Cranium
RTEC 233
Fall 2008
Week 1 & 2
Cranial Anatomy

Calvaria

Floor

Frontal

Ethmoid

Occipital

Sphenoid

Left Parietal

Left Temporal

Right Parietal

Right Temporal
The regions of the Cranial Floor

Anterior: extends form anterior frontal bone to
the lesser wings of the sphenoid


Middle: Extends from lesser wings to the apices
of petrous ridges of temporal bone


It is associated with frontal lobes of cerebellum
Accommodates temporal lobes and associated
neurovascular structures
Posterior: deep depression posterior to petrous
ridge

which protects cerebellum, pons and medulla
oblongata
Frontal Bone

Has a vertical and
horizontal portion


Vertical portion- forms
the forehead and
anterior part of the
vault
Horizontal portionforms roof of orbits,
part of the roof of
nasal cavity, and
greater part of anterior
cranial fossa.
Parietal Bone



Forms large part of
sides of the cranium
Forms posterior
portion of the cranial
floor
Parietal eminence is
used to measure width
of head
Occipital Bone




Inferosuperior portion of calvaria
Squamous portion is superior to inion
Ext. occipital protuberance – prominent bulge
Contains foramen magnum and articulates with
atlas (C1)
Ethmoid Bone

Horizontal portion is called cribiform plate

Vertical portion is called perpendicular plate

2 light spongy labyrinths
Sphenoid Bone



Resembles shape of a
bat
Consists of a body, 2
lesser wings, 2
greater wings, 2
pterygoid processes
Contains Sella turcicaimportant for
positioning errors
Sella Turcica

Lies in the MSP


¾” anterior & superior
to EAM
Deformity of the sella
is often the only clue
that a lesion exists
intracranially
Temporal Bone

Divided in 3 parts



Squamous: upper
portion forming part of
the wall of skull
Mastoid: Posterior to
EAM contains mastoid
tip (process)
Petrous: dense &
houses organs of
hearing and balance


Thickest most dense
bone in cranium
Level of TEA
Superior Cranium

Visualized more
clearly:





Sphenoid
Temporals
Occipital
Frontal
Not well visualized:


Ethmoid
Parietals
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.
Lateral Cranium
From this view you can visualize
all the cranial bones
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Infant Sutures
& Fontanels

Anterior


2 Mastoids


Close approx 2 years
2 Sphenoidal


Close approx 2 years
1-3 months old
Posterior

1-3 months
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Adult Sutures
and Junctions


Sutures:
 Coronal

Sagittal

Squamosal

Lamboidal
Junctions

Bregma

Lambda

Pterion

Asterion
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Lets compare
Infant
Adult

Anterior fontanel
Bregma

Posterior fontanel
Lambda

Sphenoidal fontanels
Pterions

Mastoidal fontanels
Asterions
Anterior Cranium

Not able to visualize:



Occipital
Ethmoid
Able to visualize:




Parietals
Frontal
Sphenoid
Temporals
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.
Cranial Topography
Surface
Landmarks

Mesocephalic:
average


Brachycephalic: Short
and broad



47 degrees
Width 80% or greater
than length
54 degrees
Dolichocephalic: long
and narrow


Width is less than 75%
than the length
40 degrees
Skull morphology
Skull Positioning Lines
Skull Topography
Be able to locate the following landmarks:






Glabella
Inner canthus
Outer canthus
Nasion
Infraorbital margin
Acanthion





Gonion
Mental point
External auditory
meatus (EAM)
Auricular point
Top of ear
attachment (TEA)
Radiographic Landmarks

Interpupillary line (IPL)


Acanthiomeatal line (AML)


Perpendicular line between pupils of eyes
From acanthion to EAM
Mentomeatal line (MML)

From mental point (center of chin) to EAM
Radiographic Landmarks

Orbitomeatal line (OML)


Infraorbitomeatal line (IOML)


From outer canthus to EAM
From infraorbital margin to EAM
Glabellomeatal line (GML)

From glabella to EAM
Positioning Aids
Use any straightedge:
•Straw
•Pen/pencil
Most Common Positioning Errors

Rotation

Tilt

Excessive Flexion

Excessive Extension

Incorrect CR angle
Rotation
Tilt
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Indications for Cranial Radiography

Skull fractures

Neoplasms




Linear
Depressed
Basal skull
Metastases



Osteolytic
Osteoblastic
Combo of both

Gunshot wounds

Multiple myeloma

Pituitary Adenomas

Paget’s Disease

Subdural hematoma

Acoustic neuroma


http://www.skullbaseinstitute.com/video_
pituitary_tumor.htm
http://www.skullbaseinstitute.com/video_a
coustic_neuroma.htm
Disinfect the Table or Bucky!!
Cleanliness




Hair and skin of face are naturally oily;
illness often increases oiliness
Cranial procedures require direct contact
of patient’s face with VBS
Clean device after each patient
Wash your hands!!!
Radiation Protection




