Ischemic stroke overview

# 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.

# Historical perspective
The history of stroke goes back to the 5th century B.C. as apoplexy. In 17th century it was discovered that the cause is sudden disruption of blood supply to the brain.

# Classification
Ischemic stroke may be classified according to the duration of onset of symptoms and causative agent. The major classification system of ischemic stroke include toast classification system, causative classification of stroke system (CCS),and sparkle classification of ischemic stroke.

# Pathophysiology
The pathophysiology of ischemic stroke may depend on the underlying cause of ischemia. Ischemic infarct may be categorized into two types depending on the area of the brain involved as focal ischemic stroke or global ischemic stroke. Hemodynamic changes in ischemic stroke results from cerebral auto regulation dysfunction as brain tissue is highly sensitive to mild changes in oxygen levels. Several minutes of hypoxia leads to irreversible injury. Cerebral auto regulation maintains the perfusion pressure in the brain between the pressure range of 60-150 mm Hg via vasoconstriction and vasodilatation. Prolonged ischemia decreases oxygen delivery to the cells causing anaerobic glycolysis and increased production of free oxygen and nitrate radicals which in turn causes cell membrane, DNA damage and cell death.

# Causes
There are several causes for stroke. Some may cause hemorrhage and some causes ischemia. Among all of them there are several lethal causes which we need to be more cautious about them.

# Differential diagnosis
The differential diagnosis of ischemic stroke may include brain tumour, hemorrhagic stroke, subdural hemorrhage, neurosyphilis, complex or atypical migraine, hypertensive encephalopathy, wernickes encephalopathy, CNS abscess, drug toxicity, conversion disorder, electrolyte disturbance, meningitis or encephalitis, multiple sclerosis exacerbation, seizure and hypoglycemia. There are also some conditions which may cause muscle weakness and paralysis such as Botulism, Myasthenia gravis, Guillian-Barre syndrome, Eaton Lambert syndrome, Electrolyte disturbance, Organophosphate toxicity, Multiple sclerosis exacerbation, Amyotrophic lateral sclerosis, Inflammatory myopathy. It is necessary to differentiate these conditions from stroke.

# Epidemiology and demographics
The worldwide incident of stroke is about 68 percent and it increases with age. It is more common in men. However, the mortality is more in women. the incident and mortality rates are high in African-American population and developing countries.

# Risk Factors
Risk factors for stroke are divided into modifiable and non modifiable risk factors. Modifiable risk factors include hypertension, diabetes mellitus, cardiac disease, cigarette smoking, alcohal consumption, hyperhomocysteinemia, hyperlipidemia, obesity, sedentary life style and oral contraceptive usage. Some of the non modifiable risk factors include advanced age, male gender, family history of ischemic stroke, african-american and hispanic race, and genetic diseases such as sicke cell disease.

# Screening
There are several screening tests for high risk patients to detect and prevent stroke: Carotid Artery Ultrasound, Abdominal Aortic Aneurysm Screening, Atrial Fibrillation, Peripheral Artery Disease.

# Natural history, complications and prognosis
Stroke can cause temporary or permanent complications based on the location and time to appropriate treatment. Delayed treatment or sever hemorrhagic or ischemic stroke can lead to death. Other may suffer from Dysphagia, Pneumonia, Myocardial infarction and arrhythmias, need for mechanical ventilation, pulmonary edema, central sleep apnea, urinary incontinence, falls, Musculoskeletal spasticity, Post-stroke seizure, Bowel incontinence, cognitive impairment. Prognosis depends on patient's age and stroke severity based on clinical evaluation and imaging.

# Diagnosis

## Physical Examination
A systematic review found that acute facial paresis, arm drift, or abnormal speech are the best findings.

## Electrocardiogram
Electrocardiogram (ECG) may be performed to determine the underlying etiology such as arrhythmias which may result in clots in the heart that may spread to the brain vessels through the bloodstream. Holter monitor may be used to identify intermittent arrhythmias.

## Echocardiography
Echocardiography may be performed to determine the underlying etiology such as arrhythmias and the resultant clots in the heart that may spread to the brain vessels through the bloodstream.

## Ultrasound
Ultrasound/doppler study of the carotid arteries can be used to detect carotid stenosis or dissection of the precerebral arteries.

## Other Imaging Findings
When a stroke has been diagnosed, various other studies may be performed to determine the underlying etiology. With the current treatment and diagnosis options available, it is of particular importance to determine whether there is a peripheral source of emboli. Test selection may vary, since the cause of stroke varies with age, comorbidity and the clinical presentation. An angiogram of the cerebral vasculature (if a bleed is thought to have originated from an aneurysm or arteriovenous malformation)

# Treatment

## Early Assessment
Early recognition of the signs of stroke is generally regarded as important. Only detailed physical examination and medical imaging provide information on the presence, type, and extent of stroke, and hence hospital attendance  even if the symptoms were brief  is advised.
Studies show that patients treated in hospitals with a dedicated Stroke Team or Stroke Unit and a specialized care program for stroke patients have improved odds of recovery.

## Medical Therapy
Treatment of stroke is occasionally with thrombolysis ("clot buster"), 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).