Skull and Nasal Cavity

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					                        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 cannot 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
• Acute
   – 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
• 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
• Osteoma
   – Slow growing, benign
   – Dense, homogenous, well marginated
Multilobular Osteochondrosarcoma (MLO)
• Neoplasia
    – 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
   – 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 tooth you 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

• Fractures
   – Additional views as needed
   – Temporomandibular joint (TMJ) luxations
      • Often rostrodorsal and concurrent with fractures
      • Usu. unilateral
      • Malocclusion

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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