Juvenile cranial hyperostosis

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Skull radiograph of a 6-month-old Bull Mastiff with craniomandibular osteopathy illustrating bony proliferation of the mandibles. Note that the temporomandibular joints are not involved.[1]

Juvenile cranial hyperostosis (Craniomandibular osteopathy, calvarial hyperostosis, lion's jaw) is an idiopathic proliferative bone disease of dogs characterized by bony malformations in the mandible and calvarium.

This self-limiting condition primarily affects the bones of the head but occasionally long bones of young dogs 3 - 8 months of age[2][3].

In the West Highland White Terrier, an autosomal recessive genetic disease is suspected[4], and is associated with generalized bony changes such as bilateral angular carpal deformity with limb bone biopsies confirming similar bony changes to those found in the mandible and calvarium[5].

In other breeds, leukocyte adhesion deficiency (Irish Setter)[6], bacterial infections (Escherichia coli) or viral (canine distemper virus[7]) is suspected as being contributing factors[1].

A breed predisposition is observed in the Pit Bull Terrier[8], Scottish Terrier, West Highland White Terrier, Boston Terrier, Cairn Terrier, Labrador Retriever[9], Great Dane[10], Doberman Pinscher[11], Boxer[12], Shetland Sheepdog[13], Pyrenean Mountain Dog[14] and English bulldog[15].

Clinical signs in affected dogs include painful mastication, pain upon opening the mouth, intermittent pyrexia, ptyalism and bilateral firm swellings of the mandible[16].

Blood tests are usually unrewarding, although mild hyperphosphatemia and changes in serum alkaline phosphatase may be found.

Diagnosis ususally requires radiographic, CT or MRI imaging, which illustrates symmetrically enlarged mandibular bodies due to dense osseous proliferation. On ultrasonography, enlarged tympanic bulla, fusion of the temporomandibular joint or auditory canal involvement may also be evident[17]. In large breed dogs, the lesions are usually confined to the mandible, while the parietal crest, frontal, lacrimal, and maxillary bones may be affected in small breed dogs.

Histopathology is usually required for a definitive diagnosis and usually reveals osteolysis of the periosteal or subperiosteal region and thickening of bony trabecula.

A differential diagnosis would include calvarial hyperostotic syndrome[18] (male Bull mastiffs only), osteomyelitis, periodontitis, nutritional secondary hyperparathyroidism, hypertrophic osteoarthropathy, hypertrophic osteodystrophy and osteosarcoma.

Treatment is usually conservative in most cases, with anti-inflammatory medication. Use of prednisolone is controversial and surgical attempts to remove excess bone have been unsuccessful, although a hemimandibulectomy may be performed as a salvage procedure for cases where the jaws can not be opened.

The prognosis is guarded when extensive bone changes involve the temporomandibular joint. Some regression of the bony changes may occur following growth plate closure.

References

  1. 1.0 1.1 Huchkowsky SL (2002) Craniomandibular osteopathy in a bullmastiff. Can Vet J 43(11):883-885
  2. Watson AD et al (1995) Craniomandibular osteopathy in dogs. Compend Contin Educ Pract Vet 17:911–922
  3. Riser WH et al (1967) Canine craniomandibular osteopathy. Am Vet Radiol Soc 8:23–30
  4. Padgett GA & Mostosky UV (1986) Animal model: The mode of inheritance of craniomandibular osteopathy in West Highland White Terrier Dogs. Am J Med Genet 25:9–13
  5. Pettitt R et al (2012) Bilateral angular carpal deformity in a dog with craniomandibular osteopathy. Vet Comp Orthop Traumatol 25(2):149-154
  6. Trowald G et al (2000) Clinical, radiological and pathological features of 12 Irish setters with canine leukocyte adhesion deficiency. J Small Anim Pract 41:211–217
  7. Munjar TA et al (1998) Comparison of risk factors for hypertrophic osteodystrophy, craniomandibular osteopathy and canine distemper virus infection. Vet Comp Orthop Traumatol 11:37–43
  8. Thompson DJ et al (2011) Idiopathic canine juvenile cranial hyperostosis in a Pit Bull Terrier. N Z Vet J 59(4):201-205
  9. Alexander JW & Kallfelz FA (1975) A case of craniomandibular osteopathy in a Labrador Retriever. Vet Med Small Anim Clin 70:560–563
  10. Burk RL & Broadhurst JJ (1976) Craniomandibular osteopathy in a Great Dane. J Am Vet Med Assoc 169:635–636
  11. Watson AD et al (1975) Craniomandibular osteopathy in Doberman Pinschers. J Small Anim Pract 16:11–19
  12. Schulz S (1978) A case of craniomandibular osteopathy in a Boxer. J Small Anim Pract 19:749–757
  13. Taylor SM et al (1995) Craniomandibular osteopathy in a Shetland sheepdog. Can Vet J 36:437–439
  14. Franch J et al (1998) Craniomandibular osteopathy in two Pyrenean mountain dogs. Vet Rec 142:455–459
  15. Hathcock JT (1982) Craniomandibular osteopathy in an English Bulldog. J Am Vet Med Assoc 181:389
  16. Alexander JW (1983) Selected skeletal dysplasias: Craniomandibular osteopathy, multiple cartilaginous exostoses, and hypertrophic osteodystrophy. Vet Clin North Am Small Anim Pract 13:55–70
  17. Hudson JA et al (1994) Computed tomography of craniomandibular osteopathy in a dog. Vet Radiol Ultrasound 35:94–99
  18. Pastor KF et al (2000) Idiopathic hyperostosis of the calvaria in five young Bullmastiffs. J Am Anim Hosp Assoc 36:439–445