Craniomandibular Osteopathy (CMO)
Dr. Arnold Plotnick
Radiographs. X-rays are needed to confirm the diagnosis of CMO. Most dogs show involvement on both sides of the face. Most of the time, the jaws are affected symmetrically, but occasionally, the dog is affected on one side only. On X-rays, proliferation of bone on both mandibles (84 percent of cases) is evident. In addition to the mandible, the tympanic bullae, which is the bony structure that houses the middle and inner ear, and the petrous temporal bone of the skull are commonly affected (51 percent of cases). Rarely, the mandible is not affected at all, but other parts of the skull show thickening or proliferative changes.
Serum chemistry profile. Complete blood counts and urinalysis are normal. Serum chemistry profiles do not show any specific changes. A few dogs have been reported to have high cholesterol, high phosphorus, high alkaline phosphatase and/or high creatine kinase, in any combination. These findings are non-specific. The increases in alkaline phosphatase and phosphorus are common findings in growing dogs, and are unlikely to be related to the presence of CMO.
Biopsy. Diagnosis of CMO is relatively easy in cases with typical clinical signs and X-ray appearance. Biopsy may be necessary only in atypical cases, as in rarely affected breeds in which the disease is confined to the mandible only, especially if the disorder is unilateral.
No satisfactory treatment trials have been done for CMO. The disease is usually self-limiting, with the progression of the disease slowing down at around 11 to 13 months of age. Sometimes, it is followed by a slow regression of the disorder, although radiographic abnormalities or impaired function may remain. Several drugs have been tried, however, with good response.
Glucocorticoids. These drugs, at anti-inflammatory dosages, may reduce pain and discomfort, although they don't have any effect on the bony changes involving the mandible.
Non-steroidal anti-inflammatory drugs (NSAIDs). NSAIDs such as aspirin or phenylbutazone have also been reported to relieve some of the pain and discomfort associated with the disorder.
Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your pet does not rapidly improve. Administer all prescribed medication as directed. Alert your veterinarian if you are experiencing problems treating your pet.
Return to your veterinarian for follow-up radiographs, to monitor progression and/or resolution of the disorder.
The prognosis for affected dogs is guarded when extensive bone changes are present and are affecting the tympanic bullae and petrous temporal bone area. These animals may develop fusion of bones in this area, permanently restricting or preventing jaw movements and hindering the act of eating. The prognosis is better in dogs that are mildly affected. The disease often stops progressing around 11 to 13 months of age, and then may regress partially or completely.