Dr Miroslav Todorov
Blue Cross Veterinary Hospital
Craniomandibular osteopathy in a young Labrador retriever.
A 4 months old Labrador retriever was presented at the BlueCross Veterinary Hospital in Sofia, Bulgaria, with the owner complaining about painful episodes after touching the head of the animal.
Clinical examination: the dog is in a good clinical stage, no pathological heart or lung sounds.
The temperature was 39,5 C. No abdominal pain or other abnormalities.
The palpation of the skull was painful for the dog, there was slight dome shape of the cranium. The masseter muscles were atrophied. After palpation of the mandibula it was noted that the lower jaw of this dog looked enlarged. Pic 1
Considering the age, breed and the affection of the specific bones, the following list of differential diagnosis was made:
- Craniomandibular osteopathy
- Calvarial Hyperosthosis
We took a blood sample for CBC and biochemistry analysis.
On the CBC there was a slight decrease of the RBC – 5,36 (5.5- 8.5 x10/12/L) but this could be normal for younger animals.
On the biochemistry there was a slight decrease of the Total protein – 49 (51- 78) g/L and Albumin – 20(26- 41) g/L. Everything else was WNL.
The patient was sent for CT of the head to search for additional characteristics of the bones of the head and confirm my suspicion about the disease. We put an injection of NSAID for the pain until the test was done.
On the CT we discovered symmetrical bone proliferation of the rami of the mandubule and bone thickening of the calvarium of the animal. No underlying bone lysis was noted. Fortunately, till this moment affection of the temporomandibular joints was not discovered, but it is possible that this could happen during the next months.
There were not clear signs of neoplastic process or osteomyelitis. As a result, considering the information that we had, a diagnosis of craniomandibular osteopathy was made.
Craniomandibular osteopathy is a non neoplastic proliferative bone disease affecting immature dogs.
Usually the clinical signs start between 3 and 8 months of age. Common clinical presentation is pain episodes, fever, trouble chewing food, drooling and in more advanced cases – inability to open the mouth and eat. The etiology of this disease is unknown.
The first written description of CMO appeared in 1958.(9) It was described in five West Highland white terriers affected within a 2-year period. The most common breeds that are affected are West Highland white Terrier, Scottish Terrier, Cairn Terrier. The disease is described in other breeds – in Labradors, Boxers, Great Dane and a few more.
It is believed that this could be an inherited disease (autosomal recessive inheritance pattern) and as such it is advised for such animals to be neutered.
Commonly the affected dogs have bilaterally symmetrical enlarged mandibles and tympanic bulles, and affection of other bones of the calvarium. In severe cases those structures could fuse and this will lead to decreased range of motion of the temporomandibular joint. On examination, the temporal and masseter muscles may be atrophied.
In advanced cases, the diagnosis of craniomandibular osteopathy can be done with good positioned x-rays of the head of the animal. The advance imaging techniques, such as CT or MRI, improve the visualization and confirm the extension of the process.
On x- ray or CT increased irregular bone density is commonly observed – symmetrical periosteal proliferation, in most of the cases primary affection of the mandibules- 84%; tymplanic bulles – 51% and in some of the cases bones of the calvarium -13%.
The treatment plan is symptomatic with painkillers and anti-inflammatory drugs – commonly used drugs are NSAID and Steoids. Such drugs are needed during pain episodes and fever. Placement of an esophagostomy or gastrostomy feeding tube may be considered in patients that have difficulty eating and their nutritional requirements are not being met. Soft or liquefied food may be easier for some patients to eat. A high protein, high caloric food should be offered in order to meet nutritional needs.
Surgery of the bone proliferated tissues is not helpful in those cases.
The prognosis for these patients depends of the extent of progression of the disease. In those cases where a severe bone proliferation develops, the result is fusion of the temporomandibular joint and the prognosis is poor. Most of those dogs are euthanized because of the extent of the disease. It has been a common observation that when the affected dog is approximately 11 to 13 months of age, the disease may become self-limiting. The growth of abnormal bone slows, often regresses, and sometimes recedes completely. This period of self-limitation coincides with the time of completion of regular endochondral bone growth and ossification.
Our patient felt great after one injection of meloxicam. He is feeling active and has no signs of pain and temperature. Unfortunately, we cannot say whether his condition will progress to the extent to affect the temporomandibular joints and lead to inability to open its mouth.
The owner will return the dog to the breeder. It was advised to watch the dog for any additional signs and painkillers were prescribed.