Get Wise About Cracks: A

Pictorial Review of the Pediatric Skull Base eEdE-203

Anna Thomas MD, John Egelhoff DO,

John Curran MD, Jeffrey Miller MD,

Richard Towbin MD.

DISCLOSURES:

• None

Objectives 1. Review the normal anatomic landmarks of the

skull base and its 3 main divisions.

2. Review normal development and progression of

ossification of the different divisions of the skull

base.

3. Review normal skull base lucencies and foramina

of the pediatric skull base.

4. Present a few cases of pediatric skull base

fractures and discuss their associated complications.

5. Review frequently associated complications

associated with specific skull base fracture locations.

Skull base: • Comprised of 7 bones:

* paired frontal

* paired temporal

* unpaired ethmoid

* unpaired sphenoid

* unpaired occipital

• 3 divisions: anterior, central,

and posterior form the floor

of the anterior, middle, and

posterior cranial fossae.

From: Baugnon, KL et al.

Neuroimag Clin N Am 24 (2014)

439–465.

Overview

Review of the Atraumatic

Skull Base

Mildly Adapted From the Textbook: Diagnostic and Surgical Imaging Anatomy of the Brain. Head & Neck. Spine.

Anterior Skull Base - Axial

From Textbook: Diagnostic and Surgical Imaging Anatomy

of the Brain. Head & Neck. Spine.

Anterior Skull Base -Sagittal

Age Related Anterior Skull Base Ossification

Birth: Nonossified.

2 years: only 4% have a fully ossified anterior

skull base.

4/+ years: fully ossified anterior skull base.

> 4 years: the foramen cecum is the only

nonossified portion.

Adapted from: Koch BL. Neuroimag Clin N Am 2014;24:513–529.

2 year old coronal CT through anterior skull base:

Ethmoid bone is now mostly ossified, particularly

crista galli & cribriform plate. Note the normal

unossified gaps in the anterior cribriform plate.

Coronal Progression of Anterior Skull Base Ossification 1 week old Coronal CT through the anterior skull

base:

Most of the anterior skull base including crista galli,

cribriform plate and perpendicular plate of ethmoid

bone are unossified. There is a large gap between the

orbital plates of frontal bones. Ethmoid air cells are

not yet developed.

18 Year old coronal CT through anterior skull base

which is completely ossified. Ethmoid air cells extend

superolateral to plane of the cribriform plate. The

fovea ethmoidalis is connected to the cribriform

plate by the lateral lamella.

Axial Progression of Anterior Skull Base Ossification

Normal Lucencies & Foramina of the anterior skull base

Foramina of the

Anterior Skull Base

Contents

Optic Nerve Canal Cranial Nerve II,

Ophthalmic artery,

and sympathetic

nerve fibers.

Superior Orbital

Fissure

Cranial Nerves III, IV,

V1, VI and the

Superior Ophthalmic

vein

Mildly Adapted From the Textbook: Diagnostic and Surgical Imaging Anatomy

of the Brain. Head & Neck. Spine.

Central Skull Base

Foramina of the central

skull Base

Contents

Foramen rotundum Cranial Nerve V2

Foramen ovale Cranial Nerve V3

Carotid canal Internal Carotid artery and

Sympathetic plexus

Foramen spinosum Middle Meningeal artery

Vidian canal Vidian nerve and artery

Foramen lacerum Cartilage

Central Skull Base Foramina & Contents

From: Nemzek WR et al. AJNR Am J Neuroradiol 2000;21:1699-1706.

Diagram of Central & Posterior Skull Base

Ossification Centers

*Indicates olivary eminence

Normal Neonatal Central Skull Base

Lucencies & Ossification Centers on the Axial

Projection

Axial CT image of the central

skull base in a 1 week old:

Olivary eminence ( ), also

called the anterior foramen is a

triangular shaped lucency seen

only in the early newborn period;

This is located posterior to the

presphenoid ( ) and anterior to

the paired postsphenoid

ossification centers ( ). Note

the posterior and centrally located

posterior foramen ( )also

called the craniopharyngeal canal.

Progression of Skull Base Ossification

From: Nemzek et al. AJNR Am J Neuroradiol 2000;21:1699-1706.

Black arrow ( )shows normal sequence of skull base ossification in a posterior to anterior direction.

Maturation of the Central Skull Base - Sagittal

Midline central skull base in a 1 week old:

A patent spheno-occipital synchondrosis ( ) and a

partially patent craniopharyngeal canal ( ) are noted.

Midline central skull base in a 2 year old:

Spheno-occipital synchondrosis ( ) is patent and its

comprising bones are more uniform in density . A thin

sclerotic line persists at expected site of the

craniopharyngeal canal ( ). Note the ossifying

cribriform plate and small ethmoid and sphenoid sinuses

Midline central skull base in an 18 year old:

The spheno-occipital synchondrosis ( ) is completely

fused. Note the completely ossified cribriform plate and

mature ethmoid and sphenoid sinuses.

Synchondroses & Sutures of the Central Skull Base

Name Location Pertinent Information

Spheno-occipital

synchondrosis

Located between and

separates the postsphenoid

ossification center from the

basiocciput

Where maximal skull base growth occurs. Remains

patent until teenage years. Small ossified bodies

can be seen at the synchondrosis during closure.

After complete closure, small divots, clefts, or

fissures on one or both sides of this synchondrosis

are often seen.

Craniopharyngeal

canal

(Posterior Foramen)

Extends from the floor of the

sella turcica to the roof of the

nasopharynx

Seen a partially patent canal in a only small

percentage of infants, with usual closure in early

infancy. Rarely, is pathologically widened from a

cephalocele containing the ectopic pituitary.