Collimate to anatomy of interest
Shield gonads/abdomen of pediatric
patients and those of reproductive age
Shield thyroid and thymus of pediatric
patient when doing so will not interfere
with demonstration of anatomy of interest
Good communication and positioning skills
reduce chance of need for repeat
radiographs
General Body Position

Hyposthenic/asthenic patients usually
need support at chest to elevate C-spine


Helps prevent downward tilt of MSP
Hypersthenic patients require radiolucent
support at head

Helps prevent upward tilt of MSP
Hyposthenic/Asthenic Patients
Hypersthenic Patients
Positioning: Lateral Skull





Seated upright or semiprone
MSP is parallel to IR
Interpupillary line is
perpendicular to IR
Suspend respiration
CR enters 2” superior to
EAM
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Positioning Trauma Lateral Skull





Supine with sponge under
head
MSP is parallel to IR
Interpupillary line is
perpendicular to IR
Suspend respiration
CR enters 2” superior to
EAM
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Lateral Skull
Lateral Skull Radiograph


Entire cranium without
rotation/tilt
SI orbital roofs, greater
wings of sphenoid, and
TMJ’s

Sella turcica in profile

Penetration of parietal

No overlap c-spine by
mandible
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Common PA projections
PA projections Skull
25 – 30 caudal
0 degrees
15 degree caudal
Frontal bone
Caldwell
Rotundum foramina,
Superior orbital
fissures
Positioning PA, PA Axial & Caldwell


Prone or seated upright
Forehead and nose
against bucky or table

OML perpendicular to IR

MSP perpendicular to IR

Respiration: suspend

CR: 0, 15 caudal or 25-30
caudal, exiting nasion
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Trauma PA and PA Axial Skull

Semi supine: 1 side
elevated to place head in
true lateral

Sponge under head

Nose and forehead
against vertical IR

OML perpendicular to IR

Direct horizontal CR
perpendicular or 15
degrees caudad to exit
nasion
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PA and Caldwell Radiographs

Entire skull with no rotation or
tilt

Petrous ridges in lower 1/3 of
orbits with 15 caudal

Petrous ridges fill orbits with
horizontal beam

Density and contrast are
sufficient

No motion

Nasion in center of film, close
collimation
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Similarities and Differences




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Exit nasion
Require close collimation

Position of petrous ridges
OML is perpendicular to
plane of IR

Best seen

Body position

Where the CR enters
All axials have caudal
angles
Respiration suspended
Positioning: AP & AP Axial Skull

Supine

OML perpendicular to IR


CR directed at nasion
with a horizontal beam or
15 degrees cephalic
Suspend respiration
AP Skull Radiograph

Entire skull with no rotation or
tilt

Petrous ridges in lower 1/3 of
orbits with 15 cephalad

Petrous ridges fill orbits with
horizontal beam

Density and contrast are
sufficient

No motion

Nasion in center of film, close
collimation

Image is magnified compared
to PA
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Positioning AP Axial (Towne)






Supine or seated upright
MSP perpendicular to plane of
IR
OML or IOML perpendicular to
IR
Suspend respiration
CR 30 degrees caudal (OML)
or 37 caudal (IOML).
CR enters 2 ½” above glabella
through the level of EAM
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AP Axial (Towne) Radiograph




Equal distance from
lateral border of skull to
foramen magnum
Symmetric petrous ridges
Dorsum sellae and
posterior clinoid
processes visible through
foramen magnum
Penetration of occipital
bone without excessive
density
Sella Turcica
Townes Comparison
Positioning PA Axial (Haas)


Prone or seated upright
Forehead and nose on table or
grid device

MSP perpendicular to the grid

OML perpendicular to IR

Suspend respiration


CR 25 degrees cephalad
entering 1 1/2 “ below occipital
protuberance.
R exits 1 ½” superior to nasion
PA Axial (Haas) Radiograph

Prone or seated upright

MSP & OML
perpendicular

Suspend respiration


Directed cephalic 25
degrees to enter 1 ½”
below the inion.
Exit 1 ½” superior to
nasion.
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Haas
PA Axial
Positioning SMV (Schüller)

Supine or seated upright

IOML parallel to IR

MSP perpendicular to IR

Suspend respiration

CR enters the MSP of the
throat between angles of
mandible and passes
through a point
¾”anterior to EAMS.
SMV (Schüller) Radiograph



Adequate penetration of
cranial base
Equal distance from
lateral border of skull to
condyles
SI of mental
protuberance over
anterior frontal bone

Condlyes anterior to
petrous ridges

Symmetric petrosae
Positioning VSM (Schüller)

Prone

Chin resting on table

MSP perpendicular to IR

Suspend respiration


CR directed perpendicular
to IOML.
CR passes through ¾”
anterior to level of EAMS
VSM (Schüller) Radiograph



Adequate penetration of
cranial base
Equal distance from
lateral border of skull to
condyles
SI of mental
protuberance over
anterior frontal bone

Condlyes anterior to
petrous ridges

Symmetric petrosae
SMV
What is wrong with this Caldwell?
What is wrong with this
lateral skull?
What is wrong with this Towne’s?