CT brain interpretation

Mnemonic

Blood Can Be Very Bad

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

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% visisble 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, homogenous 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

Blood Can Be Very Bad: CT Interpretation Course Guide
www.uic.edu/com/ferne/pdf/acep2005_spring/perron_acep2005_spring_bcbvb_course.pdf

↑ Ram K. P. Vijay. "The Cord Sign."Radiology. 2006; 240:299-300.
↑ 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.