Brachycephalic Airway Obstruction Syndrome (BAOS)
in the Cavalier King Charles Spaniel
- What It Is
- Relation to Other Disorders
- Care and Treatment
- Elongated Soft Palate
- Stenotic Nares
- Everted Laryngeal Saccules
- Laryngeal Collapse
- Breeders' Responsibilities
- What You Can Do
- Research News
- Related Links
- Veterinary Resources
Brachycephalic airway obstruction syndrome (BAOS)*, is an inherited condition in the cavalier King Charles spaniel. The breed is pre-disposed to it, due to the comparatively short length of the cavalier's head and a compressed upper jaw**.
* BAOS is also referred to as brachycephalic airway disease (BAD) and brachycephalic airway syndrome (BAS) and even brachycephalic obstructive airway syndrome (BOAS).
** Until 2011, there had been some dispute among researchers as to whether the cavalier King Charles spaniel is a brachycephalic breed or a mesaticephalic (or mesocephalic) breed. However, in a 2011 German study, the researchers concluded that the CKCS was brachycephalic but that it had a wider braincase in relation to length than in other brachycephalic breeds.
The term "brachycephalic" or "brachiocephalic" means short-nosed and refers to dogs with short muzzles, noses, and mouths. "Brachy" means short and "cephalic" means head. The throat and breathing passages in brachycephalic dogs often are undersized or flattened. The head's soft tissues are not proportionate to the shortened nature of the skull, and the excess tissues tend to increase resistance to the flow of air through the upper airway (nostrils, sinuses, pharynx and larynx).
This developmental defect is somewhat more apparent in a few other breeds: the English bulldog, pug, Boston terrier, and Pekingese, in particular. However, various degrees of BAOS predominate in the CKCS. The primary BAOS abnormalities in the cavalier include an elongated and fleshy soft palate, narrowed nostrils (stenotic nares), and everted laryngeal saccules, all of which are discussed in detail here. Other disorders may include laryngeal malformation and relatively small windpipe (tracheal hypoplasia or stenosis) and collapsing trachea*, which are not specifically covered in this article. All of these disorders cause obstruction of the upper airway, compromise the dog's ability to take in air, and may result in laryngeal collapse. BAOS in the CKCS has been attributed by some researchers as a consequence of the selection for soft, puppy-like facial features, referred to as "morphological neoteny".
In a 2010 report of BAOS surgery on 155 Australian dogs, the cavalier was the most common breed (29 dogs, 18.7%). The researchers found: "All CKCS had an elongated soft palate and accounted for 41% of the laryngeal collapse cases."
* Trachea collapse in the cavalier King Charles spaniel may also be due to an enlarged heart caused by advanced mitral valve disease. Also, a 2004 study by researchers at the Royal Veterinary College found that 53% of the brachycephalic dogs in their 92 dog sample had heart disease, compared to 24% of the non-brachycephalic dogs. See Mitral Valve Disease.
Robert N. White, a board certified veterinary soft tissue surgeon practicing at Willows Veterinary Centre and Referral Service in Solihull, West Midlands, observed in an October 2010 presentation before a meeting of the UK's Association of Veterinary Soft Tissue Surgeons, that the cavalier King Charles spaniel does not appear to be a classically brachycephalic breed, despite the extent of BAOS in the cavalier, and that the extent of both primary secretory otitis media (PSOM) and syringomyelia (SM) in the breed suggests that the CKCS may suffer from a combination syndrome of the three disorders, all associated with Chiari-like malformation.
The symptoms may vary and range in severity, depending upon which abnormality is causing them, but they typically include labored and constant open mouthed breathing, noisy breathing, snuffling, snorting, excessive snoring, gagging, retching, exercise and/or heat intolerance, general lack of energy, pale or bluish tongue and gums due to a lack of oxygen.
Also, studies have concluded that brachycephalic dogs may be predisposed to the conditions of Primary Secretory Otitis Media (PSOM), and eye problems, such as entropion, dry eye, and other disorders which may be caused by eyes not properly seated in the skull.
The brachycephalic cavalier is an inefficient panter. Increased panting can cause swelling and narrowing of the airway, resulting in collapsing or fainting. The excessive panting and episodes of other symptoms may place increased strain on the dog's heart, which cavaliers with mitral valve disease cannot afford to risk.
Care should be taken to avoid overheating and excessive excitement and excessive exercise, which may cause increased panting. Excessive barking or panting may cause the throat to swell, which could result in a totally blocked airway. Most importantly, the owner should not let the dog get too hot, particularly in the summer months, and not allow the dog to become overweight, as obesity will exacerbate the respiratory difficulties. Death from such related causes as heat stroke may be the consequence of not diagnosing and treating these symptoms early enough.
Care also should be taken when anesthesia may have to be administered. In a March 2012 report by a team of Tufts University veterinary anesthesiologists, cavaliers are among brachycephalic breeds which require special attention when being sedated and anesthetized. Their advice includes: "Avoid excessive sedation. Avoid α2-agonists. Administer acepromazine at half dose. Preoxygenate. Use short-acting induction agent. Use appropriately sized endotracheal tubes. Extubate after patient is sitting up, vigorously chewing, bright, alert."
In mild episodes, calming and cooling the dog may be sufficient. Inflammation and swelling of the airway tissues (oedema) may be treated with oxygen therapy (see photo) and corticosteroids for short term relief. Surgery is required when the abnormalities chronically interfere with breathing. Following surgery, the dog will need to be monitored closely for at least the first 24 hours, because inflammation or bleeding can obstruct the airway, making breathing difficult or impossible.
In all cases, it is strongly recommended that only board certified veterinary surgeons (who also are very experienced at airway surgery) be permitted to perform any type of airway surgery on cavaliers.
-- what it is
The palate is the roof of the mouth. It is divided into two parts, the anterior (front) bony hard palate, and the posterior (rear) fleshy soft palate. The soft palate separates the nasal passage from the oral cavity. An elongated soft palate is too long for the length of the mouth, so that its tip protrudes into the front of the airway and may get sucked into the laryngeal opening where it may obstruct the normal passage of air into the trachea. A fleshy soft palate is an abnormally thick one which reduces the dimension of the nasal air passage way. (See the soft palate at the top of the sketch, right.)
The most common and recurrent symptom of an elongated or fleshy soft palate is noisy breathing. Occasionally, the dog will make snorting sounds, which is due to the tip of the palate flapping into the trachea during respiration. This is called the "Cavalier snort" or a "reverse sneeze".* The dogs also are more likely to snore, gag, or retch, and in severe instances, they may collapse if the airflow is obstructed completely. See an example of a cavalier reverse sneezing at this YouTube video. See also, our blog entry, All that cavalier owners need to know about the “Reverse Sneeze” or “Cavalier Snort”.
* It may be confused with pharyngeal gag reflex or inspiratory proxysmal respiration.
Cavaliers with abnormally thick soft palates also are more likely to develop primary secretory otitis media (PSOM), due to the size of the soft palate impairing auditory tube drainage.
In severe cases, the palate usually is examined with the dog under light general anesthesia, using a laryngoscope. An elongated palate will obstruct the view of the larynx when the tongue is depressed. The veterinarian may take an x-ray to determine the length of the palate and airway.
If the palate is only moderately elongated and does not totally block the trachea, most cavaliers are able to pull out of these blockages by themselves. Snorting may be relieved by forcing the cavalier to breathe through its mouth instead of its nose. This may be done by holding the dog's head down and mouth open with one hand while blocking air from entering the nose with the other hand.
Treatment for recurring blockage of airflow is surgical removal of excess tissue from the palate by a veterinary surgeon. One of those procedures is "folded flap palatoplasty" (FFP), which both shortens and thins the soft palate. Post surgery prognosis is good for young dogs. They generally may be expected to breathe much easier, with significantly reduced respiratory distress, and display more energy and stamina. Older dogs may have a less favorable prognosis.
In all cases, it is strongly recommended that only board certified veterinary surgeons (who also are very experienced at airway surgery) be permitted to perform any type of airway surgery on cavaliers.
In a 2010 report of BAOS surgery on 155 Australian dogs, the cavalier was the most common breed (29 dogs, 18.7%). All of those cavaliers had an elongated soft palate.
-- what they are
Stenotic nares are abnormally narrow or obstructed nostrils (right), especially when inhaling. Dogs with this disorder tend to breathe primarily through their mouths, because breathing through the nose is unproductive. When they do breathe through their noses, they make wheezing sounds. Stenotic nares cause the dog to inhale deeper to draw air through the nose and into the lower airway, which may contribute to the development of secondary abnormalities, such as everted laryngeal saccules and laryngeal collapse.
The dog's nose appears narrow, with the nostril wings (alar folds) collapsing inward during inhalation and possibly blocking the nares. As noted above, the dog tends to breathe through its mouth, and makes wheezing sounds when breathing with its mouth closed. Symptoms typically include labored and constant open mouthed breathing, noisy breathing, snuffling, snorting, excessive snoring, and in severe cases, gagging, retching, exercise and/or heat intolerance, pale or bluish tongue and gums due to a lack of oxygen.
Stenotic nares are easily diagnosed by visual examination. In severe cases, the flow of air through the nostrils may be so poor that no air movement can be detected.
