A stroke is defined as an acute loss of neurological function due to an interruption in the blood supply to a part of the brain. Strokes can be ischaemic (reduced blood and therefore oxygen supply to an area of the brain) or haemorrhagic (caused by bleeding).
Ischaemic strokes occur when there is a blockage in a vessel within or leading to the brain caused by one of the following:
- A blood clot in a vessel
- Atherosclerotic plaques
- Embolus from another vessel
Haemorrhage strokes occur when a blood vessel ruptures or leaks into the brain tissue or subarachnoid space.
The severity of stroke and the brain territory affected determine the type and severity of residual disabilities, which might result in the following:
- Asymmetry of the face – facial droop on one side
- Weakness on one side of the body – typically, unable to raise both arms in parallel
- Slurred speech – or inability to understand or formulate speech
- Other problems, including confusion, visual disturbance, dizziness, etc.
The F.A.S.T (Face, Arms, Speech, Time) algorithm is a quick method of assessing whether a person might be experiencing a stroke and is a strong reminder that stroke is an emergency.
Stroke is an emergency
After a stroke, acute treatment to minimise the severity of the outcome, rehabilitation to recover any lost function and prevention of recurrence are of great importance.
Time is brain1
Following a stroke, approximately 1.9 million neurons are lost every minute in the ischaemic area if left untreated.1
Loss of brain tissue means loss of function and long-term disability or death.
It is therefore imperative that a stroke is recognised early, the stroke patient is taken directly to a stroke unit (preferably using an established stroke network), and diagnosis and treatment follow as quickly and efficiently as possible.
Stroke versus TIA
Stroke was defined by the World Health Organization in the 1970s, as being a "neurological deficit of cerebrovascular cause that persists beyond 24 hours or is interrupted by death within 24 hours". The arbitrarily chosen timeframe of 24 hours divided strokes from transient ischaemic attacks (TIAs).2
TIAs cause brief periods (traditionally defined as lasting less than 24 hours) of neurological deficit, which resolve completely. They are associated with a significant increase in the risk of subsequent stroke, recurrent TIA, cardiovascular events or death.3
Risk of stroke is increased after a TIA4
In 2009, the American Heart Association and American Stroke Association (AHA/ASA) suggested a new definition for TIAs, based on imaging techniques, and with the ultimate aim of reducing the number of subsequent strokes and long-term disability after a stroke.5
- 30-50% of TIAs, classified using the 24-hour definition, showed the presence of permanent neurological damage on magnetic resonance imaging (MRI).5
The proposed definition by the AHA/ASA, refers to a TIA as a "transient episode of neurological dysfunction caused by focal brain, spinal cord, or retinal ischaemia, without acute infarction".5
- Saver J. Time Is Brain – Quantified. Stroke 2006;37:263-266.
- World Health Organization (1978). Cerebrovascular Disorders (Offset Publictions). Geneva: World Health Organization. ISBN 9241700432. OCLC 4757533.
- Howard G, Evans GW, Crouse JR 3rd et al. A prospective reevaluation of transient ischaemic attacks as a risk factor for death and fatal or nonfatal cardiovascular events. Stroke 1994;25(2):342-345.
- Coull AJ, Lovett JK, Rothwell PM; Oxford Vascular Study. Population based study of early risk of stroke after transient ischaemia attack or minor stroke: implications for public education and organisation of services. Br Med J 2004;328(7435);326.
- Easton DJ, Saver, JL, Albers GW et al. Definition and Evaluation of Transient Ischemic Attack. A Scientific Statement for Healthcare Professionals From the American Heart Association/American Stroke Association Stroke Council; Council on Cardiovascular Surgery and Anesthesia; Council on Cardiovascular Radiology and Intervention; Council on Cardiovascular Nursing; and the Interdisciplinary Council on Peripheral Vascular Disease. Stroke 2009;40:2276-2293.