Stroke (CVA) Latest Facts: Etiology, Types, Clinical Features and Treatment

A cerebrovascular accident (CVA) also called a brain stroke is one of the most common yet destructive disorders. It is broadly categorized into ischemic stroke and hemorrhagic stroke. Worldwide, stroke is the second leading cause of death, causing approximately 200,000 deaths each year in the United States alone and is also one of the chief causes of disability. As increases in the incidence of cerebrovascular diseases are proportional to increases in age, it has been projected that the number of strokes will increase as the population of elderly people grow, with researchers estimating a doubling in stroke-related deaths in the United States by the year 2030.

Stroke

Stroke: Image Courtesy of James Heilman, MD

A stroke is defined as a sudden onset of a neurologic deficit due to a focal vascular cause. Therefore, the definition of a stroke is chiefly clinical, and studies such as CT scan and MRI are used to support the preliminary diagnosis. The brain anatomy is highly complex, and thus the symptoms and signs of a brain stroke can be quite variable.

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Brain infarction is tissue death caused by diminished or absent blood supply lasting long enough to cause irreversible damage whereas ischemia simply means decreased blood supply to the tissues. The symptoms of ischemia are apparent within minutes of the onset as the neurons in our brain do not possess the ability to store glucose in the form of glycogen. Therefore, any interruption to blood supply can immediately result in an energy deficit.  However, if blood flow is restored early on, there is a good probability that the neurons and tissues will recover. In such a scenario, the symptoms are only transient and hence the condition is termed as a transient ischemic attack (TIA).

For a condition to be defined as TIA, there should be a complete resolution of all neurologic signs and symptoms within 24 h without any evidence of brain infarction on imaging. In contrast, stroke is said to have occurred if the neurologic signs and symptoms persist for longer than 24 h or brain infarction is seen on imaging tests. Intracranial hemorrhage is caused by either traumatic, aneurysms, dissections or hypertensive bleeding, with blood leaking directly into the brain. The neurological symptoms seen in intracranial bleeding is due to increased intracranial pressure, the toxic effects of the blood itself as well as the mass effect exerted on the brain structures.

Etiology of ischemic stroke

In acute management of an ischemic stroke, identifying the underlying cause has almost no role in terms of therapy. However, it is still essential to determine the etiology of ischemic stroke in order to prevent another episode of stroke. This is especially true for conditions with established treatment strategies such as atrial fibrillation and carotid atherosclerosis.

The clinical presentation and examination findings often establish the cause of stroke or narrow the possibilities to a few. The judicious use of laboratory testing and imaging studies completes the initial evaluation. Nevertheless, nearly 30% of strokes remain unexplained despite extensive evaluation.

Ischemic Stroke

Cardioembolism is responsible for ~20% of all ischemic strokes. Stroke caused by heart disease is primarily due to embolism of thrombotic material forming on the atrial or ventricular wall or the left heart valves. These thrombi then detach and embolize into the arterial circulation. The thrombus may fragment or lyse quickly, producing only a TIA. Alternatively, the arterial occlusion may last longer, producing a stroke. Embolic strokes tend to occur suddenly with maximum neurologic deficit present at onset. With reperfusion following more prolonged ischemia, petechial hemorrhages can occur within the ischemic territory. These are usually of no clinical significance and should be distinguished from frank intracranial hemorrhage into the region of the ischemic stroke where the mass effect from the hemorrhage can cause a significant decline in neurologic function.

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Emboli from the heart most often lodge in the intracranial internal carotid artery, the MCA, the posterior cerebral artery (PCA), or one of their branches; infrequently, the anterior cerebral artery (ACA) is involved. Emboli large enough to occlude the stem of the MCA (3–4 mm) lead to large infarcts that involve both deep gray and white matter and some portions of the cortical surface and its underlying white matter. A smaller embolus may occlude a small cortical or penetrating arterial branch. The location and size of an infarct within a vascular territory depend on the extent of the collateral circulation.

Hemorrhagic Stroke

Hypertension, trauma or rupture of a berry aneurysm can all lead to hemorrhagic brain stroke, which has a far worse prognosis than Ischemic stroke. Among the mentioned causes, hypertension is the most common cause of hemorrhagic stroke. Hemorrhagic stroke accounts for less than 20% of all cases of stroke but due to its poor outlook, it is a more feared subtype.

Types of Strokes

Types of Strokes

What are the risk factors of CVD?

As the most common type of stroke is an ischemic stroke which itself is caused mainly by atherosclerotic plaques blocking the blood supply to the brain, atherosclerosis is the most important and yet manageable risk factor of stroke. Risk factors for stroke are almost similar to the risk factors for heart attack, which itself manifests as a consequence of atherosclerotic plaques in a majority of cases. Atherosclerosis in itself is caused by the buildup of low-density lipids on the linings of the blood vessels, which can be prevented by controlling LDL levels, and also managing other associated comorbidities of metabolic syndrome such as hypertension, obesity, dyslipidemia, and diabetes. 

Important risk factors include:

  • Hyperlipidemia
  • Hypertension
  • Diabetes mellitus
  • Smoking
  • Excessive consumption of alcohol
  • Overweight and Obesity
  • Chronic pathologies of the cardiovascular system
  • Brain tumor

In addition, heredity, age-related changes, slower metabolism, or the period of menopause in women may also be a contributing factor.

