HOW TO Treat Jawbone Enlargement (Craniomandibular Osteopathy) in Dogs

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dog healthJawbone enlargement, or craniomandibular osteopathy (CMO), is a non-cancerous disorder that almost exclusively affects the bones of the head in dog. It is also known as mandibular periostitis, temporomandibular osteodystrophy or “lion jaw,” according to reports, “Craniomandibular osteopathy is a condition by which extra bone forms along the mandible and TMJ [jaw joint], making it painful and difficult for the affected dog to open its mouth and eat. Signs are usually seen in puppies that are 4 to 8 months of age, and it is seen more in some breeds of dogs than others.”

Several breeds of dogs are susceptible to this condition.

“Breeds that are the most commonly affected are Scottish Terriers, Cairn Terriers and West Highland White Terriers. Breeds with a lesser incidence of this condition, but which also have a higher than normal diagnosis are Labrador Retrievers, Great Danes, Boston Terriers, Doberman Pinschers, Irish Setters, English Bulldogs and Boxers,” adds

What Causes Jawbone Enlargement in Dogs?

According to, “The cause of CMO is believed to be hereditary. Terriers are prone to the disorder. It has been reported in non-Terrier breeds, but this is uncommon.”

What are the Symptoms of Jawbone Enlargement?

Your dog may show some of these symptoms as listed by

i Love Dogs Pain when opening the mouth

i Love Dogs Difficulty opening the mouth

i Love Dogs Difficulty picking up food

i Love Dogs Difficulty chewing and concurrent loss of appetite

i Love Dogs Pain and difficulty eating, which gets worse with time

i Love Dogs Fever that comes and goes

i Love Dogs Eyes that seem to bulge out (exophthalmos), due to swelling within the skull

i Love Dogs Swelling in jaw

i Love Dogs Excessive drooling

“Often the body temperature will fluctuate over time, with fever occurring in phases every 10-14 days. In severely affected dogs, the masticatory muscles (those involved in chewing) may atrophy and there may be lymphadenopathy (swollen glands),” reports.

How is Jawbone Enlargement Diagnosed?

First you will need to provide your vet with a thorough history of your dog’s health leading up to the onset of symptoms advises that you “pay careful attention to your dog’s head during the examination. Your veterinarian may be able to feel a decrease in the amount of muscle on the sides of your dog’s head, along with a thickening of the bone along the sides of the jaws. There will also be obvious pain when trying to open your dog’s mouth, and it may not even open all the way.”

Your vet may need to take a biopsy if your dog is a breed that is not typically affected; that way your vet can determine it is not a tumor or cancer.

How is Jawbone Enlargement Treated?

Due to the nature of the condition there is not much you can do initially.

“Treatment with anti-inflammatory drugs for the swelling, along with pain relievers, will help to minimize your dog’s symptoms but will not effect an immediate cure. This condition has a ‘wait and see’ outlook, since there is no method for slowing the progression other than for treating the swelling. The growth typically slows down at about a year of age, when the puppy’s growth slows, and the growth will often recede as well, but many dogs will continue to have a larger than normal jaw bone, and may have difficulty chewing normally for the remainder of their lives. In some cases, surgery may be used to repair the jaw enough to make your dog more comfortable,” according to

How Can I Prevent My Dog From Developing Jawbone Enlargement?How To

There is no way to prevent your dog from getting jawbone enlargement as it is hereditary. The best advice to follow is if you are seeking to purchase or adopt purebred Terriers, especially West Highland White Terriers, be sure to question breeders carefully about the medical history oftheir dogs’ bloodlines.

“Dogs that are affected with craniomandibular osteopathy should not be used for breeding again, nor should siblings from the same litter, whether they have symptoms of the disorder or not. And it is recommended that you have your dog spayed or neutered to avoid passing this genetic abnormality along,” states

Find A Vet HOW TO articles are intended for informational purposes only. You should always consult with your veterinarian about any health issues affecting your dog.

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Kara Ogushi

Contributing writer Kara Ogushi is a pet mom to two dogs and five rabbits. When she isn't writing travel tips for pooches, she's exploring new ways to share and create media.

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