Craniomandibular Osteopathy (CMO) in the Scottish Terrier : STCA HTF Health Series No. 2
Craniomandibular Osteopathy (CMO) in the Scottish Terrier
STCA HTF Health Series No. 2
By Carole Fry Owen
What is Craniomandibular Osteopathy (CMO)
Craniomandibular Osteopathy (CMO) is a painful, non-cancerous, inherited disease that involves excess bony growth in immature dogs. Lion Jaw, Scottie Jaw and Westie Jaw are other names. CMO affects mandibles (jaws), sometimes temporomandibular joints, occasionally skull bones, even rarely long leg bones. CMO is a disease no breeder wants to produce!
What are symptoms of CMO?
Pain during chewing or jaw manipulation
Lack of appetite
Mouth may not open well
First clue may be reluctance to chew. CMO is a cyclic disease, with episodes of bone resorption and proliferation. Symptoms run in I 0- to 14-day pain/fever cycles. Severity varies. A few dogs may not open their mouths unless treated. Some dogs have mild symptoms; others have no symptoms.
Can CMO puppies become healthy pets?
Definitely! CMO is unusual. It is a disease of the young--one to "get through." CMO is painful for dogs, unpleasant for owners, and a roadblock for breeders. However, it runs its course by about one year of age. Once symptoms are gone, CMO does not affect later life. Characteristic bony growths of- ten disappear in adults. CMO is a short-term problem for owners and puppies to “survive.” It affects the young, then resolves itself. Owners are relieved to learn their puppies will recover and live a normal life span. Only rarely should a CMO-affected puppy be put down. Because the disease is misunderstood, some CMO puppies are euthanized needlessly.
When and how is CMO diagnosed?
Usual onset is four to IO months, but four to seven months is most common. Initial diagnosis is from symptoms. Experienced breeders and veterinarians can identify CMO earlier by recognizing subtle clinical signs and palpating the bony growths.
How can I be sure it is CMO?
X-rays confirm clinical diagnosis. Survey radio-graphs of the skull and mandibles including oblique, dorsoventral and lateral views, are recommended. For definitive diagnosis, a board-certified veterinary radiologist can evaluate x-rays taken by a puppy’s own veterinarian. To document unaffected status of dogs in breeding programs, x-ray before six months. Light cases may not be apparent later on x-ray.
What is the treatment for CMO?
Analgesics and anti-inflammatory drugs, including corticosteroids, reduce pain and help puppies open their mouths to eat and drink. Recognizing onset of pain cycles early is important. Medications must be administered while a puppy will let its mouth be opened. Feed a high calorie, protein rich gruel or soft diet, limit chew toys and make tug-of-war games and roughhousing off limits.
Do other breeds have CMO?
First mention of CMO in veterinary literature was 1958. Forty years later, Dr. George Padgett's book Control of Canine Genetic Diseases (1998) shows 31 breeds affected by CMO, far more than veterinary texts reflect. Eleven are terrier breeds: American Staffordshire, Border, Bull, Cairn, Dandie Dinmont, Kerry Blue, Scottie, Skye, Soft-Coated Wheaten, Staffordshire Bull and Westie. More recently a Smooth Fox Terrier also has been reported.
Club health surveys show a “guesstimated” CMO carrier incidence of.
Scotties 4.7% (1995),
Cairns 13.59% (1999) and
Westies 22.1% (1999)
How is CMO inherited?
Test breedings proved CMO is inherited by an autosomal recessive gene, at least in the three prime affected breeds: West Highland White Terriers, Cairn Terriers and Scottish Terriers. Both parents of an affected puppy are carriers of the CMO gene. Two carriers bred together statistically will produce 25% affecteds, 50% carriers and 25% non-carriers. Siblings of affected puppies have a 66 2/3% chance of being carriers. Offspring of known carriers have a 50% chance of being carriers. Affected dogs should be bred only in test matings to "clear" breeding stock. Breed known carriers only with great caution.
How can CMO be prevented?
Dogs which have produced CMO should be removed from the breeding pool, unless a breeder uses only low risk mates, accepts responsibility for affected pups and treats all offspring as possible carriers. Test breeding an affected dog to a mate of unknown carrier status is an accepted way to discover the odds that the tested dog can be used safely in a breeding program without producing affected pups or passing on the CMO gene. Documenting widely used sires as “clear” by test breeding is valuable! Offspring from test breedings are usually spayed or neutered since they carry the disease gene. Registries, pedigree risk analyses and diagnostic x-rays to prove future breeding stock is not subclinically affected are other ways responsible breeders try to prevent CMO. Westie and Cairn breeders pioneered these techniques against CMO, and Scottie breeders use them too. Research is underway to develop a DNA test to identify CMO carrier status.
CMO DNA Research
Scottie, Westie and Cairn health foundations are funding half the AKC Canine Health Foundation's research to develop a DNA-based diagnostic test for CMO in the three breeds. Thanks to Scottie owners for $15,000 toward the $90,000 expended by 2002!
DNA from affected dogs, their siblings, parents, grandparents and other close relatives is valuable to CMO research. Samples are easy to collect at home with free brush collection kits available from Dr. Venta.
Helpful CMO References:
“Craniomandibular Osteopathy” by Anne Sanders (http://www.westieclubamerica.com) outlines protocol for prednisone treatment. Westie breeder Sanders has advised owners of many breeds on CMO and can be consulted at:
Research updates and health information: Check STCA's quarterly magazine The Bagpiper, and website (http://clubs.akc.org/stca).
Copyright 2004 Scottish Terrier Club of America Health Trust Fund
Copyright 2017 Scottish Terrier Club of America. Information and images may not be reproduced or used without prior authorization from the STCA.