1. The document reviews key imaging findings and goals in traumatic brain injury (TBI) evaluation including recognizing life-threatening injuries like epidural hematoma, diffuse axonal injury, and herniations. 2. CT is recommended for rapid diagnosis in trauma but MRI is more sensitive for injuries like diffuse axonal injury. Imaging helps assess prognosis and guide management. 3. Specific lesions discussed include intraparenchymal hemorrhage, subdural hematoma, subarachnoid hemorrhage, skull fractures, cerebral edema, and traumatic vascular injuries. Characteristic appearances on CT and clinical implications are reviewed.

1. Learning Objectives
• Recognize Urgent Lesions
• Understand Acute Traumatic Lesions
• Describe four types of herniation
• Triage Acute Vascular Lesions
• Recognize Diffuse cerebral swelling

2. • 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

3. Traumatic brain injury: 2
categories
• Primary injury
– Initial injury to the brain
as a result of direct
trauma
– Example: hematoma,
diffuse axonal injury,
contusion
• Secondary injury
– Subsequent injury to
the brain after the initial
insult
– Result from systemic
hypotension, hypoxia,
elevated
– intracranial pressure
(ICP) or biochemical
insults

4. Goals of Imaging in TBI
Goals Answered by...
Rapid diagnosis of
lifethreatening
injuries
CT
Explanation of neurological
abnormality
CT (if not  MRI)
Prognosis information Clinical findings, CT, MRI,
advanced MR techniques

5. CT in TBI: When?
• Patients with mild HI with one of 7 clinical
findings need CT:

6. • Sensitivity for predicting
need for neurosurgery
– High risk 100%
– Medium risk 98.4%
• Reduced the need for
CT in mild HI to 54%
• Positivity rate = 8% (1%
of cases require
neurosurgical
intervention)

7. CT in TBI: How?
• Non-contrast, axial scan with spiral technique
• If you see maxillary hemosinus -> do facial CT
• If you see skull base fracture -> consider CTA
and skull base reformation (thin slices with
small FOV)
• If suspect C-spine fracture->  do C-spine CT

8. CT in TBI: Checklist
Look at all three windows

9. CT in TBI: Checklist
• If the study looks near-normal
– Find coup injury : look for contrecoup (can be
subtle)
– Check potential areas for contusions and DAI (esp
if low GCS)
• Recheck interpeduncular fossa for small SAH

10. MRI in TBI
• More sensitive for 10 and 20 injuries than CT
• Better differentiation of hemorrhagic and
non-hemorrhagic lesions in acute phase
Diffuse axonal injury

11. Diffuse Axonal Injury
• DAI is the widespread shearing of long axons that occurs as
the result of deceleration injury. Common clinical scenarios
include high-speed motor vehicle collisions and falls from
great height.
• The CT appearance is nonspecific: normal in the hyperacute
phase, often followed by cerebral edema over hours to days.
Punctate intraparenchymal hemorrhage may occur as well.
Often, other traumatic brain injury will be evident, such as
SDH or EDH.

12. MRI in TBI
• Intrinsic limits:
– Absolute C/I: cardiac pacemaker, ferromagnetic
foreign bodies
– Lower sensitivity for bone fractures and
hyperacute blood
• Difficult managing trauma patients in MRI
suite: metallic life support, monitoring device,
time

13. SKULL FRACTURE
• 3 layers
– Outer table
– Diploe
– Inner table
• Parts without diploe
prone to fracture
– Squamous temporal
bone / Parietal bone
– Foramen magnum, skull
bases, cribiform plates,
orbital roofs

14. Quick Anatomy

15. Quick Anatomy

16. Types of Skull Fracture
• Linear fracture
– a/w EDH, SDH
• Depressed fracture
– a/w focal parenchymal
lesions

17. Significance of Skull Fracture
• Indicator of brain injuries?...
– Present in the majority of cases with severe HI
– Absent in 1/4 of fatal injuries at autopsy
– Absent in 1/3 of severe brain injury cases
– Injuries to underlying brain structures
• Association
– 15% concomitant C-spine injury
– 10-15% concomitant facial injury

18. Skull Fracture vs. Suture
FRACTURE
• Smooth or jagged edge
• Straight line
• Angular turn
• Greater in width
• (X-ray) darker
• Any locations
SUTURE
• Serrated edge
• Curvilinear line
• Curvilinear turn
• Lesser in width
• (X-ray) lighter
• Specific anatomic location

19. Skull Fracture: CT

20. Skull Fracture: Skull Base
• Clinical clues:
– CSF otorrhea or rhinorrhea
– Hemotympanum or
laceration of EAC
– Postauricular ecchymoses
– Periorbital ecchymoses in
absence of direct orbital
trauma esp if bilateral
– Cranial nerve injury (I, VI,
VII, VIII)

