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How much should one rely on computed tomography in patients with TIA in the era of diffusion-weighted magnetic resonance imaging?

To the Editor:

We read with great interest the paper by Douglas et al in Stroke .1 The authors report that the 90-day risk of stroke in transient ischemic attack (TIA) patients with a new infarction on CT is higher than patients with normal CT. This is an important piece of information, coming out almost 20 years after the original report by Waxman and Toole that first introduced the concept that clinically transient events are not necessarily transient in the brain.2 TIAs often leave footprints, small islands of permanent injury, on the brain. Nonetheless, CT is not the best available technique to pursue such footprints of ischemia. Diffusion-weighted imaging (DWI) offers much greater power in classifying patients who have ischemia as the cause of their reversible neurological deficit. Though more expensive, the cost-effectiveness of MRI might rest in using it to prevent stroke in this subgroup with TIA-associated infarction.

Recent studies using DWI reveal that infarctions in patients …