Surgery under general anesthesia is the preferred means of treating stenotic nares. The aim is to increase the size of the nostrils by removing tissue from the wings and possibly some related cartilage. Post surgery recovery is similar to that described above under Overall Care and Treatment and treatment for elongated soft palate. Following surgery, the dog will be required to wear an Elizabethan collar to keep the surgical site clean and to protect it from rubbing.
In all cases, it is strongly recommended that only board certified veterinary surgeons (who also are very experienced at airway surgery) be permitted to perform any type of airway surgery on cavaliers.
-- what they are
Everted laryngeal saccules are a secondary abnormality to either an elongated soft palate or stenotic nares. The larynx contains the vocal chords, produces sound, and protects the trachea. It is located at the point where the upper tract divides into the trachea and the esophagus. During swallowing, the larynx closes to prevent swallowed material from entering the lungs. The laryngeal saccules are part of the mucosal lining of the laryngeal ventricles and appear as two membranous sacs that are located in recessions in front of the vocal folds.
Brachycephalic cavaliers must create more pressure when they inhale in order to fill their lungs with air. This decreases the pressure in the upper airway, causes the lining of the larynx (laryngeal ventricles) to swell, and forces the laryngeal saccules to vibrate and evert into the airway at the opening to the trachea, blocking the flow of air. Everted laryngeal saccules usually are the first stage of laryngeal collapse. (See everted laryngeal saccules in the photo here.)
The symptoms are those common to a lack of air intake, such as gagging, retching, fainting, pale or bluish tongue and gums due to a lack of oxygen.
Everted laryngeal saccules are diagnosed under anesthesia. They appear as bilateral, red, fleshy, globular sacs.
Tissue from the saccules are surgically removed under general anesthesia. A tube will be inserted through the neck into the trachea (“temporary tracheostomy”) to allow an airway during surgery and will remain until the swelling in the throat subsides enough that the dog can breathe normally. Post surgery and recovery are similar to that described above under under Overall Care and Treatment and treatment for elongated soft palate.
-- what it is
Laryngeal collapse is an advanced form of brachycephalic airway obstruction syndrome.* The primary conditions of stenotic nares and elongated soft palate, together with everted laryngeal saccules, lead to abnormal stresses on the larynx and a progressive distortion and ultimate collapse of the cartilage supporting the larynx. There are three stages of laryngeal collapse, Stage 1 being the everted laryngeal saccules described above. Stage 2 occurs when the arytenoid cartilage loses its rigidity and gradually collapses inwardly. The third and final stage is when the cartilage fails completely, and the larynx collapses.
* A similar condition is tracheal collapse, which appears less common in the CKCS. Also, laryngeal paralysis.
In a 2010 report of BAOS surgery on 155 Australian dogs, the cavalier was the most common breed (29 dogs, 18.7%). The researchers found: "All CKCS had an elongated soft palate and accounted for 41% of the laryngeal collapse cases."
When the larynx collapses, the cavalier will not be able to breathe at all. The situation will be an extreme, life-threatening emergency.
The diagnosis is made by visual examination while the dog is under light anesthesia.
Depending upon the severity of the collapse, an early option may be a partial laryngectomy to enlarge the laryngeal opening. The procedure will include anesthesia and a temporary tracheostomy. Statistical studies have shown that less than 50% of dogs treated this way survive, due to the permanent cartilage deformation and softening which results in continued collapse. Permanent tracheostomy is the only other option. Prognosis is poor, particularly for older dogs.
A 2014 report examined the insertion of silicone tracheal stoma stents for temporary tracheostomy in eighteen dogs with upper airway obstruction, including three cavaliers. The conclusion was that use of the stent beyond five days was not recommended because of granulation tissue formation, and that the long-term consequences of partial tracheal ring resection are unknown.
BAOS is a consequence of the conformation standards for the CKCS. Cavaliers with significant breathing difficulties or that have required surgery to correct airway obstruction, should not be used for breeding.
May 2015: UK researchers opine that corneal ulcers in cavaliers may be due to the breed standard favoring large eyes. In a May 2015 study by a team of researchers (Rowena M. A. Packer, Anke Hendricks, Charlotte C. Burn) from the UK's Royal Veterinary College, they measured eleven conformational features demonstrated to be breed-defining (muzzle length, cranial length, head width, eye width, neck length, neck girth, chest girth, chest width, body length, height at the withers and height at the base of tail) of 700 dogs, 31 dogs of which were affected with corneal ulcers, including three cavalier King Charles spaniels. They specifically criticized the CKCS breed standard for considering "large" eyes as a desirable feature, and also noted that the cavalier's predisposition to dry eye can lead to corneal ulcers. They stated:
"Several brachycephalic breeds have been identified as being predisposed to dry eye, including the Bulldog, Lhasa Apso, Shih Tzu, Pug, Pekingese, Boston Terrier and Cavalier King Charles Spaniel. Even moderately lowered tear production associated with dry eye may produce clinical signs in brachycephalic dogs, as a larger portion of the globe is exposed. In a UK based study, a higher proportion of brachycephalic dogs that were affected by dry eye were also affected by ulcers, than were non-brachycephalic dogs with dry eye, e.g. 36% of Shih Tzus and 30% of Cavalier King Charles Spaniels versus 17% of dogs in the overall study population."
They devised morphometric predictors for corneal ulcers, including the "craniofacial ratio" (CFR), "the muzzle length divided by the cranial length, which quantifies the degree of brachycephaly", to differentiate skull morphologies. [Photos at right: "This Cavalier King Charles Spaniel has a craniofacial ratio of 0.27 (muzzle length 28mm / cranial length 102mm), and a relative palpebral fissure width value of 33.3% ((palpebral fissure width 34mm / cranial length 102mm) *100"]
They found that brachycephalic dogs (craniofacial ratio <0.5) were twenty times more likely to have corneal ulcers than non-brachycephalic dogs. In addition, they found that: (a) a 10% increase in relative eyelid aperture width more than tripled the ulcer risk, and (b) exposed eye-white was associated with a nearly three times increased risk. They concluded that:
"The results demonstrate that artificially selecting for these facial characteristics greatly heightens the risk of corneal ulcers, and such selection should thus be discouraged to improve canine welfare."
November 2014: UK surgeons report limited success inserting tracheal stents for temporary tracheostomies. In a November 2014 study by a group of UK veterinary surgeons (T. Trinterud, P. Nelissen, R. A. S. White at Dick White Referrals), they report on the results of inserting silicone tracheal stoma stents (right) for temporary maintenance of a tracheostomy stoma for periods ranging from three hours to eight months, in eighteen brachycephalic dogs, including three cavaliers. One of the CKCSs was euthanized during its procedure and the stents in the other two cavaliers had to be removed before the dogs were discharged from the hospital.
July 2014: UK's Royal Veterinary College opens a clinic especially for brachycephalic dogs. The RVC announced on July 1:
"A specialist clinic for brachycephalic dog breeds – also known as short-muzzled dogs – such as pugs, English and French bulldogs, cavalier King Charles spaniels and Pekingese, has been opened by the RVC at its Queen Mother Hospital for Animals in Hertfordshire.
"The Brachycephaly Clinic opened on Tuesday 1 July and is the first of its kind in the country exclusively specialising in the health of short-nosed dog breeds. This type of breed is one of the most popular pet choices in the UK, but the breeding of brachycephalic dogs has lead to a variety of health issues for the animals. These include problems with their bones and gait as well as eye, heart, ear (including hearing), skin, and breathing complications."
August 2013: Canadian vet urges "Stop brachycephalism, now!", including cavaliers. In a reasoned rant in a February 2013 Canadian Veterinary Journal article, veterinary dentist Dr. Fraser Hale (right) expresses his frustration with the mouths and teeth of brachycephalic breeds, including the cavalier King Charles spaniel. In his article, he states:
"In many Canadian jurisdictions, veterinarians have advocated for and achieved a ban on tail-docking, ear-cropping, and dewclaw removal as these are considered unnecessary cosmetic procedures that cause (temporary) pain with no benefit to the animals. I believe that as protectors of animal welfare, veterinarians should start a public awareness campaign to inform people of the serious, life-long negative impacts of brachycephalism. I believe we must stop referring to these conditions as 'normal for the breed' and refer to them as 'grossly abnormal in accordance with breed standards' because there is nothing remotely normal or desirable from the animal’s perspective. I believe we must stop using photographs of these deformed but comical breeds in advertising and promotional materials as this just increases public demand because they are 'so cute.'"
While he does not mention specific breeds in his article, in a subsequent interview, he stated:
"Of course, the small brachycephalics are the worst of the bunch. Oh yes, add CKCSs to the list."
September 2012: UK Dr. Gert ter Haar heads RVC's new ear, nose, and throat clinic. UK's Royal Veterinary College has commenced an ear, nose, and throat referral clinic at the Queen Mother Hospital for Animals in London. Dr. Gert ter Haar (right) heads the unit, which offers services including diagnostics and treatment of cavaliers with brachycephalic airway obstruction syndrome (BAOS), advanced diagnostics and treatment for PSOM in cavaliers, as well as CT and BAER diagnostics for deafness (plus hearing aid implants for selected patients). Telephone 01707 666 365 for more information.
August 2012: US and Canadian researchers find that a mutation of the gene BMP3 plays a role in brachycephalic breeds. See the report here. Cavalier King Charles spaniels were included in the brachycephalic class of dogs studied.
