Normal Radiographic
Anatomy of the Skull
(and you thought the SPINE was
complicated)
Tabitha Fletcher, DVM
Goals for skull lecture
Point out need to know anatomy
 Go over some special views used for
certain anatomical structures
 Brief review of dental radiographic findings
 Feline differences
 Clinical cases

Skull Radiography
Skull radiography is performed relatively
infrequently, so it is unfamiliar
 Anatomy is very complex
 Knowledge of anatomy is essential
 There are species skull differences

1
Skull Radiography
 Skull type variation exists
Brachycephalic – ex.
Boston Terrier
Mesaticephalic – ex.
German Shepherd
Doliocephalic – ex. Collie
 Variation between
individuals within breeds
Boston Terrier
German Shepherd
Skull Radiography

Proper patient positioning and labeling is VITAL
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In order to produce standard views that avoid image
distortion that can complicate interpretation
So that oblique views will allow you to see normal
structures that are usually obscured
Types of view(s) selected will depend on the
clinical questions to be answered
General anesthesia is mandatory in all but the
simplest clinical questions (where did that
fishhook go?)
Skull Radiography
Multiple views are almost always
necessary
 Exposure factors are high
 Skull radiographs are fairly expensive
because of anesthesia, multiple views,
and technician time
 Because of the complexity of anatomy and
similar appearance of various pathology
findings are often very non-specific

2
Nasal Tumor
Skull Imaging
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STRONG CONSIDERATION
should be given to using CT
(computed tomography) or MRI
(magnetic resonance imaging) as
the PRIMARY means of imaging
the skull
CT and MRI provides MUCH more
thorough and clear information, but
are somewhat more expensive,
and certainly less available
Fluid in
R bulla
Radiographs vs. CT
Brain Tumor
Lateral View Positioning
Positioning:
 When relaxed the nose
points down and mandible
falls toward the table
 Therefore positioning
devices should be used to
elevate the nose parallel
with the table and maintain
the two halves of the
mandible parallel to each
other
 The beam should be
centered over the external
ear canal
3
Lateral View Anatomy to be
Identified
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Can indentify:
1. Calvarium
2. Cribiform plate
3. Osseous tentorium
4. External occipital
protuberance
5. Occipital condyles
6. Altanto-occipital
joint
7. Tympanic bullae
8. Petrous portion of
temporal bone
9. Zygomatic arch

