Stroke

Definition and Overview

Stroke is a condition in which blood flow to brain tissue is interrupted due to a blocked or ruptured cerebral blood vessel, resulting in acute neurological dysfunction. In traditional Korean medicine, it was historically called "jungpung," and in English medical terminology, it is also referred to as a cerebrovascular accident (CVA) ^[1].

Globally, stroke ranks as the second leading cause of death and third leading cause of disability. As of 2019, approximately 12.2 million new stroke cases and approximately 6.55 million stroke-related deaths were reported worldwide ^[1]. In Korea, cerebrovascular disease is the fourth leading cause of death, ranking among the highest in mortality as a single disease. The societal burden of stroke continues to grow due to population aging and increasing prevalence of metabolic syndrome.

Stroke is a medical emergency in which brain cell damage progresses on a minute-by-minute basis. In ischemic stroke, it is estimated that approximately 1.9 million neurons die every minute after blood flow is interrupted ^[2]. This is why the expression "Time is Brain" has become the core principle of acute stroke treatment.

Classification

Stroke is broadly classified into ischemic stroke and hemorrhagic stroke.

Ischemic Stroke

Ischemic stroke accounts for approximately 80% of all strokes ^[1]. It occurs when a cerebral blood vessel is blocked by a thrombus or embolus, interrupting oxygen and nutrient supply to the affected brain tissue. It is further subdivided by mechanism as follows.

• Large artery atherosclerosis: atherosclerotic plaque forms on the inner wall of large arteries supplying the brain, causing the vessel to narrow or become occluded.
• Small vessel occlusion (lacunar infarction): a type in which small perforating arteries deep within the brain become occluded, with hypertension as the primary cause. It produces small infarcts of 15 mm or less in diameter.
• Cardioembolism: a thrombus formed in the heart travels through the bloodstream and occludes a cerebral vessel. Atrial fibrillation is the most common cause, and the stroke risk in atrial fibrillation patients is approximately 5 times that of the general population ^[3].
• Other causes: includes arterial dissection, coagulation disorders, and vasculitis.
• Cryptogenic: cases in which the cause cannot be identified despite thorough investigation, accounting for approximately 25% of all ischemic strokes.

Hemorrhagic Stroke

Hemorrhagic stroke accounts for approximately 20% of all strokes but has a higher mortality rate than ischemic stroke ^[1]. It occurs when a cerebral blood vessel ruptures, causing bleeding within the brain tissue or in the space surrounding the brain.

• Intracerebral hemorrhage: rupture of a vessel within the brain parenchyma forms a hematoma. Arteriolar degeneration due to chronic hypertension is the most common cause, accounting for approximately two-thirds of all hemorrhagic strokes.
• Subarachnoid hemorrhage: bleeding occurs in the subarachnoid space surrounding the brain. Rupture of a cerebral aneurysm is the primary cause, characteristically presenting with sudden severe headache ("thunderclap headache").

Transient Ischemic Attack (TIA)

A transient ischemic attack (TIA) is a condition in which cerebral blood flow is temporarily reduced, producing stroke-like symptoms that fully resolve within minutes to tens of minutes. The distinguishing feature from stroke is the absence of infarction findings on imaging studies. The risk of stroke within 90 days of a TIA is reported to be approximately 10–15%, making TIA a strong warning signal for stroke ^[3].

Risk Factors

Stroke risk factors are divided into modifiable and non-modifiable factors. According to the Global Burden of Disease Study (GBD 2019), approximately 90.3% of stroke incidence is attributable to modifiable risk factors ^[5].

Modifiable Risk Factors

• Hypertension: the most powerful risk factor for stroke. For every 20 mmHg increase in systolic blood pressure, stroke risk approximately doubles ^[3]. It increases the risk of both ischemic and hemorrhagic stroke.
• Atrial fibrillation: the annual stroke incidence in patients with nonvalvular atrial fibrillation is approximately 5%, and the risk increases markedly without anticoagulation therapy ^[3].
• Diabetes mellitus: increases stroke risk by approximately 1.5–3 times, and stroke occurring in diabetic patients carries a poorer prognosis.
• Dyslipidemia: elevated LDL cholesterol contributes to carotid atherosclerosis and increased ischemic stroke risk.
• Smoking: stroke risk in smokers is approximately twice that of nonsmokers, and the risk decreases to nonsmoker levels 5 years after smoking cessation ^[3].
• Obesity and physical inactivity: abdominal obesity and lack of exercise are independent stroke risk factors.
• Excessive alcohol consumption: hemorrhagic stroke risk increases when daily alcohol intake exceeds 60 g.
• Migraine with aura: ischemic stroke risk in patients with migraine with aura is reported to be approximately twice as high, and the risk further increases with oral contraceptive use ^[3].

