The document provides guidance for imaging and interpreting head trauma on CT scans. It discusses several types of skull fractures such as linear, depressed, diastatic, basilar, and pneumocephalus and provides examples of each. It also reviews common intracranial injuries seen in head trauma including epidural hematomas, subdural hematomas, subarachnoid hemorrhage, and traumatic intraventricular hemorrhage. Examples and key findings of each type of injury are presented.

1. Imaging of Head Trauma
Part 2: Pathology
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. 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)
 Look for secondary pathology (brain herniation, midline shift)
 Look at the mastoid and sphenoid sinuses for hemorrhage
which implies skull base fractures
 Look at temporomandibular joints for fracture and/or dislocation
(this pathology causes significant long term complications)
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

3. Skull Fracture
• Etiology-Pathogenesis
– Direct blow to the skull
– Skull vault has 3 layers (outer table, diploe, and inner table)
but diploe does not form where skull is covered by muscles
(thin area, prone to fracture)
– Areas prone to fracture:
• Squamous temporal/parietal bones (most common)
• Foramen magnum, skull bases, cribiform plates, orbital roofs
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

4. Skull Fracture
• Epidemiology
– Fracture (fx) present in majority of severe head injury cases
– Skull fx absent in 1/4 of fatal injuries at autopsy. Absence of
skull fracture not excludes brain injury
– 1/3 of severely injured patients do not have skull fx
– Concomitant cervical spine injury is 15% (cervical spine
radiograph or CT may be needed)
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

5. Skull Fracture
Fracture Suture
•Smooth or jagged edge •Serrated edge
•Straight line •Curvilinear
•Angular turn •Curvilinear
•Darker on X-ray •Lighter
•Greater in width •Lesser width
•Any locations •Specific anatomic
location
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

6. Skull Fracture
• Imaging recommendation
– When suspect skull fracture
• Head CT (in bone window, and edge enhancement algorithm*)
AND Scout CT (to look for fracture ‘in plane’ with axial scan)
• Coronal and sagittal reformation is proven to be useful only
when the scans were performed in helical mode (most hospitals
scan the brain in conventional mode)
* Consult your radiologist about the different CT algorithm.
Edge enhancement algorithm is useful to detect bony lesions (in bone window) and lung lesions (in lung 6
window).
Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

7. Skull Fracture - Linear,
nondepressed
• Run through the entire thickness of bone
• Look if the fx line runs through a vascular
channel, venous sinus. (This can cause epidural
hematoma, venous sinus thrombosis and occlusion)
• Almost always overlying soft tissue edema
• Associated with extra-axial hematoma
• Axial images of CT may miss fx that is ‘in plane’.
Always check scout CT for obvious fx
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

8. 34-year-old man, fall from 10ft height
Axial CT: linear non-depressed Retrospective review of the
fracture (red arrows) of left skull x-ray shows faint fracture
parietal bone. Note soft tissue line.
hematoma overlying the fracture.
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

9. Skull Fracture - Depressed
• Fragment (s) depressed inward
• Consider open when
– Skin laceration over the fracture
– Through paranasal sinuses, middle ear structures
• Potential surgical elevation in
– Depressed > 5 mm and overlies motor or speech areas
– Depressed > skull thickness
• Causes laceration of dura, arachnoid and possible
brain parenchyma
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

10. Middle age man, MVA, severe head injury
Axial CT (bone window) shows 3D CT, although not needed for diagnosis, helps
open depressed fractures (red radiologists and clinicians ‘see’ the complexity of
arrows) of the right frontoparietal
fractures and plan for treatment.
bone and presence of
pneumocephalus (blue arrow).
Severe soft tissue edema or
hematoma.
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

11. Skull Fracture - Diastatic
• Spreading of suture, 1-2 mm more than normal
contralateral side
• Coexisting linear fracture possible
• May tear dural venous sinus, causing venous
epidural hematoma (venous EDH), venous sinus
thrombosis or occlusion
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

12. 35-year-old man,
pedestrian hit by a car
Axial CT image shows
diastasis fractures (red
arrows) through left coronal
suture and posterior portion
of the sagittal suture.
Normal suture is shown
(blue arrow). Severe soft
tissue swelling or
hematomas overly the
fractures.
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

13. Skull Fracture - Basilar
• Clue: opacified sphenoid or mastoid
• Problem associated:
– Dural tear (patients come with CSF otorrhea or rhinorrhea)
– Ear ossicles, labyrinth, cranial nerve (V, VI, VII) involvement
– Vascular injury- laceration, dissection, occlusion, infarction,
carotid-cavernous fistula
• Presentation:
– Temporal bone fx- CSF otorrhea, bruising over mastoid
(Battle sign)
– Anterior cranial fossa fx- CSF rhinorrhea, bruising around
the eyes (raccoon eyes)
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