Maxilla
 10. Hard palate
 11. Soft palate
 12. Nasopharynx
 13. Oropharynx
Mandible
 14. Body (horizontal
portion)
 15. Vertical rami
 16. Coronoid
processes
 17. Condyloid
processes (TMJ)
 18. Angular
processes
 19. Mental foramen
Lateral View Anatomy
Can indentify:
1. Calvarium
2. Cribiform plate
3. Osseous tentorium
4. External occipital
protuberance
5. Occipital condyles
6. Altanto-occipital
joint
7. Tympanic bullae
8. Petrous portion of
temporal bone
9. Zygomatic arch
1
Lateral View Anatomy
Can indentify:
1. Calvarium
2. Cribiform plate
3. Osseous tentorium
4. External occipital
protuberance
5. Occipital condyles
6. Altanto-occipital
joint
7. Tympanic bullae
8. Petrous portion of
temporal bone
9. Zygomatic arch
2
4
Lateral View Anatomy
Can indentify:
1. Calvarium
2. Cribiform plate
3. Osseous tentorium
4. External occipital
protuberance
5. Occipital condyles
6. Altanto-occipital
joint
7. Tympanic bullae
8. Petrous portion of
temporal bone
9. Zygomatic arch
3
Lateral View Anatomy
Can indentify:
1. Calvarium
2. Cribiform plate
3. Osseous tentorium
4. External occipital
protuberance
5. Occipital condyles
6. Altanto-occipital
joint
7. Tympanic bullae
8. Petrous portion of
temporal bone
9. Zygomatic arch
4
Lateral View Anatomy
Can indentify:
1. Calvarium
2. Cribiform plate
3. Osseous tentorium
4. External occipital
protuberance
5. Occipital condyles
6. Altanto-occipital
joint
7. Tympanic bullae
8. Petrous portion of
temporal bone
9. Zygomatic arch
5
5
Lateral View Anatomy
Can indentify:
1. Calvarium
2. Cribiform plate
3. Osseous tentorium
4. External occipital
protuberance
5. Occipital condyles
6. Altanto-occipital
joint
7. Tympanic bullae
8. Petrous portion of
temporal bone
9. Zygomatic arch
6
Lateral View Anatomy
Can indentify:
1. Calvarium
2. Cribiform plate
3. Osseous tentorium
4. External occipital
protuberance
5. Occipital condyles
6. Altanto-occipital
joint
7. Tympanic bullae
8. Petrous portion of
temporal bone
9. Zygomatic arch
7
Lateral View Anatomy
Can indentify:
1. Calvarium
2. Cribiform plate
3. Osseous tentorium
4. External occipital
protuberance
5. Occipital condyles
6. Altanto-occipital
joint
7. Tympanic bullae
8. Petrous portion of
temporal bone
9. Zygomatic arch
8
6
Lateral View Anatomy
Can indentify:
1. Calvarium
2. Cribiform plate
3. Osseous tentorium
4. External occipital
protuberance
5. Occipital condyles
6. Altanto-occipital
joint
7. Tympanic bullae
8. Petrous portion of
temporal bone
9. Zygomatic arch
9
Lateral View Anatomy
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Can Identify
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10.
11.
12.
13.
Maxilla
Hard palate
Soft palate
Nasopharynx
Oropharynx
10
Can evaluate the
mandible
(although its two halves
are superimposed)
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14. Body (horizontal portion)
15. Vertical rami
16. Coronoid processes
17. Condyloid processes (TMJ)
18. Angular processes
19. Mental foramen
Lateral View Anatomy
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Can Identify
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10.
11.
12.
13.
Maxilla
Hard palate
Soft palate
Nasopharynx
Oropharynx
Can evaluate the
mandible
(although its two halves
are superimposed)
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11
14. Body (horizontal portion)
15. Vertical rami
16. Coronoid processes
17. Condyloid processes (TMJ)
18. Angular processes
19. Mental foramen
7
Lateral View Anatomy
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Can Identify
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10.
11.
12.
13.
Maxilla
Hard palate
Soft palate
Nasopharynx
Oropharynx
12
Can evaluate the
mandible
(although its two halves
are superimposed)

14. Body (horizontal portion)
15. Vertical rami
16. Coronoid processes
17. Condyloid processes (TMJ)
18. Angular processes
19. Mental foramen
Lateral View Anatomy
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Can Identify

10.
11.
12.
13.
Maxilla
Hard palate
Soft palate
Nasopharynx
Oropharynx
Can evaluate the
mandible
(although its two halves
are superimposed)
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13
14. Body (horizontal portion)
15. Vertical rami
16. Coronoid processes
17. Condyloid processes (TMJ)
18. Angular processes
19. Mental foramen
Lateral View Anatomy
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Can Identify

10.
11.
12.
13.
Maxilla
Hard palate
Soft palate
Nasopharynx
Oropharynx
Can evaluate the
mandible
(although its two halves
are superimposed)

14
14. Body (horizontal portion)
15. Vertical rami
16. Coronoid processes
17. Condyloid processes (TMJ)
18. Angular processes
19. Mental foramen
8
Lateral View Anatomy
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Can Identify
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10.
11.
12.
13.
Maxilla
Hard palate
Soft palate
Nasopharynx
Oropharynx
Can evaluate the
mandible
(although its two halves
are superimposed)
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15
14. Body (horizontal portion)
15. Vertical rami
16. Coronoid processes
17. Condyloid processes (TMJ)
18. Angular processes
19. Mental foramen
Lateral View Anatomy
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Can Identify
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10.
11.
12.
13.
Maxilla
Hard palate
Soft palate
Nasopharynx
Oropharynx
16
Can evaluate the
mandible
(although its two halves
are superimposed)

