Download eEdE-141 - Rackcdn.com

eEdE-141
M Gelbman1, Z Chadnick2, S Lev1
1Nassau
University Medical Center, East Meadow , NY
University of the Caribbean, Sint Maarten
2American
Disclosure
 The
authors have no financial or nonfinancial disclosures.
Goals
 Skull
base trauma can be quite devastating,
often presenting with traumatic brain injury
and often with significant injury/morbidity
involving extra axial soft tissue structures such
as cranial nerves and blood vessels.
 We
will provide an approach to evaluating
skull base CT in the setting of trauma, review
of skull base fracture patterns, and provide a
review of related injuries and complications
involving non-osseous structures.
Anatomy
 An
understanding of general skullbase
anatomy and anatomic relationship
of nonosseous structures to the bony
skullbase will aid in accurate diagnosis of
fractures and in predicting secondary
injuries and complications.
* denotes
parts of
the
central
skull base
Anterior Fossa
• Composed of paired
frontal bones and
ethmoid bone. Seats
the anterior frontal
lobes
• Olfactory nerves
transit the cribriform
plates to enter the
olfactory bulbs which
lie within the olfactory
grooves bordered
medially by the crista
galli and laterally by
the lateral lamella.
Left Facing Arrow: Crista Galli.
Right Facing Arrow Right Lateral Lamella.
Vertical Arrow: Left Olfactory Groove.
Green Line Marks posterior margin of anterior fossa.
6
Middle Fossa
• Formed of the Sphenoid
and anterior portions of
the paired temporal
bones. Seats the temporal
lobes and Meckel’s cave.
• Many important soft tissue
structures including CN 26, cavernous sinuses,
pituitary gland, and
portions of the internal
carotids.
7
Posterior Fossa


Formed of the occipital bone
and posterior portion of the
paired temporal bones. Seats
the cerebellar hemispheres
and brainstem.
Important soft tissue
structures include CN 7-12,
petrous portions of the
ICA’s, vertebrobasilar
arteries, sigmoid transverse,
torcula, and occipital
sinuses, and the vestibular
and auditory apparatuses.
Approach

It is imperative to scrutinize thin axial images, sagittal,
and coronal reformats in the setting of head trauma. 3D
reformats may also be helpful.

Added attention to areas of soft tissue
swelling/hematoma, pneumocephalus, sinus or mastoid
air cell opacification can increase sensitivity for subtle
skullbase fractures.

If a fracture is identified soft tissue structures such as
blood vessels which may be secondarily injured should
be noted.
Anterior Skull Base

Fractures involving the anterior skullbase
and frontal bones are of special importance
and can frequently be associated with orbital
injury, CSF leak, cephalocele, and
intracranial infections.
10
Craniofrontal Smash
3-D reconstruction and noncontrast CT image show a severe
craniofrontal smash injury with extensive pneumocephalus and
cerebral edema.
Frontobasilar Fractures

Numerous classification systems of frontobasilar
fractures are described in the literature. Of special
clinical relevance in this region is whether there is
involvement of the anterior and/or posterior walls of the
frontal sinuses.
12
Central Skull Base

Transverse/coronal fractures commonly result
from high velocity impact to the lateral skull.
Can involve the sphenoid sinus.

Oblique fractures through the central skull base
are often associated with facial or frontobasilar
fractures and more commonly associated with
CSF leak.
13
Sagittal reformat demonstrates a coronally oriented linear fracture of the
sphenoid body extending through the floor of the sella.
14
Transverse fracture of the Clivus extending to the bilateral
carotid canals.
Involvement of the carotid canals should prompt the radiologist to recommend CTA to exclude injury
to the internal carotid arteries.
Transverse/oblique clival fractures: due to high velocity lateral blow to the skull. ICA injury is
common.
Longitudinal clival fractures: due to axial loading. Vertebrobasilar injury is common.
15
Temporal Bone Fractures
1.
2.
3.
4.
Temporal bone injuries are usually associated with severe head
trauma and can be blunt, penetrating, or blast related.
Intracranial pneumocephalus or opacified mastoid air cells can
help to localize subtle fractures.
Transverse fractures are traditionally associated with
sensorineural hearing loss while longitudinal fractures with
conductive.
Delayed complications can include CSF fistulas, infections and
tegmen tympani dehiscence with meningoencephaloceles.
16
Longitudinal
Longitudinal Fracture of Petrous Portion of Right Temporal Bone
Also note the non-displaced linear fracture through the squamous portion of the
temporal bone; subcutaenous emphysema and soft tissue swelling should draw
attention to this region.
17
Transverse
3D rendering in a different patient demonstrates a nondisplaced
transverse fracture of the temporal bone.
18
Posterior Skull Base