Non-Modifiable Risk Factors

• Age: stroke risk approximately doubles every 10 years after age 55.
• Sex: men have a higher stroke incidence than women, but women have higher incidence and mortality rates at older ages.
• Family history: having a first-degree relative with stroke increases risk by approximately 1.3 times.
• Race/ethnicity: incidence is relatively higher in African American and Hispanic populations.

Symptoms and FAST Assessment

Stroke symptoms vary depending on the brain region supplied by the blocked or bleeding vessel. Most symptoms occur suddenly, which is the most important characteristic of stroke.

Major Symptoms

• Unilateral paralysis: sudden onset of weakness or sensory abnormalities in one side of the face, arm, or leg. This is the most common stroke symptom.
• Speech disturbance: slurred speech (dysarthria) or aphasia (inability to understand or express language) occurs.
• Visual field deficits: sudden loss of vision in part of one or both eyes.
• Dizziness and balance impairment: sudden severe dizziness, gait instability, and coordination difficulties. Common in posterior circulation stroke.
• Sudden severe headache: particularly in subarachnoid hemorrhage, an extremely severe headache described as "the worst headache of my life" occurs suddenly.

FAST Assessment

A screening tool developed for the general public to rapidly recognize stroke.

• F (Face): check if one side of the face droops when asked to smile.
• A (Arms): check if one arm drifts downward when asked to raise both arms.
• S (Speech): check if speech is slurred or content is abnormal when asked to repeat a simple sentence.
• T (Time): if any of the above symptoms are present, call emergency services immediately. Always record the time of symptom onset.

The FAST assessment has a reported sensitivity of approximately 85% for stroke recognition and is widely used in the prehospital setting ^[2].

Diagnosis

When stroke is suspected, neurological examination and brain imaging are performed to differentiate between ischemic and hemorrhagic types and to evaluate the location of vessel occlusion and extent of brain damage.

Brain Computed Tomography (Brain CT)

This is the first examination performed upon arrival at the emergency department. With an imaging time of only a few minutes, it is suitable for acute patients. Hemorrhagic stroke is immediately confirmed as a hyperdense lesion on CT; however, hyperacute ischemic stroke may appear normal on CT. Adding CT angiography (CTA) enables rapid identification of large vessel occlusion ^[2].

Brain Magnetic Resonance Imaging (Brain MRI)

Diffusion-weighted imaging (DWI) can detect acute cerebral infarction within minutes of onset, providing higher diagnostic accuracy for ischemic stroke than CT. When combined with perfusion imaging, the extent of salvageable brain tissue (ischemic penumbra) can be assessed to guide treatment decisions ^[2].

Angiography

CT angiography (CTA), MR angiography (MRA), and digital subtraction angiography (DSA) are used to evaluate cerebrovascular stenosis, occlusion, aneurysms, and vascular malformations. DSA is invasive but offers the highest resolution, making it the standard for diagnosing microvascular lesions.

Other Tests

• Electrocardiogram and echocardiography: evaluate causes of cardioembolic stroke (atrial fibrillation, valvular disease, intracardiac thrombus).
• Blood tests: assess blood glucose, coagulation function, lipid levels, and infection markers.
• Carotid ultrasound: non-invasively evaluates the degree of carotid artery stenosis.

Acute Treatment

The core of acute stroke treatment is recanalization of the occluded vessel as quickly as possible to minimize brain damage.

Intravenous Thrombolysis (IV tPA)

This treatment involves intravenous administration of tissue plasminogen activator (tPA, alteplase) to dissolve the thrombus. Administration within 3 hours of symptom onset is standard, and the treatment window was extended to 4.5 hours based on the ECASS III trial (2008) ^[4]. In this study, the proportion of patients with favorable functional outcome (mRS 0–1) was significantly higher in the alteplase group compared with placebo at 52.4% versus 45.2% ^[4]. The earlier treatment begins, the greater the benefit, with the greatest advantage reported when administered within 90 minutes.

Mechanical Thrombectomy

In patients with anterior circulation large vessel (internal carotid artery, middle cerebral artery M1 segment) occlusion, a catheter is inserted endovascularly and the thrombus is physically removed using devices such as stent retrievers. A meta-analysis of 5 randomized controlled trials published in 2015 showed that the thrombectomy group achieved functional independence (mRS 0–2) at a significantly higher rate of 46% compared with 26.5% in controls ^[6]. The standard treatment window is within 6 hours of onset, but may be extended up to 24 hours based on perfusion imaging results ^[2].

Acute Treatment of Hemorrhagic Stroke

In hemorrhagic stroke, thrombolytics and thrombectomy are not applicable. Aggressive blood pressure control is employed to prevent hematoma expansion, and medical treatment for elevated intracranial pressure is administered. Surgical hematoma evacuation is considered depending on the size and location of the hematoma. For subarachnoid hemorrhage due to cerebral aneurysm rupture, early aneurysm clipping or coiling is performed to prevent rebleeding.