March 2012: Cavaliers are listed among brachycephalic breeds requiring extra care when being anesthetized. In a March 2012 report by a team of Tufts University veterinary anesthesiologists, cavaliers are among brachycephalic breeds which require special attention when being sedated and anesthetized. Their advice includes: "Avoid excessive sedation. Avoid α2-agonists. Administer acepromazine at half dose. Preoxygenate. Use short-acting induction agent. Use appropriately sized endotracheal tubes. Extubate after patient is sitting up, vigorously chewing, bright, alert."
December 2010: Cavaliers were most common breed for BAOS surgery among 155 Australian dogs. In a study of BAOS surgery on 155 Australian dogs, the cavalier was the most common breed (29 dogs, 18.7%). The researchers found: "All CKCS had an elongated soft palate and accounted for 41% of the laryngeal collapse cases."
October 2010: UK surgeon opines CKCS's brachycephalic disorders and PSOM are related to Chiari-like malformation. Robert N. White (right), a board certified veterinary soft tissue surgeon practicing at Willows Veterinary Centre and Referral Service in Solihull, West Midlands, observed in an October 2010 presentation before a meeting of the UK's Association of Veterinary Soft Tissue Surgeons, that the cavalier King Charles spaniel does not appear to be a classically brachycephalic breed, despite the extent of BAOS in the cavalier, and that the extent of both PSOM and SM in the breed suggests that the CKCS may suffer from a combination syndrome of the three disorders, all associated with Chiari-like malformation.
July 2010: UK researchers find association between PSOM and brachycephalic conformation in cavaliers. In their report, they find, "in CKCS, greater thickness of the soft palate and reduced nasopharyngeal aperture are significantly associated with OME [otitis media with effusion, meaning PSOM]."
This article is dedicated to a six year old male cavalier King Charles spaniel named Callie, who died in June 2006 of heat stroke due to BAOS after a brief walk with his owner in 79º weather in California, and to a six year old female cavalier named Bafi (right), who died in September 2007 from BAOS in Israel.
Upper airway obstruction surgery. Harvey C.E. J. Amer. Animal Hosp. Assn. 18: 538–544 (1982). Included CKCS.
Brachycephalic airway obstructive syndrome. Wykes PM. (1991) Problems in Veterinary Medicine 3, 188–197.
"Recognition and treatment of congenital respiratory tract defects in brachycephalics.". Hendricks, JC In Kirk's Current Veterinary Therapy XII Small Animal Practice. p. 892-894. .JD Bonagura and RW Kirk (eds.) 1995. W.B. Saunders Co., Toronto.
Brachycephalic airway obstruction syndrome – a review of 118 cases. Lorinson D., Bright R.M. and White R.A.S. Canine Practice 22: 18–21 (1997). Included CKCS.
Some Practical Solutions to Welfare Problems in Dog Breeding. P D McGreevy and F W Nicholas. Animal Welfare 1999, 8: 329-341. Quote: "As dogs made a transition from working to companion animals, selection for morphological neoteny found favour. This tendency is obvious among old and modem lap dogs. For example, with 'large dark round' eyes, pendant ears and 'compact, cushioned' feet, the Cavalier King Charles Spaniel (Kennel Club, London 1994; FCI Standard No 136) has a very puppy-like conformation."
Temporomandibular joint morphology in Cavalier King Charles spaniels. Alison M. Dickie, Tobias Schwarz, Martin Sullivan. Vet. Rad. & Ultra; May 2002; 43:260
"Brachycephalic airway syndrome." Monnet E. In: Textbook of Small Animal Surgery, 3d Ed. vol. 1, pp.808–813. D Slatter, ed. (2003) WB Saunders, Phila.
Breed Predispositions to Disease in Dogs & Cats. Alex Gough, Alison Thomas. 2004; Blackwell Publ. 44-45. Quote regarding CKCS: "Brachycephalic upper airway syndrome -- complex of anatomical deformities -- common in this breed -- a likely consequence of selective breeding for certain facial characteristics."
Material in the middle ear of dogs having magnetic resonance imaging for investigation of neurologic signs. Owen MC, Lamb CR, Targett MP. Vet. Radiology & Ultrasound, Mar 2004, 45(2):149-155.
Brachycephalic Airway Syndrome. Eric Monnet. WSAVA Proceedings 2004
Differences between breeds of dog in a measure of heart rate variability. Doxey S, Boswood A. Vet Rec. 2004 Jun 5;154(23):713-7.
"Brachycephalic airway disease." Dottie Brown, Sue Gregory. In: BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery. Daniel Brockman and David Holt, eds. Oct. 2005. Quote: "Breeds particularly predisposed to BAD [brachycephalic airway disease] with elongation of the soft palate include the Bulldog, Pug, Boston Terrier and, in the UK, the Cavalier King Charles Spaniel."
Results of surgical correction of abnormalities associated with brachycephalic airway obstruction syndrome in dogs in Australia. C. V. Torrez and G. B. Hunt. J.Sm.Anim.Prac. March 2006; 47(3):150. Quote: "Stenotic nares were present in 31 dogs (42·5 per cent), elongated soft palate in 63 (86·3 per cent) and everted laryngeal saccules in 43 (58·9 per cent). The most common breeds were the pug (19 dogs, 26 per cent), Cavalier King Charles spaniel (15 dogs, 20·5 per cent), British bulldog (14 dogs, 19·2 per cent) and Staffordshire bull terrier (4 dogs, 5·5 per cent). Laryngeal collapse was present in 34 of 64 (53 per cent) dogs. ... Clinical Significance: Laryngeal collapse is relatively common in dogs presented for surgical correction of brachycephalic airway obstructive disease. Dogs with severe laryngeal collapse often respond well to surgery. Clinical signs rarely resolve completely following surgery."
Surgical correction of brachycephalic syndrome in dogs: 62 cases (1991–2004). Todd W. Riecks, DVM; Stephen J. Birchard, DVM, MS, DACVS; Julie A. Stephens, MS. J.Amer.Vet.Med.Assn. May 1, 2007, 230( 9): 1324-1328. Included CKCS. Quote: "Elongated soft palate was the most common abnormality (54/62 [87.1%] dogs); the most common combination of abnormalities was elongated soft palate, stenotic nares, and everted saccules (16/62 [25.8%] dogs). ... Surgical treatment of brachycephalic syndrome in dogs appeared to be associated with a favorable long-term outcome, regardless of age, breed, specific diagnoses, or number and combinations of diagnoses."
Brachycephalic Syndrome: New Knowledge, New Treatments. Gilles Dupre. 2008 WSAVA Congress. Quote: "Brachycephalic breeds are usually distinguished from others by their shortened skull which results from an early ankylosis of the cartilages in this region. Different breeds are usually recognized as brachycephalic: Boston terrier, English and French bulldog, pugs, Pekinese, Shih-tzu and cavalier King Charles."
Localization of Canine Brachycephaly Using an Across Breed Mapping Approach. Danika Bannasch, Amy Young, Jeffrey Myers, Katarina Truvé, Peter Dickinson, Jeffrey Gregg, Ryan Davis, Eric Bongcam-Rudloff, Matthew T. Webster, Kerstin Lindblad-Toh, Niels Pedersen. PLOS One. March 2010. Quote: "The domestic dog, Canis familiaris, exhibits profound phenotypic diversity and is an ideal model organism for the genetic dissection of simple and complex traits. However, some of the most interesting phenotypes are fixed in particular breeds and are therefore less tractable to genetic analysis using classical segregation-based mapping approaches. We implemented an across breed mapping approach using a moderately dense SNP array, a low number of animals and breeds carefully selected for the phenotypes of interest to identify genetic variants responsible for breed-defining characteristics. Using a modest number of affected (10–30) and control (20–60) samples from multiple breeds, the correct chromosomal assignment was identified in a proof of concept experiment using three previously defined loci; hyperuricosuria, white spotting and chondrodysplasia. Genome-wide association was performed in a similar manner for one of the most striking morphological traits in dogs: brachycephalic head type. Although candidate gene approaches based on comparable phenotypes in mice and humans have been utilized for this trait, the causative gene has remained elusive using this method. Samples from nine affected breeds and thirteen control breeds identified strong genome-wide associations for brachycephalic head type on Cfa 1. Two independent datasets identified the same genomic region. Levels of relative heterozygosity in the associated region indicate that it has been subjected to a selective sweep, consistent with it being a breed defining morphological characteristic. Genotyping additional dogs in the region confirmed the association. To date, the genetic structure of dog breeds has primarily been exploited for genome wide association for segregating traits. These results demonstrate that non-segregating traits under strong selection are equally tractable to genetic analysis using small sample numbers."
Relationship between pharyngeal conformation and otitis media with effusion in Cavalier King Charles spaniels. Hayes GM, Friend EJ, Jeffery ND. Vet Rec. 2010 Jul 10;167(2):55-8. Quote: "Otitis media with effusion (OME) is a common incidental finding in otherwise normal Cavalier King Charles spaniels (CKCS). ... The incidence of OME as an incidental finding in a sample of 68 CKCS undergoing MRI was 54 per cent in this study, which is comparable to previously reported incidences of 47 per cent ... and 28 per cent ... in this breed. The CKCS in this study were reported to be ‘clinically normal’ by their owners, who did not report clinical signs of neurological disease or otitis in these dogs. ... In this study, measurements made on MRI were used to determine whether there was an association between OME and brachycephalic conformation. The results confirm that association and also demonstrate that, in CKCS, greater thickness of the soft palate and reduced naso-pharyngeal aperture are significantly associated with OME. ... An overlong soft palate has long been accepted as contributing to the [brachycephalic airway] syndrome, but more recently the importance of abnormally thick soft palates has also been recognised ... [B]rachycephalic airway syndrome may occur as a consequence of the selection for morphological neotony in this breed ... Although the aetiology is probably multifactorial, OME is more frequently found in patients with more severe anomalies of nasopharyngeal conformation. Changes within the nasopharynx may impair auditory tube drainage. ... These results suggest that auditory tube dysfunction and OME may represent a previously overlooked consequence of brachycephalic conformation in dogs."