Fractures of the posterior skull base may
typically result from a lateral blow or a blow
to the occiput.
19
Occiptal Condyle
Hypoglossal Canal
Axial MIP image demonstrates a comminuted non-displaced left sided occipital bone fracture
with involvement of the left occipital condyle and os of the left hypoglossal canal and
extension to the foramen magnum. This patient was assaulted with a baseball bat.
20
Occiptal Condyle
Coronal reformat in a different patient with an isolated left occipital condyle
fracture.
Occipital condyle fractures are
often subclassified:
Type I: Compression from axial
loading.
Type II: Posterior skull base
fracture with extension into the
condyle.
Type III: Avulsion fractor
involving the insertion of the
alar ligament.
21
Non-Contrast CT Limitations
 It
is imperative to recognize the limitations of non
contrast CT in detecting non osseous sequela of skull
base trauma.
 Thorough
understanding of the anatomic relationships
of various soft tissue structures to the skull base will
help to predict such injuries and indicate
when follow-up advanced imaging, such as
CTA/MRA, MRI, or scintigraphy, is advised.
Categories of Complications
 Vascular
 CN
injury
 Dural injury
 Infection
 Intraorbital injury
 Auditory/Vestibular injury
Vascular Complications
 Arterial
Transection
 Dissection/Occlusion
 Pseudoaneurysm
 AVF
 C-C fistula
 Sinus thrombosis
Dissection
Axial T2 weighted images in a patient s/p MVC demonstrate
replacement of L. vertebral artery flow void with high T2 signal
(arrow). There is bright signal in the median and left paramedian
medulla compatible with secondary ischemic changes.
25
Dissection
 Dissection:
Expanding hematoma within the
wall of the vertebral artery, carotid artery, or
within intracranial branches.
 Can cause ischemic or embolic strokes.
 Imaging:
Crescentic T1 hyperintensity within
expected region of vessel lumen. Angiography:
Tapered narrowing or occlusion. “String sign.”
May see intimal flap. Conventional Angiography
is gold standard.
Occlusion
Digital subtraction angiogram shows
extracranial vertebral artery occlusion in
a different patient with occipital/cervical
dislocation.
27
Bilateral Carotid Occlusion
Axial NECT in 10 y/o M demonstrates diffuse cerebral edema and the cerebellar
reversal sign. Cerebral angiogram showed delayed, slow and persistent filling of
the bilateral internal carotid arteries, with no contrast seen intracranially. There is
prominent filling of the external carotid arteries with a nasopharyngeal blush
(corresponding to the “hot nose” sign seen on brain death scintigraphy studies).
Sinus thrombosis
 Depressed
calvarial or skull-base fractures
can directly injure underlying venous
sinuses, this can lead to sinus thrombosis and
secondary infarcts. Propagation of the clot
into a cortical vein can cause secondary
intraprenchymal hemorrhage.
Axial NECT images demonstrate hyperdensity within the straight
sinus, left transverse sinus, and torcula. A secondary
intraparenchymal hematoma is seen in the left parietal region.
30
Dural AVM



Axial MRA source images demonstrate vascular lesion in the region of the right
sigmoid sinus.
Left vertebral artery DSA injection demonstrates an AVM nidus fed by branches
of the AICA
Lateral ICA injection demonstrates filling of AVM from the
meningohypophyseal trunk with deep venous drainage.
AVF/DAVM
 In
the setting of post traumatic sinus
thrombosis, neovascularization or
enlargement of underlying physiologic AV
shunts can occur leading to an acquired
fistulous malformation (Dural AV
fistula/Dural AVM).
 Presence of reflux into cortical veins
increases the risk of hemorrhage and the
benefit of treatment.
Enlargement of the left superior ophthalmic vein on CECT (left) suggests the
possibility of a CC fistula in this 42 year old trauma patient. DSA (right image)
with filling of the left cavernous sinus and superior opthalmic vein during
contralateral CCA injection confirms the presence of an indirect CC fistula.
33
Carotid-Cavernous fistula





Both direct and indirect CC fistula can result from skullbase trauma;
CC fistula should be considered in the setting of sphenoid bone
fractures.
Direct CC fistula: Laceration of the cavernous segment of the ICA
causes a direct high-flow fistula with the cavernous sinus.
Indirect CC fistula: Dural AV fistula between the cavernous sinus
and branches of the ipsilateral and/or contralateral ICA and/or ECA.
Secondary signs on cross sectional imaging: dilated superior
opthalmic vein, dilated petrosal sinuses, proptosis, enlarged
extraoccular muscles.
Gold standard imaging modality is catheter angiography.
Cranial Nerve Injuries
Cranial nerves may be compromised directly or
indirectly following trauma.
 Injuries to the base of the skull can damage nerves as
they emerge from the brain or brainstem.
 Mechanisms of injury include crushing, penetrating,
stretching and traction forces.

