By Dr. Becker
Craniomandibular osteopathy (CMO) is the technical term for an enlarged jawbone. It's a genetic condition that occurs almost exclusively in dogs. Other names for the disorder include mandibular periostitis, temporomandibular osteodystrophy, and "lion jaw."
CMO Is Characterized by Excessive Bone Growth
A dog's mouth has two primary bones – the mandible (the lower jawbone) and the maxilla (the upper jawbone). The two bones meet at the temporomandibular joint (TMJ), which is the joint that allows the jaw to open and close.
The muscles of the cheek are used to move the TMJ so the mouth can open and close.
In dogs with craniomandibular osteopathy, extra bones have formed along the mandible – the lower jaw – and the temporomandibular joint, making it difficult and painful to open their mouths to eat.
The disorder usually appears when a puppy is 4 to 8 months old and occurs equally in males and females.
Certain breeds are predisposed, especially West Highland White Terriers, as well as Scottish Terriers, Cairn Terriers, and Boston Terriers, and less often in Labrador Retrievers, Great Danes, Doberman Pinschers, Irish Setters, English Bulldogs, and Boxers.
Symptoms of Craniomandibular Osteopathy
Signs of craniomandibular osteopathy to watch for include:
Progressively worsening pain upon opening the mouth Loss of appetite Difficulty opening the mouth Intermittent fever Difficulty picking up food with the mouth Bulging eyes due to swelling inside the skull Difficulty chewing Jaw swelling Excessive drooling
Your veterinarian will take a complete history and give your dog a physical exam, paying special attention to the head. He or she might be able to feel a loss of muscle mass on the sides of the head, along with a thickening of the bone along the sides of the jaw.
A dog with CMO will typically show signs of pain when the veterinarian tries to open his mouth, and often it doesn't open all the way.
A complete blood count (CBC) will be needed, along with a chemical blood profile and biochemistry levels. Additional blood tests may be needed to check for fungal or other types of infection.
X-rays of the head are the diagnostic tool of choice for this condition, and often dogs must receive a light anesthetic in order to be x-rayed. If the problem is indeed CMO, the x-rays will show abnormal bone growth.
Rarely, it's necessary to get a sample of the bone (via a bone biopsy) to rule out conditions with similar lesions such as neoplasia, osteomyelitis, and hypertrophic osteodystrophy.
Craniomandibular osteopathy requires a wait-and-see approach, since there is currently no standard treatment that slows the progression of the enlarging jawbone.
If you find yourself in this situation with your own pet, I strongly recommend you seek out a veterinary homeopath, or someone trained in prescribing homeopathic remedies, as it's the best approach to this strange syndrome.
Jawbone growth typically stops once a dog reaches 1 year of age, and often the growth will recede as well. However, many dogs will have a larger than normal jawbone and some difficulty chewing for the rest of their lives.
Symptoms are treated as needed, and conventional veterinarians typically use anti-inflammatory drugs to control swelling, and pharmaceutical pain relievers. However, holistic vets have an arsenal of natural pain management options, and I recommend you pursue drug-free options first.
In some cases, surgery may be beneficial in relieving symptoms.
Dogs that have difficulty eating while the jawbone is growing may need a special diet of high calorie soups, broths, or other liquids to keep them nourished. Dogs that can't tolerate even a liquid diet will need to have a feeding tube inserted into the esophagus or stomach to receive nourishment.
Ultimately, your dog's quality of life will depend on how much extra bone has formed around the jaw. Some dogs require special diets or a feeding tube for the remainder of their lives. Dogs with craniomandibular osteopathy should not be bred, nor should their littermates, whether they have the condition or not.