Symptoms and Signs

CV is associated in the initial phases with symptoms such as:

  • Weakness in the face, arms, or legs
  • Difficulty in swallowing or speaking
  • Sudden onset headache
  • Changes in personality or aggressive behavior
  • Non-fluent speech, or inappropriate speech

As the symptoms progress, additional concerning symptoms may alert the patient of a serious underlying pathology. Such symptoms are:

  • Unstable gait or loss of consciousness
  • Motor disorders 
  • Visual impairments
  • Inability to produce speech

Possible long term complications

Pathological states of brain activity lead to the formation of changes in brain tissue, which is accompanied by mental and cognitive abnormalities:

  • Impaired memory, monoplegia, paraplegia or hemi-anesthesia
  • New onset of phobias with sensory hallucination
  • Ego-centricity with changes in personality and behavior
  • Disorientation in space, time, and person
  • Dementia, either retrograde or anterograde

What is TIA?

TIA i.e., Transient ischemic attack is characterized by a temporary disturbance of blood circulation resulting in transient symptoms that eventually lead to a complete recovery. In most cases, symptoms disappear within the first 24 hours. TIA although resolves in all cases it should not be ignored as many patients can eventually develop a more fatal cardiovascular accident that is not reversible. TIA can be taken as a warning sign of an underlying pathological blockage in blood supply that needs to be promptly investigated and treated. 

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How is Stroke diagnosed?

Cerebrovascular disease is often clinically diagnosed initially by a neurologist and a vascular surgeon. The focal neurological deficits visible in a patient can indicate the exact location of the stroke as well as the artery that has become blocked. The general condition is assessed with the ABC protocol that assesses the patient’s Airway, Breathing, and Circulation. Following a preliminary evaluation and diagnosis, a number of mandatory examinations are performed in all patients of stroke. These tests include:

  1. Biochemical blood tests such as homocysteine levels, as homocysteinemia has been associated with an increased risk of stroke.
  2. ECG: To check for atrial fibrillation that could have led to an embolic stroke.
  3. Carotid Doppler to check for evidence of carotid stenosis.
  4. CT scan to differentiate between Ischemic stroke and Hemorrhagic stroke as treatment protocols are completely different for these conditions.
  5. Echocardiography to evaluate the presence of intramural thrombus.

Instrumental diagnostic investigations for CVA are:

  • Angiography: It determines the exact location of blood vessel blockage using a contrast agent by detecting any thrombosis, atherosclerosis, aneurysm, or oncosis.
  • Angioscanning: It is used in the initial diagnosis of CVA. It is one of the inexpensive and quickest methods that are not dangerous even when used repeatedly.
  • Transcranial Dopplerography: Studies are performed using ultrasound, which makes it possible to determine the speed of blood flow and the presence of any vascular disorders.
  • Brain scintigraphy: It is one of the simplest methods that has almost no contraindications. It is done by injecting a radioactive substance into a vein, after which a scan is carried out after 15 minutes. During this time, the radioisotope spreads through the body and accumulates in tissues that have undergone pathological changes.

Therapeutic measures

The medical treatment is carried out in a stepwise comprehensive manner. First and foremost, all actions are aimed at minimizing the further progression of the ischemic or hemorrhagic injury. 

During initial therapy, all actions are aimed at procedures that normalize respiration, support neuroprotection, and maintain homeostasis. Once the airways have been secured, and the breathing, as well as the circulation, are stable, further treatment and investigations can be initiated. Treatment depends upon the type of brain stroke: Ischemic or Hemorrhagic.

Ischemic Stroke

Ischemic stroke is the most common type of stroke, accounting for almost 80% of all stroke cases. It occurs due to an atherosclerotic plaque or emboli blocking blood flow to different parts of the brain. Management is aimed at returning blood flow to normal. If the patient presents within 4.5 hrs of symptom onset, thrombolysis is the mainstay of therapy with drugs such as reteplase. However, if the patient presents in between 4.5 to 6 hrs after symptom onset, then thrombolysis is contraindicated, and instead, mechanical thrombectomy can be attempted. In patients presenting later than 6 hrs, treatment with thrombolytics is not attempted. In this scenario, ischemic injury is irreversible and rehabilitation becomes the only pathway to recovery which will have a significantly poorer prognosis than in patients who presented within 4.5 hrs of symptom onset. 

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Hemorrhagic Stroke

It accounts for less than 20% of all stroke cases but is associated with a markedly worse prognosis. Thrombolytic drugs are absolutely contraindicated in these patients as it will only worsen the condition. Treatment can be attempted with surgical decompression and maintenance of blood pressure to minimize intracranial pressure. Medical decompression with diuretics such as mannitol is also done, but the outlook for these patients is much poorer than ischemic stroke patients. 

Prevention and prognosis

Prevention of stroke can only be done by avoidance of the risk factors, regular health checks to ensure adequate control over blood pressure, diabetes, and cholesterol levels. Measures to prevent stroke include:

  1. Avoidance of all risk factors for stroke such as smoking
  2. Monitoring weight to maintain an ideal BMI
  3. Proper Diet: To prevent cerebrovascular diseases, it is important to try to follow a  low cholesterol diet by avoiding fried, pickled, salted, smoked products, fatty meat, etc.
  4. Perform physical exercises on a daily basis.
  5. Maintain blood pressure, glucose, and cholesterol levels
  6. After 45-50 years of age, it is necessary to undergo a check-up every year, as the risk of CVA increases in older ages. During the check-up, concomitant diseases may also be identified that may cause chronic cerebrovascular insufficiency, and their timely treatment will help to keep brain vessels healthy.

My Opinion:

Cerebrovascular disease is a serious disease that can pose a fairly serious threat to human life. A person’s life expectancy will largely depend on how timely medical care is provided. The crucial thing to remember is that cerebrovascular disease should be recognized promptly and treated immediately without delay as time is of the essence in CVA management.

Read Also: A Drug That Could Prevent Heart Attacks Without the Risk of Bleeding May Soon Be a Reality

References

https://www.nhlbi.nih.gov/health-topics/stroke

https://www.stroke.org/en/about-stroke

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