Ocular conditions affecting the brachycephalic breeds. Peter G.C. Bedford. RVC. 2010. Quote: "There are two types of disease which affect the eye of the brachycephalic breeds and both are directly or indirectly related to genetic predisposition. First and by far the commonest are those conditions which are due to be conformation of skull and are related to the exophthalmos which is the common feature of these breeds. Second there are those conditions which have been unwittingly bred into some brachycephalic breeds in the pursuit of desired breed characteristics. In this lecture I will present an overview of all the diseases that the small animal practitioner is likely to encounter in the brachycephalic breeds of pedigree dog. The fourteen breeds I have included for discussion are the Affenpinscher, Boston Terrier, Boxer, Bulldog, Cavalier King Charles and the King Charles Spaniels, (mesaticephalic) French Bulldog, Griffon Bruxellois, Japanese Chin, Lhasa Apso, Pekingese, Pug, Shih Tzu and Tibetan Spaniel. ... Corneal Lipid Dystrophy: The term applies to the characteristic cholesterol and triglyceride deposits in the superficial corneal stroma seen most commonly in the Cavalier King Charles Spaniel. It is clinically benign and seldom affects vision to any noticeable degree. ... Hereditary Cataract: Hereditary cataract is seen in the Boston Terrier and the Cavalier King Charles Spaniel. ... Microphthalmos (MoD): Again the American literature suggests that microphthalmos (MoD) may be inherited in the Cavalier King Charles Spaniel."
Brachycephalic Airway Syndrome Surgery: a Retrospective Analysis of Breeds and Complications in 155 Dogs. Joy-Maree Wetzel, Philip Moses. ANZCVS 2010 Science Week. Quote: "... The most common breeds were the Cavalier King Charles Spaniel (CKCS) (29 dogs, 18.7%) ... All CKCS had an elongated soft palate and accounted for 41% of the laryngeal collapse cases. ..."
Breed Predispositions to Disease in Dogs & Cats (2d Ed.). Alex Gough, Alison Thomas. 2010; Wiley-Blackwell Publ. 54.
Brachycephalic Airway Obstructing Syndrome: Some Further Controversies. Robert N. White. Assn. of Veterinary Soft Tissue Surgeons. Oct. 2010. Quote: "There are a number of breeds in which some individuals show signs consistent with BAOS even though the breeds themselves are not brachycephalic. Examples include the Yorkshire terrier, the Norfolk terrier and the Norwich terrier. Affected individuals rarely show the nasal aspects of the disease recognised in the true brachycephalic breeds. Rather, these breeds present with a range of issues mostly associated with their caudal nasopharynx, pharynx and larynx. ... The Cavalier King Charles spaniel also warrants further discussion. Previous reports from the UK and Australia would suggest that this breed in commonly presented for the investigation and management of BAOS (Lorinson and others 1997, Torrez and Hunt 2006) in both these countries. Surprisingly, a recent retrospective series of 62 dogs from North America (Riecks and others 2007) contained no individuals of the breed. Like the three breeds discussed above [Yorkshire terrier, the Norfolk terrier and the Norwich terrier], it is my experience that the Cavalier King Charles spaniel presented for the further investigation of ʻBAOSʼ commonly does not have the classic findings seen in the bulldog, French bulldog, Pekinese, Pug, etc. Their nasopharyngeal obstruction is often characterised by a subjectively narrow (smaller than expected for a breed of their size) nasopharyngeal space and it is quite common that they do not show evidence of overlength of the soft palate. Interestingly, a recent report (Hayes and others 2010) confirmed a significant association between the presence of otitis media with effusion (on MRI) and an increase thickness of the soft palate and reduced nasopharyngeal aperture. Many of the cases show evidence of otitis media with effusion (OME) on either otoscopic examination or other imaging studies of the tympanic bullae. Malformation of the nasopharynx and soft palate is recognised to be associated with the formation of otitis media with effusion in the dog (White and others 2009). The prevalence of caudal fossa (craniocervical junction abnormalities including occipital hypoplasia) malformations is high in the Cavalier King Charles spaniel and is considered to be associated with the presence of neurological signs observed in individuals suffering from cerebellar herniation and syringohydromyelia (Cerda-Gonzalez and others 2009). It would seem reasonable to hypothesise that the Cavalier King Charles spaniel might suffer from a syndrome of conditions (syringomyelia, OME, nasopharyngeal airway obstruction, etc.) that are all associated with the malformation of the caudal aspect of the skull."
Brachycephalic airway obstructive syndrome in dogs: 90 cases (1991–2008). Frank J. Fasanella, Jacob M. Shivley, Jennifer L. Wardlaw, Sumalee Givaruangsawat. JAVMA Nov 2010; 237(9): 1048-1051. Quote: "Objective—To determine the prevalence of individual anatomic components of brachycephalic airway obstructive syndrome (BAOS), including everted tonsils, and analyze the frequency with which each component occurs with 1 or more other components of BAOS in brachycephalic dogs. ... 90 dogs with BAOS. Results—English Bulldogs (55/90 [61%]), Pugs (19/90 [21%]), and Boston Terriers (8/90 [9%]) were the most common breeds with BAOS. The most common components of BAOS were elongated soft palate (85/90 [94%]), stenotic nares (69/90 [77%]), everted laryngeal saccules (59/90 [66%]), and everted tonsils (50/90 [56%]). Dogs most commonly had 3 or 4 components of BAOS, with the most common combination being stenotic nares, elongated soft palate, everted laryngeal saccules, and everted tonsils. Dogs with stenotic nares were significantly more likely to have everted laryngeal saccules (50/69 [72%]), and dogs with everted laryngeal saccules were significantly more likely to have everted tonsils (39/59 [66%]). Postoperative surgical complications occurred in 12% (10/83) of dogs that received corrective surgery. No specific BAOS component made dogs more likely to have complications. Conclusions and Clinical Relevance—The prevalence of components of BAOS in brachycephalic dogs of this study differed from that reported previously, especially for everted tonsils. Thorough examination of the pharynx and larynx is necessary for detection of BAOS components."
Human evolutionary history: Consequences for the pathogenesis of otitis media. Charles D Bluestone, J. Douglas Swarts. Otolaryngology -- Head & Neck Surgery; Dec 2010; 143(6):739-744. Quote: "Among veterinarians, chronic ME effusion (termed primary secretory otitis media) is a well-known disease in the Cavalier King Charles Spaniel. It has been reported to be present in up to 40 percent of these animals. The effusion is mucoid and fills the entire ME. Diagnosis is made by operating microscopic examination, computed tomography scanning, or magnetic resonance imaging (MRI), and has been confirmed at the time of myringotomy. Myringotomy and tympanostomy tube placement has been recommended for treatment. This breed has been artificially selected to have a shortened front-to-back diameter of the skull, a shape termed brachycephaly, which arises due to premature fusion of the coronal sutures. The term neotenous (retention of juvenile characteristics into adulthood) is also appropriate for these breeds. The Cavalier snores habitually like other brachycephalic dogs, including the English Bulldog, a breed that has been reported to be the only animal known to develop obstructive sleep apnea. The snoring is undoubtedly secondary to its constricted pharynx, a consequence of the shortening of the snout. ... Figure 5 compares the head shape of a Cavalier King Charles Spaniel, with its extremely short face, to that of a Golden Retriever, which has a classic prognathic snout. The Cavalier King Charles Spaniel is an animal model of chronic OM with effusion. It has been “artificially selected” (Charles Darwin's term) for its short snout and globular head, but an unintended consequence of breeding for this characteristic is the propensity for chronic OM with effusion. In a recently reported study using MRI, veterinarians from England found that not only did the Cavalier have OM (54%), but another brachycephalic breed, the Boxer, also had ME disease (32%), which was not present in Cocker Spaniels, a mesaticephalic breed. The investigators suggested that the reduced nasopharyngeal space in the Cavalier and Boxers, when compared with the Cocker Spaniel, predisposed them to OM. It might be that one or both of the paratubal muscles is dysfunctional due to the abnormal palatal anatomy in these breeds and is the cause of their OM. The underlying pathogenesis of the Cavalier's ME disease is currently under investigation in our laboratory. Analogously, one could speculate that with the loss of their prognathic face, humans became susceptible to OM, an unintended consequence of “natural selection” for another adaptation (again, Darwin's term), as described above."