21. Skull Fracture: Skull Base
• Thin slices, bone
algorithms and coronal
images
• Indirect CT signs:
– Pneumocephalus
– Air-fluid level or
opacification of mastoid
or sinuses

22. Skull Fracture: Skull Base

23. Skull Fracture: Pneumocephalus
• Gas within cranial cavity
• due to fractures of PNS
and temporal bones
(open skull fracture is
another cause)
• Most do not cause
immediate danger but
rapid expansion can lead
to brain compression
(tension
pneumocephalus)
• Usually decreases by 10-
15 days and almost never
present by 3 weeks

24. DIFFUSE AXONAL INJURY
• Traumatic
acceleration/deceleration
or violent rotation
• LOC immediately at the
time of trauma -> coma

25. Diffuse Axonal Injury (DAI)
• Frequent cause of
persistent vegetative
state / morbidity in
trauma patients
• Clinical symptoms
worse than CT findings
• Can be isolated with no
or little association with
SAH, SDH, fracture

26. Diffuse Axonal Injury
• Non-hemorrhagic 80%
of cases
• Common locations:
– Grey-white matter
interface (m/c)
– Corpus callosum
– Dorsolateral midbrain

27. Diffuse Axonal Injury
• Number and location of
lesions predict
prognosis (worse if
multiple &
supratentorial)
• MRI most sensitive
imaging but
• still underestimates real
extent

28. Diffuse Axonal Injury
• When initial head CT is
normal but the patient
is in vegetative state
– Do MRI with
susceptibility sequence
OR
– Follow up CT in 24 hours
(1/6 of DAI will evolve)
Small interpeduncular SAH and petechial
hemorrhage in dorsolateral midbrain

29. CEREBRAL CONTUSION
• Cerebral gyri impact
inner table skull
• coup and contrecoup
Injuries
• Petechial hemorrhage
of gyri -> small
hemorrhage -> large
hematoma

30. Cerebral Contusion
• Anterior base frontal,
temporal lobes (esp tip),
cortex surrounding Sylvian
fissure
• Multiple, bilateral

31. Cerebral Contusion
• Can be normal early; can
be non-hemorrhagic
• Imaging worsened with
time, most evident after 24
h

32. Cerebral Contusion: MRI
MRI is the study of choice in patients with
• Acute TBI when neurological findins are unexplained by CT
• Subacute or chronic phases when there are TBI-related symptoms

33. OTHER INTRAAXIAL LESIONS
• Traumatic intraparenchymal hematoma
• Intraventricular hemorrhage
• Traumatic lesions of deep grey structures and
brainstem

34. Intraparenchymal Hematoma
• Parenchymal vessel
rupture from blunt or
penetrating forces
• May not lose
consciousness (unlike
DAI, contusion)
• Hematoma at primary
trauma site (usually
frontal and temporal)

35. Intraparenchymal Hematoma
• Well-circumscribed
hyperdense lesion
w/wo perilesional
edema
• Up to 60% a/w SDH,
EDH
• Not always easy to
distinguish IPH from DAI
or contusion
Traumatic intraparenchymal hemorrhage with IVH

36. Intraventricular Hemorrhage
• Consequence of severe
trauma. a/w DAI and
trauma of deep grey
and brainstem
• Poor prognosis

37. Trauma of Deep Grey &
Brainstem
• Stretch and torsion
causing ruptured
perforators, or direct
impact on dorsolateral
brainstem against
tentorial incisura
• Severe trauma, poor
prognosis
• CT:
– Small hemorrhages in
brainstem surrounding
aqueduct, basal grey nuclei
– Can be normal

38. Epidural Hematoma (EDH)
• Hematoma between
inner table of the skull
and dura
• Source of bleeding
– Most common = middle
meningeal artery (90%)
– Venous EDH from dural
venous sinus

39. Epidural Hematoma (EDH)
• Most urgent of all cases of cranial trauma
– Requiring prompt Rx to relieve compression of
brainstem, tentorial herniation, acute
hydrocephalus
– EDH in posterior fossa very worrisome
– 1-4% of head injury cases, 10% of fatal cases
– Young men (20s – 40s). Rare in patients >60 y
– Almost always with skull fracture
– Lucid interval in 40% of cases

40. Epidural Hematoma (EDH)
• Delayed development in 10-25% of cases
(within 36 hrs)
• Arterial EDH: blood can flow into epidural
space only after resolution of arterial spasm
• Venous EDH bleeds slowly