14. Young man in high velocity MVA
with bleeding from the right ear.
Axial CT image shows the most
common type of skull base fx;
longitudinal fx (blue arrows)
through the right temporal bone.
Note disruption of the right ear
ossicles (red arrow). Blood in
bilateral sphenoid sinuses imply
fractures through the sinuses.
There is no fracture through the
right carotid canal (C). If there is a
suspicion of fracture through
the carotid canal, CT
angiography should be
performed to rule out vascular
injury.
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

15. Skull Fracture - Pneumocephalus
• Presence of air or gas in the cranial cavity
• Principal cause = trauma
• Indicates communication between intracranial
and extracranial spaces, e.g. paranasal sinuses or
ambient air
• Significant complications: meningitis, CSF otorrhea or
rhinorrhea
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

16. Small pneumocephalus (red arrows) is seen
in the subarachnoid space of the right frontal
convexity. This patient had right frontal sinus
fracture as a source of pneumocephalus.
Presence of pneumocephalus should raise
the suspicion of sinus fracture or open
fracture to the ambient air.
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

17. Epidural Hematoma (EDH)
• Etiology-pathogenesis
– Source of bleeding most commonly middle meningeal
artery (85-90%) > others (dural sinus - venous EDH)
– Hematoma between inner table of the skull and dura
– Underlying brain usually minimally injured. Good prognosis if
treated aggressively
– May cross midline and dural attachment
– Not cross sutures (exception: diastatic fx, large EDH)
– Most common location = squamous part of temporal
bone
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

18. Epidural Hematoma (EDH)
• Epidemiology:
– Young men (20-40’s) - older people dura strongly adheres to
inner table of the skull
– Majority has skull fx
• Clinical features:
– Significant trauma
– Loss of consciousness; Lucid interval found in 40% of
patients
– Delayed development 10-25%, within the first 36 hours
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

19. Epidural Hematoma (EDH)
• CT findings
– Hyperdense biconvex extra-axial mass
– Low density area inside hematoma represents active
bleeding (swirl sign)
– Common to have herniation
• Potential indications for surgery
– Size > 2 cm
– Active bleeding
– Pending herniation
– Corresponding neurological deficit
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

20. Epidural Hematoma (EDH)
• Venous EDH
– Usually in posterior fossa
– Depressed skull fx causes strip of the dura, giving potential
space for blood accumulation
– Tear of venous sinus (lhigh flow, low pressure)
– More benign course, subacute presentation, usually not
required surgery
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

21. Young patient in MVA
Axial CT image shows a large
lentiform-shaped homogeneous
hyperdense mass in the right
temporal convexity, consistent
with epidural hematoma (red
arrows). Nonvisualized temporal
horn of the right lateral ventricle
implies mass effect from the
hematoma and degree of brain
edema. Fracture is identified at
the right squamous temporal
bone (not shown).
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

22. 35-year-old man, fall from 12ft
Axial CT image shows a small
lentiform-shaped homogeneous
hyperdense mass in the left
parieto-occipital convexity,
consistent with epidural
hematoma (red arrows). The
proximity of the hematoma to
the transverse sinus raises the
possibility of dural venous sinus
injury. Subsequent MRV and
CTV show no evidence of
venous sinus injury. The patient
was discharged home.
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

23. Subdural Hematoma (SDH)
• Etiology-pathogenesis:
– Blood collects between dura and arachnoid
– Source of blood - torn cortical bridging veins, artery may
also be torn
• Epidemiology:
– Extremes of age - infant or elderly
– Usually coexists with other brain injuries, i.e. subarachnoid
hemorrhage
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

24. Subdural Hematoma (SDH)
• CT findings:
– Acute SDH - crescent blood collection over hemisphere,
displacing the cerebral cortex medially
– Usually hyperdense (can be mixed due to unclottted blood
or torn arachnoid)
– Can be isodense if patients are anemic or blood mixes with
CSF
– Can cross suture
– Can extend into interhemispheric fissure (thick falx), along
tentorium
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

25. 35-year-old man, fall from height
Axial CT image shows a thin
concave hematoma along the left
temporal convexity, representing
subdural hematoma (red arrows).
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

