When there is acute hemorrhage into the brain or a large thrombus (with its accumulation of red blood cells) in a vessel, the accumulated hemoglobin appears bright on a CT scan.  After the hemoglobin is removed by phagocytes, the bright area disappears.
Question
If brain tissue has actually been killed and the destroyed remnants removed (this occurs months after the injury), what would you predict about the appearance of the affected area on CT?  
Answer
  • it would be more like water-CSF, so it would look dark.


    • When there is ischemia in the brain, the water content of the affected brain tissue increases and it swells.

    Question
    How do you think this would change the density of the affected brain tissue as seen on CT scan?  
    Answer
  • the increased water content would make it look somewhat darker.


    • These changes cannot be visualized immediately!  Depending on just which area of the brain is involved, they begin to be seen on CT scans after about 12-18 hours. This means that very early ischemic strokes are not detected on CT scans. As ischemic damage continues to evolve, however, the additional changes make these areas visible on CT scans.  

    Simplified display of CT brain tissue image characteristics--STROKE


    Practical Hint: The brain is largely a symmetrical structure--when you are trying to find areas of damage, try looking for regions in which the left side and the right side appear different.

    This patient collapsed and died shortly after having a massive intracerebral hemorrhage.  Identify the hemorrhage.  Note that there is blood in brain tissue, the ventricles, and even in the subarachnoid space which outlines the sulci.

    This patient has suffered at least two ischemic strokes in previous years.  Can you find the damaged areas?  The small infarct (area of dead tissue) on the left side of the patient's brain is the result of a lacunar stroke.

    B.D. had successful coronary bypass surgery.  Four days later, however, he had sudden onset of left-sided weakness involving both his leg and arm.  He progressively regained strength in his left leg and by the time he was discharged 6 days later he was walking normally, although his grip remained weak on the left.  He has continued to improve at home.

    Question:
    Did he have a stroke or a TIA?
    Answer:
  • a stroke.
    		•


    This is a CT scan obtained at the time of B.D.'s discharge, 6 days after his symptoms began.  Recall that he had an ischemic stroke.  Can you identify the area of his brain that was affected?