TIA-related infarct

TIA-related infarctions on DWI are often very small (Ay et al. 2002 Kidwell et al. 1999 Rovira et al. 2002). As mentioned before, 96% of infarctions on DWI are smaller than 1 ml in volume. The mean infarction load (total volume of all acute infarctions if there are multiple) on DWI has been reported to be 1.5+1.8 ml (Ay et al. 2005). An infarction load of less than 1.8 ml is associated with reversible clinical deficit within 24 h with 79% sensitivity and 78% specificity. Two other DWI studies have produced similar results. Ay et al. (2002) found that the infarction size was less than 15 mm in diameter in 85% of 27 TIA patients with infarction identified by DWI, of which 83% were punctate (< 5 mm). Rovira et al. (2002) estimated TIA-related infarctions range from 2 to 40 mm in diameter (mean, 15 mm). Figures 12.3 and 12.4 present examples of small hyperintense lesions on DWI that represent the remnants or footprints of a recent ischemia. 

TIA-related infarctions on DWI can be predicted on the basis of certain clinical TIA features. Transient motor symptoms, preceding non-stereotypic attacks, the presence of an established cause of stroke, and presentation with aphasia are independent predictors of infarction on DWI (Ay et al. 2002 Crisostomo et al. 2003). In contrast, limb paresthesias, slurred speech, and brief attacks of dizziness or imbalance are not associated with occurrence of infarction. Of note, most symptoms that are not associated with infarction on DWI are based on patients subjective feelings and sensations in contrast to motor deficit or aphasia, it is not possible to objectively assess such symptoms and mark the brain as their origin. Of particular relevance to this point is that, according to a recent study, the independent predictors of infarction on DWI such as motor deficit and speech impairment are also independently associated with increased risk of stroke after TIA (Johnston et al. 2003), suggesting a potential role for DWI in the risk stratification for stroke following TIA. 

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