Acute brain ppt to address the main points in brain trauma CT-scan for medical students

1. By : Musa Abu Sabha – 4th year medical
student

2. Outline :
 Brief Brain Anatomy
 Head Trauma
 Brain Hemorrhage
 Brain Masses

3. Brain Anatomy
Image orientation : CT images of the
brain are conventionally viewed from
below, as if looking up into the top of the
head. This means that the right side of
the brain is on the left side of the viewer.
The anterior part of the head is at the
top of the image

4. Brain Anatomy : Skull bones and
sutures
 Bones of the skull -
frontal, parietal, occipital, ethmoid, s
phenoid and temporal bones - all
ossify separately and gradually become
united at the skull sutures.
 The skull has inner and outer tables of
cortical bone with central cancellous
bone called 'diploe'

6. Note the appearance of the skull sutures which are
jagged - not to be confused with fractures which
are typically straight

7. Pterion - clinical significance
• The frontal, parietal, temporal and sphenoid
bones unite at the 'pterion' - the thinnest part of
the skull
• The middle meningeal artery runs in a groove on
the inner table of the skull in this area

9.  Coronal suture - unites the frontal bone with
the parietal bones
 Sagittal suture - unites the 2 parietal bones
in the midline
 Lambdoid suture - unites the parietal bones
with the occipital bone
 Squamosal suture - unites the squamous
portion of the temporal bone with the parietal
bones
 Metopic suture - (if present) unites the 2
fontal bones

11. Cranial fossae
• Anterior cranial fossa - accommodates
the anterior part of the frontal lobes
• Middle cranial fossae - accommodate
the temporal lobes
• Posterior cranial fossa - accommodates
the cerebellum and brain stem
• Pituitary fossa (PF) - accommodates the
pituitary gland

12. Meninges
Knowledge of
anatomy of the
meninges is
essential for
understanding
the CT
appearances of
intracranial
bleeding

13. Meninges
 Dura mater, arachnoid, and the pia mater.
The dura mater and arachnoid are an
anatomical unit, only separated by
pathological processes.
 The falx cerebri and the tentorium cerebelli
are thick infoldings of the meninges which
are visible on CT imaging. Elsewhere the
meningeal layers are not visible on CT as
they are closely applied to the inner table
of the skull.

14. Meninges

15. Meninges
Dura mater = tough outermost
layer, closely applied to the inner
table of the skull
Arachnoid = thin layer closely
applied to the dura mater
Subarachnoid space = space
between the arachnoid mater and
the pia mater which contains
delicate trabeculated connective
tissue and CSF
Pia mater = very thin layer
applied to the surface of the brain

16. Meninges
Tentorium cerebelli
The tentorium cerebelli - an infolding of the dura mater - forms a tent-like
sheet which separates the cerebrum (brain) from the cerebellum
The tentorium is anchored by the petrous bones
Tentorium cerebelli - clinical significance
In the context of subarachnoid haemorrhage or subdural haematoma the tent
may become more dense due to layering of blood

17. Meninges
The falx is an infolding of the meninges which lies in the midline and
separates the left and right cerebral hemispheres
Falx cerebri - clinical significance
Pathological processes may cause 'mass effect' with deviation of the falx
towards one side

18. Meninges

19. Ventricles
Lateral ventricles
The paired lateral ventricles are located on either side of the brain
The lateral ventricles contain the choroid plexus which produces CSF
Note : The choroid plexus is almost always calcified in adults

20. Ventricles
Third ventricle
The third ventricle is located centrally
The lateral ventricles communicate with the third ventricle via small holes
(foramina of Monro).

21. Ventricles
Fourth ventricle
The fourth ventricle is located in the posterior fossa between the brain stem and cerebellum
It communicates with the third ventricle above via a very narrow canal, the aqueduct of Sylvius (not
shown)
Basal cisterns
CSF in the basal cisterns surrounds the brain stem structures

22. Cerebral cortex
Cortical grey matter
The grey matter of the cerebral cortex is formed in folds called gyri
Note that the cortex appears whiter (denser) than the underlying white matter

23. Basal ganglia and thalamus
Basal ganglia and thalamus
The thalamus and the basal ganglia are readily identifiable with CT
Basal ganglia = lentiform nucleus + caudate nucleus

24. Windowing :
Air = −1000 HU
Lung ≈ −500 HU (partially air, partially soft tissue)
Fat ≈ −50 HU (slightly less dense than simple fluid)
Water = 0 HU
Soft tissue (& blood) ≈ +50 HU (slightly more dense than simple fluid)
Bone ≈ +1000 HU (much more dense)

