Stroke: Causes, symptoms, Diagnosis, and prevention

Stroke is defined as an abrupt neurological outburst caused by impaired perfusion through the blood vessels to the brain. It is important to understand the neurovascular anatomy to study the clinical manifestation of the stroke. The blood flow to the brain is managed by two internal carotids anteriorly and two vertebral arteries posteriorly (the circle of Willis). Ischemic stroke is caused by deficient blood and oxygen supply to the brain; hemorrhagic stroke is caused by bleeding or leaky blood vessels. 

What is the pathophysiology of stroke? 

Ishemic occlusions contribute to around 85% of casualties in stroke patients generating thrombotic and embolic conditions in the brain (Kuriakose et al 2020). Thrombotic stroke is caused by narrowing of blood vessels due to atherosclerosis and blood vessel constriction due to build-up of plaque in blood vessels. Decresed blood flow to the brain causes embolism leading to severe stress and untimely cell death (necrosis). Necrosis is followed by disruption of the plasma membrane, organelle swelling and leaking of cellular contents into extracellular space, and loss of neuronal function.  

Hemorrhagic stroke accounts for approximately 10–15% of all strokes and has a high mortality rate. In this condition, stress in the brain tissue and internal injury cause blood vessels to rupture. It produces toxic effects in the vascular system, resulting in infarction. Hemorrhagic strokes are further divided into intracerebral hemorrhage (ICH) and subarachnoid hemorrhage (SAH), more specifically, nontraumatic (spontaneous) ICH and nontraumatic (spontaneous aneurysmal) SAH.  (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7589849/) 

Epidemiology

Stroke ranks as the second leading cause of death worldwide and is a major contributor to disability. Ischemic strokes account for approximately 62% of all strokes, followed by ICH at 28% and SAH at 10% (Tadi et al 2023). Although ischemic strokes are more prevalent, hemorrhagic strokes result in more fatalities and lost disability-adjusted life-years (DALYs). 

Between 1990 and 2019, ICH and SAH demonstrated more significant reductions worldwide in age-standardized rates per year, compared to ischemic stroke, for incident and prevalent strokes, deaths resulting from stroke, and DALYs due to stroke. 

Both men and women worldwide face an approximate lifetime risk of stroke of 25% starting from age 25. The risk is notably high in East Asia and Central and Eastern Europe. (https://www.ncbi.nlm.nih.gov/books/NBK535369/) 

What are the risk factors for stroke? 

A transient ischemic attack (TIA) is a temporary period of symptoms similar to those of a stroke, without permanent damage. A TIA is caused by a temporary decrease in blood supply to part of the brain. The decrease may last as little as five minutes. A transient ischemic attack is sometimes known as a ministroke. A TIA occurs when a blood clot or fatty deposit reduces or blocks blood flow to part of the nervous system. 

What are the symptoms of stroke?

Symptoms of stroke include sudden onset of following:

• Trouble speaking and understanding what others are saying. A person having a stroke may be confused, slur words or may not be able to understand speech.
• Numbness, weakness or paralysis in the face, arm or leg. This often affects just one side of the body. The person can try to raise both arms over the head. If one arm begins to fall, it may be a sign of a stroke. Also, one side of the mouth may droop when trying to smile.
• Problems seeing in one or both eyes. The person may suddenly have blurred or blackened vision in one or both eyes. Or the person may see double.
• Headache. A sudden, severe headache may be a symptom of a stroke. Vomiting, dizziness and a change in consciousness may occur with the headache.
• Trouble walking. Someone having a stroke may stumble or lose balance or coordination. (https://www.mayoclinic.org/diseases-conditions/stroke/symptoms-causes/syc-20350113) 

What are the causes of stroke?

Ischemic strokes and hemorrhagic strokes can happen for many reasons. Ischemic strokes usually happen because of blood clots. These can happen for various reasons, such as:

• Atherosclerosis 
• Clotting disorders
• Atrial fibrillation (especially when it happens due to sleep apnea).
• Heart defects (atrial septal defect or ventricular septal defect).
• Microvascular ischemic disease (which can block smaller blood vessels in your brain).

Hemorrhagic strokes can happen for several reasons also, including:

• High blood pressure, especially when you have it for a long time, when it’s very high, or both.
• Brain aneurysm can sometimes lead to hemorrhagic strokes.
• Brain tumors (including cancer).
• Diseases that weaken or cause unusual changes in blood vessels in your brain, such as moyamoya disease. (https://my.clevelandclinic.org/health/diseases/5601-stroke) 

How is stroke diagnosed?

