CT brain interpretation

Mnemonic

Blood Can Be Very Bad

1. Blood
2. Cisterns
3. Brain
4. Ventricles
5. Bone

Blood

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

Cisterns

1. 4 key cisterns:
   1. Circummesencephalic
      1. First cistern to show incr ICP (squished shut)
   2. Suprasellar
   3. Quadrigeminal
      1. "W" shaped
      2. Second cistern to show incr ICP
   4. Sylvian
      1. May see isloated distal MCA bleed
2. 2 questions:
   1. Is there blood?
   2. Are the cisterns open?

Brain

1. Compare side to side
2. Look for grey-white differentiation
   1. Grey is denser so appears lighter on CT
3. Look at gyral pattern all the way around (gyri effacement indicator of incr ICP)
4. Findings
   1. Tumor
      1. May see increased hypodensity (edema)
      2. 80% visisble w/o contrast
   2. Atrophy
   3. Abscess
   4. Hemorrhagic contusion
   5. Mass effect
   6. Stroke
   7. Intracranial air (skull fx)

Ventricles

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

Bone

1. Inspect petrous ridges for skull base fx
2. Look at mastoid air cells full of fluid (blood) for indirect e/o fracture

Overall

If no blood is seen, all 4 cisterns are present and open and no blood, the brain is symmetric w/ normal gray-white differentiation, gyral pattern is normal, the ventricles are symmetric without dilation and no blood, and there is no fx, then there is no emergent dx from the CT scan

Source

Blood Can Be Very Bad: CT Interpretation Course Guide

• www.uic.edu/com/ferne/pdf/acep2005_spring/perron_acep2005_spring_bcbvb_course.pdf