Stroke

Overview

What is Stroke?

Stroke is the second highest cause of death globally and a leading cause of disability, with an increasing incidence in developing countries. Stroke can be broadly classified into ischemic stroke and hemorrhagic stroke, the latter of which includes intracerebral hemorrhage and subarachnoid hemorrhage¹.

Ischemic stroke is defined as infarction of the brain, spinal cord or retina and represents ~71% of all strokes globally¹. Understanding treatment options for acute ischemic stroke is important to ensure prompt administration of appropriate care or referral².

The pathophysiology of stroke

Most ischemic strokes are thromboembolic in origin, with common sources of embolism being large artery atherosclerosis and cardiac diseases, particularly atrial fibrillation¹.

Less common overall, but proportionally more prevalent in younger patients, are arterial dissection, vasculitis, patent foramen ovale (PFO) with paradoxical embolism and hematological disorders. The cause of ischemic stroke is important as it can guide therapeutic strategies for the prevention of recurrent stroke¹.

Collateral blood flow¹

When an intracranial artery is occluded, alternative blood flow pathways (collaterals) can sustain viability in the penumbral brain regions for a period of time. The extent of collateral flow varies substantially between individuals and probably has both genetic and environmental determinants¹.

Ischemic cascade and reperfusion injury¹

Ischemic stroke leads to oxygen depletion in the brain, which has several cellular and molecular consequences that affect neuronal and glial function in addition to vascular alterations and inflammation¹.

Systemic effects¹

The immediate responses to a large ischemic stroke include hypertension, arrhythmias including bradycardia and pulmonary exudates, but whether these alterations are a direct result of brain injury or are secondary to other phenomena is unclear¹.

Facts about stroke

Stroke Statistics by Race and Ethnicity³

Chinese ischemic stroke patients have similar prevalence of hypertension, diabetes, smoking and alcohol, but lower prevalence of atrial fibrillation, ischemic heart disease and hypercholesterolemia as compared with Caucasian patients³.

Symptoms

Knowledge of neuroanatomical structures and vascular territories allows localization and estimation of the size of the affected territory; patterns, such as right hemiparesis with aphasia due to occlusion of the left middle cerebral artery, are common and well recognized. Stroke symptoms that are under-recognized, such as nausea, vomiting, vertigo, and decreased level of consciousness, are more common in the setting of occlusions in the posterior circulation⁴.

The clinical presentation of stroke involves the sudden onset of a focal clinical deficit, referable to a specific site in the CNS. Symptoms can include¹:

• Hemiparesis
• Hemianesthesia (numbness on one side of the body)
• Aphasia (language disorder)
• Homonymous hemianopia (loss of the same half of the visual field in each eye)
• Hemispatial inattention

Risk factors and causes

Non-modifiable risk factors for ischemic stroke include age, sex and genetic factors¹.

Age

The influence of age on the risk of ischemic stroke differs by the development status of a country¹.

Sex

The incidence of ischemic stroke was higher in men (133 cases per 100,000 person-years) than in women (99 cases per 100,000 person-years) in the 2013 Global Burden of Disease Study¹.

Genetic factors

The estimated heritability of ischemic stroke is 37.9% when calculated using genome-wide complex trait analysis¹.

Estimations indicate that approximately 90% of strokes are attributable to modifiable risk factors⁴. Stroke shares many risk factors with other cardiovascular diseases although their relative importance varies⁴:

• High blood pressure
• Smoking
• Diabetes
• Hyperlipidemia
• Physical inactivity

Arterial causes of stroke¹

• Atherosclerosis
• Small vessel disease
• Arterial dissection
• Cerebral vasculitis
• Reversible cerebral vasoconstriction syndrome

Cardiac causes of stroke^1,4

• Atrial fibrillation:
  Strokes related to atrial fibrillation tend to be larger and more disabling than are strokes due to other mechanisms⁴.
• Patent foramen ovale
• Infective endocarditis
• Hypokinetic segment with mural thrombus

Incidence and prevalence

Data from a systematic analysis for the Global Burden of Disease Study 2016. The highest age-standardized incidences of stroke were observed in east Asia, especially China (354 [95% UI 331–378] per 100,000 person-years), followed by eastern Europe, ranging from 200 (181–218) per 100,000 person-years in Estonia to 335 (301–369) per 100,000 person-years in Latvia⁵.

The prevalence of ischemic stroke increased from 1990 to 2005, then decreased from 2005 to 2013, ultimately leading to a slight, although not statistically significant, increase in the worldwide prevalence from 1990 to 2013. In those between 20 and 64 years of age, the prevalence has nearly doubled globally from 1990 to 2013, with an increase of 37.3% in associated disability-adjusted life years¹.

The stroke morbidity in Taiwan⁶

A cohort study of 8,562 stroke-free people with 4-year follow up to observe new stroke occurrence. The average annual incidence rate of first-ever stroke for people aged 36 years or older in this study was 330 per 100,000 population⁶.

The other study estimated stroke prevalence of 19.3 per 1,000 people from 2001 NHIS⁶.

Stroke is the third leading cause of death in Taiwan. According to the data from the Ministry of Health and Welfare, the proportionate mortality of stroke is 7.2% in 2012. It is about 47 stroke deaths per minute⁶.