Cephalometric Measurements and Determination of General Skull Type of Cavalier King Charles Spaniels. M. J. Schmidt, A. C. Neumann, K. H. Amort, K. Failing, M. Kramer. Vet. Rad. & Ultra, 26 Apr 2011. Quote: "The general skull morphology of the head of the Cavalier King Charles Spaniel (CKCS) was examined and compared with cephalometric indices of brachycephalic, mesaticephalic, and dolichocephalic heads. Measurements were taken from computed tomography images. Defined landmarks for linear measurements of were identified using three-dimensional (3D) models. The calculated parameters of the CKCS were different from all parameters of mesaticephalic dogs but were the same as parameters from brachycephalic dogs. However, the CKCS had a wider braincase in relation to length than in other brachycephalic breeds. Studies of the etiology of the chiari-like malformation in the CKCS should therefore focus on brachycephalic control groups. As Chari-like malformation has only been reported in brachycephalic breeds, its etiology could be associated with a higher grade of brachycephaly, meaning a shorter longitudinal extension of the skull. This has been suggested for other breeds."
Bronchomalacia in Dogs with Myxomatous Mitral Valve Degeneration. MK Singh, LR Johnson, MD Kittleson, RE Pollard. William R. Pritchard. J Vet Intern Med 2011;--- (ACVIM 29th Ann. Vet. Med. Forum Abstract Program: Abstract C-12). Quote: "Coughing in the small breed dog may be related to cardiac causes associated with myxomatous mitral valve degeneration (MMVD) including pulmonary edema and compression of the mainstem bronchus by a severely enlarged left atrium, or due to respiratory causes such as tracheal and/or bronchial collapse or chronic bronchitis. The purpose of this study was to evaluate the association between left atrial enlargement and large airway collapse in dogs with MMVD and chronic cough. We hypothesized that airway collapse was independent of degree of left atrial enlargement. ... Preliminary results failed to identify an association between left atrial enlargement and airway collapse in dogs with MMVD but did suggest that airway inflammation is common in affected dogs. Further studies are needed to identify factors contributing to airway collapse in dogs with and without MMVD."
Canine Inherited Disorders Database: http://ic.upei.ca/cidd/disorder/brachycephalic-syndrome
Underlying diseases in dogs referred to a veterinary teaching hospital because of dyspnoea: 229 cases (2003-2007). Sonja Fonfara, Lourdes de la Heras Alegret, Alexander J. German, Laura Blackwood, Joanna Dukes-McEwan, P-J. M. Noble, Rachel D. Burrow. J.Am.Vet.Med.Assn.; Nov 2011; 239(9):1219-1224. Quote: "Objective—To identify the most frequent underlying diseases in dogs examined because of dyspnea and determine whether signalment, clinical signs, and duration of clinical signs might help guide assessment of the underlying condition and prognosis. Design—Retrospective case series. Animals—229 dogs with dyspnea. (Bulldogs, Cavalier King Charles Spaniels, Staffordshire Bull Terriers, Yorkshire Terriers and Pugs were overrepresented in the dyspnoeic population.) Results—Upper airway (n = 74 [32%]) and lower respiratory tract (76 [33%]) disease were the most common diagnoses, followed by pleural space (44 [19%]) and cardiac (27 [12%]) diseases. Dogs with upper airway and pleural space disease were significantly younger than dogs with lower respiratory tract and cardiac diseases. Dogs with lower respiratory tract and associated systemic diseases were significantly less likely to be discharged from the hospital. Dogs with diseases that were treated surgically had a significantly better outcome than did medically treated patients, which were significantly more likely to be examined on an emergency basis with short duration of clinical signs. Conclusions and Clinical Relevance—In dogs examined because of dyspnea, young dogs may be examined more frequently with breed-associated upper respiratory tract obstruction or pleural space disease after trauma, whereas older dogs may be seen more commonly with progressive lower respiratory tract or acquired cardiac diseases. Nontraumatic acute onset dyspnea is often associated with a poor prognosis, but stabilization, especially in patients with cardiac disease, is possible. Obesity can be an important contributing or exacerbating factor in dyspneic dogs."
Use of the harmonic scalpel for soft palate resection in dogs: a series of three cases. J Michelsen. Austr Vet J; Nov 2011; 89(12):511-514. Quote: "Soft palate resection is performed to resect a redundant or diseased soft palate, often associated with brachycephalic airway obstructive syndrome (BAOS). Resection has been associated with numerous complications, including coughing, bleeding, pharyngeal oedema, respiratory obstruction and death. Traditionally, the surgery is performed by sharp dissection and suturing, but other reported techniques include the use of an electrothermal sealing device or a laser. Operative time for sharp dissection is approximately 12 min, but is shortened to around 5 min when using a laser, as the haemostatic properties of the instrument negates the need for post-resection oversewing. The successful use of a harmonic scalpel to resect redundant soft palates in three dogs is described. The resected soft palates were not oversewn and the surgical time was comparable with that for laser surgery. The first dog had a minor bleed 6 h postoperatively, possibly associated with suboptimal placement of the harmonic scalpel cutting jaws. The following two patients had no postoperative complications. The harmonic scalpel laparoscopic handpiece allowed excellent visualisation of the surgical field and rapid performance of the procedure. All three patients had markedly improved postoperative respiratory function. Cleaning and resterilisation permitted multiple reuse of the handpiece, making it cost-competitive with other surgical techniques."
Surgical management of laryngeal collapse associated with brachycephalic airway obstruction syndrome in dogs. R. N. White. J Sm An Prac; Jan 2012;53(1):44–50. Quote: "Objective: To describe the use of cricoarytenoid lateralisation combined with thyroarytenoid caudo-lateralisation (arytenoid laryngoplasty) for the management of stage II and III laryngeal collapse in dogs. Methods: A retrospective study of a consecutive series of 12 dogs [five breeds were represented; Cavalier King Charles spaniel (n=3), English bulldog (n=4), French bull-dog (n=2), pug (n=2) and Pekingese] suffering from life-threatening stage II or III laryngeal collapse associated with brachycephalic airway obstruction syndrome. Results: Pre-operatively, either stage II collapse (2/12) or stage III collapse (10/12) was confirmed on visual examination. In all cases, a left-sided arytenoid laryngoplasty was performed. Two dogs were euthanased postoperatively as a result of persistent life-threatening respiratory compromise. The procedure resulted in subjective enlargement of the rima glottidis and an associated improvement in respiratory function in the remaining 10 dogs. Follow-up, long-term outcome (median, 3·5 years) in these dogs indicated that all owners considered that the surgery had resulted in marked improvements in their dog's respiratory function, tolerance to exercise, and quality of life. Clinical Significance: Combined cricoarytenoid and thyroarytenoid caudo-lateralisation may be a useful procedure for treatment of stage II and III laryngeal collapse in the dog."
Breed-Specific Anesthesia. Stephanie Krein, Lois A. Wetmore. NAVA Clinicians Brief; March 2012; 17-20. Quote: "Certain breed differences can lead to greater risks for airway obstruction, increased responsiveness to anesthetic drugs, and delayed recovery, all of which can result in increased anesthesia-related morbidity and mortality. ... If cardiac disease is suspected, a full cardiac workup with a veterinary cardiologist is recommended. ... Brachycephalic Breeds (e.g. bulldog, pug, Boston terrier, boxer, Cavalier King Charles spaniel, Pekingese). Problem: Brachycephalic airway syndrome; increased respiratory effort; potential for upper airway obstruction. Avoid excessive sedation. Avoid α2-agonists. Administer acepromazine at half dose. Preoxygenate. Use short-acting induction agent. Use appropriately sized endotracheal tubes. Extubate after patient is sitting up, vigorously chewing, bright, alert. ... Brachycephalic breeds have anatomic considerations that may affect anesthetic outcome.Most brachycephalic breeds suffer from brachycephalic airway syndrome (BAS), which is characterized by stenotic nares, elongated soft palate, everted laryngeal saccules, and hypoplastic trachea. Affected dogs have narrower upper airways than do dogs with normal anatomic features. Because in brachycephalic breeds additional airway contraction can occur with stress (ie, increased respiratory effort, turbulent flow), clinicians need to be prepared for possible upper airway obstruction. Furthermore, brachycephalic dogs must be monitored closely after premedication, throughout anesthesia and the postoperative period, and after extubation. An oxygen source and endotracheal tube should be readily available. Many brachycephalic dogs respond well to acepromazine in conjunction with an opioid; however, the sedative dose should be half of that used for nonbrachycephalic dogs. Full mu-opioid agonists can be used but because they may cause excessive respiratory depression, a reversal agent should be available. Dexmedetomidine should be avoided because of the presence of high vagal tone in these breeds. Anticholinergics, such as glycopyrrolate, may be used to decrease airway secretions and counteract high vagal tone. Preoxygenation is recommended before dogs with BAS are induced. Propofol or a similar short-acting drug should be used for induction and intubation should be completed as rapidly as possible.Mask inductions should be avoided, and smaller endotracheal tubes should be used. Because brachycephalic breeds tend toward obesity, controlled or mechanical ventilation is often necessary.Most problems associated with mechanical ventilation occur during induction and recovery, so monitoring is particularly important. Extubation should be postponed until the patient is bright, alert, swallowing—even chewing on the endotracheal tube. If extubation is attempted while the patient is sedated and groggy from anesthesia, there is increased risk for upper airway obstruction. If upper airway obstruction occurs, the patient should be reintubated."
