Rathachai Kaewlai

1. Imaging of Head Trauma
Part 1: Introduction
Rathachai Kaewlai, MD
Specialized in Body Imaging and Emergency Radiology
rathachai@gmail.com
December 2006
The author is willing to receive any input, comments and corrections,
Please do not hesitate to contact at the email address provided above. 1
Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

2. Outline
• When to do brain imaging in trauma setting?
• What imaging is appropriate?
• Advantage and disadvantage of each imaging
modality
• Review of important cranial CT anatomy
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

3. Introduction
• Significance of craniocerebral injuries
– Common cause of hospital admission following trauma
– High morbidity and mortality particularly in adolescent and
young adults
• Concepts
1. Brain is contained within the skull which is a rigid and
inelastic container, so only small increases in volume can
be tolerated (Intracranial volume = Brain + CSF + Blood
volume)
2. Cerebral perfusion pressure (CPP) in injured areas is
pressure-passive flow (no autoregulation, cerebral blood
flow dependent on blood pressure)
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

4. Introduction
• Traumatic brain injury: 2 categories
1. Primary injury
– Initial injury to the brain as a result of direct trauma
– Example: hematoma, diffuse axonal injury, contusion
2. Secondary injury
– Subsequent injury to the brain after the initial insult
– Result from systemic hypotension, hypoxia, elevated
intracranial pressure (ICP) or biochemical insults
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

5. When to Do Imaging
and What to Do?
• Minor or mild acute closed head injury (GCS > 13)
– Without risk factors or neurologic deficit head CT without
contrast can be performed also known to be low yield (see
next page)
– With risk factors or neurologic deficit head CT without
contrast most appropriate and should be performed, brain
MRI reserved for problem solving
– Children < 2 years old head CT without
contrast most appropriate and should be performed
According to American College of Radiology (ACR) Appropriateness Criteria 5
Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

6. When to Do Imaging
and What to Do?
• Indications for CT in patients with minor head
injury
– Haydel MJ et al. Indications for CT in patients with minor
head injury. N Engl J Med 2000;343:100-5.
• 520 patients with minor head injury who had a normal Glasgow
Coma Scale and normal findings on a brief neurologic
examination underwent CT scans: 36 patients (6.9%) had
positive scans
• All patients with positive scans had one of the clinical findings:
short-term memory deficity, drug or alcohol intoxication,
physical evidence of trauma above clavicles, age > 60 yr,
seizure, headache, vomiting, or coagulopathy
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

7. When to Do Imaging
and What to Do?
• Indications for CT in patients with minor head
injury
– Haydel MJ et al. Indications for CT in patients with minor
head injury. N Engl J Med 2000;343:100-5.
• Results were tested in another 909 patients; using at least one
of the clinical findings above, the sensitivity of seven clinical
findings was 100%.
• CT abnormalities in 93 patients with positive CT scans: cerebral
contusion (none had surgery), subdural hematoma (6% had
surgery), subarachnoid hemorrhage (none had surgery),
epidural hematoma (22% had surgery), depressed skull
fracture (20% had surgery)
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

8. When to Do Imaging
and What to Do?
• Moderate or severe acute closed head injury
– Head CT without contrast most appropriate and should be
performed
– X-ray and/or CT of cervical spine also appropriate and
recommended
– MRI reserved for problem solving
• Rule out caroid or vertebral artery dissection
– MRI with MRA, or CT with CTA of the head and neck most
appropriate
– Cerebral angiography reserved for problem solving
According to American College of Radiology (ACR) Appropriateness Criteria 8
Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

9. When to Do Imaging
and What to Do?
• Penetrating injury, stable, neurologically intact
– Head CT without contrast most appropriate and should be
performed
– Skull x-ray also appropriate if calvarium is the site of injury
– C spine x-ray or CT appropriate if neck or C-spine is the site
of injury
– CTA of head and neck if vascular injury suspected
• Skull fracture
– Head CT without contrast most appropriate and should be
performed
– CTA of head and neck if vascular injury suspected
According to American College of Radiology (ACR) Appropriateness Criteria 9
Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

10. Skull Radiography
• 1/3 of patients with severe brain injury don’t have
fracture
• Role of skull radiography in acute head injury
– Calvarial fractures
• Linear fracture that is ‘in plane’ with axial CT scan can be
missed. Scout image of head CT, or CT reformation is useful
– Penetrating injuries
• Provide rapid assessment of degree of foreign body
penetration, e.g. stab wounds
– Radiopaque foreign bodies
• Example: patients with gunshot wounds to the head (to screen
for retained intracranial bullet fragments)
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

11. Computed Tomography (CT)
• Advantages
– High sensitivity for demonstrating mass effect, ventricular
size and configuration, bone injury, acute hemorrhage
regardless of location
– Widespread availability, rapid scanning, compatibility with
other medical and life support devices
• Limitations
– Insensitivity to detect small and nonhemorrhagic
lesions such as contusion, particularly when adjacent to
bony surfaces, diffuse axonal injury
– Relatively insensitive to detect early brain edema, hypoxic-
ischemic encephalopathy (HIE)
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

12. Computed Tomography (CT)
• Role of CT in acute head injury
– Patients with moderate-risk or high-risk for intracranial injury
should undergo early noncontrast CT to look for…
• Intracerebral hematoma
• Midline shift
• Increased intracranial pressure
– Patients with low-risk for intracranial injury: clinical selection
for CT is still problematic
• CT may be able to triage this patient group to admission,
surgery or discharge
• CT may lower the cost of hospital admission for observation
• Trade-off with greater use of CT in emergency setting
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

