<li>Garbled (incomprehensible) speech</li>
	<li>Seizures</li>
	<li>Memory deficits and difficulty in general understanding 
	&nbsp;</li>
</ul>

Several circulatory conditions can increase the risk of clots and plaque formation in the vessels of the brain. The following are some common risk factors of acute ischemic stroke: 
&nbsp;

<ul>
	<li>High blood pressure</li>
	<li>Atherosclerosis</li>
	<li>High cholesterol</li>
	<li>Atrial fibrillation</li>
	<li>History of a heart attack</li>
	<li>Obstructive sleep apnea</li>
	<li>Sickle cell anemia</li>
	<li>Any clotting disorders</li>
	<li>COVID-19 infection</li>
	<li>Congenital heart defects 
	&nbsp;</li>
</ul>

Some other risk factors include:

<ul>
	<li>Diabetes</li>
	<li>Smoking</li>
	<li>Birth control pills</li>
	<li>Being overweight or obese</li>
	<li>Alcohol consumption</li>
	<li>Use of drugs like cocaine or methamphetamines (crystal meth) 
	&nbsp;</li>
</ul>

The following are the non-modifiable risk factors of acute ischemic stroke:

<ul>
	<li>Age - People older than 55 years of age are at an increased risk of stroke.</li>
	<li>Race - The incidence of acute ischemic stroke is higher in African Americans and Hispanics.</li>
	<li>Gender - Although men have a higher risk of stroke, women are more likely to die from the disease.</li>
	<li>Fibromuscular Dysplasia</li>
	<li>Family History - A family history of stroke, heart attack, or transient ischemic attack also increases one&rsquo;s risk of acute ischemic stroke.</li>
	<li>History - A history&nbsp;of migraine headaches. 
	&nbsp;</li>
</ul>

The following measures can help reduce the risk of stroke:

<ul>
	<li>Quitting smoking and alcohol</li>
	<li>A healthy diet with low saturated and trans fats</li>
	<li>Regular exercise</li>
	<li>Losing weight</li>
	<li>Controlling hypertension</li>
	<li>Managing diabetes</li>
	<li>Avoiding illegal drugs</li>
	<li>Treating obstructive sleep apnea 
	&nbsp;</li>
</ul>

Moreover, anti-platelet drugs (e.g., aspirin, clopidogrel) and anticoagulants (e.g., heparin, warfarin) may be prescribed in patients who&rsquo;ve had an ischemic stroke. These medications can reduce the risk of another stroke. 
&nbsp;

Key Points

<ul>
	<li>Strokes can be classified into ischemic, subarachnoid, or hemorrhagic. Ischemic stroke is the most common type, accounting for 87% of all stroke cases.</li>
	<li>An acute ischemic stroke is a medical emergency and is caused by reduced blood flow to a part of the brain.</li>
	<li>Thrombotic event is essentially an obstructed blood vessel because of an abnormality in the vessel itself. This is usually due to atherosclerosis where fatty deposits called plaque narrow the arteries. Thus, reducing the flow of oxygen and nutrients to the brain cell.</li>
	<li>In an embolic event, a blood clot from elsewhere in the body travels via the vessels to the brain.</li>
	<li>In an acute ischemic stroke, signs and symptoms typically develop rapidly and evolve over hours. The symptoms typically depend on the cerebral artery that is affected.</li>
	<li>Hypertension, diabetes, hypercholesterolemia, and cardiovascular disease are the most common modifiable risk factors of ischemic stroke.</li>
	<li>People experiencing an acute ischemic stroke will typically present with a facial droop, weakness or numbness in the arm, confusion, and difficulty speaking.</li>
	<li>The acronym, B.E. F.A.S.T., is used to screen people for signs and symptoms of stroke.</li>
	<li>A non-contrast computed tomography (CT) scan is the first imaging study used for detecting strokes. It helps differentiate ischemic stroke from tumors or bleeding in the brain.</li>
	<li>The aim of treatment in acute ischemic stroke is to preserve tissue in areas of decreased perfusion. Other than restoring blood flow, the doctor may attempt to decrease any pressure buildup in the brain. Restoring blood flow can help prevent any irreversible brain injury.</li>
	<li>The mainstay treatment for an ischemic stroke is the intravenous tissue plasminogen activator (tPA), which has the ability to dismantle clots. It works most efficiently when it is administered within four and a half hours from the initiation of a stroke</li>
	<li>If tPA fails to work, a surgical approach is taken to remove the clots mechanically using a stent retriever.</li>
	<li>&nbsp;If left untreated or treatment is delayed, acute ischemic stroke can lead to complications, such as permanent weakness, difficulty talking or swallowing, seizures, and memory deficits. 
	&nbsp;</li>
</ul>

[1] Hui C, Tadi P, Patti L. Ischemic Stroke. [Updated 2022 Jun 2]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-.

[2] Stroke. Mayo Clinic.

[3] Hacking C. Ischemic stroke: Radiology reference article. Radiopaedia Blog RSS.

[4] Edward C Jauch MD. Ischemic stroke. Practice Essentials, Background, Anatomy.

[5] Hersh E. Ischemic stroke: Symptoms, treatment, recovery, and more. Healthline.

[6] Types of stroke: Ischemic, hemorrhagic, and Tia. WebMD.

[7] B.E. F.A.S.T. can help spot a stroke: Health Focus SA: University Health. University Health System.

[8] Paciaroni M, Bogousslavsky J. Primary and secondary prevention of ischemic stroke. European Neurology. 2010;63(5):267-278. doi:10.1159/000285183.

[9] Stroke facts. Centers for Disease Control and Prevention.

[10] Khan MI, Khan JI, Ahmed SI, Haq U (2018) The Epidemiology of Stroke in a Developing Country (Pakistan). J Neurol Stroke 8(1): 00275. DOI: 10.15406/jnsk.2018.08.00275.

[11] Sherin A, Ul-Haq Z, Fazid S, Shah BH, Khattak MI, Nabi F. Prevalence of stroke in Pakistan: Findings from Khyber Pakhtunkhwa integrated population health survey (KP-IPHS) 2016-17. Pak J Med Sci. 2020;36(7):1435-1440. doi:10.12669/pjms.36.7.2824