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A 65-year-old man awakened from an afternoon nap and noted a complete hemiparesis involving his arm, face, and leg. His wife called EMS and he was brought to the ED within half an hour.

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A noncontrast head CT was obtained immediately after the patient’s arrival (Figure 1). The CT was initially interpreted as normal.

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  • On which side was the patient’s hemiparesis?
  • What are the early CT signs of an ischemic stroke?
  • Should thrombolytic agents be administered?

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The principal role of CT in patients with a stroke is to exclude intracranial hemorrhage (10–15% of strokes) or other lesions such as a tumor, abscess, or SDH, which could be the cause of the patient’s neurological deficit. CT has a limited ability to detect acute ischemic changes within 12–24 hours of onset, although subtle signs of early ischemia can be detected in a substantial proportion of patients, even within 3 hours of stroke onset. After 24 hours, CT is better able to detect an ischemic stroke because there is more pronounced cerebral edema.

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With the advent of thrombolytic therapy for patients that present within 3 hours of stroke onset, CT plays two additional roles in emergency patient care. First, and foremost, CT detects hemorrhage, which is an absolute contraindication to thrombolytic therapy. Second, a large area of early ischemic change is considered by some clinicians to be a contraindication to the use of thrombolytic therapy because it is associated with an increased risk of hemorrhage. A third potential role of imaging would be to confirm the diagnosis of an acute ischemic stroke, although CT has a limited ability to do this.

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CT Signs of Ischemic Stroke

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There are three stages in the evolution of an ischemic stroke as depicted on CT.

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Acute ischemic changes occur within 24 hours and may be visible within three hours of the onset of stroke. These early ...

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