13. Computed Tomography (CT)
• Repeat head CT
– Required for clinical or neurologic deterioration, especially
within 72 hours after trauma
– Detection of delayed hematoma, hypoxic-ischemic lesions
and cerebral edema
• Pediatric patients
– Lower threshold for doing a CT scan
• Clinical criteria for scanning is less reliable, particularly in
children less than 2 years
– CT order needs to be balanced with risk of radiation
exposure
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

14. Magnetic Resonance Imaging (MRI)
• Advantages
– Sensitive for detection of diffuse axonal injury or
contusion with susceptibility sequence (T2 gradient
echo), distinguish different ages of blood
– Useful for screening of vascular lesions such as thromboses,
pseudoaneurysms, or dissection
• Limitations
– Insensitive for subarachnoid hemorrhage, air and fracture
– Certain absolute contraindications, e.g. pacemaker
– Limited availability in acute setting, longer imaging time
(than CT), incompatibility with some medical devices
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

15. Magnetic Resonance Imaging (MRI)
• Role of MRI in acute head injury
– Problem solving tool when CT is inconclusive or high clinical
suspicion
• Diffuse axonal injury: CT is less sensitive than MRI. For
example, patients with severe head injury but normal CT
• Brain contusion
– Vascular examinations of the brain and neck
• Suspicion of dissection, aneurysm or thrombosis
• CT angiography also has a competitive role as MR angiography
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

16. Brain CT: Normal Anatomy
• Make sure to look at all 3 different window
displays on one brain CT exam.
Brain window Subdural window Bone window
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

17. 3 1 3
Make sure the first image
include the foramen
magnum (red circle),
1 otherwise you will miss
(impending) tonsillar herniation
2
1 = cervicomedullary junction
2 = CSF space (should be dark)
3 = Cerebellar tonsils (tonsils are
not midline structures)
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

18. 5 = Pons (usually not clearly seen due to
‘beam hardening artifact’ from bony skull
base)
6 = Middle cerebellar peduncle
(structure that connects pons and
cerebellar hemispheres)
7 = Cerebellar hemisphere
8 = Forth ventricle (CSF cavity behind
the brainstem, slit-like appearance when
normal)
5
6
7
8
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

19. 7 = Cerebellum
9 = Midbrain (heart-shaped structure
normally surrounded by CSF. Effacement of
CSF may suggest early brain herniation)
10 = Temporal lobe
11 = Temporal horn of lateral
13 ventricle (Look for earliest hydrocephalus
here. Normally slit-like, or curvilinear)
10 12 = Uncus (Most medial portion of
12 temporal lobes; uncal herniation is called
when uncus displaces medially and obliterates
11 9 the CSF space on the side of midbrain)
13 = CSF cistern (Not seeing CSF around
midbrain may be abnormal; that’s what
7 radiologists call ‘effacement of the cistern’ as a
sign of cerebral herniation. Also a place to
look for subarachnoid hemorrhage)
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

20. 14 = Anterior falx (Know where it is, so
14 you can draw a ‘midline’ to see if there is
‘midline shift’ or not)
15 = Posterior falx
16 = Basal ganglia (Lateral to the
frontal horn of lateral ventricle)
17 = Thalamus (lateral to the third
ventricle which is very narrow here)
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16 18 = Sylvian fissure (CSF space
dividing frontal from temporal lobes. Look for
subarachnoid hemorrhage here)
17 Red line = Cerebral convexity (Look
for extra-axial hemorrhage here, better seen
in ‘subdural window’)
• Intra-axial = any pathology ‘in’ the brain
parenchyma
• Extra-axial = any pathology ‘not in the
parenchyma’ e.g. subarachnoid, subdural
and epidural pathology
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

21. 19 = Lateral ventricle
20 = Septum pellucidum (midline
structure dividing right and left lateral
ventricles; helps in measuring degree of
midline shift)
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20
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

22. 2 = CSF space (Look for subarachnoid
hemorrhage here)
2
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

23. Red lines = Temporomandibular
joint (socket)
21 = Condyle of mandible (ball;
should sit in the socket. Missing fracture or
dislocation in this region will cause patients’
long term disability)
21 22 = Mastoid air cells (should be
filled with air density, otherwise fracture of
the skull base should be suspected)
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

24. 23 = Sphenoid sinus (Look for fluid or
blood density, air-fluid level which may
represent skull base fracture)
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

25. Checklist for Trauma Brain CT
 Have 3 different windows to look for different pathology
(brain, subdural and bone windows)
 First image includes foramen magnum
 Look first for the pathology that needs emergent Rx
 Hydrocephalus
 Look for primary pathology (hemorrhage in different compartments,
depressed skull fracture)
 Look for secondary pathology (brain herniation, midline shift)
 Look at the mastoid and sphenoid sinuses for hemorrhage
which implies skull base fractures
 Always look at scout CT image for fracture ‘in plane’ with
axial scans
 Look at temporomandibular joints for fracture and/or dislocation
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

26. Traumatic brain pathology will be continued on ‘Part 2’
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

27. • The information provided in this presentation…
– Does not represent the official statements or views of the
Thai Association of Emergency Medicine.
– Is intended to be used as educational purposes only.
– Is designed to assist emergency practitioners in providing
appropriate radiologic care for patients.
– Is flexible and not intended, nor should they be used to
establish a legal standard of care.
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD