Skull and Nasal Cavity

By Donald Robertson,2014-05-09 22:26
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Skull and Nasal Cavity

    Skull and Nasal Cavity

Radiography of the Skull

     Anesthesia required it is imperative that the patient be under anesthesia

    symmetry is very important when comparing one side to the other. Also, since we restrain most patients by hand the techs hand can not be removed form the beam if the head is being imaged. Also for some views, the mouth needs to be held open this can be done with a mouth gag.

     Perfect positioning is critical (especially for lateral and DV) Evaluate for asymmetry its nice we have the opposite side to compare too Obtain special views as needed

     Radiographs are nice but they are no CT or MRI image :-) Radiographs of

    the skull are difficult to interpret do to superimposition of structures. Cross

    sectional imaging is definitely superior.

Special or Additional Views

     Intraoral DV or VD/ open mouth VD

     Eliminates superimposition of mandibles/ maxilla

    Intra Oral DV great for maxilla and nasal cavity non screen film is best

    Open Mouth DV

     Rostrocaudal frontal sinus it is important to do this view so the frontal sinuses are not superimposed on each other or over the skull

     Neoplasia, sinusitis, trauma

     Open mouth rostrocaudal the bulla walls can usually be evaluated pretty well with this view.

     Evaluation of bullae

     Variation (30 degree VD) in Cats

Oblique views

     Bullae, maxilla, mandible

     Left dorsal-right ventral

     Right dorsal-left ventral

     Labeling can get confusing

Shots Summary

     Nasal Series

     Minimum = *VD open mouth and lateral

     Special = rostro-caudal frontal sinus

     Special = *intra oral

     * These provide the best evaluation of the nasal cavity in general

     Knowing normal anatomy is critical

Nasal Disease

     Neoplasia, infection, foreign body, fracture, fungal History of nasal discharge

     Unilateral or bilateral

     Serous, purulent, hemorrhagic

Radiographic Interpretation

     Change in opacity

     Bony lysis is there evidence of bony lysis of turbinates or surrounding

    bones (maxilla)

     Increased soft tissue or fluid increased soft tissue opacity can be seen

    over the nasal cavity though it is not specific it can just be due to fluid

    accumulation in the nasal cavity

     Or BOTH often seen

     Are the nasal turbinates still visualized? This is important so the

    aggressiveness of the change can be determined

     Use the opposite side for comparison of increased opacity

     Radiographic changes are not always specific for a specific disease

Rhinitis / Infectious


     Viral, bacterial, allergic, FB (usu. not seen)

     Increased opacity (exudate in nasal cavity or thickening of mucosal

    turbinate covering) without turbinate destruction Chronic

     Usu. seen in cats with a viral upper respiratory disease

     Turbinates may be deformed but not destroyed

Destructive Rhinitis

     Aspergillus sp. Infection

     Young animals

     Medium and long nosed dogs

     Rarely seen in brachycephalic which is very fortunate since the snouts of

    brachycephalic dogs are so small and imaging the nasal cavity and

    interpretation are more difficult. (same thing for cat snouts) Fungal rhinitis usually causes focal turbinate destruction

Nasal aspergillosis

     Saprophytic fungal organism

     Destructive rhinitis/ sinusitis

     Radiographic findings

     Lysis of turbinates

     Increased intranasal ST

     Differential diagnosis is neoplasia usually = ST mass, adjacent bony

    lysis, frontal sinus opacity

     Cryptococcus neoformans

     Usually cats and nondestructive

Nasal Tumors

     1-2% of all tumors in dogs and cats

     2/3 are carcinomas (Adenocarcinoma, SCC)

     1/3 are sarcomas (FSA, OSA, chondrosarcoma)

     Intranasal lymphoma (more commonly cats)

     Diagnosis usually occurs late thus making treatment even more difficult.

    Treatment for adenocarcinoma often is with radiation therapy. A CT scan is

    usually preformed to be certain the carcinoma has not metastasized to the

    olfactory lobe of the brain by crossing the cribriform plate.

     Hemorrhage often seen

Radiographic findings

     Increased intranasal soft tissue opacity

     Soft tissue mass or accumulation of nasal exudate

     Lysis of nasal turbinates

     +/- Lysis of cribriform plate= extent into brain

     Does it involve one side or has it crossed the nasal septum?

     Often begin in the region of the ethmoid turbinates this area is more

    difficult to visualize than the more rostral portion of the nasal cavity in

    general which is unfortunate since many being there.

     CT great for nasal tumors can see if a mass is present and can also

    evaluate definitively for bony lysis

Shots Summary - Skull

     Minimum = lateral and DV view

     Special = obliques

     Special = teeth, tympanic bullae, TMJ’s, foramen magnum, nasal cavity and frontal sinus (as per nasal shots)

     Knowing anatomy is critical

     Very complex area

     Does not evaluate the brain


     Excess CSF within skull the lateral ventricles enlarge and keep enlarging due to the excess fluid accumulation. As the fluid amount builds, the cortical portion of the brain gets squished and atrophies.

     Congenital or acquired

     Maltese, Yorkie, Chihuahua

Radiographic Signs

     Doming and cortical thinning of calvarium

     Open fontanelles sometimes when an open fontanelles is present the

    brain can be imaged with ultrasound though the hole. The excess fluid

    accumulation is quite easy to see. The “amount” of remaining cortical

    matter is more difficult to determine. CT or MRI are best for complete


     Lateral projection best

     Ground glass look the skull looks empty no sulci seen

Occipital Dysplasia

     Congenital malformation of the foramen magnum (keyhole shape) may be

    seen with AA sub lux and hydrocephalus Herniation of the brain stem is a possibility.

     Mini and Toy breeds

     Special view = rostrodorsal caudoventral of foramen magnum

Feline Mucopolysaccharidosis

     Inherited lysosomal storage disease not too common to see

     Siamese (VI) there are multiple “numbers” associated with FMPS but VI is often seen in the Siamese cat

     Skull deformity broad flat face with widely spaced eyes

     Epiphyseal dysplasia, short maxilla, small frontal sinus, thick nasal

    turbinates, small dens and hyoid bones

     Also have vertebral abnormalities

Neoplasia - Skull

     Osteosarcoma 10-15% arise from the skull we often think of osteosarcoma

    occurring in the appendicular skeleton and forget about the skull but it does


     Usually productive, well marginated a “bump” is often noted on the

    animals head on clinical examination


     Slow growing, benign

     Dense, homogenous, well marginated

Multilobular Osteochondrosarcoma (MLO)


     Aka Multilobular tumor of bone, Multilobular osteoma

     Often arise from temporo-occipital area

     Granular, osteoproductive mass with lysis

    A biopsy of the area should be preformed to definitively diagnosis the cause of the bump. However, a prioritized differential list can be made.

Skull Trauma

     HBC, fights, gunshot wounds

     Often see depression skull fractures the skull in general is very strong and it takes a very hard hit to fracture the skull.

     May cause cerebral edema, epistaxis and neurologic signs Fairly rare to see skull fractures

Metabolic Abnormalities

     Primary hyperparathyroidism

     Parathyroid nodule or parathyroid hyperplasia Secondary hyperparathyroidism

     Nutritional or renal causes (Ca and P levels messed up)

     Both situations lead to increased PTH and bone resorption Radiographic findings

     Loss of lamina dura

     Demineralization of mandible and maxilla = “floating teeth” “rubber jaw”

Neoplasia Mandibular or Maxillary

     Squamous Cell Carcinoma

     More aggressive/ worse prognosis in cats

     Rostral mandible - dogs

     FSA, OSA, Chondrosarcoma

     Malignant melanoma metastasis if quick to the lungs MOM is bad

     Epulis = benign tumor of periodontal ligament (dogs)

     Fibromatous, Ossifying = Osteoproductive

     Acanthomatous = Invasive, Lytic can be removed with good margins

    radiation therapy can also be used

    Dentigerous Cyst - Odontoma

Otitis externa the external ear canals are affected

     Stenosis, soft tissue opacity or mineralization of external ear canal

     VD view best

Otitis media the tympanic bullae are affected

     Increased opacity in bulla

     Thickening of bulla walls they should normally be egg shell thin

     Obliques or open mouth rostrocaudal views

     **25% of dogs with normal bulla radiographs had otitis media at surgery

     Nasopharyngeal polyp

     Cats - sneezing

     Non neoplastic

     Originate from mucous membrane of auditory tube or middle ear

     Younger cats can extend into external ear canal, osseous bulla or the


Tooth root (periapical) abscess

     Lysis of periapical alveolar bone

     Resorption of tooth root

     Widening of periodontal space

     Sclerosis surrounding apex

     Loss of lamina dura th Dogs - 4 maxillary premolar (carnassial tooth) remember the maxillary

    PM4 roots sits in the maxillary recess so tooth root infection of this tooth

    can cause a sinusitis

     External fistulous tract below eye

Normal Dental Formulas I would prefer you use Right or Left Maxillary or

    Mandibular and then which tooth it is such as PM4. The numbering systems people use are all different and it is very confusing. This is the simplest way and

    everyone will know which too your are concerned about. Cat

     Deciduous 2 x (I 3/3 C 1/1 P 3/2) = 26

     Permanent 2 x (I 3/3 C 1/1 P 3/2 M 1/1) = 30 Dog

     Deciduous 2 x (I 3/3 C 1/1 P 3/3) = 28

     Permanent 2 x ( I 3/3 C 1/1 P 4/4 M 2/3) = 42


     Additional views as needed

     Temporomandibular joint (TMJ) luxations

     Often rostrodorsal and concurrent with fractures

     Usu. unilateral


Cranial Mandibular Osteopathy

     Westies, Scotties, Cairn, Boston terriers

     Autosomal recessive in Westies

     +/- Link to hypertrophic osteodystrophy (HOD)

     Young dogs (3-8 months)

     Mandibular swelling

     Difficulty/ pain chewing

     Pyrexia, Self- limiting must make sure the patient is receiving adequate

    nutrition since often they cannot open their mouth. A PEG tube can be

    placed as necessary.

     Radiographic signs

     Bony proliferation on mandibles, bulla, petrous temporal bone,


Interpretation of Common Diseases

     Important final points about skull and nasal radiographs

     Perfect radiographs of an anesthetized patient are necessary

     Know the limitations of radiography

     Computed tomography superior

     Extent of nasal/ maxillary tumors, otitis media

     Treatment planning (surgery, radiation therapy)

     Radiographs may be sufficient for fractures, tooth root

    abscessation….but not intranasal/ intracranial disease.

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