Atlantoaxial Instability in Dogs

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Key takeaways

Atlantoaxial instability (AAI) in dogs affects the first two neck bones in the spine: the atlas (vertebra C1) and axis (vertebra C2), which give the head and neck stability. Changes to the bone(s) or ligaments in these joints can cause instability, resulting in dislocation and spinal cord compression. 

  • Common symptoms are neck pain, back pain, and neurological signs such as gait abnormalities or paralysis
  • The cause of AAI is congenital malformation of the atlantoaxial joint, injury, or a combination of both
  • AAI is diagnosed through diagnostic imaging (CT, MRI, X-ray) and physical examination
  • Treatment requires stabilization of the joint through conservative therapy (neck brace, rest, pain medications, steroids) or surgical intervention
  • Prognosis depends on the extent of spinal cord damage; with good response to management, prognosis is positive
  • In severe cases of paralysis, symptoms may be permanent or fatal
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A closer look: Atlantoaxial Instability in Dogs


The vertebrae are the individual bones in the spinal cord. Any abnormality or injury to the vertebrae has the potential to damage or inhibit function of the spinal cord, leading to changes in mobility. Any time there are symptoms of neurological abnormalities like uncoordinated movements, difficulty walking, and severe spinal pain, emergency veterinary care is needed.

Prognosis depends on the extent of spinal cord damage. In severe cases of paralysis, symptoms may be permanent. Rarely, respiratory paralysis leads to death. With good response to management, prognosis ranges from fair to excellent.

Risk factors


AAI is uncommon in dogs. Toy and small breed dogs are more likely to have AAI and around 50% of dogs affected by AAI are under 1 year old at time of presentation.

Symptoms vary depending on the extent of spinal cord compression. In rare cases, AAI may cause damage to the brainstem, resulting in symptoms like facial paralysis, trouble swallowing and lack of balance/coordination. In severe cases, this may cause respiratory paralysis and death.

Possible causes


Some dog breeds are more likely to have dislocation of the atlantoaxial joint because their bones, ligaments, or both were not formed properly during fetal development. Traumatic injury is the other potential cause. Often, dogs with congenitally abnormal atlantoaxial joints do not show signs of AAI until they incur minor trauma.

Main symptoms


Symptoms of AAI are associated with compression of the spinal cord.

Testing and diagnosis


The first step of diagnosing a possible case of AAI is a full physical and neurological exam. Imagining such as spinal X-rays, CT, and MRI are necessary to evaluate the atlantoaxial joint.

Steps to Recovery


Treatment can be conservative for mild cases, involving 6–8 weeks of crate rest, use of a neck brace, and painkiller and anti-inflammatory medications.

Surgical stabilization of the atlantoaxial joint is necessary for many cases which. Post-surgical prognosis varies with the age and overall health of the dog, the severity of symptoms, and the amount of damage to the spinal cord. Depending on the degree of spinal cord compression, dogs may recover fully after treatment, but recurrence of symptoms is common.

Some dogs may not recover even with medical or surgical intervention. Humane euthanasia may be considered in cases where prognosis is poor and quality of life is impacted.

Prevention


There is no specific way to prevent congenital AAI. Affected dogs should not be bred. Traumatic AAI may be preventable in some cases by avoiding potential injury.

Is Atlantoaxial Instability in Dogs common?


AAI is uncommon in dogs.

Typical Treatment


Conservative

  • Neck brace
  • Crate rest 6-8 weeks
  • Analgesics
  • Anti-inflammatories
  • Rehabilitation

Surgical stabilization

  • Neck brace
  • Crate rest 6-8 weeks
  • Rehabilitation
  • Analgesics
  • Anti-inflammatories

References


Michael Kearley, DVM - Writing for PetMD
Malcolm Weir, DVM, MSc, MPH; Catherine Barnette, DVM - Writing for VCA Animal Hospitals
Rodney Bagley DVM DipACVIM - Writing for Vetlexicon
No Author - Writing for American College of Veterinary Surgeons

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