What does brachycephalic mean?
Brachy means shortened and cephalic means head. Brachycephalic cats have skull bones that are shortened in length, giving the face and nose a pushed-in appearance.
The shorter bones of the face and nose alter the related soft tissue structures they support. Some of these changes can cause physical problems, particularly with breathing. Persian, Himalayan, and Burmese cats are the most well-recognized brachycephalic cat breeds.
What is brachycephalic obstructive airway syndrome (BOAS)?
Brachycephalic obstructive airway syndrome (BOAS) refers to a particular set of upper airway abnormalities that affect brachycephalic cats and dogs. This syndrome is also called brachycephalic respiratory syndrome, brachycephalic syndrome, brachycephalic airway syndrome (BAS), and congenital obstructive upper airway disease.
The upper airway abnormalities that occur in this syndrome may include one or more of the following:
- Stenotic nares. Stenotic nares are abnormally narrowed or small nostrils that restrict the amount of air that can flow through the nostrils to the lungs.
- Elongated soft palate. The soft palate is the soft part of the roof of the mouth. An elongated soft palate is too long for the length of the mouth; the excess length partially blocks the entrance to the trachea (windpipe) at the back of the throat. An elongated soft palate and stenotic nares are the most common abnormalities in brachycephalic cats.
- Everted laryngeal saccules. The laryngeal saccules are small sacs or pouches that are part of the larynx (voice box). A cat with BOAS must work harder to breathe, causing increased pressure in the airway, which in turn can cause the laryngeal saccules to evert (turn outwards) or get sucked into the airway. Everted laryngeal saccules will further obstruct airway flow.
- Hypoplastic trachea. A hypoplastic trachea is a trachea (windpipe) with a smaller diameter than normal.
What other problems can occur due to BOAS?
BOAS has been linked to changes in the lungs, gastrointestinal tract, teeth, eyes, and skin.
- If facial conformation is severely affected, it can impact brain development and cognitive function.
- Affected cats may experience vomiting and regurgitation if they develop a hiatal hernia secondary to the negative airway pressure.
- Teeth are often not lined up properly (malocclusion), and affected cats may have an underbite, both of which can lead to significant dental issues.
- Eyes often have abnormalities, such as chronic tearing and tear staining due to face conformation.
- Skin infections can occur in the folds around the nose.
What are the signs of BOAS?
Any upper airway abnormalities can cause increased airway resistance, which increases the effort required to inhale. The more abnormalities are present, the more severe the signs are. Most cats with this syndrome breathe more easily through their mouth than their nose, so the most common sign seen with this syndrome is mouth breathing.
Mildly affected cats will make some increased noise when they breathe, or they may snore when they are relaxed or sleeping. Severely affected cats have more pronounced airway noise, appear to tire easily with exertion, and may collapse or faint after playing or exercising. Occasionally, affected cats will have other signs, such as coughing, gagging, retching, or vomiting. Signs are often worse in hot or humid weather.
Over time, severely affected cats may develop other problems, including inflammation of other structures in the airways. In the long term, the increased effort associated with breathing can put increased strain on the heart.
How is BOAS diagnosed?
This syndrome will be diagnosed based on your cat's breed, clinical signs, and results of a physical examination. Stenotic nares can usually be diagnosed with visual inspection. Diagnosis of an elongated soft palate, everted laryngeal saccules, or other associated anatomical changes within the mouth will require heavy sedation or full general anesthesia.
Since cats with this syndrome have an increased risk of complications associated with general anesthesia, your veterinarian will recommend pre-anesthetic blood work and chest X-rays to evaluate your cat’s general health prior to the diagnostic procedure. If your cat undergoes general anesthesia to diagnose this condition, your veterinarian will likely recommend that any necessary surgical correction be performed at the same time.
What is the treatment for BOAS?
Obesity worsens the symptoms of BOAS, so weight loss is an important part of treatment if your cat is overweight. For cats with mild or intermittent symptoms, the condition may be managed conservatively by controlling exercise levels, avoiding hot or humid conditions, keeping the cat in an air-conditioned area during the summer, and avoiding stress.
Corticosteroids, nonsteroidal anti-inflammatory drugs (NSAIDs), and oxygen therapy may all be useful for short-term relief of airway inflammation or respiratory distress. However, medical management of this condition does not correct the underlying anatomical abnormalities.
Surgery is the treatment of choice whenever the anatomical abnormalities interfere with a cat’s breathing. Stenotic nares can be surgically corrected by removing a wedge of tissue from the nostrils, allowing improved airflow through the nostrils. An elongated soft palate can be surgically shortened to a more normal length. Everted laryngeal saccules can be surgically removed to eliminate the obstruction in the larynx. These procedures may be best performed at a referral center with a board-certified surgeon.
How successful is surgery?
The earlier that abnormalities are corrected, the better the outcome, since the condition worsens over time and may cause other abnormalities. Early correction of stenotic nares and/or an elongated soft palate will significantly improve airway function and may prevent the development of everted laryngeal saccules. In the early post-operative period, the surgical sites may swell and interfere with breathing, so your veterinarian will closely monitor your pet after surgery. The degree of monitoring necessary depends on the surgical procedures that were performed.
What is the prognosis for a cat with BOAS?
The overall prognosis for cats with BOAS depends on how many anatomic abnormalities are present and how old your cat is at the time of diagnosis and treatment.
Cats that only require surgical correction for stenotic nares and/or an elongated soft palate have a better prognosis than cats with more defects. Cats with hypoplastic trachea have a variable prognosis. Cats that have other problems, such as allergic airway disease, or that have developed secondary problems from airway distress, have a poorer prognosis. However, appropriate management can significantly improve the quality of life for these cats.
What else can I do to help my cat with BOAS?
This syndrome is directly related to the conformation or breed standard for brachycephalic cats. Cats with pronounced breathing difficulty or cats that require surgery to correct airway obstruction should not be used for breeding. It is usually recommended that these cats be spayed or neutered at the same time as surgical correction is performed. Unfortunately, this syndrome has been perpetuated by selecting and breeding cats for their cosmetic appearance rather than their breathing abilities.