Do dog owners perceive the clinical signs related to conformational inherited disorders as ‘normal’ for the breed? A potential constraint to improving canine welfare. RMA Packer A Hendricks, and CC Burn. Animal Welfare May 2012; 21(S1): 81-93. Quote: "Selection for brachycephalic (foreshortened muzzle) phenotypes in dogs is a major risk factor for brachycephalic obstructive airway syndrome (BOAS). Clinical signs include respiratory distress, exercise intolerance, upper respiratory noise and collapse. Efforts to combat BOAS may be constrained by a perception that it is ‘normal’ in brachycephalic dogs. This study aimed to quantify owner perception of the clinical signs of BOAS as a veterinary problem. A questionnaire-based study was carried out over five months on the owners of dogs referred to the Queen Mother Hospital for Animals (QMHA) for all clinical services, except for Emergency and Critical Care. Owners reported the frequency of respiratory difficulty and characteristics of respiratory noise in their dogs in four scenarios, summarised as an ‘owner-reported breathing’ (ORB) score. Owners then reported whether their dog currently has, or has a history of, ‘breathing problems’. Dogs (n = 285) representing 68 breeds were included, 31 of which were classed as ‘affected’ by BOAS either following diagnostics, or by fitting case criteria based on their ORB score, skull morphology and presence of stenotic nares. The median ORB score given by affected dogs’ owners was 20/40 (range 8–30). Over half (58%) of owners of affected dogs reported that their dog did not have a breathing problem. This marked disparity between owners’ reports of frequent, severe clinical signs and their perceived lack of a ‘breathing problem’ in their dogs is of concern. Without appreciation of the welfare implications of BOAS, affected but undiagnosed dogs may be negatively affected indefinitely through lack of treatment. Furthermore, affected dogs may continue to be selected in breeding programmes, perpetuating this disorder."
Normal for the breed? Rowena Packer. Vet. Nurse. June 2012;3(5):326. Quote: "Brachycephalic dogs are at high-risk of brachycephalic obstructive airway syndrome (BOAS). Clinical signs include noisy and laboured breathing, breathing difficulties even on short walks and easily overheating. These difficulties can prevent dogs from being able to enjoy simple pleasures such as exercise, play, food and sleep. In severe cases dogs can experience almost continuous breathing difficulties and collapse due to lack of oxygen. Due to the chronic and prevalent nature of clinical signs, they may be ‘accepted’ by owners and not perceived as abnormal, with only particularly acute or severe attacks alerting owners to present their dog to their veterinary practice. This is of additional concern as clinical signs often get worse over time if they are left untreated, and prognosis is improved with early intervention. ... Without appreciation of the welfare implications of BOAS, affected but undiagnosed dogs may be negatively affected indefinitely through lack of treatment. As such, this is an area that the veterinary profession should aim to tackle by raising awareness through client education. For example, we urge the veterinary team to make clients aware of what clinical signs such as snoring, snorting and difficulty exercising may indicate in these breeds, even if their dogs are not presented for these signs but are suspected to have BOAS."
Effect of brachycephalic, mesaticephalic, and dolichocephalic head conformations on olfactory bulb angle and orientation in dogs as determined by use of in vivo magnetic resonance imaging. Aseel K. Hussein, Martin Sullivan, Jacques Penderis. Am.J.Vety.Res. July 2012; 73(7):946-951. Quote: "Objective: To determine the effect of head conformation (brachycephalic, mesaticephalic, and dolichocephalic) on olfactory bulb angle and orientation in dogs by use of in vivo MRI. Animals: 40 client-owned dogs undergoing MRI for diagnosis of conditions that did not affect skull conformation or olfactory bulb anatomy. Procedures: For each dog, 2 head conformation indices were calculated. Olfactory bulb angle and an index of olfactory bulb orientation relative to the rest of the CNS were determined by use of measurements obtained from sagittal T2-weighted MRI images. Results: A significant negative correlation was found between olfactory bulb angle and values of both head conformation indices. Ventral orientation of olfactory bulbs was significantly correlated with high head conformation index values (ie, brachycephalic head conformation). Conclusions and Clinical Relevance: Low olfactory bulb angles and ventral olfactory bulb orientations were associated with brachycephalia. Positioning of the olfactory bulbs, cribriform plate, and ethmoid turbinates was related. Indices of olfactory bulb angle and orientation may be useful for identification of dogs with extremely brachycephalic head conformations. Such information may be used by breeders to reduce the incidence or severity of brachycephalic-associated diseases."
Brachycephalic Airway Syndrome: Pathophysiology and Diagnosis. Dena L. Lodato, Cheryl S. Hedlund. Compendium. July 2012; 34(7).
Brachycephalic Airway Syndrome: Management. Dena L. Lodato, Cheryl S. Hedlund. Compendium. Aug 2012; 34(8).
Variation of BMP3 Contributes to Dog Breed Skull Diversity. Jeffrey J. Schoenebeck, Sarah A. Hutchinson, Alexandra Byers, Holly C. Beale, Blake Carrington, Daniel L. Faden, Maud Rimbault, Brennan Decker, Jeffrey M. Kidd, Raman Sood, Adam R. Boyko, John W. Fondon, III, Robert K. Wayne, Carlos D. Bustamante, Brian Ciruna, Elaine A. Ostrander. PLoS Genet. 2012 August; 8(8): e1002849. Quote: "As a result of selective breeding practices, modern dogs display a multitude of head shapes. Breeds such as the Pug and Bulldog popularize one of these morphologies, termed “brachycephaly.” A short, upward-pointing snout, a massive and rounded head, and an underbite typify brachycephalic breeds. Here, we have coupled the phenotypes collected from museum skulls with the genotypes collected from dogs and identified five regions of the dog genome that are associated with canine brachycephaly [including the cavalier King Charles spaniel]. Fine mapping at one of these regions revealed a causal mutation in the gene BMP3. Bmp3's role in regulating cranial development is evolutionarily ancient, as zebrafish require its function to generate a normal craniofacial morphology. Our data begin to expose the genetic mechanisms unknowingly employed by breeders to create and diversify the cranial shape of dogs."
Do dog owners perceive the clinical signs related to conformational inherited disorders as ‘normal’ for the breed? A potential constraint to improving canine welfare. (Owner recognition of breathing disorders in brachycephalic dogs). RMA Packer, A Hendricks and CC Burn. Animal Welfare. 2012;21(S1):81-93. Quote: "Selection for brachycephalic (foreshortened muzzle) phenotypes in dogs is a major risk factor for brachycephalic obstructive airway syndrome (BOAS). Clinical signs include respiratory distress, exercise intolerance, upper respiratory noise and collapse. Efforts to combat BOAS may be constrained by a perception that it is ‘normal’ in brachycephalic dogs. This study aimed to quantify ownerperception of the clinical signs of BOAS as a veterinary problem. A questionnaire-based study was carried out over five months on the owners of dogs referred to the Queen Mother Hospital for Animals (QMHA) for all clinical services, except for Emergency and Critical Care. Owners reported the frequency of respiratory difficulty and characteristics of respiratory noise in their dogs in four scenarios, summarised as an ‘owner-reported breathing’ (ORB) score. Owners then reported whether their dog currently has, or has a history of, ‘breathing problems’. Dogs (n = 285) representing 68 breeds were included, 31 of which were classed as ‘affected’ by BOAS either following diagnostics, or by fitting case criteria based on their ORB score, skull morphology and presence of stenotic nares. The median ORB score given by affected dogs’ owners was 20/40 (range 8–30). Over half (58%) of owners of affected dogs reported that their dog did not have a breathing problem. This marked disparity between owners’ reports of frequent, severe clinical signs and their perceived lack of a ‘breathing problem’ in their dogs is of concern. Without appreciation of the welfare implications of BOAS, affected but undiagnosed dogs may be negatively affected indefinitely through lack of treatment. Furthermore, affected dogs may continue to be selected in breeding programmes, perpetuating this disorder."
Stop brachycephalism, now! Fraser Hale. Can.Vet.J. Feb. 2013;54(2):185-186. Quote: "In many Canadian jurisdictions, veterinarians have advocated for and achieved a ban on tail-docking, ear-cropping, and dewclaw removal as these are considered unnecessary cosmetic procedures that cause (temporary) pain with no benefit to the animals. I believe that as protectors of animal welfare, veterinarians should start a public awareness campaign to inform people of the serious, life-long negative impacts of brachycephalism. I believe we must stop referring to these conditions as 'normal for the breed' and refer to them as 'grossly abnormal in accordance with breed standards' because there is nothing remotely normal or desirable from the animal’s perspective. I believe we must stop using photographs of these deformed but comical breeds in advertising and promotional materials as this just increases public demand because they are 'so cute.'"
Laryngeal Disease in Dogs and Cats. Catriona MacPhail. Vet. Clinics of N.A.: Sm. Anim. Prac. Jan. 2014;44(1):19-31. Quote: "Brachycephalic airway syndrome refers to the condition of obstructive airway distress attributable to anatomic abnormalities of breeds such as English and French bulldogs, pugs, Boston terriers, and Cavalier King Charles spaniels."