25. Windowing :

26. Windowing :

27. Head Trauma :
SKULL
FRACTURES
Linear
Depressed
Basilar
Diastatic

28. Head Trauma :
Diagnosis of fracture
• skull x-rays are still performed but are
being used less and less
• CT head is the first line investigation
• MRI is insensitive to fractures
Presentation
head injury following impact
trauma, e.g. fall, RTA
symptoms associated with
underlying injury
• extradural hemorrhage
• subdural hemorrhage
• subarachnoid hemorrhage
there may be an associated
base of skull injury
• CSF rhinorrhea
• Battle sign (bruising over
mastoid process)
• raccoon eye
Pathophysiology
mechanism
children and elderly: simple fall
adults: usually high-energy impact
trauma, e.g. RTA
Different types of fractures
• linear
• depressed skull fracture
• diastatic (widening suture lines
in childhood)
• base of skull fracture
Associations
• bone fragments under the
fracture
• other penetrating injuries
• intracranial hemorrhage

29. Head Trauma :

30. Head Trauma :

31. Head Trauma :
Skull fracture v suture
At the interface of a suture the surface of each bone is covered by a layer of
cortical bone which is continuous with inner and outer tables of the skull
At the site of a skull fracture the bones are not corticated
Note how straight the fracture is compared to the jagged suture

32. linear skull fracture
• Run through the entire
thickness of bone
• Almost always
overlying soft tissue
edema
• Associated with extra-
axial hematoma

33. linear skull fracture
• Run through the entire thickness of bone
• Almost always overlying soft tissue edema
• Associated with extra-axial hematoma

34. linear skull fracture
• linear (red arrows) of left parietal bone. With soft tissue hematoma
overlying the fracture.

35. Depressed skull fracture
Depressed skull
fracture
• Severe trauma to the
skull may result in
depression of the skull
bones
• The bone window
images provide good
detail of the
depressed skull
fracture
• The brain windows
show the
accompanying
intracranial hematoma

36. Depressed skull fracture
These mostly (~75%) occur
in the frontoparietal region.
CT The modality of choice in
head trauma. The fracture is
shown in detail along with
any associated injuries
Depressed skull fracture are
associated with higher rates
of infection (~10%), seizure
(~15%), neurological deficits,
and death

37. DIASTATIC FRACTURES
Spreading of suture, 1-2 mm more than normal
Etiology
• traumatic
• raised intracranial pressure, e.g. intracerebral tumor, hydrocephalus or
subdural collection
• infiltration of the sutures, e.g. leukemia, lymphoma or neuroblastoma
• metabolic, e.g.hyperparathyrodism , rickets or hypophosphatemia

38. DIASTATIC FRACTURES
RADIOLOGICAL FINDINGS:
widening of the sutures may be appreciated on plain
radiograph and is better still appreciated on CT
the following widths are considered to be diagnostic of
sutural diastasis
• >10 mm at birth
• >3mm at two years
• >2mm at three years
in cases of trauma, it may be associated with or without
fractures

39. DIASTATIC FRACTURES
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.

40. DIASTATIC FRACTURES

41. Basal skull fracture
 BASILAR FRACTURES :
 are a common form of skull fractures,
particularly in the setting of severe traumatic
head injury.
 The majority of basilar fractures occur as a
result of motor vehicle accidents, with sports
injuries, falls and assault
Specific types of base of skull fractures include:
• petrous temporal bone fracture
• transsphenoidal basilar skull fracture
• occipital condyle fracture

42. Basal skull fracture

43. Basal skull fracture

44. Basal skull fracture
Basal skull fracture
Fractures of the basal skull can be difficult to identify In the setting of acute
head injury, a fluid level (blood) in the sphenoid sinus can be a helpful sign
of a basal skull fracture

45. PNEUMOCEPHALUS
Presence of air or gas in the
cranial cavity
Principal cause = trauma
Indicates communication between
intracranial and extra cranial
spaces, e.g. paranasal sinuses or
ambient air

46. fracture with bone
fragments

47. Brain Hemorrhage

48. Brain Hemorrhage
 Intracranial bleeding is either intra-axial (in
the brain) or extra-axial (outside the brain).
 There are three types of extra-axial
hemorrhage:
1- Epidural hematoma: forms a lens-shaped
collection
2- Subdural hematoma: forms a crescent-
shaped collection.
3- Subarachnoid hemorrhage: Blood occupies
the CSF spaces - sulci, fissures, ventricles, basal
cisterns.

