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# Overview
Stroke is the rapidly developing loss of brain functions due to a disturbance in the blood vessels supplying blood to the brain. This can be due to ischemia (lack of blood supply) caused by thrombosis or embolism, or due to a hemorrhage.
Stroke is a medical emergency and can cause permanent neurological damage, complications and death if not promptly diagnosed and treated. It is the third leading cause of death and the leading cause of adult disability in the United States and Europe. It is predicted that stroke will soon become the leading cause of death worldwide. WHO defines stroke as, a neurological deficit of cerebrovascular cause that persists beyond 24 hours or is interrupted by death within 24 hours.
Risk factors for stroke include advanced age, hypertension (high blood pressure), previous stroke or transient ischaemic attack (TIA), diabetes mellitus, high cholesterol, cigarette smoking, atrial fibrillation, migraine with aura, and thrombophilia. In clinical practice, blood pressure is the most important modifiable risk factor of stroke; however many other risk factors, such as cigarette smoking cessation and treatment of atrial fibrillation with anticoagulant drugs, are important. Treatment of  ischemic stroke is occasionally with thrombolysis, but usually with supportive care (physiotherapy and occupational therapy) and secondary prevention with antiplatelet drugs (aspirin and often dipyridamole), blood pressure control, statins and anticoagulation (in selected patients). Hemorrhagic stroke is a medical emergency, rapid diagnosis and management is crucial because early deterioration is common in the first few hours after ICH onset.

# Causes
The following table lists causes for stroke.

# Classification

## Transient ischemic attack
- A transient ischemic attack is caused by the temporary disturbance of blood supply to a restricted area of the brain, resulting in brief neurologic dysfunction that usually persists for less than 24 hours.

## Stroke

# Differential diagnosis
Stroke, must be differentiated from other diseases that may cause, altered mental status, motor and or somatosensory deficits. The table below, summarizes the differential diagnosis for stroke:

# Differential diagnosis
Stroke should be differentiated from other causes of muscle weakness and paralysis. The differentials include the following:

# Epidemiology and Demographics

## Stroke in USA
- Stroke is a leading cause of serious long-term disability
- In USA, the incidence and mortality rates of stroke has significantly decreased compared to previous years.
- From year 2003 to 2013, the mortality rates due to stroke declined by 18.5%.
- In 2013, stroke became the fifth leading cause of death.
- The case fatality rate of stroke is estimated to be 41.7 deaths per 100, 000 population
- The incidence of new (610, 000) or recurrent stroke (185, 000) is estimated to be 795000 people annually or 250 cases per 100, 000.
- It is estimated that one incidence of stroke happens every 4 sec with death occurs every 4 min.
- About 87% of all strokes are ischemic strokes
- Stroke costs the United States an estimated $34 billion each year

## Worldwide
- According to WHO, the incidence of stroke is estimated to be 15 million people annually, worldwide..
- Out of these, 5 million die and 5 million are left permanently disabled..

## Age
- Stroke can occur in all age groups. However, the incidence of stroke is less among individuals age less than 40 years of age and the risk increases with increasing age. 
- According to WHO, stroke also occurs in about 8% of children with sickle cell disease..
- In 2009, 34% of people hospitalized for stroke were younger than 65 years
- The incidence of stroke in people aged 18 to 50 years is estimated to be approximately 10%. 
- The rate of decline in mortality rates of stroke in different age groups is as follows:
- Older then 65 years: from 534.1 to 245.2 per 100,000
45-65 years of age: from 43.5 to 20.2 per 100,000
18 to 44 years of age: from  from 3.7 to 2.0 per 100,000
- Older then 65 years: from 534.1 to 245.2 per 100,000
- 45-65 years of age: from 43.5 to 20.2 per 100,000
- 18 to 44 years of age: from  from 3.7 to 2.0 per 100,000

## Gender
There is increased incidence of stroke in men as compared to women.

## Race
- The risk of incidence of first stroke is twice in African-American population as compared to Caucasians with increased mortality rates.

## Geographical distribution
- There is increased incidence and mortality rates of stroke in developing countries as compared to developed countries due to low socioeconomic status and heath facilities.
- In the USA, the highest death rates from stroke are in the southeastern United States.

# Diagnosis
Almost 10% of cerebrovascular events that present to the emergency department are not detected during evaluation. This is more common when "presenting neurologic complaints are mild, nonspecific, or transient".
- Diagnosis is based on history of symptoms development, physical examination and imaging findings.
- CT scan and magnetic resonance imaging (MRI) are both reasonable for initial evaluation.
- CT scan without contrast is the initial test performed to diagnose ischemic stroke and rule out hemorrhagic stroke.
- CT is very sensitive for identifying acute hemorrhage and is considered the gold standard.
- Gradient echo and T2 susceptibility-weighted MRI are as sensitive as CT for detection of acute hemorrhage and are more sensitive for identification of prior hemorrhage.
- MR diffusion weighted imaging is the most sensitive and specific test for diagnosing ischemic stroke and may help detect presence of infarction in few minutes of onset of symptoms. It may also help differentiate viable tissue from infarct area if combined with MR perfusion. For diagnosing ischemic stroke in the emergency setting, MRI scan has the sensitivity and specificity of 83% and 98% respectively.
- MRI scan is superior to CT scan for being more sensitive and specific in detection of lacunar and posterior fossa infarcts, differentiation between acute and chronic stroke and detection of microbleeds. Another additional advantage is absence of ionising radiation compared to CT scan. Some of the disadvantages of MRI scan may include lack of availability in acute setting, higher cost, inability to use it in patients with metallic implants. MRI with contrast cannot be used in patients with renal failure.