Chinchilla skull – notice the large bullae! The Skull Melanie Eagan Chinchilla skull – notice the large bullae!

Indications for skull rads 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 Arrow pointing to cribiform plate 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)

Rads or CT? CT 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 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 Otitis Tumors 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

Transverse CT image: Bilateral true ankylosis TMJ ankylosis Transverse CT image: Bilateral true ankylosis

TMJ tumors Most common: Characteristic appearance on rads, CT, MRI 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.