Prevention

Primary Prevention

Strategies to prevent the first occurrence of stroke in individuals who have never had one.

• Blood pressure management: lowering systolic blood pressure by 10 mmHg in hypertensive patients reduces stroke risk by approximately 30–40% ^[3].
• Smoking cessation: stroke risk decreases significantly 2–5 years after quitting.
• Regular exercise: moderate aerobic exercise for 30 minutes or more, 3–5 times per week is recommended.
• Dietary management: sodium restriction, increased fruit and vegetable intake, and the Mediterranean diet are associated with reduced stroke risk.
• Atrial fibrillation management: initiation of anticoagulation therapy is determined based on the CHA2DS2-VASc score.
• Diabetes and dyslipidemia management: blood glucose and LDL cholesterol should be maintained below target levels.

Secondary Prevention

Strategies to prevent recurrence in patients who have experienced stroke or TIA. The following are added to primary prevention strategies.

• Antiplatelet agents: aspirin, clopidogrel, and other antiplatelet agents are administered for non-cardioembolic ischemic stroke ^[2].
• Anticoagulants: direct oral anticoagulants (DOACs) or warfarin are administered for atrial fibrillation-related stroke.
• Statins: high-dose statin therapy is recommended for atherosclerosis-related stroke.
• Carotid intervention: carotid endarterectomy (CEA) or carotid artery stenting (CAS) is considered when symptomatic carotid stenosis is 70% or greater.

Relationship Between the Autonomic Nervous System and Stroke Risk

Autonomic nervous system dysfunction is closely related to stroke occurrence and prognosis. Reduced heart rate variability (HRV) has been identified as an independent predictor of cardiovascular events, and sympathetic hyperactivation promotes increased blood pressure variability, endothelial dysfunction, and atherosclerosis progression ^[7]. Even after stroke onset, insular cortex damage can lead to autonomic dysregulation, potentially causing complications such as arrhythmia, blood pressure instability, and myocardial injury ^[7].

Autonomic imbalance also contributes to the development of atrial fibrillation, and changes in sympathovagal balance are being investigated as one of the triggering mechanisms of atrial fibrillation. Therefore, autonomic function assessment can be a useful tool for early detection and management of stroke risk factors ^[7].

Rehabilitation

Post-stroke rehabilitation is a process aimed at maximizing recovery of impaired neurological function, minimizing disability, and facilitating return to daily life. The first 3–6 months after stroke represent the period of greatest neuroplasticity, making intensive rehabilitation during this window critically important.

Major Rehabilitation Areas

• Physical therapy: restores motor function through strengthening exercises, balance training, and gait training.
• Occupational therapy: restores the ability to perform activities of daily living (ADL) such as dressing, eating, and grooming.
• Speech therapy: improves language expression and comprehension in patients with aphasia and dysarthria.
• Swallowing rehabilitation: provides training for safe eating in patients with dysphagia. Dysphagia accompanies approximately 37–78% of acute stroke patients.
• Psychological support: post-stroke depression occurs in approximately 30% of patients and negatively impacts rehabilitation motivation and functional recovery, requiring active management.

Rehabilitation Principles

The three principles of rehabilitation are early initiation, sufficient intensity, and task-oriented repetitive training. Rehabilitation should begin within 24–48 hours after stroke when the patient's condition permits ^[2]. The rehabilitation program should be individualized according to the patient's functional level and goals, and is carried out by a multidisciplinary team including physicians, physical therapists, occupational therapists, speech therapists, nurses, and social workers.

Lifestyle Guide

Daily management guidelines for stroke prevention and recurrence prevention are as follows.

• Home blood pressure monitoring: measure and record blood pressure morning and evening at home. The target blood pressure is generally below 130/80 mmHg.
• Regular exercise: practice moderate aerobic exercise such as walking, swimming, or cycling for 30 minutes or more, 3–5 times per week.
• Smoking cessation and alcohol moderation: quit smoking immediately and limit alcohol to no more than 2 drinks per day for men and 1 drink per day for women.
• Balanced diet: reduce sodium intake to 5 g or less per day and maintain a diet centered on fruits, vegetables, whole grains, and fish.
• Maintain appropriate weight: maintain a BMI of 18.5–24.9 and manage waist circumference to below 90 cm for men and 85 cm for women.
• Medication adherence: do not discontinue prescribed medications (antiplatelet agents, anticoagulants, antihypertensives, diabetes medications, statins) without medical advice.
• Regular check-ups: regularly monitor blood pressure, blood glucose, lipid levels, and ECG, and address abnormalities early.
• Stress management: chronic stress promotes blood pressure elevation and vascular damage through sympathetic hyperactivation; manage with diaphragmatic breathing, meditation, and adequate sleep.

Familiarizing yourself with stroke warning signs (FAST) and calling emergency services immediately when symptoms occur to receive treatment within the golden time window is essential for survival and functional preservation.