Orbital apex fractures can involve the optic canal and/or superior orbital
fissure (SOF) with associated injuries to the optic nerve or SOF contents
(including Cranial Nerves 3,4,V1,6)
This trauma patient with a left orbital apex fracture developed sudden loss of
vision.
Traumatic optic neuropathy can result from fracture fragments or hematoma
compressing CN2. Transection of CN2 can be readily identified on CT images by
discontinuity of the nerve.
CN I injury
This patient with multiple frontal contusions and a
fracture of the right cribriform plate went on to develop
anosmia.
•
Shearing injuries and
fractures at the
cribiform plate can
lacerate the olfactory
nerves.
•
Inferior frontal
hematomas can
compress CN I.
Complications Related to
Violation of Dura and Other
Barriers
 CSF
leak
 Meningitis
 Abscess
 Cephalocele
 Cholesteatoma
CSF Leak
Sagittal and coronal reformats of CT cisternogram performed in a
trauma patient with CSF rhinorrhea. A bony defect at the roof of the left
sphenoid sinus is seen with transit of intrathecal contrast from the
basal cisterns into the left sphenoid sinus.
39
CSF Leak
Consider in the setting of anterior or central skull base
fracture.
 May present with CSF rhinorrhea or otorrhea. Can be
confirmed with fluid analysis for β2-transferrin.
 If CSF leak is suspected in setting of multiple fractures,
or a discrete fracture is not identified, localization can
be performed with CT or radionuclide (Tc-99 DTPA or
In-111 DTPA) cisternography.
 Treatment: Often resolve within 1-2 weeks with
conservative management although surgical intervention
is required if persistent.

Meningitis
A
B
C
Axial contrast enhanced CT (A, B) and axial contrast enhanced T1W MR (C)
demonstrate leptomeningeal pattern of enhancement with diffuse
enhancement within the sulci.
Meningitis
 Direct spread of infection via dural/bony defects.
 Gold standard for diagnosis is LP with CSF
analysis.
 Imaging: May be normal. May show
leptomeningeal enhancement pattern on CECT
and T1+Gd. Imaging is most useful in
demonstrating complications such as abscesses.
 Treatment:
generally antibiotics.
Epidural Abscess with
Mastoiditis
Axial T1 post contrast MR demonstrates a rim enhancing collection with convex
borders resulting in mass effect of the temporal lobe.
Fluid is noted in the right mastoid cells on axial T2 MR image.
Abscess
Direct spread of infection via bony and dural defects can
lead to:
• Epidural Abscess
• Subdural Empyema
• Intraparenchymal abscess.
• Ventriculitis.
Imaging: Subdural/Epidural Empyema:
Peripherally enhancing fluid collection with
diffusion restriction.
Treatment: surgical drainage
Cephalocele
Coronal CT reformat demonstrates a left orbital roof “blow-in” fracture
with suggestion of herniation of left frontal lobe tissue into the orbit.
Sagittal T1 MRI image confirms the presence of an orbital encephalocele.
Cephalocele
Refers to herniation of intracranial contents
via a bony defect. Two types:
 Meningocele: Herniation of meninges and
CSF.
 Encephalocele: Herniation of brain tissue.

46
Cholesteatoma
Axial Noncontrast CT
through the temporal
bone shows scutum
erosion and
destruction of the long
process of the incus.
Cholesteatoma
Can cause cranial nerve dysfunction, headache,
mixed conductive hearing loss, otorrhea.
 Keratin filled and encapsulated by stratified
squamous epithelium.
 Acquired cholesteatomas- arise from retraction
pockets in the pars flaccida or in the pars tensa
of the eardrum, grow into the middle ear.

48
Injury to the Auditory and Visual
Apparatus
 Skull
base fractures can be associated with a
myriad of injuries to the intraorbital
structures and to the conductive and
sensorineural auditory system.
Traumatic ossicular dislocation
An air-filled space is seen interposed between the left incus and
malleus in this patient with a transverse temporal bone fracture.
50
Conclusion
 It
is imperative for the radiologist to develop
a methodical and organized approach to skull
base fractures for prompt diagnosis and to
recognize and mitigate the adverse
consequences of associated injuries.
References






Baugnon, K.L. and Hudgins, P.A., 2014, Skull Base Fractures and Their
Complications, Nauroimag Clin N AM, v. 24, p. 439-465
Jones, A.L and Jones, K.E., 2009, Orbital Roof “Blow-in” Fracture: A Case report
and Review, J Radiol Case Rep. v. 3(12) p. 25-30
Piccrilli, M., Anichini, G., Cassoni, A,. Ramieri, V., Valenitni, V., and Santoro, A.
2012 Anterior Cranial Fossa Traumas: Clinical Values, Surgical Indications, and
Results a Retrospective Study on a Series of 223 Patients J Neurol Surg B Skull
Base. v. 73(4) p. 265-272
Netter FH. Atlas of Human Anatomy. 5th ed Philadelphia, PA: Saunders/Elsevier;
2011
Osborn AG., Blaser SI., Salzman KL., Katzman GL., Provenzale J., Castillo M.,
Hedlund GL., Illner A., HarnsbergerHR., Cooper JA., Jones BV., and Hamilton BE.,
Diagnostic Imaging Brain. 1st ed Salt Lake City, UT: Saunders/Elsevier; 2004
http://www.Statdx.com