CT brain interpretation

Mnemonic

Blood Can Be Very Bad

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

Blood

1. Is blood present?
2. If so, where is it?
3. If so, what effect is it having?

Acute blood is bright white (once it clots) Blood becomes isodense at 1wk (exact time depends on size of clot) Blood becomes hypodense at 2weeks (exact time depends on size of clot)

Epidural (blood problem) Lens shaped Does not cross sutures Classically described w/ 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 Can have small Subdural but with major shift (2/2 brain injury/oozing/swelling) Marker for severe head injury (mortality approaches 80%) -Chronic subdural usually slow venous bleed and well tolerated

SAH

• Blood in the cisterns/cortical gyral surface
• Aneurysm: 80%

AVM: 5%

• May see in interhemispheric fissure also

• Suprasellar cistern is first place see SAH (circle of willis)

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Intraventricular/intraparenchymal hemorrhage Not typically subtle Doesn't matter if intraventricula rruptured into parenchyma or vice-versa

Cisterns

4 key cisterns:

1. Circummesencephalic
2. Suprasellar
3. Quadrigeminal
4. Sylvian

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)

1. Tumor: may see increased hypodensity (edema)
   1. 80% visisble w/o contrast

Atrophy Abscess

(contrast lights at areas of breakdown in BBB)

Hemorrhagic contusion (deceleration injury from brain banging into frontal fossa)

1. Hyperdensities

Mass effect Stroke Intracranial air (skull fx)

Ventricles

1. Check all 4 for size and for hemorrhage
   1. Size: Differentiate between hydrocephalus from incr pressure versus from atrophy (ex-vacuo)
      1. Are the gyri effaced?

If ventricles enlarged --> hydrocephalus

Bone

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

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

• Circummescephalic cistern is first one that shows incr ICP (squished shut)
• Quadrigeminal cistern ("W" shaped) is second one that shows incr ICP

• Temporal tips (comma-shaped) of lateral ventricle is first place where see hydrocephalus (incr intraventricular pressure)
  • 1/5 pts w/ SAH hemorrhage develop hydrocephalus

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can view suprasellar cistern and temporal tips all in one view

Sylvian cistern is where distal MCA bleeds sometimes are seen

1. Brain density-grey vs white matter
2. midline shift
3. Subarach space-syl fissure - look for sulci
4. vent system - look at temp horns
5. Corner shots - eyes / bones

Source

Blood Can Be Very Bad: CT Interpretation Course Guide

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