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BRACHYCEPHALIC SYNDROME |
What is brachycephalic syndrome?
The full name of this disorder is brachycephalic
airway obstruction syndrome (BAOS).
Brachycephalics are those breeds which have a
comparatively short head. Because of their
anatomy, virtually all dogs of these breeds have
some degree of increased work associated with
breathing from the time they are born. Many have
varying degrees of obstruction to their airways,
which causes signs ranging from noisy breathing
to collapse.
The most common anatomical features that lead to
the respiratory difficulties typical of these
breeds, include an elongated and fleshy soft
palate, and narrowed nostrils. Many affected
dogs also have changes to the larynx (everted
laryngeal saccules) and a relatively small
trachea (hypoplastic trachea).
How is brachycephalic syndrome inherited?
Selection for exaggerated features has resulted
in the respiratory difficulties in these breeds.
For example breed standards for the English
bulldog specify that the face should be very
short, as should the distance between the tip of
the nose and where it is set deep between the
eyes. It is hardly surprising that this leaves
little room for the structures involved in
normal breathing.
What breeds are affected by brachycephalic
syndrome?
These problems are generally most common and
severe in the English bulldog. Other
brachycephalic breeds in which this syndrome is
found include the pug, Boston terrier,
Pekingese, Cavalier King Charles spaniel,
Chinese shar-pei, French bulldog, Lhasa apso,
and shih tzu.
For many breeds and many disorders, the studies
to determine the mode of inheritance or the
frequency in the breed have not been carried
out, or are inconclusive. We have listed breeds
for which there is a consensus among those
investigating in this field and among veterinary
practitioners, that the condition is significant
in this breed.
What does brachycephalic syndrome mean to your
dog & you?
Problems associated with this syndrome range in
severity, with most brachycephalic dogs
snuffling and snorting to some degree. Some will
have no further difficulties, but many will have
problems such as increasingly noisy breathing,
coughing and gagging, fainting or collapsing
episodes, and a decreased tolerance for exercise
(ie. they tire easily). Over the long term, this
also puts an increased strain on the heart. Some
dogs, such as English bulldogs, may have
frequent episodes of sleep-disordered breathing.
Overheating is especially dangerous in these
breeds, because increased panting (the normal
mechanism for cooling in dogs) can cause further
swelling and narrowing of the already
constricted airways, which will increase your
dog's anxiety. Excitement, exercise, or warm
weather (and especially a combination of these
factors) can trigger this vicious cycle. These
dogs can also have gastrointestinal problems,
because of difficulties coordinating swallowing
when they are working so hard at breathing. This
can result in vomiting ar gagging because of
swallowing so much air, or aspiration pneumonia,
because of breathing in saliva or food
particles.
All dogs of these breeds have an increased risk
associated with sedation and anesthesia, for
which your veterinarian will take extra
precautions.
How is brachycephalic syndrome diagnosed?
These problems are usually evident from a young
age. If your dog has respiratory difficulties,
your veterinarian may discuss this syndrome with
you as part of a regular visit, or you may bring
your dog in because of an episode such as
collapsing after exercise.
Because some changes in anatomy are common to
all dogs of these breeds, diagnosis is really a
question of the degree of abnormality. The
overlong soft palate is best examined under
general anesthesia, and so, because of the
associated risks, your vet will most likely ask
your permission in advance to surgically correct
it at the same time if necessary. Neutering can
often be performed at the same time.
How is brachycephalic syndrome treated?
Medical treatment (oxygen therapy,
corticosteroids) can be used for short term
relief of airway inflammation. Surgery is
required where severe anatomic faults interfere
with breathing. Most commonly this involves
removal of some of the excess fleshy soft
palate, and widening of air passages at the
nostrils.
It is important to keep your dog from becoming
overweight, as this will worsen his or her
respiratory difficulties in the long run.
For the veterinarian: In mild episodes of
obstruction, short-acting steroids, oxygen
therapy, and cooling the dog while it calms down
may be sufficient. Bear in mind that sedation
without intubation will relax upper airway
muscles and may increase obstruction, and that
hyperthermia may develop in an oygen tent or
cage and exacerbate the problem.
These dogs, particularly the English bulldog,
have an increased risk of aspiration pneumonia
following surgery to correct airway problems.
Breeding advice
This syndrome is directly related to the
conformation or standards for these breeds.
Although so common as to be accepted as normal
for brachycephalics, BAOS causes serious
physical problems and discomfort for individual
dogs. Breed improvement by breeding away from
the extremes of conformation that cause these
problems, is a challenge for responsible
breeders.
Dogs with pronounced breathing difficulties or
that have required surgery to correct airway
obstruction, should not be used for breeding.
These dogs should be neutered at the time
surgical correction is performed.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE
SEE YOUR VETERINARIAN.
Resources
Hendricks, JC. 1995. Recognition and treatment
of congenital respiratory tract defects in
brachycephalics. In JD Bonagura and RW Kirk
(eds.) Kirk's Current Veterinary Therapy XII
Small Animal Practice.p. 892-894. W.B. Saunders
Co., Toronto.
Copyright © 1998 Canine Inherited Disorders
Database. All rights reserved.
Revised: August 23, 2008.
This database is a joint initiative of the Sir
James Dunn Animal Welfare Centre at the Atlantic
Veterinary College, University of Prince Edward
Island, and the Canadian Veterinary Medical
Association.
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