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ATLANTOAXIAL INSTABILITY. Atlantoaxial Joint Atlanto-Axial Joint.

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Presentation on theme: "ATLANTOAXIAL INSTABILITY. Atlantoaxial Joint Atlanto-Axial Joint."— Presentation transcript:

1 ATLANTOAXIAL INSTABILITY

2 Atlantoaxial Joint Atlanto-Axial Joint

3 Atlantoaxial Instability (Subluxation) 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 Diagnosis— – Radiographs: lateral x-ray of neck in slight ventroflexion avoid further spinal cord damage with positioning

4 Atlantoaxial Instability (Subluxation) CT scan: dens is marked by * Normal toy breed dogToy breed dog with atlantoaxial subluxation X-rays of same dogs; note separation of C1 and C2 when dog’s neck is flexed in B Narrowed spinal canal

5 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 Client info— – prognosis is fair to good for animals with mild signs – animals should not be used for breeding; may be hereditary

6 Atlantoaxial Instability: Surgical Correction Stabilization using screws and bone cement Stabilization using trans-articular screws

7 Cervical Spondylomyelopathy: Wobbler Cervical spinal cord compression as a result of caudal vertebral malformation or misarticulation. – Large breed dogs (Great danes and Dobermans) Signs – 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

8 Cervical Spondylomyelopathy: Wobbler Dx – Radiographs to show malalignment and narrowing of spinal canal – Myelogram is essential to locate the region of compression – CT and MRI if available

9 Cervical Spondylomyelopathy: Wobbler Rx—without treatment, prognosis is poor – Medical Anti-inflammatory doses of corticosteroids Neck brace Cage confinement – Surgical Decompression of spinal cord by laminectomy Stabilize vertebral column – screws and wire dorsally – spinal fusion ventrally

10 Cervical Spondylomyelopathy: Wobbler Client info – 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

11 Degenerative Myelopathy Etiology—unclear – May be autoimmune response to antigen in nerv sys – Degeneration of white matter in ascending and descending tracts Signs – 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

12 Degenerative Myelopathy Dx— – Neurologic Exam ↓ proprioception ↑ patellar reflexes Lack of pain Normal sphincter tone; normal panniculus (pin prick) reflex Radiographs usually normal Rx—none; symptoms will progress to paralysis Client info— – 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

13 Degenerative Myelopathy

14 Deafness: Causes 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 – 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

15 Deafness Dx – Inability to rouse sleeping animal with loud noise (e,g,. blast from air horn) is diagnostic Rx: No treatment is available in most cases – Hearing aids are available for animals, but most will not tolerate something in ear canal Client info – 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

16 Laryngeal Paralysis 3 types ( always be cautious of laryngeal paralysis because of the chance of rabies) – Hereditary: seen in Bouvier des Flandres and Siberian Huskies Seen at 4-6 mo of age – Acquired: can occur from lead poisoning, rabies, trauma, inflammation of vagus nerve 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

17 Laryngeal Paralysis Signs: – Inspiratory stridor – Resp distress – Loss of endurance – Voice change – Dyspnea/cyanosis/complete resp collapse Dx: laryngoscopy will show laryngeal abductor m. dysfunction Rx: surgical intervention including: – Arytenoidectomy – Removal of vocal folds Client info: prognosis is guarded to good; do not breed if hereditary

18 Laryngeal Paralysis

19 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 – Acquired—may be seen at any age; Pb tox; may be associated with neuropathies (e.g., myasthenia gravis, tick paralysis) Signs – Regurgitation of undigested food – Respiratory problems (aspiration pneumonia) – Lack of growth

20 Megaesophagus Esophagus is 3 times normal diameter Dx—barium swallow

21 Megaesophagus Rx – 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 – Prognosis—guarded to poor – Treatment aim is to reduce clinical signs and prevent aspiration pneumonia – There is no cure

22 Tick Paralysis Cause—female tick (Dermacenter variablis, D. andersoni) → salivary neurotoxin – Neurotoxin interfered with Ach at neuromuscular jct – Not seen in cats; humans are affected Signs— – 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 Rx – Remove ticks (manually or with dip) Usually resolves in 1-3 d – Supportive care until dog recovers Ventilation required for resp paralysis

23 Tick Paralysis

24 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 Signs: similar to tick paralysis and rabies – 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) Rx: supportive nursing care Client info – 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

25 Idiopathic Facial Nerve Paralysis Etiology—unknown Occurrence – Cocker Spaniels, Corgis, Boxers, Eng Setter, DLH cats Signs— – 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

26 Idiopathic Facial Nerve Paralysis Rx—efficacy of corticosteroids unknown – Artificial tears to prevent corneal ulcers – Keep oral cavity clear of food Client info— – Cause is unknown – Complete recovery does not usually occur – May develop keratoconjunctivitis sicca (dry eye) – Animals may require life-long maintenance


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