1. Head CT: The Basics
Stephen Magill
Radiology Rotation
August, 2012

2. Computed Tomography: Intro
Uses X-Rays (radiation) to create cross sectional images (tomographs) through the human body
Findings are always described based in relative “densities” (vs MRI “intensity”)

3. CT: Relative Density Bright (High Density) Dark (Low Density) Bone
Contrast
Acute Blood
Soft Tissue:
Gray matter
White matter
Water
Fat
Air
Bone is

4. How To Describe A Head CT
Always start with this sentence:
“This is a
[non-contrast vs contrast enhanced]
[axial vs sagittal vs coronal]
head CT showing…”

5. Normal Axial Head CT
TOP (Superior)
BOTTOM (Inferior)
23 yr old

6. Important Places to look:
Basilar
Cistern B
Ventricle Size
Make sure no hydrocephalus
- Evans ratio (A/B) < 0.3
Also check temporal horns
Cisterns
Should be plenty of CSF
(Black space)
No blood/compression

7. Lesion Location: Intra- vs Extraparenchymal
Intraparenchymal:
Located within brain tissue
Extraparenchymal:
Located within the bony casing of CNS
BUT outside the brain tissue itself

8. Lesion Location: Extraparenchymal
Two examples of meningioma
Extraparenchymal tumor (not in the brain tissue)
The tumor is slow growing which is reflected in by the mild displacement of the other brain structures; acute extraparenchymal lesions (bleeds) will cause marked displacement or herniation

9. Lesion Location: Intraparenchymal
Two examples of glioblastoma
Intraparenchymal tumor (within the brain tissue)
Dark regions (gray arrow) within the tumor are necrotic cavities

10. Head CT in Acute Situation
Anytime someone has head trauma with altered mental status they should have a head CT
You are looking for acute blood, which is bright
All MD’s should know what acute blood looks like and be able to describe its general location:
Epidural
Subdural
Subarachnoid (SAH)
Intraventricular (IVH)
Intraparaenchymal (IPH)
Location (Cause)
Between Skull and Dura (Trauma)
Between Dura and Arachnoid (Trauma)
Cisterns or Sulci (Trauma, Aneurysm rupture)
Ventricles (Trauma, HTN hemorrhage)
Brain Tissue (Tra./Tmor, HTN hem)
OUT IN

11. Locations of blood around/in the brain

12. Locations of blood around/in the brain
IPH

13. Examples of bleeding in different locations
EDH
Blood spread
limited by
suture lines
Midline shift
IPH
SAH filling sulci
SDH
Blood crosses
suture lines
Calcified choroid
Plexus (normal)
IVH
Saatman et al (2008) J Neurotrauma

14. Examples of bleeding in different locations
IVH

15. Examples of bleeding in different locations
SAH in the basilar cistern
and extending out into the fissures A classic CT after rupture of a Circle of Willis aneurysm
So called “Star of Death”

16. Considering hypertensive hemorrhage Head CT shows…
Case example
68 y/o female brought in by ambulance to ED after rapid mental status deterioration
Obtunded on exam
BP: 210/106
Considering hypertensive hemorrhage
Head CT shows…

17. Try to describe it as you would present it.
Case example
What do you see?
Try to describe it as you would present it.

18. Case example “This is a non-contrast, axial head CT showing…
Surrounding soft tissue edema (dark areas)
Midline shift
IPH
“This is a non-contrast, axial head CT showing…
…a large left-sided intraparenchymal hemorrhage with surrounding edema and significant midline shift”

19. Case example “This is a non-contrast, axial head CT showing…
Surrounding soft tissue edema (dark areas)
Midline shift
IPH
“This is a non-contrast, axial head CT showing…
…a large left-sided intraparenchymal hemorrhage with surrounding edema and 2.2 cm of midline shift”

20. Case example “This is a non-contrast, axial head CT showing…
More caudal slice of previous axial head CT
Herniating Uncus
Notice the lack of space where the basilar cistern should be; it is filled with brainstem
Inferior portion of IPH
“This is a non-contrast, axial head CT showing…
…a large left-sided intraparenchymal hemorrhage with surrounding edema and 2.1 cm of midline shift. There is also left sided uncal herniation and compression of the basilar cistern due to likely brainstem herniation.”

21. Taken to OR for clot evacuation Post op-head CT shows…
Case Example
Taken to OR for clot evacuation
Post op-head CT shows…

22. Case Example
Pneumocephalus
Markedly improved midline shift
Drain
Some new IVH
Residual IPH
Removal of the majority of the clot and improvement in midline shift. Also notice the drain that is left in place.
Pneumocephalus (air in the head) is also present, a normal post-operative finding

23. Case Example Decompression allows improvement in herniation
Basilar cistern is now open and decompressed
Pneumocephalus where inferior portion of IPH was located
Decompression allows improvement in herniation
Basilar cistern now wide open
Neurological exam improved post-operatively

24. The End