PART 2
ATLANTOAXIAL
INSTABILITY
Atlantoaxial Joint
Atlanto-Axial Joint
Atlantoaxial Instability
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Signs
Toy and miniature breeds
Reluctance to be patted on head
Neck pain
May have tetraparesis (weakness in all 4 limbs) or
tetraplegia (paralysis in all 4 legs)
Sudden death due to respiratory paralysis
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Diagnosis
Radiographs: lateral x-ray of neck in slight ventroflexion
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avoid further spinal cord damage with positioning
Atlantoaxial Instability
Normal toy breed dog
Toy breed dog with atlantoaxial subluxation
Narrowed spinal canal
CT scan:
dens is
marked
by *
X-rays of same dogs; note separation of C1 and C2 when dog’s neck is flexed in B
Atlantoaxial Instability (Subluxation)
 Treatment
 Medical
 splint neck in extension with cage confinement x 6 w
 treat like other spinal cord trauma
 Surgical (if unresponsive to medical Rx)
 stabilize/decompress
 attach dorsal process of axis to arch of atlas
 fuse atlas and axis joint with pins and bone graft
 hemilaminectomy to relieve spinal cord compression
Atlantoaxial Instability: Surgical Correction
Stabilization using
trans-articular
screws
Stabilization using screws and bone cement
Atlantoaxial Instability
 Client info
 prognosis is fair to good for animals with mild signs
 animals should not be used for breeding; may be
hereditary
Cervical Spondylomyelopathy: Wobbler
 Cervical spinal cord compression as a result of
caudal vertebral malformation or misarticulation.
 Large breed dogs (Great danes and Dobermans)
 Signs
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Progressive hind-limb ataxia (wobbly gait)
Pelvic limbs cross each other when walking
Abduct widely/tend to collapse
May drag toes (wears dorsal surface of nails)
Impaired proprioception
Signs may also be present in front limb
Crouching stance with downward flexed neck
Rigid flexion of neck; may have neck pain
Cervical Spondylomyelopathy: Wobbler
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Diagnosis
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Radiographs to show malalignment and narrowing of
spinal canal
Myelogram is essential to locate the region of
compression
CT and MRI if available
Cervical Spondylomyelopathy: Wobbler
 Treatment: without treatment, prognosis is poor
 Medical
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Anti-inflammatory doses of corticosteroids
Neck brace
Cage confinement
 Surgical
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Decompression of spinal cord by laminectomy
Stabilize vertebral column
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screws and wire dorsally
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spinal fusion ventrally
Cervical Spondylomyelopathy: Wobbler
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Client info
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Prognosis is guarded
Most likely a hereditary disease
Multiple levels of compression less favorable prognosis
than a single area of compression
Surgery is risky and costly
Degenerative Myelopathy
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Etiology: unclear
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May be autoimmune response to antigen in nervoussys
Degeneration of white matter in ascending and descending
tracts
Signs
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Mainly in G Shep and Shep mixes (>5 yr)
Progressive ataxia and paresis of hind limbs
Loss of proprioception is first sign
Dog “falls down” when trying to defecate
Muscle wasting of back muscles along caudal thoracic and
lumbosacral areas
Symptoms progress until animal is unable to support weight on
hind limbs
Degenerative Myelopathy
Degenerative Myelopathy
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Diagnosis
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Neurologic Exam
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↓ proprioception
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↑ patellar reflexes
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Lack of pain
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Normal sphincter tone; normal panniculus (pin prick)
reflex
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Radiographs usually normal
Treatment: none - symptoms will progress to paralysis
Client info
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Degenerative myelopathy is a progressive, incurable disease
Although symptoms are similar at early stages, it is a different
disease from hip dysplasia
When dog cannot support weight, quality of life should be
evaluated
Deafness
 damage to auditory pathway
 chronic otitis
 rupture of tympanic membrane
 damage to middle ear (ossicles)
 damage to auditory nerve
 hereditary or congenital
 bull terriers, Dobes, Rotts, Pointers, blue-eyed white cats,
Dalmations, Aust Heelers, Aust shepherds, Eng setters, Catahoula
 related to drug therapy
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aminoglycosides (gentamicin, streptomycin, kanamycin
topical polymyxin B
Chloramphenicol
Chlorhexidine w/ centrimide
 normal old age—usually due to atrophy of nerve ganglia or
cochlear hair cells
Deafness
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Diagnosis
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Inability to rouse sleeping animal with loud noise (e,g,. blast from
air horn) is diagnostic
Treatment: No treatment is available in most cases
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Hearing aids are available for animals, but most will not tolerate
something in ear canal
Client info
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Hearing loss is permanent
If hereditary, do not breed
Animals can be taught to hand signals rather than words
Animals should not be off leash when outside
Hearing aids are available for dogs but are usually not tolerated;
would only be appropriate for hearing impaired
Laryngeal Paralysis
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3 types (always be cautious of laryngeal paralysis because of the chance
of rabies)
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Hereditary: seen in Bouvier des Flandres and
Siberian Huskies
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Acquired: can occur from lead poisoning, rabies,
trauma, inflammation of vagus nerve
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Seen at 4-6 mo of age
1.5 to 13 yr of age
Idiopathic: seen in middle-age to old large- and
giant-breed dogs; castrated dogs and cats have a
higher incidence than female and non-neutered
males
Laryngeal Paralysis
Laryngeal Paralysis
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Signs:
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Inspiratory stridor
Resp distress
Loss of endurance
Voice change
Dyspnea/cyanosis/complete resp collapse
Laryngeal Paralysis
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Diagnosis: laryngoscopy will show laryngeal abductor m.
