Page 299 - Small Animal Internal Medicine, 6th Edition

CHAPTER 16
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Clinical Manifestations

of Laryngeal and

Pharyngeal Disease

CLINICAL SIGNS inhalation of air more difficult. During expiration, pressures
are positive in the extrathoracic airways, “pushing” the soft
LARYNX tissues open. Nevertheless, expiration may not be effortless.
Regardless of the cause, diseases of the larynx result in Some obstruction to airflow may occur during expiration
similar clinical signs, most notably respiratory distress and with fixed obstructions, such as laryngeal masses. Even with
stridor. Gagging or coughing may also be reported. Voice the dynamic obstruction that results from laryngeal paraly-
change is specific for laryngeal disease, though not always sis, in which expiration should be possible without any
present. Clients may volunteer that they have noticed a blockage of flow, resultant laryngeal edema and inflamma-
change in the dog’s bark or the cat’s meow, but specific ques- tion can interfere with normal expiration. On auscultation,
tioning may be necessary to obtain this important informa- referred upper airway sounds are heard and lung sounds are
tion. Localization of disease to the larynx can generally be normal to increased.
achieved with a good history and physical examination. A Stridor, a high-pitched wheezing sound, is typically heard
definitive diagnosis is made through a combination of laryn- predominantly during inspiration. It is audible without a
geal radiography, laryngoscopy, and laryngeal biopsy. Fluo- stethoscope, although auscultation of the neck may aid in
roscopy and computed tomography (CT) can be useful for identifying mild disease. Stridor is produced by air turbu-
dynamic disease and improved imaging of mass lesions or lence through the narrowed laryngeal opening. Narrowing
anatomic abnormalities, respectively. of the extrathoracic trachea less commonly produces stridor,
Respiratory distress resulting from laryngeal disease is more often producing a coarse stertorous sound.
due to airway obstruction. Although most laryngeal diseases When patients are not presented for respiratory distress
are progressive over several weeks to months, animals fre- (e.g., patients with exercise intolerance or voice change), it
quently present in acute distress. Dogs and cats seem to be may be necessary to exercise the patient to identify the char-
able to compensate for their disease initially through self- acteristic breathing pattern and stridor associated with
imposed exercise restriction. Often an exacerbating event laryngeal disease (Video 16.1).
occurs, such as exercise, excitement, or high ambient tem- Some patients with laryngeal disease, particularly those
perature, resulting in markedly increased respiratory efforts. whose laryngeal paralysis is an early manifestation of more
These increased efforts lead to excess negative pressures on diffuse neuromuscular disease or those presenting with dis-
the diseased larynx, sucking the surrounding soft tissues into tortion of normal laryngeal anatomy, have subclinical aspira-
the lumen and causing laryngeal inflammation and edema. tion or overt aspiration pneumonia resulting from the loss
Obstruction to airflow becomes more severe, leading to even of normal protective mechanisms. Patients may show clinical
greater respiratory efforts (Fig. 16.1). The airway obstruction signs reflecting aspiration, such as cough, lethargy, anorexia,
can ultimately be fatal. fever, tachypnea, and abnormal lung sounds. (See Chapter
A characteristic breathing pattern can often be identified 22 for a discussion of aspiration pneumonia.)
on physical examination of patients in distress from extra-
thoracic (upper) airway obstruction, such as that resulting PHARYNX
from laryngeal disease (see Chapter 25). The respiratory rate Space-occupying lesions of the pharynx can cause signs of
is normal to only slightly elevated (often 30-40 breaths/min), upper airway obstruction as described for the larynx, but
which is particularly remarkable in the presence of overt overt respiratory distress occurs only with advanced disease.
distress. Inspiratory efforts are prolonged and labored, rela- More typical presenting signs of pharyngeal disease include
tive to expiratory efforts. The larynx tends to be sucked into stertor, reverse sneezing, gagging, retching, and dysphagia.
the airway lumen as a result of negative pressure within the Stertor is a loud, coarse sound such as that produced by
extrathoracic airways that occurs during inspiration, making snoring or snorting. Stertor results when excessive soft tissue

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