41. Epidural Hematoma:
CT Appearance
• Biconvex or lens shape
• hyperdense lesion (rare
to be isodense)
• May cross midline and
dural attachment
• Do not cross suture
(except diastatic
fracture, large EDH)

42. Epidural Hematoma:
Potential Indications for Surgery
• Size > 2 cm
• Active bleeding
• Impending herniation
• Corresponding
neurologic deficit

43. Epidural Hematoma: Swirl Sign
• Small rounded lesion
isodense to the brain,
representing active
extravasation of
unclotted blood
• Clotted component is
hyperdense (50-70 HU)

44. Venous EDH
• Tear of venous sinus
(high flow, low pressure
system)
• More benign course,
subacute presentation,
usually not require
surgery
• Posterior fossa venous
sinus > sagittal sinus

45. Subdural Hematoma (SDH)
• Blood collects between
dura and arachnoid
• Torn cortical bridging
veins
• 10-20% of all cranial
trauma cases
• Clinic:
– Elderly (60-80y) with brain
atrophy,
– Large intracranial
subarachnoid spaces
– “Shaken baby syndrome”

46. Subdural Hematoma (SDH)
• Usually co-exist with
other brain injuries
– Esp. contusion-typed
injuries > skull fractures
• Acute: within 3 days
from trauma
• Subacute: within 3 mo
• Chronic: after 3 months
Layer of acute blood on pre-existing CSF-like subdural
collection in the right cerebral convexity

47. Subdural Hematoma:
CT Appearance
• Crescentic hyperdense
• Collection
• Can cross suture
• Can extend to
interhemispheric
fissure, along tentorium
cerebelli
coup (Rt.) and contrecoup (Lt.) pattern.
This SDH is a contrecoup injury

48. Subdural Hematoma:
Value of Coronal Reformats

49. Bilateral Subdural Hematomas

50. “Isodense” Subdural Hematoma
• Usually takes 2-6 weeks
for acute SDH to
become isodense
• At Hb 8-10 g/dL, blood
will be isodense to grey
matter
• • Anemic patients can
present with acute
isodense SDH

51. Acute On Chronic SDH
• New hemorrhage
superimposed on
chronic SDH
• Recurrent trauma
• Can be spontaneous
• Blood-fluid level , blood
clot organization,
membranes

52. Comparison of EDH and SDH

53. Subdural Hygroma
• Extraaxial collection
ofbCSF caused by
extravasation of CSF from
SA space through a
traumatic tear in
arachnoid mater
• Acute: Children >> adults
• Subacute and chronic:
Following surgery for
head injuries in operative
bed or opposite site
1 week after injury

54. TRAUMATIC SUBARACHNOID
HEMORRHAGE (TSAH)
• Blood collects beneath
arachnoid
• Tear of veins in SA space
• Usually associated with
other brain injuries
(common with contusions)
• ‘Nearly all cases of
traumatic SAH have other
lesions to suggest traumatic
cause’
• – Isolated SAH in trauma
patients – possible
ruptured aneurysm causing
trauma
SAH with SDH

55. TRAUMATIC SUBARACHNOID
HEMORRHAGE (TSAH)
• Site
– Next to brain contusion,
under SDH/fracture/
scalp lac
– Can be distant because
blood diffuses in SA
space
• IVH may co-exist due to
retrograde flow through
foramen of Luschka and
Magendie

56. Subarachnoid Hemorrhage
• Subtle SAH –
interpeduncular fossa

57. TRAUMATIC VASCULAR
LESIONS
• Rare
• Can be overlooked initially
• ICA injury (dissection, aneurysm, occlusion) –
Base of skull fracture
• Traumatic carotid-cavernous fistula (TCCF)

58. Traumatic ICA Injury
• Common cause of
ischemic stroke in the
young
• Extracranial ICA much
more common (esp just
proximal to petrous
bone)
• Dissection ->occlusion
or thromboembolism
At initial trauma, there were diffuse subarachnoid hemorrhage, pneumocephalus, facial
fractures and C-spine injury. Days after the injury (image C) , the patient developed left
ICA territory infarction. Angiiography (D) confirmed occlusion of the cervical ICA.

