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Neuroimaging of acute ischemic stroke

Jamary Oliveira Filho, MD, MS, PhD
Section Editors
Scott E Kasner, MD
Eric D Schwartz, MD
Deputy Editor
John F Dashe, MD, PhD


Imaging studies are used to exclude hemorrhage in the acute stroke patient, to assess the degree of brain injury, and to identify the vascular lesion responsible for the ischemic deficit. Some advanced CT and MRI technologies are able to distinguish between brain tissue that is irreversibly infarcted and that which is potentially salvageable, thereby allowing better selection of patients likely to benefit from therapy. The use of this technology is dependent upon availability, and its role in guiding treatment decisions is still under study.

Neuroimaging during the acute phase (first few hours) of an ischemic stroke will be reviewed here. Other aspects of the acute evaluation of stroke, the clinical diagnosis of various types of stroke, and the subacute and long-term assessment of patients who have had a stroke are discussed separately. (See "Initial assessment and management of acute stroke" and "Clinical diagnosis of stroke subtypes" and "Overview of the evaluation of stroke".)


The main advantages of CT are widespread access and speed of acquisition. In the hyperacute phase, a noncontrast CT (NCCT) scan is usually ordered to exclude or confirm hemorrhage; it is highly sensitive for this indication. A NCCT scan should be obtained as soon as the patient is medically stable. The presence of hemorrhage leads to very different management and concerns than a normal scan or one that shows infarction. Immediate CT scanning of all patients with suspected stroke is also the most cost-effective strategy when compared with alternate strategies such as scanning selected patients or delayed rather than immediate imaging [1].

The utility of CT for acute stroke has been enhanced by the advent of additional CT techniques including CT perfusion imaging (CTP) and CT angiography (CTA). Multimodal CT evaluation that employs the three techniques (NCCT, CTA, and CTP) combined shows improved detection of acute infarction when compared with NCCT evaluation alone [2-5]. In addition, multimodal evaluation that includes CTA and CTP may permit assessment of the site of vascular occlusion, infarct core, salvageable brain tissue and degree of collateral circulation [6,7].

Early signs of infarction on noncontrast CT — The sensitivity of standard noncontrast CT for brain ischemia increases after 24 hours. However, in a systematic review involving 15 studies where CT scans were performed within six hours of stroke onset, the prevalence of early CT signs of brain infarction was 61 percent (standard deviation +/- 21 percent) [8].


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Literature review current through: Sep 2016. | This topic last updated: Apr 4, 2016.
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