Craniomandibular Osteopathy

Also known as: Lion jaw

Introduction

Craniomandibular osteopathy is a non-neoplastic, non-inflammatory proliferative disease of the bones of the head.

Primary bones affected include the mandibular rami, occipital and parietal bones, tympanic bullae and the zygomatic portion of the temporal bone.

Symmetrical involvement is common.

The aetiology is unknown but there may be a link with infection.

Signalment

Craniomandibular osteopathy is seen most commonly in West Highland White Terriers, Scottish, and Cairn terriers although it has been reported in other breeds too.

The condition is believed to be hereditary, and it is an autosomal recessive trait in West Highland White Terriers and possibly in Scottish Terriers. It has been reported in other breeds such as the Labrador, Great Dane and Doberman.

The condition usually occurs in growing puppies between the age of 4 and 8 months.

Clinical Signs

Puppies present with swollen mandibles, inappetance and reluctance to open, and pain on opening the mouth. The owner may report that the dog has difficulty in prehension, mastication and swallowing of food, and that it has pain around the mouth area.

Temporal and masseter muscle atrophy are common.

There may be palpable irregular thickenings of the mandibular rami or the temporomandibular joint caused by periosteal proliferation of the body of the mandible, sometimes incorporating the tympanic bullae or temporomandibular joint.

The dog will be unable to fully open its jaw, even under anaesthesia. There may be bilateral exophthalmos and pyrexia, up to 40°C. Less commonly, there may be swelling and lameness in one or several limbs.

Diagnosis

Clinical signs and radiography are used to diagnose the condition.

Radiographic findings include: uneven, beadlike osseous proliferation of the mandible or tympanic bullae, extensive periosteal new bone formation affect the temporomandibular joint, fusion of the tympanic bullae and angular process of the mandible.

CT may help evaluate the osseous involvement of the temporomandibular joint.

Bone biopsy may reveal osteogenesis and resorption of periosteum, endosteum and trabeculae of the mandible, variable infiltration of lymphocytes, neutrophils and plasma cells, mosaic appearance.

Bone culture may help to rule out osteomyelitis if the diagnosis is uncertain.

Treatment

Craniomandibular osteopathy follows an intermittent progressive course but is self-limiting and treatment is only palliative. The condition usually regresses at about a year of age, corresponding with the completion of jaw growth and ossification.

Analgesics and anti-inflammatories form the mainstay of therapy, and may include NSAIDs such as carprofen.

High-calorie, protein-rich food should be provided to help maintain adequate nutrition, and feeding tube placement may be considered in severe cases.

The animal should be reexamined frequently to ensure adequate nutritional balance and pain control.

Pain and discomfort may diminish at skeletal maturity at approximately 12 months.

Lesions may then regress completely.

Prognosis depends on the involvement of the temporomandibular joint, as ankylosis and adhesions may permanently restrict jaw movement and eating.

Rostral mandibulectomy may be a useful salvage procedure.

Euthanasia may be the only option in severely affected animals.

Affected animals should not be used for breeding.

Craniomandibular Osteopathy Learning Resources
Flashcards Test your knowledge using flashcard type questions	Small Animal Orthopaedics Q&A 09

References

Niemiec, B. (2010) A colour handbook of small animal dental and maxillofacial diseases Manson Publishing

Lobprise, H. (2007) Blackwell's Five Minute Veterinary Consult: Small animal dentistry Wiley-Blackwell

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