A stroke (sometimes called a cerebrovascular accident (CVA))is the rapidly developing loss of brain function(s) due to disturbance in the bloodsupply to the brain, caused by a blocked or burst blood vessel. This can bedue to ischemia(lack of glucose and oxygen supply) caused by thrombosisor embolismor due to a hemorrhage.As a result, the affected area of the brain is unable to function, leading to inability tomove one or more limbs on one side of the body, inability to understandor formulate speech, or inability to see one side of the visual field.
A stroke is a medical emergency and can cause permanent neurologicaldamage, complications, and death. It is the leading cause of adult disabilityin the United States and Europe. It is the number two cause of death worldwideand may soon become the leading cause of death worldwide. Riskfactors for stroke include advanced age, hypertension(high blood pressure), previous stroke or transient ischemic attack (TIA), diabetes,high cholesterol, cigarettesmoking and atrial fibrillation. High blood pressure is themost important modifiable risk factor of stroke.
A stroke is occasionally treated with thrombolysis("clot buster"), but usually with supportive care (speech and language therapy, physiotherapyand occupational therapy) in a "strokeunit" and secondary prevention with antiplateletdrugs (aspirinand often dipyridamole), blood pressure control, statins, and inselected patients with carotid endarterectomy and anticoagulation
The traditional definition of stroke, devised by the World Health Organization in the 1970s,is a "neurological deficit of cerebrovascular cause that persists beyond24 hours or is interrupted by death within 24 hours". This definition wassupposed to reflect the reversibility of tissue damage and was devised for thepurpose, with the time frame of 24 hours being chosen arbitrarily. The 24-hourlimit divides stroke from transient ischemic attack, which is arelated syndrome of stroke symptoms that resolve completely within 24 hours.With the availability of treatments that, when given early, can reduce strokeseverity, many now prefer alternative concepts, such as brain attack andacute ischemic cerebrovascular syndrome (modeled after heart attack and acute coronary syndrome respectively), thatreflect the urgency of stroke symptoms and the need to act swiftly
Signs and symptoms
Stroke symptoms typically start suddenly, over seconds to minutes, and inmost cases do not progress further. The symptoms depend on the area of thebrain affected. The more extensive the area of brain affected, the morefunctions that are likely to be lost. Some forms of stroke can cause additionalsymptoms: in intracranial hemorrhage, the affected area may compress otherstructures. Most forms of stroke are not associated with headache, apartfrom subarachnoid hemorrhage and cerebral venous thrombosis and occasionallyintracerebral hemorrhage.
Various systems have been proposed to increase recognition of stroke bypatients, relatives and emergency first responders. A systematicreview, updating a previous systematic review from 1994, looked at a numberof trials to evaluate how well different physical examination findings are able topredict the presence or absence of stroke. It was found that sudden-onset faceweakness, arm drift (e.g. if a person, when asked to raise both arms,involuntarily lets one arm drift downward) and abnormal speech are the findingsmost likely to lead to the correct identification of a case of stroke ( likelihoodratio of 5.5 when at least one of these is present). Similarly, when allthree of these are absent, the likelihood of stroke is significantly decreased(– likelihood ratio of 0.39). While these findingsare not perfect for diagnosing stroke, the fact that they can be evaluatedrelatively rapidly and easily make them very valuable in the acute setting.
Proposed systems include FAST (face, arm, speech, and time), as advocated bythe Department of Health (UnitedKingdom) and The Stroke Association, the Los AngelesPrehospital Stroke Screen (LAPSS) and the Cincinnati Prehospital Stroke Scale (CPSS).Use of these scales is recommended by professional guidelines.
For people referred to the emergencyroom, early recognition of stroke is deemed important as this can expeditediagnostic tests and treatments. A scoring system called ROSIER (recognition ofstroke in the emergency room) is recommended for this purpose; it is based onfeatures from the medical history and physical examination.
If the area of the brain affected contains one of the three prominent Centralnervous system pathways—the spinothalamic tract, corticospinal tract, and dorsalcolumn (medial lemniscus), symptoms may include:
In most cases, the symptoms affect only one side of the body (unilateral).The defect in the brain is usuallyon the opposite side of the body (depending on which part of the brain isaffected). However, the presence of any one of these symptoms does notnecessarily suggest a stroke, since these pathways also travel in the spinal cordand any lesion there can also produce these symptoms.
In addition to the above CNS pathways, the brainstemalso consists of the 12 cranial nerves. A stroke affecting the brain stemtherefore can produce symptoms relating to deficits in these cranial nerves:
- altered smell, taste, hearing, or vision (total or partial)
- drooping of eyelid (ptosis) and weakness of ocular muscles
- decreased reflexes: gag, swallow, pupil reactivity to light
- decreased sensation and muscle weakness of the face
- balance problems and nystagmus
- altered breathing and heart rate
- weakness in sternocleidomastoid muscle with inability to turn head to one side
- weakness in tongue (inability to protrude and/or move from side to side)
If the cerebralcortex is involved, the CNS pathways can again be affected, but alsocan produce the following symptoms:
If the cerebellumis involved, the patient may have the following:
- trouble walking
- altered movement coordination
- vertigo and or disequilibrium
Loss of consciousness, headache, and vomiting usuallyoccurs more often in hemorrhagic stroke than in thrombosis because of theincreased intracranial pressure from the leaking blood compressing on thebrain.
If symptoms are maximal at onset, the cause is more likely to be asubarachnoid hemorrhage or an embolic stroke.