49. Epidural Hematoma
 Epidural hematoma is a post-traumatic event resulting from
injury to an intracranial artery, most commonly the middle
meningeal artery.
 Leakage from an injured artery results in collection of blood
which strips the dura mater away from the inner table of the
skull.
 Epidural hematoma results in formation of a lens-shaped
collection. This is because the dura mater is strongly adhered
to the skull in the region of the sutures. Stripping of the dura
from the skull is limited at these points resulting in limitation of
the extent of a collection

50. Epidural Hematoma
 Venous epidural hemorrhages are a relatively
uncommon subtype.
 They occur as a result of damage to the Dural venous
sinuses and often result in the displacement of the
sinus away from the underlying bone.
 vertex
 anterior middle cranial fossa arise from the sphenoparietal
sinus
 occipital posterior fossa :arise from the transverse sinus
 sagital sinus diastatic fx,and large EDH cross
the sutures

51. Epidural haematoma
• A lens-shaped collection has formed following trauma to the left side of the
head
• Note the collection of blood is limited at the points of the sutures
• There was no accompanying fracture in this case (don't forget to check the
bone windows)

52. Vertex Epidural Hemorrhage Massive Epidural
Hemorrhage crossing the
suture lines

53. Occipital posterior fossa

54. When acute bleeding is occurring at the
time of CT scanning the non-clotted fresh
blood is typically less hyperdense, and a
swirl sign may be evident
The swirl sign is identified as a small area
of low attenuation within an intracranial
hyperattenuating clot on (CT) scans of the
brain, which represents active bleeding

55. Subdural Hematoma
 The cerebral veins are fragile. Risk of injury to these veins
is increased in elderly and anti-coagulated patients.
 Subdural hematoma may result from minor trauma. There
is often no clear history of trauma at all.
 A subdural collection is not limited by the attachment
points of the dura to bone, as is seen in an epidural
hematoma. The result is the formation of a crescent-
shaped collection.
 The arachnoid remains intact and so blood does not pass
into the sulci.

56. Subdural hematoma
• A large crescent-shaped collection is seen over the left side of the brain
• The collection is of high density material due to the presence of clotted blood
• There is no blood extending into the sulci
• The sulci on the side of the hematoma are partially effaced indicating 'mass
effect'

57. NOTE
 Blood must clot in order to be
hyperattenuating (high density ).
 Hyperacute unclotted blood (and clotted
blood in a patient with severe anemia)
may be close to water attenuation on
CT.

58. Subarachnoid hemorrhage
 Subarachnoid hemorrhage is commonly associated
with trauma or spontaneous bleeding from an
intracranial aneurysm.
 Aneurysms are only visible on conventional CT
images if they are large.
 Less frequently, subarachnoid hemorrhage is due to
spontaneous bleeding from a congenital
arteriovenous malformation or spontaneous bleeding
from the veins around the brain stem
(perimesencephalic subarachnoid hemorrhage).
 Small foramina connect the subarachnoid space with
the fourth ventricle. Blood due to a subarachnoid
hemorrhage can, therefore, pass into any part of the
CSF spaces: sulci, fissures, basal cisterns or
ventricles.

59. Subarachnoid hemorrhage
Dense blood (white) is seen filling the basal cisterns, fissures and the fourth
ventricle

60. Subarachnoid hemorrhage - Ventricular blood
• Subarachnoid hemorrhage may result in blood collecting in the ventricles
• Occasionally a layer of blood in the ventricles is the only sign

61. Subarachnoid hemorrhage - Sulcal blood
• Blood within the subarachnoid space is seen in a sulcus of the left
cerebral hemisphere
• This may be a subtle finding only seen on a few slices

62. Intracerebral hemorrhage
 Intra-axial hemorrhage, or intracerebral
hemorrhage (ICH), may be spontaneous
or due to trauma.
 The radiological appearances may be
identical as trauma does not always
cause an accompanying fracture.

63. Spontaneous ICH
• A large area of high density material (blood) is surrounded by low density
(edema)
• This patient had a previous history of intractable hypertension and presented
with sudden onset of right side weakness

64. Traumatic ICH
• This intracerebral hemorrhage has the same characteristics as the image
of spontaneous hemorrhage shown previously
• The bone window image (inset) shows an adjacent skull fracture in this
patient following head injury

65. Combined intra and extra-
axial hemorrhage
 Very often, intracerebral hemorrhage -
whether spontaneous or traumatic - is
accompanied by extension of bleeding
into the extra-axial spaces (outside the
brain).

