Transient ischemic attack: definition, diagnosis, and risk stratification

Abstract

Transient ischemic attack (TIA) can convey a high imminent risk for the development of a major stroke and is therefore considered to be a medical emergency. Recent evidence indicates that TIA with imaging proof of brain infarction represents an extremely unstable condition with early risk of stroke that is as much as 20 times higher than the risk after TIA without tissue damage. The use of neuroimaging in TIA is therefore critical not only for diagnosis but also for accurate risk stratification. In this article, recent advances in diagnostic imaging, categorizations, and risk stratification in TIA are discussed.

Figure 1

An 86 year old woman with incoherent speech and left facial droop for 5 minutes. The FLAIR image shows several scattered and confluent periventricular and subcortical white matter hyperintense foci (the left image). Diffusion-weighted images (middle and right images) demonstrate two punctate foci of restricted diffusion representing acute infarcts involving the left precentral gyrus and posterior left parietal lobe (arrows). Notice that lesions observed on FLAIR images are not associated with restricted diffusion on diffusion-weighted images, indicating that they are not acute.

Figure 2

A 53 year old man with a 2 minute episode of tingling and clumsiness of the left hand. The diffusion-weighted images shows a 7 mm focus of restricted diffusion involving the right precentral gyrus (arrow). Notice the punctate nature of the lesion.

Figure 3

A 65 year old man with a 5 minute episode of slurred speech on the day of admission. Diffusion-weighted images show multiple, mostly punctate foci of restricted diffusion (arrows) in both right and left hemispheres suggesting embolism from a proximal source.

Figure 4

An 82 year old man with 2 distinct episodes of aphasia, one lasting for 30 minutes and the other for 15 minutes, within a two-hour period on the day of admission. There is no evidence of acute infarction on the diffusion-weighted image (the left image). The time to peak map (the right image), on the other hand, demonstrates signal changes consistent with hypoperfusion in the entire left MCA territory (arrows), marking ischemia as the cause of his transient episodes.