Ischaemic Stroke – Causes And Symptoms

Overview 

Partly due to an increase in lifestyle-related diseases such as diabetes and obesity, the incidence of stroke is rising. Currently, stroke is the second largest cause of death in humans worldwide.¹ 

However, fortunately, the development of early detection techniques and medications has improved outcomes after experiencing a stroke.⁴ Therefore, it is important to know the causes and symptoms of stroke to have a better chance of recognizing it if it happens to you or others around you, understand it, and to know how to reduce the risk of having an ischaemic stroke.

What is ischaemia?

Your body’s cells need oxygen to survive and function. When the flow of blood carrying the oxygen supply to cells is blocked or decreased, the affected cells begin to die. This process is called ischaemia.

Types of strokes

Strokes are caused by blocked blood flow to the brain (ischaemic stroke) or sudden bleeding in the brain (haemorrhagic stroke):

• Ischaemic stroke – occurs because of an insufficient supply of oxygen to brain cells
• Haemorrhagic stroke – occurs due to a ruptured blood vessel in the brain, causing a bleed in the brain. The blood that accumulates in the brain exerts pressure on nearby structures, leading to the death of cells in these structures in the brain

Around 85% of strokes are the ischaemic type. An ischaemic stroke in the brain occurs with a similar pathophysiology as a heart attack from coronary artery disease. 

How do ischaemic strokes occur? 

Atherosclerosis is a disease that starts with damage to your arteries. Other medical conditions, your genes and unhealthy lifestyle factors can all contribute to this damage which then leads to plaque build-up at the injury sites on the inside walls of arteries anywhere in the body. Plaques consist of fat, cholesterol, calcium, and other substances found in the blood. Your arteries progressively narrow as the plaque builds up, which diminishes the supply of oxygen-rich blood to tissues of vital organs in the body – in this instance, the brain.

If a plaque ruptures (bursts) blood platelets stick to the walls of the vessels and form clots. When a clot occurs locally in the brain, it is called a thrombus and the condition is called thrombosis. The clot can form a blockage which restricts the blood flow in the brain's blood vessels, reducing the oxygen supply and causing an ischaemic stroke. If the clot has travelled from another part of the body through the blood vessels and lodges within another part of the body (in this case the brain), the clot is called an embolus and the condition is called embolism.¹

Symptoms of stroke: the effect of stroke on our bodies

At the same time that the clot stops or diminishes blood flow to a particular area, the cells in that region begin to die as a consequence. The damage to the area can become permanent if blood flow is not restored swiftly. Therefore, medical help should be sought immediately and treatment initiated as soon as possible to prevent the damage from becoming permanent. 

The area of the brain where the stroke occurs and the amount of damage govern the particular effects experienced. Generally, body functions will be affected, but a stroke can also alter how you think and feel.

Strokes may present in the following ways:

• As slurred speech, and/or an inability to understand speech – confusion about what people around are talking about 
• One side of the body can become numb, weak, or paralysed. There is visible drooping of the mouth to one side and an inability to raise the arm
• Vision defects like blurring and blackening in one or both eyes can occur. Some people even develop diplopia (double vision)
• A sudden headache with vomiting, dizziness, and unconsciousness may also occur.
• Gait (walking) may also become unbalanced and may lack coordination³

Identifying a stroke

The letters F.A.S.T. can be helpful for remembering some of the more obvious signs of a stroke and the importance of immediate action: 

• Face – the face droops on one side
• Arm – the arm is difficult to lift
• Speech – speech becomes slurred
• Time – time must not be lost

If a person shows any of the above, then quick action is required to get medical attention. The interval between the recognition of stroke symptoms and treatment should be minimal to prevent brain damage and disability.

Transient ischaemic attack or TIA 

Transient Ischaemic Attack also known as TIA or mini-stroke, is similar to an ischaemic stroke but usually lasts for a shorter time. TIAs often last for a few minutes to a few hours but do not usually persist beyond 24 hours. However, ultimately, a TIA has the potential to turn into a full ischaemic stroke.⁵

Risk factors for stroke 

To recap, strokes are caused by blocked blood flow to the brain (ischemic stroke) or sudden bleeding in the brain (hemorrhagic stroke). Many things raise your risk of stroke. Some of these risk factors can be modified to help prevent a stroke or future strokes. Stroke is a result of a combination of these nonmodifiable and modifiable risk factors.

