Attenuated stroke severity after prodromal TIA : A role for ischemic tolerance in the brain?

Ischemic tolerance has been extensively studied in experimental models of heart and brain ischemia. While there is some clinical evidence of ischemic tolerance in the heart, it is not known whether the same is true for the human brain. We conducted a retrospective case-control study in 148 stroke patients with and without antecedent TIA. Despite no significant differences in baseline characteristics, independence (Rankin scale score of 0 to 1) and favorable outcome (Glasgow Coma Scale score of 5) were significantly associated with prior TIA in univariate analysis. After correction for other cardiovascular risk factors, TIA before stroke also was an independent predictor of mild stroke (Canadian Neurological Scale score of > or= 6.5) in multivariate models (absolute difference 21.6%; P=0.01). Assuming that a TIA represents an adequate stimulus to elicit ischemic tolerance, our results suggest that ischemic tolerance might occur in the human brain.