By Dr. Becker
Atlantoaxial instability, also called atlantoaxial subluxation, is a rare condition in dogs in which the first two cervical vertebrae in the neck are not firmly attached to each other. In healthy dogs, the first cervical vertebra, or atlas, and the second cervical vertebra, the axis, are attached by ligaments and are further secured by a protrusion or a "hook" at the end of the axis called the dens, which seats into a hole in the atlas. It's a bit like a lock-and-key system.
Causes of Atlantoaxial Instability
Atlantoaxial instability can be present at birth or caused by trauma to the neck. Dogs with the congenital form of the disease are born without the ligaments to support the atlantoaxial joint, and may also be born without a dens.
Certain breeds are at risk for the congenital form of the condition, including all toy breeds, especially Chihuahuas, Pomeranians, Pekingese, Toy Poodles, and Yorkshire Terriers.
Traumatic injury to a dog's neck can cause tearing of the ligaments or fracture of the dens, resulting in atlantoaxial subluxation. Any dog of any age and breed is at risk for the condition after a traumatic neck injury.
Symptoms and Diagnosis of Atlantoaxial Instability
Atlantoaxial instability can lead to cervical spinal injury, which produces symptoms that include a "drunk" or staggering gait, paralysis of all four limbs, and even sudden death. In dogs born with the condition, symptoms usually appear before they're a year old, and can be triggered by normal activities like jumping on or off furniture. Dogs with congenital atlantoaxial instability should never be bred.
If your dog is showing symptoms of atlantoaxial instability, your veterinarian will need to take a complete history of the progression of the condition, including how old your dog is, whether there was a traumatic event that caused injury, what symptoms you've noticed and for how long, and any treatments you may have already tried.
Your vet will also give your dog a complete physical examination and a neurologic exam to determine the severity of the condition. X-rays, which often require general anesthesia, will also be taken to look for abnormal positioning of the atlantoaxial joint.
Treatment Options for Atlantoaxial Instability
Atlantoaxial instability can be treated conservatively or with surgery. Medical treatment typically involves several weeks (anywhere from 4 to 15) of cage rest to allow fibrous connective tissue to form around the atlantoaxial joint. The cervical vertebral column is stabilized in a mildly extended position through the use of a neck brace. Short-term steroid therapy may also be given to decrease inflammation of the spinal cord.
In a study of 19 dogs with acute subluxation (meaning the dogs were symptomatic for less than 30 days) published in the Journal of the American Veterinary Medical Association,1 it was suggested that conservative treatment using a neck brace produced a good long-term outcome in about 62 percent of the cases, or 11 to 12 of the dogs.
Unfortunately, conservative treatment often results in a return of symptoms, in which case surgery is recommended. The atlantoaxial joint is either stabilized with pins or other orthopedic devices, or is fused during the surgical procedure. The success rate of surgical treatment varies from 61 to 91 percent according to the JAVMA study.
Post-surgical care usually involves 4 to 6 weeks of strict cage rest, restricted activity, the use of a neck brace, medications to control pain and inflammation, and frequent rechecks with your vet or veterinary surgeon to address any potential problems that might develop.
Your dog's vet or surgeon will also decide when it's time to begin rehabilitation therapy. The orthopedic surgeon who treats my patients recommends laser therapy beginning immediately after surgery, and acupuncture starting 48 hours after surgery.
Additional rehab therapies are typically instituted after suture removal.