Stroke

  • Stroke is a disease in which blood vessels that carry oxygen and nutrients to brain, are either blocked or ruptured.
  • There are three types of stroke including transient ischemic, ischemic and hemorrhagic stroke.
  • Symptoms include severe headache, nausea, vomiting, slurred speech, numbness of arms and legs etc.
  • Early treatments of stroke include painkillers and antidepressants while antithrombotic therapy or carotid endarterectomy may be required after initial stabilization.
  • Incidence of stroke may be prevented by controlling risk factors like hypertension, hyperlipidemia, diabetes mellitus, tobacco use, diet and obesity.

Introduction

Stroke is a neurological disease/state caused by blockage in a blood vessel due to some clots or bursts (ruptures). This blockage results in an interrupted blood flow and restricted supply of oxygen and nutrients to the neurons resulting in the brain cell death and permanent disabilities.

Stroke is one of the leading causes of death and disability in the world. Ischemic stroke appears to be the most prevalent form of stroke (80–90%) while primary intracranial hemorrhage and subarachnoid hemorrhage (SAH) account for 10–20% of all the stroke incidences.

There were an estimated 5.3 million intracranial hemorrhage (ICH) cases worldwide in 2010 with approximately 3 million deaths in people from developing countries (Krishnamurthi et al. 2013).

Types of Strokes

There are three main types of stroke.

1. Transient Ischemic attack

Transient ischemic attack (TIA) is also known as a mini-stroke. It occurs due to a temporary lack of blood flow in a certain part of brain. It shows stroke like symptoms which resolve within 24 hours.

It does not cause permanent brain impairments like other types of strokes. It is commonly caused by blood clotting, hypertension, atherosclerosis, and diabetes mellitus. TIA is transient episode of neurological dysfunction caused by inadequate blood supply to various parts of the brain including focal brain, spinal cord or retina (Easton et al. 2009).

2. Ischemic stroke

The most common type of stroke is ischemic stroke caused by obstruction in an artery due to a blood clot. The main cause of ischemic stroke is atherosclerosis (hardening of the inner lining of arterial walls due to deposition of fats). An ischemic stroke of brain, spinal cord or retinal cell contributes to some permanent dysfunctions (Sacco et al. 2013).

An ischemic stroke can be embolic or thrombotic based on origin of blood clots in the brain. The nature of ischemic stroke depends on the formation of blood clots. In embolic stroke blood clots do not originate in the brain itself but travel from another part of body to the brain.

The irregular, often rapid heartbeat contributes to embolic type of strokes. A thrombotic stroke caused by the formation of clots in the blood vessel of brain. Nearly one-half of ischemic stroke or TIA survivors are at higher risk of recurrent stroke within first few days or weeks of the initial stroke (Arsava et al. 2016)

3. Hemorrhagic stroke

Hemorrhagic stroke involves bleeding into the brain due to ruptures or breaks of blood vessel. There are following three possible causes of ruptured blood vessels in the brain.

Aneurysm:  It involves the rupture of a portion of the weakened blood vessel.

Arteriovenous malformation (AVMs): It involves the rupture of abnormally formed blood vessels.

Weakening of small blood vessels: Small vessels may be weakened due to high blood pressure and result in bleeding inside the brain.

Side effects of hemorrhagic stroke may include increased intracranial pressure (ICP). Pressure builds up due to elevated level of cerebrospinal fluid or blood.

Bleeding may disturb the normal circulation to brain that deprives brain of normal oxygen leading to stroke (Zoerle et al. 2015).  

According to its location, a hemorrhage is categorized into two main types, i.e. intracerebral hemorrhage and subarachnoid hemorrhage

Intracerebral hemorrhage (ICH):  It occurs due to bursting of intracerebral arteries which leads to bleeding inside the brain. Intracerebral hemorrhage (ICH) is the most common subtype of hemorrhagic stroke, accounting for 10-15% of all strokes and affecting between 10 and 30 people per 100,000.

Subarachnoid hemorrhage (SAH): It involves bleeding in the space between the brain and its surrounding tissues (Kim and Bae, 2017).   

Symptoms of stroke

The different types of stroke cause similar symptoms because each affects the blood flow into the brain. There are various symptoms including nausea, vomiting, slurred speech, numbness of the face, sudden confusion, such as difficulty in understanding, paralysis of arms, legs, face or body, difficulty in walking, sudden dizziness, loss of coordination, severe headache without any other known cause and difficulty in vision.

Treatments of Stroke

Early treatments of stroke include stabilizing breathing and blood pressure. Painkillers and antidepressants are given to brain hemorrhage patients. However, if there is too much bleeding, surgery may be required (Kim and Bae, 2017).

Antithrombotic therapy

The AHA/ASA (American Heart Association/American Stroke Association) guidelines recommend the use of antiplatelet agents to reduce the risk of a recurrent stroke. Three options are approved by the U.S. Food and Drug Administration: aspirin, clopidogrel (Plavix) and aspirin/ dipyridamole (Aggrenox) (Kernan et al. 2014).

Treatments for TIA include taking medications that will help prevent future strokes. These medications include antiplatelets and anticoagulants. Antiplatelets decrease the chances that components of the blood platelets will stick together and result in the formation of a clot.