26. 35-year-old man, fall from height
Axial CT image (subdural window)
shows thin bilateral hyperdense
blood along the right parietal and
left temporal convexities,
representing acute subdural
hematoma (red arrows). Small
subarachnoid hemorrhage is also
noted in the sulci of the right
parietal lobe (blue arrow). Bilateral
subdural hematoma can be subtle
and easily missed on ‘brain
window’.
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

27. Traumatic Subarachnoid
Hemorrhage (tSAH)
• Etiology-pathogenesis:
– Tear of veins in subarachnoid space
• Epidemiology:
– Most common cause of subarachnoid hemorrhage is trauma
– tSAH usually associated with cerebral contusion, SDH, or
other lesions. Nearly all cases of tSAH have other lesions to
suggest traumatic cause
– Isolated SAH in trauma patients; there is a possibility of
ruptured aneurysm causing sudden loss of consciousness
and then later trauma (ruptured aneurysm while driving, or
having activities)
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

28. Traumatic Subarachnoid
Hemorrhage (tSAH)
• CT findings:
– High density blood in sulci/cisterns
– Location - next to contusion or under SDH/skull fx/scalp
laceration (otherwise, look similar to aneurysmal SAH)
– Traumatic intraventricular hemorrhage (tIVH) can coexist
• Seen as blood-CSF level in the ventricles
– Subtle tSAH
• Blood in the interpeduncular fossa may be the manifestation
of subtle SAH
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

29. 58-year-old man, found down
at home
Coronal reformatted CT image
shows subarachnoid
hemorrhage insinuated in the
cerebral sulci of left parietal
and right temporal lobes.
Ruptured cerebral aneurysm
is the main differential
diagnosis in the patients
presenting with pure
subarachnoid hemorrhage with
equivocal history of trauma.
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

30. Cerebral Contusion
• Etiology-pathogenesis:
– Initial injury causes the contusion due to cerebral gyri impact
inner table of the skull (rough edges and ridges)
– Evolve from petechial hemorrhage -> small hemorrhage ->
large hematoma (imaging worsened with time)
– More evident after 24h
• Epidemiology:
– Most common parenchymal lesion in head trauma
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

31. Cerebral Contusion
• CT findings
– Low density cortex (edema) mixed with high density
blood (petechial hemorrhage)
– Classic location: anterior base of frontal and temporal
lobes
– Multiple, bilateral
– Can be normal early
– Can be non-hemorrhagic
• MRI is better for detection, delineating extents of
contusions
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

32. 38-year-old man, fall from height
Axial CT image shows an ill-
defined area of hypodensity and
loss of grey-white matter
differentiation in the tip of the left
temporal lobe (red arrows); a
typical location of this non-
hemorrhagic contusion.
Contusion without hematoma
is difficult to appreciate on CT
scan. MRI is more sensitive.
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

33. Middle age man, fall from height
Hemorrhagic contusion (red arrows) at the frontal bases,
right more than left, is noted as an ill-defined area of
hypodensity in CT and high signal intensity zone in MRI T2-
WI. MRI is more sensitive to depict the extent of this injury.
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

34. Diffuse Axonal Injury (DAI)
• Frequent cause of persistent vegetative state and
morbidity in traumatic brain injury patients
• Etiology-pathogenesis
– Traumatic deceleration injury: shearing/rotational forces in
areas of greater density differential in the brain (= grey-white
matter interface)
• Can be an isolated finding in traumatic brain
injury
– No (or little) association with presence of subarachnoid,
subdural hemorrhage, or skull fracture
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

35. Diffuse Axonal Injury (DAI)
• Clinical features
– Usually results in instantaneous loss of consciousness.
Clinical symptoms worse than CT findings
– Most patients (90%) remains in vegetative state (rarely
causes death because brainstem function typically
unaffected)
• General imaging features
– Can be either hemorrhagic or non-hemorrhagic (the latter is
more common)
– Grey-white matter interface, brain stem, corpus callosum
– Number and location of lesions predict prognosis (worst
when multiple, and in supratentorial location)
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

36. Diffuse Axonal Injury (DAI)
• CT findings
– May be normal (microscopic, nonhemorrhagic lesions can
be missed by CT)
– Small hemorrhagic foci in typical locations
• MR findings
– MRI is the imaging of choice to detect DAI
– Susceptibility sequence needed for detection of hemorrhagic
DAI (called T2 GRE, or T2*). Hemorrhagic lesions will be
dark.
– Non-hemorrhagic lesions are bright on T2-WI and FLAIR
T2 GRE = T2 gradient echo, T2* = T2 star
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