14. Body (horizontal portion)
15. Vertical rami
16. Coronoid processes
17. Condyloid processes (TMJ)
18. Angular processes
19. Mental foramen
Lateral View Anatomy

Can Identify

10.
11.
12.
13.
Maxilla
Hard palate
Soft palate
Nasopharynx
Oropharynx
Can evaluate the
mandible
(although its two halves
are superimposed)

17
14. Body (horizontal portion)
15. Vertical rami
16. Coronoid processes
17. Condyloid processes (TMJ)
18. Angular processes
19. Mental foramen
9
Lateral View Anatomy

Can Identify

10.
11.
12.
13.
Maxilla
Hard palate
Soft palate
Nasopharynx
Oropharynx
Can evaluate the
mandible
(although its two halves
are superimposed)

18
14. Body (horizontal portion)
15. Vertical rami
16. Coronoid processes
17. Condyloid processes (TMJ)
18. Angular processes
19. Mental foramen
Lateral View Anatomy

Can Identify

10.
11.
12.
13.
Maxilla
Hard palate
Soft palate
Nasopharynx
Oropharynx
Can evaluate the
mandible
(although its two halves
are superimposed)

14. Body (horizontal portion)
15. Vertical rami
16. Coronoid processes
17. Condyloid processes (TMJ)
18. Angular processes
19. Mental foramen
19
Lateral View Anatomy
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Can evaluate nasal
cavity and frontal
sinuses (although
superimposed)
 Nasal turbinates
 Ethmoid turbinates
 Frontal sinus
Note: some brachycephalic dogs do not have a
fontal sinus!
10
Lateral View Anatomy
Bones
of the HYOID apparatus
Stylohyoid
Epihyoid
Ceratohyoid
Basihyoid
(unpaired)
Thyrohyoid
Dorsoventral View
Positioning:
 The head has natural
parallel positioning
devices for this view – the
mandibles.
 Therefore place the
animal in sternal
recumbency and let it’s
mandibles do the
positioning for you
 Beam should be centered
over level of interest
Dorsoventral View Anatomy
Should be able to
identify:
1. Calvarium
2. Mandible
3. Temporo-mandibular
joint
4. Zygomatic Arch
5. Cribiform plate
6. Occipital condyles
1
11
Dorsoventral View Anatomy
Should be able to
identify:
1. Calvarium
2. Mandible
3. Temporo-mandibular
joint
4. Zygomatic Arch
5. Cribiform plate
6. Occipital condyles
2
Dorsoventral View Anatomy
Should be able to
identify:
1. Calvarium
2. Mandible
3. Temporo-mandibular
joint
4. Zygomatic Arch
5. Cribiform plate
6. Occipital condyles
3
Dorsoventral View Anatomy
Should be able to
identify:
1. Calvarium
2. Mandible
3. Temporo-mandibular
joint
4. Zygomatic Arch
5. Cribiform plate
6. Occipital condyles
4
12
Dorsoventral View Anatomy
Should be able to
identify:
1. Calvarium
2. Mandible
3. Temporo-mandibular
joint
4. Zygomatic Arch
5. Cribiform plate
6. Occipital condyles
5
Dorsoventral View Anatomy
Should be able to
identify:
1. Calvarium
2. Mandible
3. Temporo-mandibular
joint
4. Zygomatic Arch
5. Cribiform plate
6. Occipital condyles
6
Dorsoventral View Anatomy
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Should be able to
identify:
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External ear canals
Tympanic bullae
and Petrous
temporal bones
which are
superimposed
13
Dorsoventral View Anatomy
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Should be able to identify:
Osseous nasal septum
(also called the Vomer)
Nasal turbinates
Ethmoid turbinates
Frontal sinuses (maybe)
Open-mouth VD View
Positioning:
 The animal must be
anesthetized for this view
 The endotracheal tube
must be positioned onto
the mandible so as not to
superimpose on the
maxilla/nasal cavity
 The tube must be angled
at 25-30º
Open Mouth VD
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Can identify:
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Structures usually
seen on the DV view
that are rostral to the
cribiform plate
 nasal cavity, nasal
and ethmoid
turbinates
 Vomer/osseous
nasal septum
 maxilla
As well as the palatine
fissures *
*
*
14
Open-mouth VD View
Advantage is absence of superimposition of
the mandible and tongue
 Disadvantage is mild distortion (because the
beam is not perpendicular to film)
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Same dog
DV View
Intraoral Views
