Transient ischemic attacks before ischemic stroke:: Preconditioning the human brain?: A multicenter magnetic resonance imaging study

Background and Purpose - We investigated whether transient ischemic attacks ( TIAs) before stroke can induce tolerance by raising the threshold of tissue vulnerability in the human brain. Methods - Sixty-five patients with first-ever ischemic territorial stroke received diffusion- and perfusion-weighted MRI within 12 hours of symptom onset. Epidemiological and clinical data, lesion volumes in T2, apparent diffusion coefficient ( ADC) maps and perfusion maps, and cerebral blood flow and cerebral blood volume values were compared between patients with and without a prodromal TIA. Results - Despite similar size and severity of the perfusion deficit, initial diffusion lesions tended to be smaller and final infarct volumes were significantly reduced ( final T2: 9.1 [interquartile range, 19.7] versus 36.5 [91.2] mL; P = 0.014) in patients with a history of TIA ( n = 16). This was associated with milder clinical deficits. Conclusions - The beneficial effect of TIAs on lesion size in ADC and T2 suggests the existence of endogenous neuroprotection in the human brain.