Stroke

A stroke happens when blood supply to the brain is reduced or stopped, preventing oxygen and nutrients from reaching brain tissue. It can also be caused by bleeding within or around the brain. Within minutes, brain cells in the affected area begin to die, and the longer blood flow remains interrupted, the greater the extent of lasting damage.

This is why stroke is often described in medicine with the phrase "time is brain" — every minute of delay in treatment can mean the loss of millions of brain cells.

Understanding the Brain's Blood Supply

The brain is an extremely metabolically active organ, using a large share of the body's oxygen and glucose despite its relatively small size. It receives blood through two main pairs of arteries — the carotid arteries in the front of the neck and the vertebral arteries at the back — which join and branch into a network supplying every region of the brain.

Different parts of the brain control different functions: movement, sensation, speech and language, vision, balance, and the basic life-sustaining processes such as breathing and heart rate. Because blood flow is organised regionally, the specific effects of a stroke depend heavily on which blood vessel is affected and which part of the brain it supplies — which is why two strokes of similar size can produce very different symptoms depending on their exact location.

What is a Stroke?

A stroke happens when blood supply to the brain is reduced or stopped, preventing oxygen from reaching it. It can also be caused by bleeding in the brain. This interruption causes brain cells in the affected part of the brain to die, damaging the brain and causing issues with walking and speaking, as well as visible signs such as facial drooping on one side, slurred speech, and inability to raise the arms. Early action is crucial in reducing brain damage and other complications.

There are two main types of stroke. Ischemic stroke is caused by a blood clot that blocks vessels in the brain, often due to a build-up of plaque associated with high blood pressure and high cholesterol levels. Ischemic strokes can also be caused by small blood clots that travel through the bloodstream and lodge in the arteries supplying the brain. Hemorrhagic stroke is due to the rupture of a blood vessel, causing a build-up of pressure that is potentially fatal and leads to more severe damage.

Types of Stroke

• Ischemic Stroke (about 85% of strokes): Caused by a blood clot that blocks a vessel supplying the brain, cutting off oxygen. This may result from arteriosclerosis, a build-up of fatty plaque, cholesterol and cells along blood vessel walls, often driven by high blood pressure or high cholesterol. It can also occur when a clot forms elsewhere in the body — commonly the heart — and travels to the brain (an embolic stroke).
• Hemorrhagic Stroke: Occurs when a blood vessel in or around the brain becomes brittle and weak and bursts, causing blood to leak into or around brain tissue. This causes a build-up of pressure within the brain and under the skull, sometimes with a pounding sensation in the head and light-headedness. Hemorrhagic strokes are generally more serious than ischemic ones, as they are potentially fatal and can cause more severe damage.
• Transient Ischemic Attack (TIA): Sometimes called a mini-stroke, a TIA involves a temporary blockage of blood flow to the brain. Symptoms mirror those of a stroke but typically resolve within minutes to a few hours. A TIA does not cause permanent damage but is a serious warning sign of a significantly increased risk of a full stroke in the near future.

Transient Ischemic Attack: A Critical Warning Sign

A transient ischemic attack, or TIA, is sometimes referred to as a "mini-stroke" because it produces stroke-like symptoms that resolve on their own, typically within minutes to a few hours, without causing lasting damage visible on standard imaging. Despite its temporary nature, a TIA should never be dismissed or treated as a false alarm.

A TIA is one of the strongest known warning signs that a person is at significantly elevated risk of a full stroke in the near future, sometimes within days. Anyone experiencing symptoms consistent with a TIA — even if they resolve completely — should be assessed promptly, as identifying and treating the underlying cause can meaningfully reduce the risk of a subsequent, potentially more damaging stroke.

Recognising a Stroke: The FAST Test

The FAST acronym is a simple, widely used test to quickly identify the three most common signs of stroke, plus the crucial fourth step of acting on them.