dysfunction
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Treatment: surgical intervention including:
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Arytenoidectomy
Removal of vocal folds
Client info: prognosis is guarded to good; do not breed if
hereditary
Megaesophagus
 Causes-lack of esophageal peristalsis (3 types):
 Hereditary—a gene for the disease is identified in wire-
haired fox terriers and min schnauzers
 Congenital—Great Danes, German Shepherd, Irish
Setters, Newfies, Sharpeis, Greyhounds (no gene ID’ed)
evident about weaning time when solid food is introduced
Due to incomplete nerve development in esophagus
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 Acquired—may be seen at any age
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lead toxicity
may be associated with neuropathies (e.g., myasthenia gravis, tick
paralysis)
 Signs
 Regurgitation of undigested food
 Respiratory problems (aspiration pneumonia)
 Lack of growth
Diagnosis - barium swallow
Megaesophagus
Esophagus is 3 times normal diameter
Megaesophagus
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Treatment
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Elevated feeding (on platform, stairs)
Liquid or soft diet high in calories
Give several small feedings daily
Gastrostomy tube (long term) is an option
Client info
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Prognosis—guarded to poor
Treatment aim is to reduce clinical signs and prevent
aspiration pneumonia
There is no cure
Tick Paralysis
Cause: female tick (Dermacenter variablis, D. andersoni) →
salivary neurotoxin
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Neurotoxin interfered with Ach at neuromuscular jct
Not seen in cats; humans are affected
Signs
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Gradual onset of voice changes and hind-limb ataxia (motor deficit)
progressing to a flaccid, ascending paralysis (1-3 d)
Sensation is intact
Ticks on the dog
Treatment
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Remove ticks (manually or with dip)
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Usually resolves in 1-3 d
Supportive care until dog recovers
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Ventilation required for resp paralysis
Tick Paralysis
Coonhound Paralysis (Polyradiculoneuritis )
 thought to be an immune response to an unknown etiologic factor in raccoon
saliva
 some dogs will get it 1-2 wk after exposure, others exposed to same raccoon will
not
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Signs: similar to tick paralysis and rabies
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Weakness begins in hind limbs with paralysis progressing rapidly to a
flaccid tetraplegia
Alert, afebrile animal
Loss of spinal reflexes (patella tap, etc)
Loss of voice; labored breathing; inability to lift head
May die of respiratory failure
May last for 2-3 mo (usually good Px)
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Rx: supportive nursing care
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Client info
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Dogs can be affected without exposure to raccoon
May require long-term nursing care
Some animals will regain total function, while more severely affected
animals may not
Idiopathic Facial Nerve Paralysis
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Etiology: unknown
Occurrence
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Cocker Spaniels, Corgis, Boxers, Eng Setter, DLH cats
Signs
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Older dogs (>5 y)
Ear droop
Lip paralysis
Sialosis (drooling)
Deviation of nose
Collection of food in paralyzed side of mouth
Absence of menace and palpebral reflex
Idiopathic Facial Nerve Paralysis
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Treatment efficacy of corticosteroids unknown
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Artificial tears to prevent corneal ulcers
Keep oral cavity clear of food
Client info
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Cause is unknown
Complete recovery does not usually occur
May develop keratoconjunctivitis sicca (dry eye)
Animals may require life-long maintenance
Grey’s Anatomy
Memory Center