CT brain interpretation

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Lobes of the brain.
Bones of the cranium.
Example of a normal head CT with IV contrast.

Blood Can Be Very Bad

  • Blood
  • Cisterns
  • Brain
  • Ventricles
  • Bone


  • Questions
    • Is blood present?
    • If so, where is it?
    • If so, what effect is it having?
  • Physiology
    • Acute blood is bright white (once it clots)
    • Blood becomes isodense at 1wk (exact time depends on size of clot)
    • Blood becomes hypodense at 2wks (exact time depends on size of clot)
  • Findings
    • Epidural hematoma (blood problem)
      • Lens shaped
      • Does not cross sutures
      • Classically described with injury to middle meningeal artery
      • Low mortality if treated prior to unconsciousness (<20% morbidity/mortality)
    • Subdural (brain problem)
      • Sickle shaped
      • Crosses sutures but not midline
      • Marker for severe head injury (mortality approaches 80%)
        • Small amount of bleed can be associated with major shift (secondary to brain injury/oozing)
    • SAH
      • Blood in the cisterns/cortical gyral surface/interhemispheric fissure
        • Suprasellar cistern is first place see SAH (location adjacent to circle of willis)
      • Aneurysm: 80%
      • AVM: 5%
    • Intraventricular/Intraparenchymal Hemorrhage
      • Typically obvious findings
      • Unimportant if intraventricular ruptured into parenchyma or vice-versa


  • 4 key cisterns:
    • Circummesencephalic
      • First cistern to show increased ICP (squished shut)
    • Suprasellar
    • Quadrigeminal
      • "W" shaped
      • Second cistern to show increased ICP
    • Sylvian
      • May see isloated distal MCA bleed
  • 2 questions:
    • Is there blood?
    • Are the cisterns open?


  • Compare side to side
  • Look for grey-white differentiation
    • Grey is denser so appears lighter on CT
  • Look at gyral pattern all the way around (gyri effacement indicator of increased ICP)
  • Findings
    • Tumor
      • May see increased hypodensity (edema)
      • 80% visible without contrast
    • Atrophy
    • Abscess
    • Hemorrhagic contusion
    • Mass effect
    • Stroke
    • Intracranial air (skull fracture)
    • Hyperdense middle cerebral artery or basilar artery sign
      • Suggests thrombosis of vessel
    • Suggestive of Cerebral venous thrombosis :
      • Empty delta sign: dense triangle in superior sagittal sinus
      • Cord sign: hyperattenuated, homogeneous linear or round foci in cerebral sinus [1]
      • Vein Sign: hypoattenuated foci in the deep vein [2]


  • Check all 4 for size and for hemorrhage
    • Temporal tips (comma-shaped) of lateral ventricle first place to show hydrocephalus
    • If enlarged must differentiate between hydrocephalus from increased pressure versus atrophy:
      • Are the gyri effaced? If yes suggestive of increased pressure


  • Inspect petrous ridges for skull base fracture
  • Look at mastoid air cells full of fluid (blood) for indirect evidence of fracture


See Also


  • Blood Can Be Very Bad: CT Interpretation Course Guide
  • www.uic.edu/com/ferne/pdf/acep2005_spring/perron_acep2005_spring_bcbvb_course.pdf
  1. Ram K. P. Vijay. "The Cord Sign."Radiology. 2006; 240:299-300.
  2. Linn J, Pfefferkorn T. "Noncontrast CT in Deep Cerebral Venous Thrombosis and Sinus Thrombosis: Comparison of Its Diagnostic Value for Both Entities."AJNR Am J Neuroradiology. 2010; 30: 728-735.