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Summary
This uncommon disease of the bones of the jaw and head is typically seen in small breeds, most often in West Highland white terriers. This inherited disease is also known as "mandibular periostitis," "temporomandibular osteodystrophy" or "lion jaw."
Craniomandibular Osteopathy (CMO) is the result of bone swelling during the growth of the bones of the skull and jaw. Sometimes, only the jaw is involved. As such, young dogs between the ages of three and eight months are the most commonly afflicted. Though its severity may vary, all affected dogs experience significant pain.
Thankfully, the condition is self-limiting. That is to say, the dogs "grow out of it" and by one year of age the symptoms usually resolve.
Symptoms and Identification
Pain when opening or moving the jaw (as for barking and prehending food or chewing) is the most common sign. Excessive salivation (drooling) may be the only obvious sign in some cases. Visible or palpable swelling can also occur, as can non-specific signs of pain (such as lethargy and inappetance). Additionally, dogs with CMO may suffer intermittent fevers.
Diagnosing the disease can be confusing for some veterinarians. That's because the disease is no longer considered prevalent. In other words, it's not the kind of process that's on the tip of every veterinarian's tongue. And yet, it's easy to diagnose. Breed type and their standard symptoms, along with X-rays of the skull, are generally enough to arrive at this diagnosis, even when the accompanying fever is not present.
Affected Breeds
Young, growing dogs in the terrier family are the targets of this disease. It affects males and females equally, but early spaying and neutering seem to improve the odds of acquiring it. When larger breeds are affected with CMO, the pain related to the condition seems to be significantly reduced.
Though this disease has been studied extensively in West Highland white terriers (Westies) and has been found to have a hereditary origin, strictly speaking, we cannot say the same for all dogs as the disease has not been sufficiently studied in non-Westies. Despite the possibility of viral or bacterial involvement, it's widely held, however, that this is a disease of genetic origin.
Apart from Westies, the following breeds are known to rank among the most affected breeds:
Treatment
Treatment for this self-limiting condition primarily revolves around pain relief. Dogs are often given corticosteroids (such as prednisone), NSAIDs (non-steroidal anti-inflammatory drugs) such as carprofen (Rimadyl) or meloxicam (Metacam) or opiates (such as tramadol).
But, make no mistake, it's a terrible thing to watch your dog experience pain. Some dogs are so uncomfortable, despite medications, that some owners elect to euthanize them.
Veterinary Cost
Because most dogs "grow out of it," treatment with medications lasts only a few months. The expense of this kind of treatment is not insignificant (usually a few hundred dollars) but consider that the diagnosis may require sedation X-rays and/or a specialist's opinion (a few hundred more).
Prevention
The mainstay of prevention for this genetic disease is through spaying and neutering of all affected dogs. Dogs who produce pups with this trait should be similarly removed from the breeding pool.
References
Johnson, KA; Watson, ADJ. Skeletal diseases. In Ettinger, S. (ed). Textbook of Veterinary Internal Medicine. W.B. Saunders Co. Philadelphia, PA; 2000.
Riser, WH; Newton, CD. Craniomandibular osteopathy. http://cal.nbc.upenn.edu/saortho/chapter_54/54mast.htm
Roush, JK. Diseases affecting developing bone. In Birchard, SJ; Sherding, RG (eds.) Saunders Manual of Small Animal Practice. W.B. Saunders Co. Philadelphia, PA; 1994.
Elizabeth LaFond, DVM, Diplomate ACVS, Gert J. Breur, DVM, PhD, Diplomate ACVS and Connie C. Austin, MPH, PhD; Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Purdue University, West Lafayette, Indiana 47907.