What is a Transient Ischemic Attack (TIA)?
A TIA is a brief episode of neurological dysfunction caused by focal brain or retinal ischemia, typically lasting less than 1 hour, with no evidence of infarction on imaging. 1, 2
Modern Definition and Key Characteristics
The definition of TIA has fundamentally shifted from a time-based to a tissue-based approach:
The traditional 24-hour cutoff is obsolete – modern neuroimaging reveals that many patients with symptoms lasting less than 24 hours actually have brain infarction, making them stroke patients, not TIA patients 3, 1
The current definition emphasizes three critical elements: brief duration (typically <1 hour), absence of infarction on imaging (CT or MRI), and focal nature of the ischemic disturbance 1, 2
Patients with transient symptoms but visible lesions on diffusion-weighted MRI are now classified as having ischemic stroke, not TIA 2
Clinical Presentations by Vascular Territory
TIA symptoms vary based on which blood vessel is affected:
Anterior circulation (carotid territory): unilateral weakness, speech disturbance without weakness, or amaurosis fugax (transient monocular blindness when the ophthalmic artery is involved) 2, 4
Posterior circulation: symptoms affecting the brainstem or cerebellum 3
Retinal ischemia: amaurosis fugax represents a TIA of the retina and should be managed identically to cerebral TIA 5
Why TIA is a Medical Emergency
TIA is not a minor event – it is a medical emergency that demands urgent evaluation and treatment. 5, 4
The stroke risk following TIA is alarmingly high:
8.8% risk of stroke at 7 days and 11.6% at 90 days in general TIA populations 1, 2
The greatest stroke risk occurs within the first week after TIA, making immediate intervention critical 1, 2
In patients with symptomatic carotid disease, the 90-day risk of ipsilateral stroke jumps to 20.1% 1, 2
Long-term risk extends to approximately 13% in the first 90 days and up to 30% in the first 5 years 2
Common Pitfalls to Avoid
Do not dismiss TIA because symptoms resolved – patients and families often ignore TIA since symptoms naturally subside, but this transient nature does not diminish the urgency 4
Do not confuse TIA with syncope, isolated dizziness, drop attacks, or global amnesia – these are uncommonly caused by cerebral ischemia and require different diagnostic considerations 6
Do not delay evaluation beyond 24-48 hours – the window for maximum benefit from interventions like carotid endarterectomy narrows rapidly, with benefit decreasing considerably after 2 weeks 2