1. Head CT Interpretation in the ED: The Complete Primer
Brian A. Stettler, MD
Assistant Professor
Department of Emergency Medicine
University of Cincinnati

2. Objectives Discuss the utility of Head CT
Discuss what Head CT will miss
Review basic interpretation of the Head CT
Discuss a few specific disease processes 54 2 54

3. Clinical History CC: Headache and weakness
HPI: 67 year old female with several months of dull headaches relieved by Tylenol and subjective “dizziness” without falls. Symptoms worsened today about 2 hours ago and she now complains she cannot walk secondary to dizziness 54 3 54

4. ED Presentation PMHx: DM, HTN, CAD Meds: Atenolol, HCTZ, ASA, Insulin
All: NKDA
SocHx: 1PPD, Occasional Etoh, denies drugs
ROS: mild anorexia, weight loss approx 5 lbs over past month, o/w neg 54 3 54

5. ED Presentation PE: 176/94, 65, 16, 98.8, 93% RA
Gen: alert and conversive, sl uncomfortable appearing
HEENT: WNL
Pulm: sl wheezes, otherwise WNL
CV: WNL
Neuro: strength 4/5 throughout, gait unsteady without overt ataxia, no deficits to cranial nerves 54 3 54

6. Points of Discussion
In addition to other labs, a non-contrast head CT is ordered
How is this study interpreted?
What findings affect the treatment of the patient?
What findings portend a bad outcome for the patient? 54 2 54

7. Non-contrast Head CT
The most common neuroimaging tool employed in the ED
Performed in seconds, usually read in minutes
No IV access required
Available 24 hours/day in most EDs
No real contraindications
Good sensitivity and specificity for many disease processes 54 2 54

8. Non-contrast Head CT Benefits:
Gold standard in assessment for acute hemorrhage
Very good at documenting mass effect and herniation
Will visualize acute ischemia, neoplasm, localized intracranial infection
Good at visualizing skull fracture 5 17

9. Non-contrast Head CT Drawbacks
Poor at visualizing disease in the posterior cranial fossa, especially ischemia
Poor at diagnosing intracranial mass that does not have significant mass effect
Sensitivity is not high enough to completely eliminate SAH
Will miss delayed disease, such as delayed SDH 5 17

10. Head CT Interpretation
Scout, assessment for adequacy
Quick look
Detailed look (force yourself)
Extra-axial blood
Mass effect
Ischemia
Ventricles
Vessel density
Bone windows
Extras (sinuses, mastoids)
Compare to old 54 54 2

11. Head CT Interpretation
Look at the scout
Adequate study?
Minimize motion
Subject to artifact from metal 5 17

12. Head CT Interpretation
Quick look
Get the gestalt
Assess for gross abnormalities 54 2 54

13. Head CT Interpretation
Extra-axial hemorrhage
Epidural hematoma
Subdural hematoma
Subarachnoid hemorrhage
Intracerebral hemorrhage
Intraventricular hemorrhage 54 2 54

14. Epidural Hematoma “Lens” shaped Does not cross suture lines
Typically acute or hyperacute
Frequently associated with mass effect 54 2 54

15. Subdural Hematoma Located along calvarium, falx, tentorium
Crosses suture lines, usually spreads more extensively than epidural
Acute 54 54 2

16. Subdural Hematoma Can be acute, subacute, or chronic
Density on CT helps to age hematoma
Can frequently be a mix of ages
Can have mass effect that ranges from none to severe
Subacute 54 54 2

17. Subdural Hematoma Not all SDH are bright white
Chronic
Not all SDH are bright white
MUST follow gyri/sulci to edge of calvarium on every cut
Falx may be calcified but should be thin
Osborn, Diagnostic Imaging Brain 2004 54 54 2

18. Subarachnoid Hemorrhage
Can be present in cisterns, around gyri and sulci
Almost always acute
Sensitivity of NCHT
Not well known or agreed upon
Probably in the high 90’s early
Decreases as time progresses from onset of symptoms 54 2 54

19. Subarachnoid Hemorrhage
Source:
Post-traumatic
Aneurysmal
AVM
Other
Hounsfield units
Blood is (80) 54 2 54

20. Intracerebral Hemorrhage
Location can be anywhere in the parenchyma
Can be caused by hypertension, AVM, amyloid
Typically present with headache, focal neurologic findings, AMS, N/V 54 2 54

21. Intracerebral hemorrhage
CT findings that affect outcome
Volume of hemorrhage
Location of hemorrhage (supra vs infratentorial)
Presence of intraventricular hemorrhage
Also describe:
Presence of midline shift
Presence of herniation
Presence of hydrocephalus 54 2 54

22. Volume of Hemorrhage (A x B x C)/2
A and B are perpendicular dimensions in the slice that shows the maximal amount of hemorrhage
C is the total number of slices that show hemorrhage x the slice thickness
Ex: 4cm x 5.5 cm by (8 x 5mm slices)/2
4 x 5.5 x 4/2 = 45cc 54 2 54

23. Mass Effect and Midline Shift
Mass effect can be local or generalized
When generalized, typically seen as shift of the midline structures away from the area of mass effect
Midline shift
Use drawing tools to draw line down center of skull
Measure from midline structure (pineal gland, falx, septum pellucidum) to line drawn 54 2 54

24. Herniation Herniation is an ominous sign on CT Types
Uncal (3rd nerve palsy – the “blown pupil”)
Transtentorial
Sub-falcine
Tonsillar
Look for structures where they should not be

25. Tying it Together Spontaneous ICH Supratentorial (L basal ganglia)
Approx 45cc
8mm of midline shift
Evidence of uncal herniation 54 2 54

26. Trauma - Contusions
Patchy hemorrhage contained to the superficial grey matter
Frequently associated with local edema
Caused by brain impact to bone
Locations most commonly temporal lobes and frontal, but can occur anywhere 54 2 54

27. Trauma - Contusions
Contusions frequently evolve from small petechiae to large areas of edema and hemorrhage over the course of 1-2 days
Osborn, Diagnostic Imaging Brain 2004

28. Ischemia Very early CT typically negative Early findings
Loss of grey-white differentiation
Insular “ribbon”
Basal ganglia/internal capsule
Effacement of ventricles and local mass effect
Hyperdense artery 54 2 54

29. Ischemia
ASPECTS
Larger areas of grey-white changes on initial CT have worse outcomes
Score < 7 had OR 82 for worse functional outcome
Barber, Lancet 2000 54 54 2

30. Being Thorough Use bone windows on every trauma
Don’t forget the extras
Sinuses, mastoid air cells
Air where it shouldn’t be
Orbits
Old infarcts
If abnormal, look for an old CT 54 2 54

31. Case Follow-up
Pt’s CT showed a small, ill-defined parenchymal hemorrhage
Follow-up MRI showed multiple enhancing lesions suspicious for mets
Pt undergoing treatment for metastatic lung CA 54 2 54

32. Head CT - Conclusions Scan early and often
Beware the lurking slit subdural
Contusions can be tiny – at first
Ischemia can be subtle
You still can’t completely trust the negative SAH CT
Negative early doesn’t always mean negative late – and vice versa 5 17

33. Head CT - Conclusions
Useful imaging screening tool for many life-threatening neurologic processes
May miss early findings in hemorrhage or ischemia
Interpretation must be done thoroughly
The same way every time
Assess not only primary pathology, but factors contributing to outcome 54 2 54

34. Questions?