Craniomandibular Osteopathy (CMO), also known as Lion Jaw or Westie Jaw, is a non-cancerous condition characterised by abnormal bone growth in the jaw and skull of dogs. This condition is typically self-limiting, meaning it resolves over time. It usually affects young dogs between 3 to 8 months of age and is most commonly seen in certain terrier breeds of either sex. The exact cause of CMO is unknown, but it is believed to be a genetic condition with an autosomal recessive inheritance pattern (this means that parent dogs may be carriers, but have no clinical signs). It most commonly affects small terrier breeds, including West Highland White Terriers, Scottish Terriers, Cairn Terriers, Boston Terriers. Other breeds that can be affected, though less commonly, include Boxers, Labrador Retrievers, Great Danes, and Dobermann Pinschers.

Dogs with CMO may exhibit a range of symptoms, including:

• Swelling of the jaw, appearing relatively the same on both sides of the jaw.
• Pain when opening the mouth.
• Difficulty eating or picking up food.
• Excessive drooling (salivation).
• Intermittent fever, lethargy, and loss of appetite.
• Bulging eyes.
• Jaw swelling.

Diagnosis of CMO is typically based on the dog's age, breed, clinical signs, and radiographic findings. X-rays of the jaw can reveal the characteristic bone changes associated with CMO. In some cases, additional diagnostic tests such as CT scans or biopsies may be used to obtain additional information and rule out other possible diagnoses.

Unfortunately, there is no cure for CMO, but treatment options are available to manage the condition and alleviate symptoms:

• Pain management: non-steroidal anti-inflammatory drugs (NSAIDs) or other pain medications can help reduce pain and inflammation. In some cases, corticosteroids may be used under strict veterinary supervision to manage severe pain.
• Supportive care: providing supportive care at home is crucial for managing CMO. Offer your dog soft or gruel-like food to make eating easier and reduce the pain associated with chewing. Hand feeding may be necessary if your dog has difficulty eating on their own. Ensure your dog has a comfortable and quiet environment to rest, as stress can exacerbate symptoms. Using raised food and water bowls can also help reduce strain on the jaw.
• Monitoring: regular veterinary check-ups are important to monitor the progression of the condition and adjust treatment as needed. Your veterinarian may recommend periodic blood tests and imaging to assess the severity of bone growth and inflammation.

Since CMO is believed to be a genetic condition, responsible breeding practices are crucial in preventing its occurrence. Breeders should avoid breeding dogs known to carry the gene for CMO and should consider genetic testing to identify carriers.

If your dog is diagnosed with CMO, work closely with your veterinarian to develop a management plan. Regular check-ups and appropriate pain management can help ensure your dog's comfort and quality of life. Your vet will guide you on the best ways to support your dog's health and well-being.  

When monitoring a dog with CMO at home, it's important to keep an eye on several key signs to ensure your dog is comfortable and to detect any changes that may require veterinary attention. Here are the signs to monitor:

• Swelling and pain: look for swelling around the jaw and signs of pain, such as whimpering, reluctance to be touched around the head, or avoiding activities that involve jaw movement.
• Difficulty eating: notice if your dog has trouble picking up food, chewing, or swallowing. They may drop food frequently or show a preference for softer foods.
• Excessive drooling: increased drooling can be a sign of discomfort or difficulty with jaw movement.
• Fever: monitor your dog's temperature, as intermittent fevers can occur with CMO. Fevers may come and go every 10-14 days.
• Behavioral changes: watch for signs of depression, lethargy, or changes in behavior, such as reduced activity levels or reluctance to play.
• Jaw movement: observe if your dog has difficulty opening their mouth or if they seem to be in pain when doing so.