Aspirin and clopidogrel (Plavix) are antiplatelet medications (Furie et al. 2011). Anticoagulants are medications that reduce the buildup of clotting proteins. Different types of anticoagulant medications including warfarin (Coumadin) and dabigatran (Pradaxa) are currently in use.

Carotid endarterectomy

A surgical procedure called carotid endarterectomy may also be used to remove plaque in the carotid artery of neck which is the major cause of stroke. Hemorrhagic stroke treatments try to stop bleeding in the brain and reduce the side effects associated with brain bleeding such as increased intracranial pressure.

Surgical procedures including clipping or coiling are designed to keep the blood vessel from bleeding further (Halliday et al. 2010).

In a recent study, scientists have used gene therapy involving NeuroD1 gene that converts glial cells in brain to neurons. Administration of NeuroD1 gene helps to repair the brain cell damage in neurons caused by stroke. This experiment has produced promising results in the laboratory mice and is expected to be used for treatment of stroke in near future.

Risk Factor Management For Stroke Prevention

It has been suggested that up to 80% of recurrent strokes may be prevented by addressing the variable risk factors. Stroke prevention requires management of the major risk factors including hypertension, hyperlipidemia, diabetes mellitus, tobacco use, obesity and physical activity.

Hypertension

Hypertension is a major and most common risk factor for ischemic stroke and its treatment can drastically reduce the risk of recurrent ischemic stroke (Kernan et al. 2014).

Certain lifestyle changes for lowering blood pressure are highly recommended such as exercise and balanced diet, lower salt intake, weight loss, use of a diet rich in fruits, vegetables and low-fat dairy products and also regular aerobic physical activity and limited alcohol consumption (Appel et al.1997).

Several medications have been used for lowering blood pressure but angiotensin-converting enzyme inhibitors, thiazide diuretics and calcium channel blockers being extensively tested in prevention of stroke.

Nevertheless, specific patient characteristics should also be considered like extracranial artery disease, renal impairment, cardiac disease and diabetes mellitus (Kernan et al. 2014).

Hyperlipidemia

Hyperlipidemia refers to abnormally high levels of plasma lipids or lipoproteins like cholesterol, phospholipids, triglycerides, low density lipoproteins (LDL) and high density lipoprotein (HDL).

One type of hyperlipidemia called hypercholesterolemia occurs due to increased level of LDL cholesterol (bad cholesterol) in the blood. This condition increases fatty deposits in the arteries and boost the risk of strokes. Hyperlipidemias are classified into primary and secondary subtypes (Mishra et al. 2011)

Primary hyperlipidemia (familial): It is usually caused due to genetic abnormalities such as a mutation in a receptor protein.

Secondary hyperlipidemia (acquired): It arises due to other disorders like diabetes that leads to alterations in plasma lipid and lipoprotein metabolism.

Diabetes Mellitus

Diabetes mellitus type 1 or type 2 and other metabolic glucose syndrome like prediabetes (accumulation of abnormal blood glucose) are major risk factors for stroke. These disorders are highly prevalent in patients with stroke; about 28% have prediabetes and 25% to 45% have diabetes mellitus (Kernan et al. 2014).

Metformin, a preferred drug is often recommended at a dose of 500 mg twice a day. Repeat hemoglobin A1c test to diagnose diabetes and prediabetes is performed after 3 months of treatment to observe a decreased glucose blood level up to less than 7% in most adults (Chamberlain et al. 2016).

Tobacco Usage

Tobacco use is a significant risk factor for stroke. Smokers have at least a doubled risk of stroke, and increased use of tobacco increases the risk of stroke (Meschia et al. 2014). In addition, environmental exposure to smoke has also been identified a risk factor which increases the incidence of stroke up to 30% (Malek et al. 2015).

Diet and Nutrition

Diet and nutrition play an important role in risk factor management for strokes. The AHA/ASA guidelines recommend certain lifestyle modifications to lower blood pressure such as use of a Mediterranean diet, reduced sodium intake, regular aerobic physical activity and limited alcohol consumption (James et al. 2014).

The Mediterranean diet is characterized by high intake of fruits and vegetables, extra virgin olive oil, nuts, whole grains with moderate intake of fish and poultry, low intake of dairy products, less use of red and processed meats and sweets (Tsivgoulis et al. 2015).

Additional findings show that extra virgin olive oil may reduce the risk of increased heartbeat while decreased use of the Mediterranean diet is associated with increased atherosclerotic stroke (Tuttolomondo et al. 2015).

Obesity

The role of obesity in the stroke is clearly linked with adipose tissues which are repository fat cells contributing to insulin resistance, hyperglycemia (high blood glucose level) that subsequently promote atherosclerosis.

Obesity is an established risk factor for ischemic stroke and epidemiologic studies have shown that for an increase in weight to about 7 pounds, the risk for ischemic stroke rises by about 5%.

Among overweight (BMI = 25 to 29 kg/m2) and obese (BMI >30 kg/m2) individuals, weight reduction is recommended for reducing the risk of stroke (Meschia et al. 2014).

Conclusion

It is concluded that occurrence of death from various types of strokes may be prevented by early management and appropriate treatment including surgery. In addition, risk factors of stroke may be controlled by making simple changes in diet and lifestyle.

References

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