Assoziation zephalometrischer Parameter mit dem Auftreten der Syringomyelie beim Cavalier King Charles Spaniel mit Chiari-ähnlicher Malformation [Association of anatomical parameters with the occurrence of syringomyelia in the Cavalier King Charles Spaniel with Chiari malformation]. Annabell Johanna Grübmeyer. Giessener Elektronische Bibliothek. Jan. 2014. Quote: "Until now the Chiari-like malformation was only diagnosed in brachycephalic dog breeds. Based on the decreased length-breadth ratio of its skull the Cavalier King Charles Spaniel can be classified as a highly brachycephalic dog. Therefore it could be assumed that the grade of brachycephaly is a pathophysiological factor for the development of syringomyelia and a retarded length growth of the skull might be the cause for the changes found in the Chiari-like malformation. The question is, if a shortening of the cranial base gives rise to the pathological changes in Chiari-like malformation. Based on this question we examined the anatomical parameters of 107 Cavalier King Charles Spaniels in relationship to the occurrence of syringomyelia. The study should give information about the pathogenesis of the Chiari-like malformation and the development of syringomyelia and if there is a difference in the cranial base length in Cavalier King Charles Spaniels with or without syringomyelia. The 107 Cavalier King Charles Spaniels examined in this study were mostly presented for breeding examinations, but some were also presented because of clinical signs. The age of the examined dogs ranged from 6 month to 9 years. We performed computed tomography of the skull and magnetic resonance imaging of the skull and spine of all patients. The examination of the spine in patients introduced for breeding examinations, were performed until the 5th cervical vertebra. In patients with neurological signs the examination included also the caudal cervical, thoracic and lumbar spine. Changes consistent with the Chiari-like malformation were found in all 107 Cavalier King Charles Spaniels. 63 of the 107 dogs showed a syringomyelia at the point of examination. The results of the study showed that the incidence of syringomyelia is correlated to the variables age (p less than 0,007), SBI [skull base index] (p less than 0,0192), PI [presphenoid index] (p less than 0,0447) and BI [basisphenoid index] (p less than 0,0206). Furthermore it is shown that Cavalier King Charles Spaniels with a decrease in SBI have an increased risk to develop syringomyelia (odds ratio 1,26). In addition also the presphenoid and the basioccipital bone showed a reduced length, with an increase in breadth in dogs with syringomyelia. This study showed, that a reduced length of the cranial base represents a risk factor for the occurrence of syringomyelia. These results support the assumption of other authors that the cause of the Chiari-like malformation and syringomyelia is up to a growth disturbance of the cranial base."
Tracheal Collapse in Dogs. Mary Dell Deweese, Karen M. Tobias. Clinicians Brief. May 2014;83-87.
Evaluation of a novel tracheal stent for the treatment of tracheal collapse in dogs. D. Clarke, E. de Madron, R. Presley. J.Vet.Int.Med. July 2014;28(4):1364. Quote: "The purpose of this study was to evaluate the safety, efficacy, and satisfaction associated with a novel variable diameter tracheal stent designed specifically for canine anatomy and tracheal collapse. This was a multicenter retrospective study of 27 consecutive cases of tracheal collapse treated with the stent. Data forms requiring chart review and client interviews were distributed to the veterinarian placing each stent. Information was collected that compared symptoms pre- and post-stenting as well as a number of other parameters relating to the procedure and subsequent clinical course to assess stent performance and ease of use. Symptoms were graded on a visual line scale of 0-10. Paired t-tests or sign rank tests were used to determine changes in symptoms following stenting. A two-sided p-value of <0.05 was considered statistically significant. Responses were obtained from 20 of 27 cases. Data was normally distributed. The mean duration of follow-up was 3 months (range >1 to 17 months). There were no procedural complications. Operative mortality was 0%. There were no stent fractures or stent related deaths; symptomatic granulation tissue developed in one case. Statistically significant improvement was seen in cough, respiratory function, quality of life, and exercise tolerance. All veterinarians stated they would use the stent again. 95% of clients would repeat the procedure and 90% expressed satisfaction with the outcome. Tracheal stenting performed with the novel implant is both safe and subjectively effective in significantly improving clinical symptoms. Veterinarians and clients expressed a positive perception regarding outcomes associated with the stent."
Introducing breathlessness as a significant animal welfare issue. Beausoleil N, Mellor D. N.Z.Vet.J. July 2014;8:1-22. Quote: "Breathlessness is a negative affective experience relating to respiration, the animal welfare significance of which has largely been underestimated in the veterinary and animal welfare sciences. In this review, we draw attention to the negative impact that breathlessness can have on the welfare of individual animals and to the wide range of situations in which mammals may experience breathlessness. At least three qualitatively distinct sensations of breathlessness are recognised in human medicine - respiratory effort, air hunger and chest tightness - and each of these reflects comparison by cerebral cortical processing of some combination of heightened ventilatory drive and/or impaired respiratory function. Each one occurs in a variety of pathological conditions and other situations, and more than one may be experienced simultaneously or in succession. However, the three qualities vary in terms of their unpleasantness, with air hunger reported to be the most unpleasant. We emphasise the important interplay among various primary stimuli to breathlessness and other physiological and pathophysiological conditions, as well as animal management practices. For example, asphyxia/drowning of healthy mammals or killing those with respiratory disease using gases containing high carbon dioxide tensions is likely to lead to severe air hunger, while brachycephalic obstructive airway syndrome in modern dog and cat breeds increases respiratory effort at rest and likely leads to air hunger during exertion. Using this information as a guide, we encourage animal welfare scientists, veterinarians, laboratory scientists, regulatory bodies and others involved in evaluations of animal welfare to consider whether or not breathlessness contributes to any compromise they may observe or wish to avoid or mitigate."
Brachycephalic obstructive airway syndrome: a growing problem. Terry Emmerson. J. Small Animal Practice. November 2014;55(11):543-544. Quote: "The Cavalier King Charles spaniel (CKCS) is often considered a brachycephalic breed and can present with typical brachycephalic airway signs such as respiratory noise, snoring, stertor and exercise intolerance. They are represented in reviews of dogs undergoing corrective airway surgery for BOAS and dogs requiring tracheostomies (Torrez & Hunt 2006). However these dogs often do not demonstrate the typical abnormalities of the brachycephalic breeds. They often do not have an overlong palate as judged by standard criteria or stenotic nares or everted laryngeal ventricles. Some present with isolated laryngeal collapse and we have seen some dogs with concurrent laryngeal paralysis. As a breed they often have a particularly thick soft palate and small nasopharynx which may be the main factors driving the signs in this breed. Other breeds that can present with BOAS-like symptoms but often without the typical abnormalities include the bull terrier and Mastiff breeds. Like the CKCS, these breeds often do not have a surgically correctable problem. BOAS is a complex problem which currently we do not fully understand. We need to better understand the anatomical and breed variations in these cases and their relationship to severity of signs and postsurgical outcome. Current surgical options offer a way to alleviate signs and can provide significant improvement. However, there is still a frustrating subset of cases with poor outcomes that we struggle to identify pre-operatively. Surgery should be performed on affected dogs to improve quality of life and as a welfare issue. However, ultimately, the only way to truly improve this condition is by education of the public and breeders regarding the problems of these breeds and with breeding aimed at improving conformation."
Use of silicone tracheal stoma stents for temporary tracheostomy in dogs with upper airway obstruction. T. Trinterud, P. Nelissen, R. A. S. White. J. Small Animal Practice. November 2014;55(11):551-559. Quote: "Objectives: To report the use of silicone tracheal stoma stents for temporary tracheostomy in dogs with upper airway obstruction. Methods: Retrospective review of medical records for dogs in which silicone tracheal stoma stents were placed. Results: Eighteen dogs [including three cavalier King Charles spaniels] had a silicone tracheal stoma stent placed for maintenance of a tracheostomy stoma for periods ranging from three hours to eight months. No intra-operative or immediate postoperative complications were recorded. In 11 dogs the stent was removed by simple traction after a period ranging from 36 hours to 6 weeks, and the tracheal stoma was left to heal by second intention. Five of the 18 dogs were determined as being tracheostomy dependent and underwent conversion to permanent tracheostomy after a period ranging from five days to eight months following stent placement. One dog was euthanased after three months, with the stent still in place, because of poor respiratory function, and one dog [a CKCS] died of unrelated reasons ["severe immune-mediated thrombocytopenia (ITP)"]. In 6 of 10 dogs (60%) where the stent was in place for five days or more, granulation tissue formation caused dislodgement of the stent. Clinical Significance: Silicone tracheal stoma stents may be used as an alternative to conventional trache-ostomy tubes in selected dogs with upper airway obstruction. Long-term use of the stent beyond five days is not recommended because of granulation tissue formation. The long-term consequences of partial tracheal ring resection are unknown."
