Craniomandibular Osteopathy

What is Craniomandibular Osteopathy?
Craniomandibular osteopathy is a bone disease in which some of the bones of the skull, including the lower jaw (mandible), the bone surrounding the middle ear (tympanic bullae), and the skull around the temples, grow too much.  It is most often, but not exclusively, seen in terriers. The condition begins in late puppyhood and the bone usually stops growing by a year of age. Depending on severity, the condition can be painful and may affect chewing and swallowing.  It is usually bilaterally symmetrical.

How does my dog get Craniomandibular Osteopathy?
The exact cause is not known, but is hereditary in at least West Highland White Terriers, the breed in which it's most common.

How do I know if my dog has Craniomandibular Osteopathy?
You may first notice signs when your puppy is between 4 and 8 months of age. The jaws may appear swollen, and he may have a hard time opening his mouth wide. If you try to force the mouth open, he may cry out in pain. He may drool. In some cases, he will have an intermittent fever occurring every 10 to 14 days. As the condition worsens, the muscles controlling his jaws may atrophy from disuse. Your veterinarian will take radiographs of your dog's head.  If your dog is from one of the commonly affected breeds, this may be enough for a diagnosis. If your dog is from a breed that does not commonly have craniomandibular osteopathy, the veterinarian may wish to do more tests, such as a bone biopsy, to make sure the condition is not something else such as cancer, hypertrophic osteodystrophy, or osteomyelitis.

What can I do about Craniomandibular Osteopathy? 
There is no therapy to stop the progression of the disease, but it does usually stop by itself, and even improve, after a year of age. If the excess bone is surgically removed, it grows back. It is important to make sure your dog is not in pain, so your veterinarian will usually prescribe pain relief medication and possibly anti-inflammatory medicine such as corticosteroids. It's also important that he eat, which may be difficult if it hurts to chew. You may need to give him a gruel of high calorie food, or in some cases, feed him through a stomach tube your veterinarian can place. Some dogs are left with permanent chewing problems, which may or may not be improved with surgery.

Is there anything I can do to prevent my dog from getting Craniomandibular Osteopathy?
There is no prevention, except not to breed affected animals, or repeat the breeding that produced affected animals. If you are buying a dog from a breed known to be commonly affected, mostly, West Highland Whites, ask to see evidence that the parents have been cleared of the disorder. There is some evidence that neutering may increase the risk; ask your veterinarian about the pros and cons of postponing neutering until after a year of age if your dog is from an at-risk breed.

Are there certain breeds that get Craniomandibular Osteopathy more often?
The condition is most commonly seen in terrier breeds, especially (but not exclusively) West Highland White Terriers, Scottish Terriers, and Cairn Terriers. It has also been seen in Boxers, Labrador Retrievers, Great Danes, Boston Terriers, Bulldogs, Irish Setters, and Doberman Pinschers.