What Causes a Stroke? Types, Risk Factors, and Investigation

1. What is a Stroke? Definition and Main Types

• Definition: A stroke occurs when blood supply to part of the brain is interrupted or reduced, depriving tissue of oxygen and nutrients. Brain cells begin to die within minutes.

• Ischaemic Stroke: The most common type, caused by a blood clot (thrombus or embolus) blocking a blood vessel supplying the brain.

• Haemorrhagic Stroke: Occurs when a weakened blood vessel within or around the brain ruptures, causing localized bleeding.

• Transient Ischaemic Attack (TIA): A temporary disruption of blood flow where symptoms resolve within 24 hours. It causes no permanent damage but serves as a critical warning sign for future strokes.

2. Common Causes of Ischaemic Stroke

• Atherosclerosis: Plaque buildup that narrows and hardens the large arteries leading to the brain, such as the carotid arteries.

• Small Vessel Disease: Damage and narrowing of the smaller, deeper cerebral arteries, usually driven by chronic high blood pressure.

• Cardioembolism: Blood clots that form in the heart and travel to the brain, frequently triggered by atrial fibrillation (AF) or a recent heart attack.

3. Common Causes of Haemorrhagic Stroke

• Chronic Hypertension: Long-term, uncontrolled high blood pressure is the leading cause, typically resulting in bleeding within deep brain structures.

• Aneurysm Rupture: A burst bulge in a weakened segment of an artery wall.

• Arteriovenous Malformations (AVMs): Congenital, abnormal tangles connecting arteries directly to veins, which are prone to rupture.

• Anticoagulant Use: Prescription blood-thinning medications that increase the risk and severity of bleeding complications.

4. Rare Causes of Stroke

• Arterial Dissection: A structural tear in an artery wall (e.g., carotid or vertebral arteries), a common cause in younger patients.

• Systemic Vasculitis: Inflammatory vessel conditions, such as systemic lupus erythematosus (SLE) or giant cell arteritis (GCA).

• Other Medical Conditions: Antiphospholipid antibody syndrome (APS), cerebral vein thrombosis, Fabry disease, and fibromuscular dysplasia (FMD).

5. Risk Factors for Stroke

• High Blood Pressure (Hypertension): The single most significant modifiable risk factor, as chronic high pressure damages and weakens cerebral blood vessels over time.

• Cardiovascular Disease: Conditions like atrial fibrillation (AF), recent heart attacks, or heart valve defects can cause blood clots to form and travel to the brain.

• Lifestyle Factors: Smoking, a sedentary lifestyle, high-cholesterol diets, and excessive alcohol consumption accelerate plaque buildup (atherosclerosis) in the arteries.

• Diabetes and Metabolic Conditions: High blood sugar damages blood vessels throughout the body, significantly increasing the likelihood of an ischaemic blockage.

• Age and Family History: The risk of stroke doubles every decade after age 55, and a family history of cerebrovascular disease or genetic vascular conditions elevates personal risk.

6. Initial Assessment and Investigation

• Clinical Evaluation: Neurological examination and the National Institutes of Health Stroke Scale (NIHSS) to quantify stroke severity, alongside urgent blood panels (FBC, U&Es, clotting screen, and glucose).

• Urgent CT Head Scan: The primary, immediate tool used to differentiate between a blockage and a bleed, which dictates if clot-busting treatments are safe.

• Advanced Imaging (MRI & Angiography): MRI identifies subtle tissue damage, while CTA or MRA scans map the vascular anatomy to find blockages or malformations.

• Cardiac & Carotid Workup: ECG and echocardiograms check for arrhythmias like atrial fibrillation and heart defects, while a Carotid Doppler ultrasound scans neck arteries for narrowing (stenosis).

Other resources

• National Institute for Health and Care Excellence (NICE). (2019). Stroke and transient ischaemic attack in over 16s: diagnosis and initial management
• Royal College of Physicians. (2016). Sentinel Stroke National Audit Programme (SSNAP).