Diffusion–perfusion MRI for triaging transient ischemic attack and acute cerebrovascular syndromes

Abstract

Time from symptom onset to treatment is considered to be the key variable that influences the indication of recanalization therapy for treatment of acute brain infarction. Symptom duration less than 24 h defines transient ischemic attack (TIA). The evolution of multimodal brain MRI demonstrates that neuroimaging findings of tissue injury may be more important predictors of clinical outcomes than arbitrary time thresholds. Preliminaries studies suggest that stroke victims with a significant penumbra estimated by the diffusion/perfusion mismatch on MRI benefit from thrombolysis beyond the currently recommended time window of 4.5 h. New software programs can automatically produce reliable perfusion and diffusion maps for use in clinical practice. Combined diffusion and perfusion MRI reveals an acute ischemic lesion in about 60% of TIA patients. Patients with transient symptoms and a restricted diffusion lesion on MRI are considered by the American Heart Association (AHA) scientific committee to have suffered a brain infarction and have a very high risk of early stroke recurrence. Multimodal MRI provides critical real-time information about ongoing tissue injury as well as the risk of additional ischemic damage. It is becoming an essential tool for the diagnosis, management and triage of acute TIA and brain infarction.