Olivary eminence Triangular shaped,

cartilaginous lucency seen in

early newborn period between

presphenoid and the paired

postsphenoid bodies

Seen only in early newborn period. Rarely visible as

a sclerotic remnant in a small percentage of

children over 9 months of age.

Canalis basilaris

medianus

Midline lucency in the

basiocciput posterior to the

spheno-occipital

synchondrosis

Very rarely seen as incidental finding that may be

associated with nasopharyngeal cysts. Variable in

shape and patency ( can be complete /incomplete).

Posterior Skull Base

Both images are from Textbook:

Diagnostic and Surgical Imaging

Anatomy of the Brain. Head & Neck.

Spine.

Posterior Skull Base Foramina & Contents

Foramina of the Posterior

skull Base

Contents

Internal Auditory Canal Cranial nerves VII & VIII and

labyrinthine artery

Stylomastoid Foramen Cranial nerve VII &

stylomastoid artery

Jugular Foramen Cranial nerves IX, X, & XI,

internal jugular vein, inferior

petrosal vein & sigmoid sinus

Hypoglossal Canal Cranial nerve XII

Foramen Magnum Medulla oblongata, ascending

spinal fibers of cranial nerve

XI, vertebral arteries, and

anterior & posterior spinal

arteries

Posterior Skull Base Ossification Mastoid and

Petrous Temporal

bone segments

Cartilaginous & Membranous Components of the

Skeletally Immature Occipital Bone

Note: ( ) refers to mendosal suture.

Skull Base Trauma

2 year old s/p MVA with magnified coronal (above)

and axial ( left) images through the right temporal

bone:

Blue arrow: right temporal bone fracture.

Yellow arrow: resultant disruption of right middle ear

ossicles and loss of normal ice cream cone configuration of the

incudomalleal joint.

2 year old who was backed over by a car:

White arrow: vertical fracture through sphenoid

extending to the sella. This child manifested with

clinical signs of Diabetes insipidus within days of

this injury.

Yellow arrows: preclival soft tissue swelling.

Magnified image of the sphenoid bone in the

same patient:

White arrow: vertical fracture through sphenoid

extending to the sella. This child manifested with

clinical signs of Diabetes insipidus within days of this

injury.

Yellow arrows: preclival soft tissue swelling.

7 year old ejected from car during MVA:

Blue arrow - marked thickening of preclival

soft tissues.

Yellow arrow - retroclival hematoma.

7 year old ejected

during MVA:

Far right sagittal CT

image demonstrates

abnormal widening of

the joint space

between the right

occipital condyle with

right superior C1 facet

(blue arrow) in this

patient with

atlantoccipital

dislocation.

7 year old ejected

during MVA:

Coronal image

demonstrates

abnormal widening of

the joint space

between the occipital

condyle and the

superior C1 facet on

both sides (blue

arrows) in this patient

with atlantoccipital

dislocation.

8 year old with focal expansion of the skull .

Yellow arrows: Note the focal abnormal expansion of the right sigmoid fossa and this

abnormality was in the region of an old fracture. There is a post-traumatic dural tear with

leptomeningeal herniation at the fracture site resulting in progressive skull erosion at the

fracture site from continuous CSF pulsations.

8 year old s/p head injury with left

posterior calvarial fracture and resultant

post traumatic thrombosis of left

transverse sinus:

White arrows: obliquely oriented fracture

through left occipital bone extending across

left lambdoid suture into petrous segment of

left temporal bone.

Yellow arrow: intracranial air adjacent to left

sigmoid sinus.

Blue arrows: abnormal isointense T2 signal

( thrombus) replacing normal dark flow void of

the left transverse sinus.

Orange arrows: left transverse sinus is

absent on the MRV.

Fracture Location: Common Complications:

Anterior Skull Base Intraorbital Injury

Sinonasal CSF leak/meningoencephalocele

Central Skull Base

Internal carotid artery injury

Injury to Cranial Nerves II, III, IV, V, or VI

Horner Syndrome

Posterolateral Skull Base

(Nonsquamous Temporal Bone)

Internal carotid artery injury

Injury to Cranial Nerves VII or VIII

Mastoid CSF leak/meningoencephalocele

Injury to middle and inner ear structures

Central Posterior Skull Base

Major venous vessel injury

Vertebrobasilar arterial injury

Injury to Cranial Nerves IX, X, XI, or XII

Injury to craniocervical junction/upper cervical

spine

Common Complications Associated with Specific

Skull Base Fracture Locations

Adapted from: Baugnon, KL et al. Neuroimag Clin N Am 24 (2014) 439–465.

References:

1. Baugnon KL, Hudgins PA (2014) Skull Base Fractures and Their

Complications. Neuroimag Clin N Am 24:439-465.

2. Koch BL. Pediatric Considerations in Craniofacial Trauma (2014)

Neuroimag Clin N Am 24:513–529.

3. Nemzek WR, Brodie HA, Hecht ST , Chong BW, et al (2000) MR, CT,

and Plain Film Imaging of the Developing Skull Base in Fetal

Specimens AJNR Am J Neuroradiol 21:1699-1706.

4. Madeline LA, Elster AD (1995 ) Suture closure in the human

chondrocranium: CT assessment. Radiology 196: 747-756.

5. Harnsberger HR, Osborn AG, Macdonald A, Ross J (2006)

Diagnostic and Surgical Imaging Anatomy of the Brain. Head &

Neck. Spine. Amirsys Incorporated.