Spinal Column Malformation in Dogs

Atlantoaxial Instability in Dogs

Atlantoaxial instability results from a malformation in the first two vertebrae in the neck of an animal. This causes the spinal cord to compress and results in pain or even debilitation for the pet. The disorder is uncommon in older dogs and larger breeds of dogs. It is generally found in smaller, toy breeds. To ensure the best possible chance for a full recovery, it is important to treat the animal once an occurrence or sign of distress is observed.

The condition or disease described in this medical article can affect both dogs and cats. If you would like to learn more about how this disease affects cats, please visit this page in the PetMD health library.

Symptoms and Types 

Dogs suffering from atlantoaxial instability may collapse frequently or even suffer from paralysis, depending on the severity of the spinal cord injury. Many animals also exhibit severe neck and back pain and a lack of desire to exercise.


The most common cause of atlantoaxial instability is an abnormal formation of ligaments in the animal's vertebrae, often leading to fractures. The formation may also be the consequence of an accident, especially for smaller dogs that jump from tall structures.


The veterinarian will look for signs of trauma, seizures, tumors (neoplasia), severe exercise intolerance, and disk herniation. An X-ray or radiograph of the animal's spine may be taken to see if there are any injuries to the neck or spine. In addition to radiographs, CAT scans (computed tomography) may be used to view the soft tissue structures in the dog’s neck and spine. If the disorder goes untreated, it often leads to acute spinal cord trauma, respiratory arrest, and possible death.

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