Comparison of the Relationship between Cerebral White Matter and Grey Matter in Normal Dogs and Dogs with Lateral Ventricular Enlargement. Martin J. Schmidt, Steffi Laubner, Malgorzata Kolecka, Klaus Failing, Andreas Moritz, Martin Kramer, Nele Ondreka. PLoS ONE 10(5): e0124174. May 2015. Quote: "Large cerebral ventricles are a frequent finding in brains of dogs with brachycephalic skull conformation, in comparison with mesaticephalic dogs. It remains unclear whether oversized ventricles represent a normal variant or a pathological condition in brachycephalic dogs. There is a distinct relationship between white matter and grey matter in the cerebrum of all eutherian mammals. The aim of this study was to determine if this physiological proportion between white matter and grey matter of the forebrain still exists in brachycephalic dogs with oversized ventricles. The relative cerebral grey matter, white matter and cerebrospinal fluid volume in dogs were determined based on magnetic-resonance-imaging datasets using graphical software. In an analysis of covariance (ANCOVA) using body mass as the covariate, the adjusted means of the brain tissue volumes of two groups of dogs were compared. Group 1 included 37 mesaticephalic dogs of different sizes with no apparent changes in brain morphology, and subjectively normal ventricle size. Group 2 included 35 brachycephalic dogs [including 7 cavalier King Charles spaniels, 4 of which were diagnosed with syringomyelia] in which subjectively enlarged cerebral ventricles were noted as an incidental finding in their magnetic-resonance-imaging examination. Whereas no significant different adjusted means of the grey matter could be determined, the group of brachycephalic dogs had significantly larger adjusted means of lateral cerebral ventricles and significantly less adjusted means of relative white matter volume. This indicates that brachycephalic dogs with subjective ventriculomegaly have less white matter, as expected based on their body weight and cerebral volume. Our study suggests that ventriculomegaly in brachycephalic dogs is not a normal variant of ventricular volume. Based on the changes in the relative proportion of WM and CSF volume, and the unchanged GM proportions in dogs with ventriculomegaly, we rather suggest that distension of the lateral ventricles might be the underlying cause of pressure related periventricular loss of white matter tissue, as occurs in internal hydrocephalus. ... The influence of ventriculomegaly on brain function in dogs is unclear. Detailed behavioural studies of the impact of WM loss on the full functional integration of the nervous system are necessary to clarify whether ventriculomegaly might be an indication for CSF shunting procedures in dogs."
Impact of Facial Conformation on Canine Health: Corneal Ulceration. Rowena M. A. Packer, Anke Hendricks, Charlotte C. Burn. PlosOne. May 2015. Quote: "Concern has arisen in recent years that selection for extreme facial morphology in the domestic dog may be leading to an increased frequency of eye disorders. Corneal ulcers are a common and painful eye problem in domestic dogs that can lead to scarring and/or perforation of the cornea, potentially causing blindness. Exaggerated juvenile-like craniofacial conformations and wide eyes have been suspected as risk factors for corneal ulceration. ... Several brachycephalic breeds have been identified as being predisposed to dry eye, including the Bulldog, Lhasa Apso, Shih Tzu, Pug, Pekingese, Boston Terrier and Cavalier King Charles Spaniel. Even moderately lowered tear production associated with dry eye may produce clinical signs in brachycephalic dogs, as a larger portion of the globe is exposed. In a UK based study, a higher proportion of brachycephalic dogs that were affected by ulcers, than were non-brachycephalic dogs with dry eye, e.g. 36% of Shih Tzus and 30% of Cavalier King Charles Spaniels versus 17% of dogs in the overall study population. ... This study aimed to quantify the relationship between corneal ulceration risk and conformational factors including relative eyelid aperture width, brachycephalic (short-muzzled) skull shape, the presence of a nasal fold (wrinkle), and exposed eye-white. A 14 month cross-sectional study of dogs entering a large UK based small animal referral hospital for both corneal ulcers and unrelated disorders was carried out. Dogs were classed as affected if they were diagnosed with a corneal ulcer using fluorescein dye while at the hospital (whether referred for this disorder or not), or if a previous diagnosis of corneal ulcer(s) was documented in the dogs’ histories. Of 700 dogs recruited, measured and clinically examined, 31 were affected by corneal ulcers. Most cases were male (71%), small breed dogs (mean± SE weight: 11.4±1.1 kg), the most common being the Pug (n = 12 affected), the Shih Tzu (n = 4), the Bulldog and the Cavalier King Charles Spaniel (n = 3). ... Morphometric data were collected for each dog using previously defined measuring protocols, measuring 11 conformational features that were demonstrated to be breed-defining: muzzle length, cranial length, head width, eye width, neck length, neck girth, chest girth, chest width, body length, height at the withers and height at the base of tail (all in cm). ... A further morphometric predictor of interest for corneal ulcers was craniofacial ratio, (CFR): the muzzle length divided by the cranial length, which quantifies the degree of brachycephaly, was used to differentiate skull morphologies. [Photos at right: "This Cavalier King Charles Spaniel has a craniofacial ratio of 0.27 (muzzle length 28mm / cranial length 102mm), and a relative palpebral fissure width value of 33.3% ((palpebral fissure width 34mm / cranial length 102mm) *100"] ... [B]rachycephalic dogs (craniofacial ratio <0.5) were twenty times more likely to be affected than non-brachycephalic dogs. A 10% increase in relative eyelid aperture width more than tripled the ulcer risk. Exposed eye-white was associated with a nearly three times increased risk. The results demonstrate that artificially selecting for these facial characteristics greatly heightens the risk of corneal ulcers, and such selection should thus be discouraged to improve canine welfare."
Can we breathe easy about Brachycephalic Obstructive Airway Syndrome? Effects of severity on canine play, exercise and feeding behaviour. Monica Anghaei, Charlotte C. Brun. Conference: Canine Behaviour & Genetics. June 2015. Quote: "Brachycephalic Obstructive Airway Syndrome (BOAS) forms a continuum from mild to severe. It is most common in dogs with brachycephalic conformations and as such, this genetic predisposition exposes dogs to a series of respiratory complications. BOAS impairs canine quality of life when severe, but little is known about its effects on key positive aspects of behaviour when less severe. It is hypothesised that beyond certain severities, BOAS will: i. reduce ability to exercise and haemoglobin oxygenation following walking, ii. reduce playfulness, and iii. reduce appetite and increase difficulty eating. Quantitative behavioural observations were conducted on 47 brachycephalic dogs. Behaviour during (i) a 6-minute walk test, (ii) a play test (iii) and an appetite test was recorded. BOAS severity was measured using a previously validated Owner Reported Breathing (ORB) score: 0 = unaffected; 40 = maximum severity. Increasing BOAS severity tended (non-significantly) to decrease oxygenation after exercise [at right, a CKCS is being measured with a pulse a oximeter after exercise], increased time to ingest per food pellet , and decrease in energetic play behaviours e.g. Play Bow; and increase breathing noises in all three domains. An owner questionnaire conducted on 2265 brachycephalic dogs [including cavalier King Charles spaniels] indicated the severity scores for mild BOAS are 8-15, moderate BOAS are 16-26 and severe are 27-40 ORB score, with owner-perceived canine welfare significantly declining as severity increased. Mild BOAS has less effect on canine welfare than sometimes assumed. However, moderate BOAS affects at least two of the welfare domains tested and severe BOAS is recognised to negatively impacts all exercise, appetite and play domains. This information would will help make recommendations for owners, breeders and veterinarians on appropriate treatment to maximise welfare in affected dogs.
Epidemiological associations between brachycephaly and upper respiratory tract disorders in dogs attending veterinary practices in England. Dan G. O’Neill, Caitlin Jackson, Jonathan H. Guy, David B. Church, Paul D. McGreevy, Peter C. Thomson, Dave C. Brodbelt. Canine Genetics & Epidemiology. July 2015;2:10. Quote: "Background: Brachycephalic dog breeds are increasingly common. Canine brachycephaly has been associated with upper respiratory tract (URT) disorders but reliable prevalence data remain lacking. Using primary-care veterinary clinical data, this study aimed to report the prevalence and breed-type risk factors for URT disorders in dogs. Results: The sampling frame included 170,812 dogs attending 96 primary-care veterinary clinics participating within the VetCompass Programme. Two hundred dogs were randomly selected from each of three extreme brachycephalic breed types (Bulldog, French Bulldog and Pug) and three common small-to medium sized breed types (moderate brachycephalic: Yorkshire Terrier and non-brachycephalic: Border Terrier and West Highland White Terrier). Information on all URT disorders recorded was extracted from individual patient records. Disorder prevalence was compared between groups using the chi-squared test or Fisher’s test, as appropriate. During the study, 83 (6.9 %) study dogs died. Extreme brachycephalic dogs (median longevity: 8.6 years, IQR: 2.4-10.8) were significantly younger at death than the moderate and non-brachycephalic group of dogs (median 12.7 years, IQR 11.1-15.0) (P < 0.001). A higher proportion of deaths in extreme brachycephalic breed types were associated with URT disorders (4/24 deaths, 16.7 %) compared with the moderate and non-brachycephalic group (0/59 deaths, 0.0 %) (P = 0.001). The prevalence of having at least one URT disorder in the extreme brachycephalic group was higher (22.0 %, 95 % confidence interval (CI): 18.0-26.0) than in the moderate and non-brachycephalic group (9.7 %, 95 % CI: 7.1-12.3, P < 0.001). The prevalence of URT disorders varied significantly by breed type: Bulldogs 19.5 %, French Bulldogs 20.0 %, Pugs 26.5 %, Border Terriers 9.0 %, West Highland White Terriers 7.0 % and Yorkshire Terriers 13.0 % (P < 0.001). After accounting for the effects of age, bodyweight, sex, neutering and insurance, extreme brachycephalic dogs had 3.5 times (95 % CI: 2.4-5.0, P < 0.001) the odds of at least one URT disorder compared with the moderate and non-brachycephalic group. Conclusions: In summary, this study reports that URT disorders are commonly diagnosed in Bulldog, French Bulldog, Pug, Border Terrier, WHWT and Yorkshire Terrier dogs attending primary-care veterinary practices in England. The three extreme brachycephalic breed types (Bulldog, French Bulldog and Pug) were relatively short-lived and predisposed to URT disorders compared with three other small-to-medium size breed types that are commonly owned (moderate brachycephalic Yorkshire Terrier and non-brachycephalic: Border Terrier and WHWT)."