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DV intraoral to evaluate maxilla and nasal
structures
VD intraoral to evaluate mandible
Provides higher detail, but more limited view
(due to constraints of mouth anatomy)
Place corner of cassette (or non-screen film) into
mouth
“dental radiographs” are a subset of intraoral
views
Intraoral Views
•DV Intraoral
•VD Intraoral
to see the maxilla
to see the mandible
15
Intraoral Views
•DV Intraoral
•VD Intraoral
to see the maxilla
to see the mandible
Abnormally thickened bone on R maxilla
Fractured Right Mandible
Lateral Oblique Views
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Lift and angle either the mandible or maxilla off
the table with positioning devices
With the mouth open one side of the maxilla,
mandible or dental arcades can be visualized
Either tympanic bulla can be highlighted
Oblique views may also be used to evaluate the
frontal sinuses or frontal bones
Lateral Oblique Views
Also can be used to improve visualization
of the TMJ
 Oblique the rostral portion of the head 2530º to better
visualize the TMJ
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16
Lateral Oblique Views
Positioning and labeling are confusing
Try to be consistent in both
 Always use both the left and right marker
 Markers no longer indicate the animals
recumbency but now it tries to indicate the
sides of the head
 One side will be projected dorsally to the
other
 Convert 3D patient into 2D image
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Lateral Oblique Views
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To evaluate Maxilla or
Tympanic bulla similar
technique and labeling
To evaluate the right side,
place animal in right
recumbency and use a
wedge under the
mandible to lift and angle
it
This will project the right
maxilla (or tympanic
bulla) ventral in the final
image
Lateral Oblique Views
Right side is Ventral
17
Lateral Oblique Views
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To evaluate Mandible
For the right side,
place animal in right
recumbency and use
a wedge under the
maxilla to lift and
angle it
This will project the
right mandible dorsal
in the final image
Lateral Oblique Views
Right side is Dorsal
Frontal View
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Positioning
Dorsally
recumbent
 Point nose straight
up toward tube
 Mouth closed
 Center beam over
frontal sinuses and
collimate other
structures out
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 Can evaluate
 Frontal Sinuses
 Frontal Bones
 Other structures are to
distorted and superimposed
to be useful
18
Frontal View
Basilar View
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Positioning
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Same as for a frontal
view but open the
mouth
May have to adjust
angle of animals head
depending on breed
Again, other structures
not really helpful,
collimate as much as
practical
Use to evaluate:
 TMJ
 Tympanic bullae
 Dens (safe?)
Basilar View
Dens
TMJ
Normal
Diseased
Tympanic Bullae
19
Another View for Tympanic Bullae
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It may be difficult to
achieve a basilar view
on some
brachycephalic
breeds and cats
This Rostro-10º
ventral to caudodorsal
oblique view can be
used
Mouth closed, tilt
head 10º dorsally
Feline differences
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Cats vary much less between
breeds and have some
distinct differences from dog
The shape of the skull is
different on the lateral view
having more convex shaped
frontal and nasal bones
Reduced nasal chambers
and prominent ethmoid
turbinates
Two compartments of the
tympanic bullae
Prominent osseous tentorium
Feline Differences
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Laterally-protruding
zygomatic arches
noted on the
dorsoventral view
Large post-orbital
processes
20
Clinical Correlation
Fractured Skull
Fractured Mandible
21
Cranial Osteosarcoma
Ear Disease
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Mass in middle ear
Questions?
22