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Chapter 19: Brachycephalic Syndrome

Chapter 19: Table of Contents

Brachycephalic Syndrome

Brachycephalic airway syndrome (BAS) includes a variety of primary and secondary abnormalities that result in upper airway obstruction.  Primary abnormalities include stenotic nares, elongated soft palate and hypoplastic trachea.  The increased negative pressure that develops because of the primary abnormalities leads to secondary abnormalities that include everted laryngeal saccules, everted tonsils, pharyngeal and soft palate edema / hyperplasia and possibly mild or severe laryngeal collapse.

Most commonly affected breeds include French and English Bulldogs, Boston Terrier, Pug, Shih-Tzu and Lhasa apso as well as larger breeds including Boxers, Shar-pei and mastiffs.  Clinical signs associated with BAS include stridorous breathing, increased inspiratory noise and dyspnea, increased respiratory effort, exercise intolerance, vomiting and regurgitation, excessive salivation and in severe cases collapse / syncope.  Excess stress, exercise as well as heat and humidity frequently make clinical signs worse, and may lead to an emergency situation.

Medical management may include cage rest, sedation, oxygen supplementation, and use of steroid antiinflammatories.  Limiting exercise, promoting weight loss and ensuring a cool environment is recommended and may be helpful in less affected patients but is rarely successful in patients with more severe signs.

Dogs of predisposed breeds should ideally be assessed for primary abnormalities at a young age (as early as 3-4 months of age for stenotic nares and between 4 and 24 months for elongated soft palate) and prior to developing clinical symptoms in order to prevent or reduce the development of secondary abnormalities that may be irreversible.  At this young age, stenotic nares can be corrected and the palate assessed for length.  If saccules are already everted they should be resected at this time.  If not treated at a young age, dogs will present at any age with moderate to severe signs of upper airway obstruction and sometimes as an emergency.  Though surgery is recommended at an early age to prevent or reduce secondary changes, advanced age is not a contraindication to treatment.

Presumptive diagnosis is often based on client reports, breed predisposition and suspicion.  A physical examination can determine the presence of stenotic nares but a sedated airway exam is necessary to assess the palate and saccules.  Hypoplastic trachea can be diagnosed by palpation and radiography.  Thoracic radiographs will also serve to assess the cardiac silhouette, the presence of hiatal hernia and rule-out concurrent aspiration pneumonia.  Current recommendation is to initiate treatment with a promotility agent (we use metroclopramide 0.5mg/kg and maropitant) and to continue these into the postoperative period in all patients but especially those with a history of gagging, retching, and regurgitation. 

Oropharyngeal examination is performed under heavy sedation or general anesthesia.  One should assess laryngeal function at induction but laryngeal paralysis is not typically an issue in dogs with BAS unless secondary changes such as laryngeal collapse are suspected (older, more severely affected dogs).  Examination is typically performed prior to intubation.  I typically first assess for everted saccules, I note the position of the tonsils and then determine whether or not the soft palate is elongated.  Positioning is quite important when assessing soft palate length and one wants to ensure the dog’s head is straight and that the tongue is not pulled out (as is often the case when using a laryngoscope).   Using a mouth gag and suspending the dog by the maxilla may help ensure that the tissues lie in their natural position. (Lodato et al. 2014)  The saccules sit just rostral to the vocal cord within their respective crypts.  If everted, the saccules will appear as glistening light pink to white, edematous, oval structures located just rostral to, and somewhat obscuring the vocal cord.   Both saccules are typically everted.  An elongated soft palate extends at least a few mm but typically more than one cm beyond the tip of the epiglottis.   The elongated soft palate of older dogs is often thick and inflamed.  The tonsils normally sit within the tonsilar crypts but may be inflamed, enlarged or even everted in dogs with BAS.  Dogs with laryngeal edema, pharyngeal hyperplasia and laryngeal collapse are best treated by a board certified surgeon and should be referred to a facility with 24h care for postoperative recovery. 

Once I have assessed the patient for all abnormalities, I typically begin by resecting the everted laryngeal saccules and then proceed to intubate the patient.  Once intubated, I proceed with staphylectomy if indicated and then finish with the nare resection.  

Withholding non-steroidal analgesic (NSAID) treatment is always wise after BAS surgery to allow for use of steroids, if required, upon recovery.  Once I have confirmed that the patient has recovered well enough from anesthesia and seems to be doing well, I administer an NSAID (*if steroids were not administered prior to presentation).  I also administer a dose of antibiotics (typically ampicillin @ 22mg/kg) perioperatively, typically prior to cutting the tissues.

Reference
Lodato D, Mauterer J.  Techniques for performing corrective surgery: Dogs with brachycephalic airway syndrome.  Today’s Vet Practice Jan/Feb 2014:78-83.

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