• Face: Ask the person to smile. Does one side of the face droop, or does their mouth or eye sag on one side?
• Arms: Ask the person to raise both arms. Does one arm drift downward, or are they unable to raise one arm fully?
• Speech: Ask the person to repeat a simple phrase. Is their speech slurred, strange, or difficult to understand? Can they understand what you are saying?
• Time: If any of these signs are present, note the time symptoms started and call for emergency medical services immediately. The time of onset is critical information for the medical team, as it directly affects which treatments can be safely given.

Other Symptoms of Stroke

• Loss of consciousness
• Sudden loss of vision, coordination and the ability to understand speech
• Sudden numbness in the face, arm, or leg on one side of the body
• Sudden loss of balance, nausea and vomiting
• A sudden, severe headache
• Sudden dizziness, unsteadiness or falling suddenly

Symptoms may vary from person to person, but they tend to come on suddenly, distinguishing stroke from conditions that develop more gradually.

Causes of Stroke

Both major types of stroke ultimately result from a disruption to the brain's blood supply, but the underlying mechanisms differ.

• Arteriosclerosis and plaque build-up: A gradual build-up of fatty plaque, cholesterol and cells along the walls of blood vessels narrows the artery and can eventually block blood flow entirely, or cause a clot to form at the narrowed site.
• Blood clots (emboli): A clot that forms elsewhere in the body — often in the heart as a result of an irregular heart rhythm — can travel through the bloodstream and lodge in a smaller artery supplying the brain.
• High blood pressure: Chronically elevated blood pressure weakens and damages blood vessel walls over time, making them more prone to both narrowing and rupture.
• Aneurysms and abnormal blood vessels: A weak spot in a blood vessel wall (an aneurysm) or an abnormal tangle of blood vessels can rupture, leading to a hemorrhagic stroke.

Risk Factors for Stroke

• Previous stroke or transient ischemic attack (TIA): Your chances of getting a stroke are higher if you have already had a stroke or suffered a TIA.
• High blood pressure or cholesterol: High blood pressure is a leading cause of stroke. Excess cholesterol can lead to the narrowing of arteries, stroke and other problems.
• Existing heart disease: Common heart diseases may increase your risk of a stroke, such as coronary artery disease due to the build-up of plaque in the arteries, and irregular heart rhythms such as atrial fibrillation.
• Diabetes: Diabetes is the increase of blood sugars, which prevents oxygen and nutrients from getting to various parts of your body, including your brain.
• Eating a diet high in saturated and trans fat: A diet high in 'bad' fats and sodium has been linked to an increased risk of stroke and related conditions, such as heart disease.
• Excessive alcohol consumption: Too much alcohol may raise your blood pressure and your risk of a stroke. It also increases the level of triglycerides, a form of fat in your blood, resulting in the hardening of your arteries.
• Smoking: Smoking damages blood vessel walls, raises blood pressure, and makes blood more likely to clot, all of which increase stroke risk.
• Physical inactivity: A lack of regular physical activity is associated with higher rates of obesity, high blood pressure and diabetes, all of which independently raise stroke risk.
• Age and sex: Stroke risk rises significantly with age, and men have a somewhat higher risk than women at most ages, though women face unique risk factors related to pregnancy and hormone use.

How Stroke Affects the Brain and Body

The effects of a stroke depend heavily on which part of the brain is affected and how much tissue is damaged before treatment restores blood flow or the bleeding is controlled.

Possible Long-Term Effects and Complications

Beyond the immediate effects on movement and speech, a stroke can lead to further complications in the days, weeks and months that follow.

