Page 307 - Small Animal Internal Medicine, 6th Edition

CHAPTER 18 Disorders of the Larynx and Pharynx 279

outcome following surgical intervention was not related to
presurgical esophageal dysfunction. In this study, 232 dogs
VetBooks.ir that underwent unilateral lateralization procedures had 1-,
2-, 3-, and 4-year survival rates of 94%, 89%, 84%, and 75%,
respectively. These numbers are quite positive, particularly
considering the median age and body weights of these dogs
were 10.6 years and 35 kg. At 1-, 3-, and 4-year follow-up,
aspiration pneumonia occurred in 19%, 32%, and 32% of
dogs. Risk factors for aspiration pneumonia were postopera-
tive megaesophagus and postoperative administration of
opioid analgesics before discharge. In contrast to previously
held conventional wisdom, preoperative aspiration pneumo-
nia was not a negative prognostic indicator. A good progno- A
sis was reported for a small number of cats undergoing
unilateral arytenoid lateralization (Thunberg et al., 2010).

BRACHYCEPHALIC AIRWAY SYNDROME

The term brachycephalic airway syndrome, or brachycephalic
airway obstruction syndrome (BOAS), refers to the multiple
anatomic abnormalities commonly found in brachycephalic
dogs and, to a lesser extent, in short-faced cats such as Hima-
layans. The predominant, readily identified, anatomic abnor-
malities include stenotic nares, elongated soft palate, and, in
Bulldogs, hypoplastic trachea. However, with the common
use of computed tomography and rhinoscopy, it is now
known that abnormal, obstructing nasal turbinates contrib- B
ute significantly to the breathing abnormalities of dogs with
this conformation (Oechtering, 2010; Oechtering et al., FIG 18.1
Two Bulldog puppies (A) and a Boston Terrier (B) with
2016). Prolonged upper airway obstruction resulting in brachycephalic airway syndrome. Abnormalities can include
increased inspiratory efforts may lead to eversion of the stenotic nares, elongated soft palate, everted laryngeal
laryngeal saccules and, ultimately, to laryngeal collapse (see saccules, laryngeal collapse, and hypoplastic trachea.
Fig. 17.5). The severity of these abnormalities varies, and one Abnormal nasal turbinate development contributes
or any combination of these abnormalities may be present in significantly to obstruction.
any given brachycephalic dog or short-faced cat (Fig. 18.1).
Concurrent gastrointestinal signs such as ptyalism, regur-
gitation, and vomiting are common in dogs with brachyce-
phalic airway syndrome (Poncet et al., 2005) Underlying As a result, some dogs may be presented with life-threatening
gastrointestinal disease may be a concurrent problem in upper airway obstruction that requires immediate emer-
these breeds of dogs or may result from or may be exacer- gency therapy. Concurrent gastrointestinal signs are com-
bated by increased intrathoracic pressures generated in monly reported.
response to the upper airway obstruction.
Diagnosis
Clinical Features A tentative diagnosis is made on the basis of breed, clinical
Abnormalities associated with the brachycephalic airway signs, and appearance of the external nares (Fig. 18.2). Ste-
syndrome impair the flow of air through the extrathoracic notic nares are generally bilaterally symmetric, and the alar
(upper) airways and cause clinical signs of upper airway folds may be sucked inward during inspiration, thereby
obstruction, including loud breathing sounds, stertor, worsening the obstruction to airflow. Laryngoscopy (see
increased inspiratory efforts, cyanosis, and syncope. Clinical Chapter 17) and radiographic evaluation of the trachea (see
signs are exacerbated by exercise, excitement, and high envi- Chapter 20) are necessary to fully assess the extent and sever-
ronmental temperatures. The increased inspiratory effort ity of abnormalities. Computed tomography and rhinoscopy
commonly associated with this syndrome may cause second- would be required to fully assess the turbinates; however,
ary edema and inflammation of the laryngeal and pharyn- availability of treatment by laser turbinectomy is currently
geal mucosae and may enhance eversion of the laryngeal limited. Most other causes of upper airway obstruction (see
saccules or laryngeal collapse, further narrowing the glottis, Chapter 25 and Boxes 16.1 and 16.2) can also be ruled in or
exacerbating the clinical signs, and creating a vicious cycle. out on the basis of the results of these diagnostic tests.