Transient ischaemic attack

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).

NICE guidance emphasises the need for review within 24 hours of a patient with a TIA (2):

• initial management of suspected and confifirmed TIA
  • offer aspirin (300 mg daily), unless contraindicated, to people who have had a suspected TIA, to be started immediately
  • refer immediately people who have had a suspected TIA for specialist assessment and investigation, to be seen within 24 hours of onset of symptoms
  • do not use scoring systems, such as ABCD2, to assess risk of subsequent stroke or to inform urgency of referral for people who have had a suspected or confirmed TIA
  • offer secondary prevention, in addition to aspirin, as soon as possible after the diagnosis of TIA is confirmed

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:

• (1) Hatano S (1976) Experience from a multicentre stroke register: a preliminary report. Bulletin of the World Health Organization 54: 541-53.
• (2) NICE (May 2019). The diagnosis and acute management of stroke and transient ischaemic attacks