• Physical impairment: Weakness, stiffness (spasticity), or paralysis on one side of the body that may improve substantially with rehabilitation but can persist to some degree long-term
• Communication difficulties: Difficulty producing or understanding speech (aphasia), or difficulty coordinating the muscles used for speech (dysarthria)
• Swallowing difficulties (dysphagia): Difficulty swallowing safely, which increases the risk of choking or food and liquid entering the lungs, potentially leading to pneumonia
• Cognitive changes: Reduced attention, memory or problem-solving ability, ranging from mild to significant, depending on the areas of the brain affected
• Emotional and mood changes: Depression and anxiety are common after stroke, related both to the emotional impact of the event and to changes in brain chemistry caused by the stroke itself
• Deep vein thrombosis: Reduced mobility after a stroke increases the risk of blood clots forming in the legs, which can potentially travel to the lungs
• Seizures: Some stroke survivors develop seizures, particularly in the weeks following the stroke or when there is significant damage to the brain's outer layer (the cortex)

How Strokes Are Diagnosed

Because timing is critical in stroke care, diagnosis is designed to happen as quickly as possible once a person reaches medical attention.

• Blood Test: A complete blood count will be done to check the sugar level in your blood, how fast it takes to clot, platelet levels, as well as increased white blood cells that signal a possible infection.
• CT Scan: Usually the first imaging test performed in a suspected stroke, as it can quickly distinguish between an ischemic stroke and a hemorrhagic stroke — a distinction that determines which treatments can be safely given.
• MRI: Provides more detailed images of brain tissue and can detect areas of stroke damage earlier and more precisely than a CT scan, though it typically takes longer to perform.
• Carotid Ultrasound: Checks for fatty deposits, or plaque, in the carotid arteries in the neck, which supply much of the blood flow to the brain and are a common source of clots leading to ischemic stroke.
• Electrocardiogram (ECG) and Echocardiogram: An ECG checks the heart's electrical rhythm for irregularities, such as atrial fibrillation, that can lead to clot formation, while an echocardiogram examines the heart's structure for a possible source of a travelling clot.
• Cerebral Angiogram: A more detailed imaging test that maps the blood vessels in and leading to the brain, used when more precise information is needed about a blockage, aneurysm or abnormal blood vessel.
• Physical and Neurological Examination: The heart is examined and blood pressure is checked, along with an assessment of strength, coordination, speech and sensation to determine the pattern and severity of any deficits.

Stroke Rehabilitation and Recovery

Rehabilitation is a central part of stroke recovery, often beginning within the first day or two after a stroke, once the patient is medically stable, and continuing for months afterward.

• Physiotherapy: Focuses on rebuilding strength, balance and coordination, and relearning movements needed for walking and daily activity
• Occupational therapy: Helps patients relearn skills needed for daily living, such as dressing, cooking and using the affected arm or hand, and may recommend adaptive equipment
• Speech and language therapy: Addresses difficulties with speech, language and swallowing, helping patients communicate effectively and eat safely
• Cognitive and psychological support: Helps address memory, attention, problem-solving and emotional changes that can follow a stroke

Most recovery occurs in the first three to six months after a stroke, though many patients continue to see gradual improvement well beyond this period with ongoing therapy and practice. The extent of recovery varies significantly from person to person, depending on the size and location of the stroke, how quickly treatment was received, and individual health factors.

How to Reduce Your Risk of Stroke

Many of the most significant risk factors for stroke are modifiable, meaning that meaningful lifestyle and medical measures can substantially lower risk.

• Regular monitoring and treatment of high blood pressure is one of the single most effective ways to reduce stroke risk
• Managing cholesterol levels through diet, exercise and, where needed, medication helps reduce plaque build-up in the arteries
• Keeping blood sugar well controlled reduces the vascular damage associated with diabetes
• Adopting a diet lower in saturated and trans fats and sodium, with more fruits, vegetables and whole grains, supports healthy blood vessels
• Regular physical activity supports healthy blood pressure, weight and cholesterol levels
• Limiting alcohol intake reduces the associated rise in blood pressure and blood fat levels
• Quitting smoking significantly reduces stroke risk over time, with benefits beginning within just a few years of quitting
• For those with an irregular heart rhythm such as atrial fibrillation, appropriate blood-thinning medication substantially reduces the risk of clot-related stroke
• Attending regular health screenings helps identify and manage risk factors such as high blood pressure, high cholesterol and diabetes before they lead to a stroke