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Transient ischaemic attacks are focal CNS disturbances caused by vascular events such as microemboli and occlusion leading to ischaemia where the symptoms last less than 24 hours and there are no permanent neurological sequelae. Transient ischaemic attacks are a risk factor for subsequent stroke or myocardial infarction. Diagnosis rests critically upon the patient's history since the attacks are seldom witnessed by a physician and there are no confirmatory tests.
Emboli are the major cause.
Stroke is defined by the World Health Organization as a clinical syndrome consisting
of 'rapidly developing clinical signs of focal (at times global) disturbance
of cerebral function, lasting more than 24 h or leading to death with no apparent
cause other than that of vascular origin' (1).
Notes:
- there are limitations to these definitions of stroke and TIA outlined
- for example, they do not include retinal symptoms (sudden onset of monocular
visual loss), which should be considered as part of the definition of stroke
and TIA. The symptoms of a TIA usually resolve within minutes or a few hours
at most, and anyone with continuing neurological signs when first assessed
should be assumed to have had a stroke
- definition of stroke excludes transient ischaemic attacks, subdural haematomas,
and infarction or haemorrhage due to infection or tumour. However, practically
it is often difficult to discriminate between a small stroke and a transient
ischaemic attack
- the term 'brain attack' is sometimes used to describe any neurovascular
event and may be a clearer and less ambiguous term to use
Reference:
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