59. Traumatic CCF
Most common traumatic AV fistula = CCF , Clues on CT: proptosis, bulging
cavernous sinus, enlargedarterialized ophthalmic vein

61. Herniation: Tonsillar
•Downward displacement of tonsils through foramen magnum
Seen with
– Up to ½ of all descending transtentorial herniation
– Up to 2/3 of ascending transtentorial herniation

62. Herniation: Subfalcine and
Midline Shift
Shift of cingulate gyrus across midline below falx
• Thinner ipsilateral ventricle, dilated opposite ventricle (CSF
obstruction at foramen of Monro)

63. Herniation: Subfalcine and
Midline Shift
Measured at level of foramen of Monro
Distal ACA may be compressed against falx

64. Herniation:
Descending Transtentorial
• Medial and caudal shift of
uncus and
parahippocampal gyrus of
temporal lobe beyond
tentorium cerebelli
• Asymmetric prepontine
cisterns and CP angle
(wider on side of lesion)
• AchA, PCoA, PCA may be
compressed against
tentorium

65. Herniation:
Descending Transtentorial

66. Herniation:
Ascending Transtentorial
• Cranial shift of vermis
and parts of
superomedial cerebellar
hemisphere through
tentorium incisura
• Compressed superior
cerebellar, vermian
cisterns and forth
ventricle

67. Posttraumatic Cerebral Edema
• Increased water content of brain and/or
increased intravascular blood volume
• Severe condition. Can be fatal
• Can be unilateral or bilateral
• Vasogenic and cytotoxic edema coexist
• Evolves over 24-48 hours
• Generally resolved in 2 weeks

68. Posttraumatic Cerebral Edema
• Generalized obliteration
of cortical sulci and SA
spaces of suprasellar,
perimesencephalic and
compressed/thin
ventricles
• Diffuse hypodensity, loss
of grey-white matter
interface
• Hyperdense cerebellum
• Often w/ transtentorial
herniation

69. Posttraumatic Ischemia/Infarct
• cause = herniation
• location = occipital (PCA
infarct from descending
transten)
• 2nd location = frontal
(ACA infarct from
subfalcine h)
• Rare = basal ganglia
(perforator/choroidal
infarct against base
skull)

70. Posttraumatic
Secondary Hemorrhages
• Small hemorrhagic foci
in tegmen
– Classic in midline of
pontomesencephalic
junction
– May be multiple or
extending into cerebellar
peduncles
– Necrosis/hemorrhage of
contralateral cerebral
peduncle “false
localizing sign” Hemorrhage in the midline near
pontomesencephalic junction. Also note
intraventricular hemorrhage in the 4th
ventricle

71. Hydrocephalus
• Acute hydrocephalus can
occur 2/2 brain
herniation or IVH
• Delayed hydrocephalus
usually 2/2 adherence of
meninges over cerebral
convexity, basal cisterns
or aqueduct resulting in
obstruction at level of
ventricles and arachnoid
granulations
Look for “early sign” of hydrocephalus at temporal
horns of lateral ventricles.
When acute with high ICP, there may be hypodensity
around the frontal horns of lateral ventricles

72. Brain Death
• Severe increased ICP
decreases cerebral blood
flow, then irreversible
loss of brain function
• Clinical criteria: coma +
absent brainstem reflexes
+ apnea test
• No flow in intracranial
arteries/venous sinuses
• Diffuse cerebral edema,
• hyperdense cerebellum

73. Conclusions
• CT = primary modality for head trauma,
enough for most parts
• MR to help predicting prognosis by detection
of subtle injuries i.e., contusion and DAI
• Primary vs secondary lesion. Often,
• secondary lesion more important

75. EPIDURAL HEMATOMA
• Significant trauma
• Fracture & concussion
(l.o.c.)
• Lucid Interval:40%
• Delayed neurologic Sx
(hrs. Later)
• Herniation, coma and
death

76. EPIDURAL HEMATOMA
• Trauma -> fracture &
concussion
• Tearing/stripping of both
layers of dura away from inner
table
• Laceration of outer periosteal
layer of dura
• Laceration of meningeal
vessels
• Inner (meningeal dura) intact
• Blood between naked bone
and dura
• NORMAL arterial pressure
continues to dissect

77. Four Types of Brain Herniation
• „ Transcalvarial – cerebral cortex „
• Subfalcial – Cingulate Gyrus „
• Transtentorial „Downward – Uncus and
Temporal Lobe „Upward – Vermis „
• Foramen Magnum – Tonsils and Medulla

78. Brain Herniation Syndromes
Supratentorial
herniation
1.Uncal
(transtentorial)
2.Central
3.Cingulate
(subfalcine)
4.Transcalvarial
Infratentorial
herniation
5.Upward (upward
cerebellar or upward
transtentorial)
6.Tonsillar (downward
cerebellar)

80. SUBFALCINE HERNIATION
• most common
• supratentorial mass in
one hemicranium
• affected hemisphere
pushes across the midline
under the inferior "free"
margin of the falx,
extending into the
contralateral
hemicranium