Transient Ischemic Attack: Definition, Diagnosis, and Risk Stratification

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Clinical diagnosis of TIA

According to the World Health Organization criteria proposed in 1988, TIA is defined as rapidly developed clinical signs of focal or global disturbance of cerebral function, lasting less than 24 hours, with no apparent nonvascular cause.8 The National Institute of Neurologic Disorders and Stroke Report published in 1990 defines TIA as brief episodes of focal loss of brain function for less than 24 hours, thought to be caused by ischemia, which can usually be localized to that portion of the

Brain imaging findings in TIA

The introduction of first computed tomography (CT) and later magnetic resonance imaging (MRI) to the evaluation of TIA have challenged the conventional view by demonstrating that clinically transient events are not necessarily transient at the tissue level. Approximately one-third of patients with the clinical syndrome of TIA develop a clinically relevant brain infarct.10, 20, 21 The first report of imaging proof of brain infarct in patients with TIA dates back to 1979. Perrone and coworkers22

Tissue-based definition of TIA

Advances in diagnostic imaging of TIA have led to the proposition of a new tissue-based definition.29 This new definition classifies TIA as a transient episode of neurologic dysfunction caused by focal brain, spinal cord, or retinal ischemia, without evidence of acute infarction. All remaining neurologic events, regardless of whether symptoms are transient or permanent, are called ischemic stroke, as long as they are associated with brain infarction. The tissue-based definition provides a safe

Prediction of stroke risk after TIA

Although the stroke risk after TIA is high (approximately 10% in 7 days), most TIAs (approximately 90%) do not pose an imminent risk of stroke. Accurate differentiation of the 10% at risk from the remaining 90% is critical for optimal stroke prevention. Individualization of TIA management requires a risk-based approach, whereby high-risk and low-risk individuals follow different paths.6, 47 High-risk patients are expected to benefit from urgent referral to specialized stroke centers, timely

Summary

Recent advances in neuroimaging have enhanced the understanding of TIA. Accumulated evidence indicates that clinically transient spells are not transient at the tissue level and leave infarct on the brain in nearly one-third of patients. TIA-related acute infarcts are typically extremely small and often are not detected by CT and conventional MRI. DWI is currently the preferred method of imaging in TIA. Recognition of acute infarcts in patients with TIA has challenged the long-standing

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    Disclosures: HA: NIH grant R01-NS059710 and AGS: NIH grant R01-NS038477. Full disclosures are listed in http://www.biomarkers.org/NewFiles/disclosures.html.

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