Odontoid process dysplasia

What is ... ?: 

These diseases involve a malformation of the second vertebral bone in the neck. The first two vertebrae of the neck have distinctive shapes. The joint between these two bones is also unique, as it allows rotation of the head — movement at this joint lets you shake your head to say "no". One special feature of the second neck vertebra which allows this rotation is a peg-like projection of bone called the dens or odontoid process. "Odontoid process dysplasia" means that this projection is missing or is abnormally small. Dogs with a malformed dens have a weak link at the joint between the first two neck vertebrae, and can dislocate this joint. If the joint dislocates, their spinal cord is compressed, which is a serious problem causing pain, weakness, or paralysis. Sometimes the dens is normal, but dislocation can happen because the ligaments supporting the joint are weak.

How is ... inherited?: 


What does ... mean to your dog & you?: 

This disease often leads to dislocation of the joint between the first two vertebrae, causing spinal cord compression. Spinal cord compression is a serious problem which causes pain, weakness, or inability to get up or walk, and usually requires surgery. You will probably not know that your dog has this disease until dislocation occurs. This is most common in young dogs (up to one year of age).

How is ... diagnosed?: 

X-rays will show if the dens is normal or malformed. If your dog has signs of cervical spinal cord compression (pain, weakness, or paralysis), your veterinarian will take radiographs (x-rays) to determine the cause of the compression.

How is ... treated?: 

If your dog has spinal cord compression caused by dislocation of the joint between the first two vertebrae, surgery is generally required. In addition to relieving the compression, the surgeon will have to stabilize the joint so it does not dislocate again. He/she may have to implant wires, screws, or plates to stabilize the joint.
In certain mild cases, your dog may only need medical management and stabilization with a foam collar (similar to the neck collar used with human neck injuries).

Breeding advice: 

Dogs in whom this condition has been identified should not be used for breeding. Although little is known about the inheritance of this disorder, it is preferable to avoid breeding their parents as well.


Bailey CS, Morgan JP. 1992. Congenital spinal malformations. Veterinary Clinics of North America: Small Animal Practice. 224(4):985-1015.

Coates JR, Kline KI. 1995. Congenital and inherited neurologic disorders in dogs and cats. In JD Bonagura and RW Kirk (eds) Kirk's Current Veterinary Therapy XII Small Animal Practice. pp. 111-1120. WB Saunders Co., Toronto.
LeCouteur RA, Child G. 1995. Diseases of the spinal cord. In EJ Ettinger and EC Feldman (eds) Textbook of Veterinary Internal Medicine, pp. 629-696. WB Saunders Co., Toronto.