Stroke

            A stroke, previously known medically as a cerebrovascular accident (CVA), is the rapidly developing loss of brain function(s) due to disturbance in the blood supply to the brain. This can be due to ischemia (lack of blood flow) caused by blockage (thrombosis, arterial embolism), or a hemorrhage (leakage of blood). As a result, the affected area of the brain is unable to function, leading to inability to move one or more limbs on one side of the body, inability to understand or formulate speech, or an inability to see one side of the visual field.

A stroke is a medical emergency and can cause permanent neurological damage, complications, and even death. It is the leading cause of adult disability in the United States and Europe and it is the number two cause of death worldwide. Risk factors for stroke include advanced age, hypertension (high blood pressure), previous stroke or transient ischemic attack (TIA), diabetes, high cholesterol, cigarette smoking and atrial fibrillation. High blood pressure is the most important modifiable risk factor of stroke.

A stroke is occasionally treated in a hospital with thrombolysis (also known as a "clot buster"). Post-stroke prevention may involve the administration of antiplatelet drugs such as aspirin and dipyridamole, control and reduction of hypertension, the use of statins, and in selected patients with carotid endarterectomy, the use of anticoagulants. Treatment to recover any lost function is stroke rehabilitation, involving health professions such as speech and language therapy, physical therapy and occupational therapy.

Strokes can be classified into two major categories: ischemic and hemorrhagic. Ischemic strokes are those that are caused by interruption of the blood supply, while hemorrhagic strokes are the ones which result from rupture of a blood vessel or an abnormal vascular structure. About 87% of strokes are caused by ischemia, and the remainder by hemorrhage. Some hemorrhages develop inside areas of ischemia ("hemorrhagic transformation"). It is unknown how many hemorrhages actually start as ischemic stroke.

Signs and symptoms

Stroke symptoms typically start suddenly, over seconds to minutes, and in most cases do not progress further. The symptoms depend on the area of the brain affected. The more extensive the area of brain affected, the more functions that are likely to be lost. Some forms of stroke can cause additional symptoms. For example, in intracranial hemorrhage, the affected area may compress other structures. Most forms of stroke are not associated with headache, apart from subarachnoid hemorrhage and cerebral venous thrombosis and occasionally intracerebral hemorrhage.

It was found that sudden-onset face weakness, arm drift (e.g. if a person, when asked to raise both arms, involuntarily lets one arm drift downward) and abnormal speech are the findings most likely to lead to the correct identification of a case of stroke (+ likelihood ratio of 5.5 when at least one of these is present). Similarly, when all three of these are absent, the likelihood of stroke is significantly decreased (– likelihood ratio of 0.39). While these findings are not perfect for diagnosing stroke, the fact that they can be evaluated relatively rapidly and easily make them very valuable in the acute setting.

Proposed systems include FAST (face, arm, speech, and time),] as advocated by the Department of Health (United Kingdom) and The Stroke Association, the American Stroke Association (www.strokeassociation.org) , National Stroke Association (US www.stroke.org), the Los Angeles Prehospital Stroke Screen (LAPSS) and the Cincinnati Prehospital Stroke Scale (CPSS). Use of these scales is recommended by professional guidelines.

Diagnosis

Stroke is diagnosed through several techniques: a neurological examination (such as the Nihss), CT scans (most often without contrast enhancements) or MRI scans, Doppler ultrasound, and arteriography. The diagnosis of stroke itself is clinical, with assistance from the imaging techniques. Imaging techniques also assist in determining the subtypes and cause of stroke. There is yet no commonly used blood test for the stroke diagnosis itself, though blood tests may be of help in finding out the likely cause of stroke.

Physical examination

A physical examination, including taking a medical history of the symptoms and a neurological status, helps giving an evaluation of the location and severity of a stroke. It can give a standard score on e.g. the NIH stroke scale.

Imaging

For diagnosing ischemic stroke in the emergency setting:

•           CT scans (without contrast enhancements)

sensitivity= 16%

specificity= 96%

•           MRI scan

sensitivity= 83%

specificity= 98%

For diagnosing hemorrhagic stroke in the emergency setting:

•           CT scans (without contrast enhancements)

sensitivity= 89%

specificity= 100%

•           MRI scan

sensitivity= 81%

specificity= 100%

For detecting chronic hemorrhages, MRI scan is more sensitive.

Prevention

Given the disease burden of strokes, prevention is an important public health concern. Primary prevention is less effective than secondary prevention (as judged by the number needed to treat to prevent one stroke per year). Recent guidelines detail the evidence for primary prevention in stroke. Because stroke may indicate underlying atherosclerosis, it is important to determine the patient's risk for other cardiovascular diseases such as coronary heart disease. Conversely, aspirin prevents against first stroke in patients who have suffered a myocardial infarction or patients with a high cardiovascular risk.

http://stroke.ahajournals.org/

http://health.indiamart.com/emergencies/stroke.html

http://www.ninds.nih.gov/disorders/stroke/stroke.htm

Courtesy: Various Sources Over Internet.