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 Hydrocephalus • 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 evaluation – 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 happen – 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 nasopharynx • 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 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, calvarium 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.