Small Animal Neuroradiology Small Animal Neuroradiology

Small Animal 

Neuroradiology 

Kari L. Anderson, DVM 

College of Veterinary Medicine 

University of Minnesota 

Small Animal 

Neuroradiology 

• Knowledge of anatomy 

extremely important 

• Exact positioning critical 

– General anesthesia 

• Multiple views needed – skull 

• Complementary studies – 

myelogram, , CT, MRI 

Spinal Congenital 

Abnormalities 

• Common in “screw tail” breeds – Pug, 

Boston Terrier, Bulldog, Manx cat, but 

others as well 

• Often incidental 

• Spina bifida, hemivertebra, , block vertebra, 

transitional vertebra 

• May see spinal conformational abnormality – 

scoliosis, kyphosis, lordosis 

• Need additional imaging to assess neural 

tissue – myelogram, , CT, MRI 


Abnormalities 

• Spina bifida 

– Incomplete development of dorsal portion 

– Commonly in thoracic and lumbar 

– Often incidental but may have clinical 

signs 

– If clinical, varying degrees of protruding 

neural tissue occurs 


Abnormalities 

Radiographic findings - 

Spina bifida: 

• Unfused dorsal 

spinous process 

• Cleft dorsal spinous 

process 

• Lack of DSP or 

lamina 


Abnormalities 

• Block vertebra


Abnormalities 

• Hemivertebra 


Abnormalities 

• Transitional 

vertebra 

Atlantoaxial Subluxation 

• Miniature and toy breeds – Yorkshire 

terrier, Chihuahua, Toy Poodle, 

Pekinese 

• Young dogs 

• Developmental anomaly 

– Hypoplasia of dens 

– Cord compression caused by abnormal 

rotation of C2 into spinal canal 

Atlantoaxial Subluxation 

Radiographic findings: 

• Hypoplastic or 

absent dens 

• Widened space 

between C1 and C2 

• Abnormal 

angulation of C2 

Spondylosis Deformans 

• Degenerative change – related to 

instability and degeneration – may be 

secondary to many abnormalities 

• Common 

• Rarely clinically significant 

Intervertebral Disk 

Protrusion 

• Chondrodystrophoid breeds – Hansen Type 

1 herniation associated with chondroid 

metaplasia and disk degeneration 

• Nonchondrodystrophoid breeds – Hansen 

• Type 2 herniation associated with fibroid 

metaplasia and disk degeneration 

• Intervertebral disk degeneration: 

mineralized disk material in the disk space 

• Uncommon in cranial thoracic spine – WHY?


Protrusion 


Protrusion 


• Narrowed or wedged IVD 

space 

• Decreased size of IV foramen 

• Increased opacity of IV 

foramen 

• Narrowed articular facet space 

• Endplate sclerosis and 

spondylosis 

• Extradural compression on 

myelogram 

Cervical 

Spondylomyelopathy 

• AKA: Wobbler syndrome, cervical 

vertebral malformation- 

malarticulation syndrome, cervical 

vertebral instabilitiy 

• Common in middle age to older 

Dobes and younger Great Danes 

• Multiple underlying spinal 

abnormalities 

Cervical 

Spondylomyelopathy 


• Malformed 

vertebrae 

• Coning or stenosis 

of canal 

• Dorsal tipping of 

vertebrae 

• Facet proliferation 

and/or spondylosis 

Degenerative 

Lumbosacral Stenosis 

• Multifactorial disease: 

– Stenotic spinal canal 

– Lumbosacral malalignment 

– Lumbosacral instability 

– Herniated IVD 

– Spondylosis – may impinge on nerve 

roots 

• Large breed dogs – GSD

Degenerative 

Lumbosacral Stenosis 


• Best evaluated with CT 

or MRI 

• Endplate sclerosis and 

spondylosis 

• Narrowing and 

wedging of LS disk 

space 

• LS subluxation 

• Stenotic canal 

Discospondylitis 

• Infection of disk space with extension 

to adjacent vertebrae 

• Often multiple spaces affected 

• Generally hematogenous – commonly 

associated with urogenital infections 

• Staph spp, E. coli, Brucella canis, 

mycoses, mycobacterium 

Discospondylitis 

Spinal Neoplasia 


• Irregular endplate lysis 

• Bony sclerosis and 

proliferation 

• Widening or collapse of 

disk space 

• Spondylosis deformans 

Spinal Trauma 

Hydrocephalus 

• Congenital form – small, toy, and 

brachycephalic breeds (Yorkshire 

terrier, Chihuahua, Maltese, Toy 

Poodle, etc) 

• Radiographic abnormalities seen in 

congenital form 

• Better evaluated with US, CT, MRI

Hydrocephalus 


• Domed cranium 

• Fontanelles and 

open sutures 

• Cortical thinning 

• Homogenous 

appearance to brain 

Craniomandibular Osteopathy 

(CMO) 

• Young dogs 3-83 

8 months of age 

• Terrier breeds, Labs, Dobes, , GSD, 

Boxers 

• Osteoproliferative disorder that is self- 

limiting and slows at 7-87 

8 months of 

age 

• Secondary TMJ fusion can occur 

Craniomandibular Osteopathy 

(CMO) 


• Irregular, opaque 

new bone 

• Generally bilateral 

• Ankylosis of TMJ 

may occur 

• Ceases with 

maturity 

Otitis Externa and Media 

• Radiographs very helpful in evaluation 

– even better with CT 

• Otitis interna is clinical diagnosis! 

• Rule-out trauma, tumor, 

nasopharyngeal polyps 

Otitis Externa and Media 


• No abnormalities 

• Narrowing, obliteration, 

mineralization of 

external ear canals 

(otitisotitis externa) 

• Otitis media 

– Soft tissue/fluid opacity 

in tympanic bulla 

– Bony changes of bulla

Nondestructive Rhinitis 

Etiologies: 

• Infection 

• Foreign bodies 

• Nasopharyngeal polyps 

• Allergies 

• Coagulopathy 

Nondestructive Rhinitis 


• Increased soft 

tissue/fluid opacity of 

nasal passages and 

frontal sinuses 

• May see radiopaque 

foreign body 

• Should not see lysis 

unless very chronic 

infection or foreign 

body 

Destructive Rhinitis 

• Etiologies: 

– Nasal tumor 

– Fungal infection 

– Chronic infection or foreign bodies 

• Most common clinical sign is epistaxis 

• CT or MRI offers better evaluation 

Destructive Rhinitis 


• Early may mimic 

nondestructive 

• Irregular opacities in nasal 

passages and frontal 

sinuses 

• Bony lysis of ethmoid 

turbinates or nasal septum 

• May see extranasal 

extension

Hyperparathyroidism 

• Primary vs 

secondary 


• Loss of lamina dura 

• Demineralization of 

maxilla and 

mandible 

• Floating teeth

Small Animal Neuroradiology Small Animal Neuroradiology

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