Several diagnostic tests can be performed to confirm the diagnosis: 

• A physical exam which includes cardiac auscultation, measuring blood pressure and going through neurological examination. Neurological examination includes cranial nerve testing, muscle tone and strength testing, balance and co-ordination test and functional activity performance tests. 
• Blood tests to check sugar levels, clotting time or presence of infection.
• Computerized tomography (CT) scan can show bleeding in the brain, an ischemic stroke, a tumor or other conditions. A dye may be injected into the bloodstream to view the blood vessels in the neck and brain in greater detail. This type of test is called a computerized tomography angiography.
• Magnetic resonance imaging: An MRI uses powerful radio waves and a magnetic field to create a detailed view of the brain. The test can detect brain tissue damaged by an ischemic stroke and brain hemorrhages. Sometimes a dye is injected into a blood vessel to view the arteries and veins and highlight blood flow. This test is called magnetic resonance angiography or magnetic resonance venography.
• Carotid ultrasound waves create detailed images of the inside of the carotid arteries in the neck. A carotid ultrasound can show buildup of fatty deposits called plaques and blood flow in the carotid arteries.
• Cerebral angiogram: A thin, flexible tube called a catheter is inserted through a small incision, usually in the groin. The tube is guided through the major arteries and into the carotid or vertebral artery in the neck. Then a dye is injected into the blood vessels to make the arteries visible under X-ray imaging. (https://www.mayoclinic.org/diseases-conditions/stroke/diagnosis-treatment/drc-20350119) 

Is stroke preventable? 

It is possible to reduce the risk of getting stroke by making healthy lifestyle choices. 

• Control high blood pressure: This is one of the most important things you can do to reduce your stroke risk. If you've had a stroke, lowering your blood pressure can help prevent a TIA or stroke in the future. Healthy lifestyle changes and medicines often are used to treat high blood pressure.
• Lower the amount of cholesterol and saturated fat in your diet: Eating less cholesterol and fat, especially saturated fats and trans fats, may reduce buildup in the arteries. If you can't control your cholesterol through dietary changes alone, you may need a cholesterol-lowering medicine.
• Quit tobacco use: Smoking raises the risk of stroke for smokers and nonsmokers exposed to secondhand smoke. Quitting lowers your risk of stroke.
• Manage diabetes: Diet, exercise and losing weight can help you keep your blood sugar in a healthy range. If lifestyle factors aren't enough to control blood sugar, you may be prescribed diabetes medicine.
• Maintain a healthy weight: Being overweight contributes to other stroke risk factors, such as high blood pressure, cardiovascular disease and diabetes.
• Exercise regularly: Aerobic exercise reduces the risk of stroke in many ways. Exercise can lower blood pressure, increase the levels of good cholesterol, and improve the overall health of the blood vessels and heart. It also helps you lose weight, control diabetes and reduce stress. Gradually work up to at least 30 minutes of moderate physical activity on most or all days of the week. The American Heart association recommends getting 150 minutes of moderate-intensity aerobic activity or 75 minutes of vigorous aerobic activity a week. Moderate intensity activities can include walking, jogging, swimming and bicycling.
• Reduce alcohol intake: Drinking large amounts of alcohol increases the risk of high blood pressure, ischemic strokes and hemorrhagic strokes. Alcohol also may interact with other medicines you're taking. However, drinking small to moderate amounts of alcohol may help prevent ischemic stroke and decrease the blood's clotting tendency. A small to moderate amount is about one drink a day. Talk to your healthcare professional about what's appropriate for you.
• Treat obstructive sleep apnea (OSA): OSA is a sleep disorder that causes you to stop breathing for short periods several times during sleep. Your healthcare professional may recommend a sleep study if you have symptoms of OSA. Treatment includes a device that delivers positive airway pressure through a mask to keep the airway open while you sleep.
• Don’t use illicit drugs: Certain illicit drugs such as cocaine and methamphetamine are established risk factors for a TIA or a stroke.
• Using preventive medication: anti-platelet drugs or blood thinners (anti-coagulants) can be used to reduce the risk of stroke. 

Healthy diet: Eating five or more servings of fruits or vegetables every day may reduce the risk of stroke. The Mediterranean diet, which emphasizes olive oil, fruit, nuts, vegetables and whole grains, may be helpful.