37. Diffuse Axonal Injury (DAI)
• Imaging recommendation for suspected DAI
– When initial brain CT is normal but the patient is in
vegetative state
• MRI with susceptibility sequence
OR
• Follow up brain CT in 24 hours (1/6 of DAI will evolve, may be
seen in subsequent CT)
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

38. 24-year-old woman, MVA, severe head injury, GCS 4T
Axial CT image shows mild diffuse Same day MRI (Susceptibility
brain swelling without intracranial sequence) shows multiple tiny areas
hemorrhage. Small subgaleal of blood products (red arrows) in the
hematoma is present (red arrow). grey-white matter junctions and deep
grey nuclei consistent with DAI.
Blue arrow represents a vascular flow
void. Blue star is an artifact.
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

39. Vascular Effects of Trauma
• Hemodynamic alterations common with traumatic
brain injury
• Spectrum of vascular abnormalities due to trauma
– Vasospasm, ischemia, infarction
– Pseudoaneurysm, arterio-venous fistula
– Laceration, dissection
• Ischemia/infarction due to…
– Vasospasm
– Embolism from vascular injury
– Secondary to brain herniation
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

40. 39-year-old man, fall from height
Axial CT image done at day 2
after the injury shows a large
right middle cerebral artery
territory infarction (red
arrows), in conjunction with
acute subdural (blue star) and
intraparenchymal hemorrhage in
the right frontal base. The high
density structure in the left
parasagittal region is a part of
an intracranial pressure
monitoring device.
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

41. Cerebral Edema
• Increased brain water (astroglial swelling)
• Two types (vasogenic and cytotoxic edema) often
coexists
• In trauma:
– Vasogenic edema occurs immediately then cytotoxic edema
within hours
– Usually adjacent or mixed with brain contusion
– Generally resolves within 2 weeks
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

42. 23-year-old woman, MVA
Axial CT image shows
edematous brain with loss of
grey/white matter interface
(red stars), compressed
ventricle (arrow) and
effacement of the sulci (not
seeing any cerebral sulci) in this
patient who had DAI confirmed
by MRI.
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

43. Herniations
• Usually more deteriorating than primary injury
• Etiology-pathogenesis
– Hemorrhage accumulates within closed space, CSF spaces
compressed then mechanical displacement of brain occurs
– May cause secondary ischemia or infarction
– If not correct, brain death
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

44. Midline Shift & Subfalcine Herniation
Axial CT image shows a midline
shift to the left due to large right
extra-axial hemorrhage (red stars)
and intraparenchymal hemorrhage.
The degree of midline shift (red line)
is usually measured at the level of
maximal deviation of the midline
structure (septum pellucidum is a
useful anatomy).
Subfalcine herniation is defined
as herniation of cingular gyrus (blue
star) underneath the falx cerebri.
Presence of midline shift usually
signify subfalcine herniation, and
vice versa. ACA occlusion may
become occluded.
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

45. Obstructive Hydrocephalus &
Descending (central)
transtentorial herniation
Hydrocephalus is one of the
most emergent finding to look
for, because it is treatable. This
patient had dilated left lateral
ventricle from asymmetric brain
edema (right more than left).
Central herniation is defined as
both temporal lobes descend
through the tentorial incisura,
which can be seen as
effacement of the cistern
around the midbrain (star).
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

46. Tonsillar Herniation
Make sure the lowest cut of CT
image includes foramen
magnum! Presence of space-
occupying lesion in the brain,
cerebellar tonsils (red stars) in the
same cut as foramen magnum,
obliteration of CSF space and
displaced portions of
cervicomedullary junction (M) are
signs of tonsillar herniation.
Tonsils can be low lying as a
normal variation or a Chiari
malformation.
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

47. Brain Death
• Etiology-pathogenesis:
– Severe increased ICP decreases cerebral blood flow, then
irreversible loss of brain function
• Clinical criteria: coma + absent brainstem
reflexes + apnea test
• Imaging may confirm but does not substitute for
clinical criteria
• CT findings:
– No flow in intracranial arteries/venous sinuses
– Diffuse cerebral edema
– Hyperdense cerebellum (much denser than cerebrum)
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

48. 49-year-old woman, ruptured cerebral aneurysm
Contrast-enhanced axial CT (Left) shows diffuse SAH (blue stars)
in the cerebral cisterns, diffuse cerebral edema. There is no
intracranial blood flow either in arteries or venous sinuses.
Both images show normal enhancement of extracranial vessels
(red arrows). The patient had bilateral ventricular shunt placement.
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Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD

49. • 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