Non-modifiable risk factors are factors that individuals cannot do anything about including:

• Age – the incidence doubles for each decade after the age of 55 years
• Sex – premenopausal people assigned female at birth have a stroke risk that is as high as or higher than the risk in men. This is mostly due to the risks involved with pregnancy (e.g., pre-eclampsia, which essentially causes raised blood pressure in pregnancy) and the use of certain contraceptives (e.g., the combined oral contraceptive pill) increasing the risk of having a stroke³
• Family history – certain genetic factors are associated with an increased risk of strokes. There is also an increased risk of having a stroke if another family member has previously had one
• Ethnicity – for example, African Caribbean people in the UK have double the risk of stroke in comparison to their white counterparts¹
• Inflammatory diseases like rheumatoid arthritis and lupus also raise risk³
• Environmental risk factors – people living or working in areas with more air pollution can be more prone to having a stroke. Also, long stressful working conditions leading to anxiety and depression can precipitate stroke²

Modifiable risk factors are things that individuals can do something about to reduce their impact on potential cardiovascular complications –which relate to increased stroke risk – either through lifestyle changes or through medical treatment:

• Lifestyle risk factors
  • Being overweight or obese – obesity is associated with elevated blood pressure, diabetes, and heart disease, which are all risk factors that will increase the likelihood of a stroke
  • Physical inactivity – lack of physical exercise may result in obesity³
  • Poor diet – can lead to hyperlipidaemia and diabetes
  • Heavy or binge drinking – high quantities of alcohol are associated with increased stroke risk²
  • Smoking – doubles the risk of stroke. It increases the likelihood of atherosclerosis and stimulates clotting factors in the brain. The risk of rupture of vessels decreases 2 years after stopping smoking 
  • Use of illegal drugs such as cocaine and methamphetamine – cocaine and amphetamine consumption damages blood vessels. These drugs rupture the blood vessels and cause bleeding. Certain chemicals within these drugs cause narrowing of the lumen (the hollow middle) of blood vessels and lead to strokes¹

• High blood pressure – this is the most important risk factor overall for stroke that can be altered favourably by lifestyle changes and medication. Around half of all stroke patients have a history of high blood pressure¹
• Hyperlipidaemia – the liver produces cholesterol which is a building block for many chemicals in the body such as hormones. There are two types of cholesterol: HDL and LDL. LDL is perceived as ‘bad cholesterol’. Raised LDL levels can cause the build-up of atherosclerosis in the blood vessels, thereby decreasing the lumen ( the hollow tube through which blood flows) size. The ideal level of LDL in blood should be 130 mg/dl. Levels beyond 160 mg/dl predispose individuals to heart attack or stroke. A healthy diet and exercise keeps cholesterol levels in check³
• Cardiovascular disease – such as heart infections, heart defects, heart failure, atrial fibrillation and small vessel disease increase stroke risk 
• Diabetes – sugars that concentrate in the blood cause damage to the vessels that carry them. Individuals with diabetes are also more likely to have high blood pressure. If blood sugar levels are high at the time of stroke, the damage is severe
• Obstructive sleep apnoea^2,3,4 

Causes of ischaemic stroke 

Blood vessels get damaged due to high blood pressure. It causes atherosclerosis which then leads to heart attacks and stroke.^2,4 Other conditions besides atherosclerosis can also cause ischaemic stroke. These include:

Cerebral small vessel disease

In small vessel disease, very small blood vessels supplying tissue deep inside the brain get damaged and inflamed. The blood vessels become narrower diminishing blood flow, and increasing the likelihood of a stroke. It can also lead to a series of many small strokes. A common cause of small vessel disease is damage and inflammation of the vessel walls due to high blood pressure.

Heart conditions

Atrial fibrillation

When the upper chambers of the heart (the atria) contract, they push blood into the lower chambers of the heart (the ventricles). In atrial fibrillation, atrial contraction is disorganised and ‘wiggly’, so blood is not completely pumped into the ventricles. This results in the stagnation of blood in the atria. Stagnation causes blood clots to form that can then travel up to the brain and cause a blockage.

Other heart conditions

A recent heart attack or a mechanical valve replacement can increase the likelihood of clot formation and thus ischaemic stroke. 

Other health conditions

Additionally, stroke can be associated with other health conditions such as infections in the heart and inherited blood clotting disorders.

FAQs

How long does a stroke last?

The symptoms of a stroke persist as long as there is a lack of blood supply to regions of the brain. Without treatment, the cells in the brain die, and the damage is permanent.

How can I avoid a stroke?

Stroke can be avoided by following a healthy lifestyle, exercising, eating a balanced diet, and taking the appropriate medication for any other underlying disease that increases stroke risk. 

Does having high blood pressure make a person more susceptible to stroke?

Yes, high blood pressure damages the blood vessels and can even cause blood vessels to burst. Keeping the blood pressure under control through lifestyle modifications or prescription medication reduces the risk of stroke.

Summary

Ischaemic stroke occurs because of an insufficient supply of oxygen to brain cells due to blockage of blood vessels carrying oxygen-rich blood to the brain.

Stroke presents itself with features such as drooping of the face and slurred speech which are important to recognize because fast action is required to obtain medical treatment to restore blood circulation, and oxygen supply and so avoid the permanent damage caused by cell death as a result of insufficient oxygen supply.

Stroke is generally a result of a combination of non modifiable and modifiable risk factors.

The risk of experiencing a stroke can be decreased and preventative treatment can occur through healthy lifestyle modifications and medication to reduce modifiable risk factors.⁴