Radiologic evaluation of hyperacute brain infarction: a review

Imaging cerebral infarction in first few hours after the onset of clinical symptoms is a challenge. The role of stroke imaging underwent a paradigm shift from confirmation of infarction from and exclusion of hemorrhage to the detection of the tissue at risk that may be rescued with restoration of circulation. Computed tomography (CT) is generally performed before starting the therapy in order to exclude the presence of bleeding and tumors. Although CT may show findings of infarction as early as 3-6 hours after ictus 30% of CT scans are normal in the first few hours after ischemic insult. Conventional spin-echo MR imaging is more sensitive and specific than CT in the detection of cerebral ischemia during the 1st few hours symptom onset. Lesion conspicuity can be further optimized by using an FLAIR sequence. Diffusion-weighted MR imaging is a technique that is more sensitive than conventional MR imaging for detection of hyperacute cerebral ischemia, within minutes after the onset of ischemia, a profound restriction in water diffusion occurs in affected brain tissue and DWI is sensitive to diffusion restriction. But DWI only shows areas that are already irreversibly damaged. Around this core, there is believed to be a region of ischemic penumbra where reversible cell death occurred. An imaging technique that accurately identifies this tissue at risk could have a tremendous impact on patient management by thrombolysis. Perfusion imaging allows depiction of both areas of irreversible ischemia and areas of reversible ischemia. Both MR and CT Perfusion imaging help define the tissue at risk. The introduction of intravenous thrombolysis with tPA has radically changed the role of neuroimaging for stroke evaluation. The ECASS trial prescribed for treatment with intravenous tPA with stroke symptoms of less than 6 hours in duration and who did not have identifiable infarction of greater than one- third of the middle cerebral artery (MCA) territory on CT images. The NINDS trial established that intravenous tPA treatment is efficacious if administered less than 3 hours after symptom onset. The experience of interventional cardiologists in treating acute myocardial infarction may predict the future of intervention neuro in treating ischemic stroke.