66. ICH with subarachnoid extension
• This image shows a small intracerebral hemorrhage with surrounding
edema
• High density material within the sulci indicates leaking of blood into the
subarachnoid space
• Note that the other images previously also show extension of bleeding into
the subarachnoid space

67. Intracranial Masses
 Intracranial masses are classified either as
intra-axial lesions (in the brain) or extra-
axial lesions (outside the brain). The
distinction is not always easy to determine.
 Intra-axial lesions
 Intra-axial lesions are most commonly
neoplastic and malignant rather than benign. In
general, a single intra-axial lesion which
enhances post-contrast is most likely to be a
primary malignant mass (glioma), whereas
multiple intra-axial lesions are usually
metastatic.

68. Intracranial Masses
 Meningiomas - the commonest extra-
axial masses - are located in close
proximity to a meningeal surface.
 Cerebral abscess is an important
differential diagnosis of a ring enhancing
mass

69. Glioma - CT brain/pre-contrast image
• This patient presented with a history of worsening postural headaches
• A large irregular-shaped area of low density is seen in the right hemisphere
• Mass effect is present: effacement of the sulci, lateral ventricle and basal
cisterns

70. Glioma - CT brain/post-contrast image
• (Same patient as image previous )
• A post-contrast CT of the brain was
performed
• There is 'ring-enhancement' of an
irregular-shaped mass
• Central low density is due to necrosis
• Surrounding low density is due to
edema
Cerebral abscesses have similar
enhancement characteristics and should
be considered as a differential diagnosis of
a ring enhancing lesion

71. Cerebral metastases - CT brain
• Multiple lesions were seen on both sides of the brain in this patient who had
a known diagnosis of lung cancer
• The post-contrast image shows ring enhancement of the lesions

72.  Extra-axial lesions
 Meningiomas are the most common extra-axial mass.
Although benign, they may grow very large and can
be surrounded by a large area of adjacent cerebral
edema, often appearing to be intra-axial on initial
assessment.
 Characteristics of meningiomas include a smooth
edge, a rounded shape, central calcification, and
bright enhancement of the whole lesion post-contrast.
 Meningiomas arise from the meninges, with which
they remain in contact, and often have a 'dural tail'
which tapers from the mass to a point on the surface
of the meninges.

73. Meningioma - CT brain/post contrast image
• A large mass enhances brightly following administration of intravenous
contrast
• A large area of edema is seen adjacent to the mass
• The mass makes broad contact with the meninges (the falx in this case)
• There is a 'dural tail' - tapering of the mass to a point on the meningeal
surface

74. Mass effect
 As the intracranial volume cannot change, any
intracranial lesion which is 'space-occupying' may
increase intracranial pressure and displace the soft
tissues of the brain. This is known as 'mass effect'.
 Intracranial pathological processes, such as
masses and hemorrhage, can cause mass effect.
 Surrounding cerebral edema often worsens mass
effect, and in the case of infarcts, which are not in
themselves 'space-occupying', the mass effect is
solely due to edema.

75. Stages of mass effect
 Stage I : Effacement of the sulci adjacent to
the lesion.
 Stage II : Partial or complete effacement of
the adjacent ventricles.
 Stage III : Displacement of midline structures.
 Stage IV : Effacement of the contralateral
ventricles and sulci.

76. Stages of mass effect
 In extreme cases CT may demonstrate
herniation of structures through the incisura
tentorii (the gap at the top of the tent normally
occupied by the brain stem and basal cisterns),
or coning (extrusion of the posterior fossa
structures through the foramen magnum).
 These uncommon features are associated with
extremely poor outcome

77. Sulcal effacement
• A space occupying lesion - below the level of this CT slice - is causing mass
effect with effacement of the sulci over the whole left cerebral hemisphere
• Compare with the contralateral side which shows normal sulci

78. Ventricular effacement
• This image shows a small intracerebral bleed with surrounding edema
• The combination of the blood and edema is causing mass effect:
effacement of the adjacent sulci and partial effacement of the adjacent
lateral ventricle
• The left hemisphere structures appear normal

79. Shift of midline structures - Post-contrast CT brain
• This image shows an intracerebral tumor (glioma) which, along with
surrounding edema, is causing mass effect
• The right hemisphere sulci are effaced and the right lateral ventricle is totally
effaced
• Structures normally found in the midline are deviated to the contralateral side

80. Contralateral mass effect
• A large acute left subdural hematoma is causing severe mass effect
• The left hemisphere sulci and lateral ventricle are effaced
• The midline structures are shifted to the right
• The contralateral sulci are effaced
• The right lateral ventricle is distorted - effaced anterior horn and focal
hydrocephalus of the posterior horn