The Skull
Melanie Eagan
Chinchilla skull – notice the large bullae!
Indications for skull rads
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Neurological problems
Nasal problems
Mandibular problems
Maxillary problems
1̊ tumors of skull
Mass behind eye
Teeth diseases
Middle ear problems
Views
• Careful positioning is necessary
• Sedation or GA usually necessary
• Positioning aids to elevate cassette
Intraoral dorsoventral view
• Good for rostral aspect of nasal cavities
Ventrorostral-dorsocaudal oblique
• Good for more caudal aspect of nasal cavities
• More difficult to assess rostral aspect of nose
(shortened by angulation of x-ray beam)
Rostrocaudal view
• Patient positioning for rostrocaudal rads of
frontal sinuses taken with vertical beam
Rostrocaudal view
• Used for viewing frontal sinuses
• Rotation of head must be avoided so view is not “obliqued”
• Open mouth rostrocaudal used to view tympanic bullae and foramen
magnum
Lateral oblique used to
view:
-Tempromandibular joint
-Teeth in mandible/maxilla
-Fractures in mandible/maxilla
differences in the cat skull
Dog skull – left
Cat skull – right
Cats have:
-greater doming on frontal and nasal bones
-smaller frontal sinuses (may be absent in Persians)
-more complete bony orbits
-wider skulls ( due to wider zygomatic arches)
Arrow pointing to
cribiform plate
Rads or CT?
• CT
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Elimination of superimposition
Ability to display images in multiple planes
Shorter imaging time
Higher contrast resolution
Higher cost
Lower availability
• CT and rads both underestimate presence of mild middle ear
disease
• CT more consistent for moderate/severe middle ear disease
nasopharyngeal polyps in cats
• Polyps:
– Benign growths
– Nasopharynx, middle ear, external ear canal
• Diagnostic Imaging:
– Rads of skull with emphasis on tympanic cavities
– Lateral oblique and open mouth views to see changes
in tympanic bullae (normally contain air)
– Rad changes suggesting polyps:
• Soft tissue densities in bullae
• Evidence of chronic otitis media (bony thickening)
CT – otitis media
Nasopharyngeal polyps
• Rads: only partially sensitive diagnostic
tool for otitis media
– 25% of animals with middle ear disease have
no radiographic abnormalities
• CT or MRI:
– Define extent of mass in middle ear
– Determines invasion into inner ear, pharynx,
outer ear more clearly than rads
Nasopharyngeal polyps
Nasopharyngeal polyps
Feline skull
Nasopharyngeal polyps
Other Skull Problems
• Tempromandibular joint disease
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Canine craniomandibular osteopathy
TMJ dysplasia
Luxation/subluxation
Fracture
Ankylosis
• Otitis
– Externa
– Media
– Interna
• Tumors
TMJ
TMJ “hinge joint” – condyloid process of mandible articulates with
mandibular fossa of temporal bone
DV of left TMJ
M= mandible
PC=coronoid process of ramus of mandible
Z= zygomatic arch
C= condyloid process of mandible
a = angular process of mandible
F= mandibular fossa
P= articular process of temporal bone
Between arrowheads = thin, radiolucent
TMJ space
Canine CranioMandibular
Osteopathy
• Unknown etiology
• Common in West Highland, Scottish, and
Cairn terriers
• Extensive, bilateral, irregular, periosteal
reaction of mandible
– Extend to TMJ, tympanic bullae, calvarium
• Rads to investigate TMJ
– Dogs have difficulties opening mouth during
mastication
Craniomadibular Osteopathy
TMJ Luxation
• Consequence of trauma, dysplasia, degeneration,
idiopathic condition
• Condylar process of mandible luxated rostrodorsally
• Dental malocclusion present
• Unilateral luxation w/ mandibular fx (dogs)
• Unilateral luxation with or without mandibular fx (cats)
TMJ luxation
Mandibular fossa of temporal bone is not articulated with condyloid process
of mandible. The condyloid process has rotated forward and upward.
TMJ ankylosis
• Relatively uncommon or undiagnosed
• Abnormal immobility and consolidation of a joint
• Consequence of untreated intra-articular (true
ankylosis) or extra-articular (false ankylosis) trauma
• Hemarthrosis syspected as initiating factor
– Cat falling from great height
• From extensive new bone formation
– otitis media or canine craniomandibular osteopathy
TMJ ankylosis
Transverse CT image: Bilateral true ankylosis
TMJ tumors
• Most common:
– Osteosarcoma
– Multilobular osteochondrosarcoma
• Characteristic appearance on rads, CT,
MRI
– Rounded, well defined, osseous mass
– Course, granular architecture arising from
mandible, zygomatic arch or other flat bones
of skull
TMJ tumor
Transverse (A) and Dorsal (B) plane images: lobulated bony mass arising from left
maxilla and zygomatic bone with compression (not invasion) of adjacent bone.
Characteristic of multilobular osteochondrosarcoma.