Laryngeal disorders are characterized by stridor and can often lead to death if untreated. Depending on the specific condition, medical or surgical treatment may be indicated, and emergency tracheostomy may be necessary in cases of severe airway impairment. Presumptive diagnosis is largely based on clinical signs; definitive diagnosis is based on direct or endoscopic examination of the larynx.
Laryngitis, inflammation of the laryngeal mucosa or cartilages, may result from upper respiratory tract infection or direct irritation from inhalation of dust, smoke, or irritating gas; foreign bodies; or the trauma of intubation, excess vocalization, or injury from roping or restraint devices (in production animals).
Laryngitis can accompany a variety of diseases in animals:
infectious tracheobronchitis and distemper in dogs
infectious rhinotracheitis and calicivirus infection in cats
infectious rhinotracheitis and calf diphtheria in cattle
strangles, herpesvirus 1 infection, viral arteritis, and infectious bronchitis in horses
Fusobacterium necrophorum and Trueperella pyogenes infections in sheep
Edema of the mucosa and submucosa is often an integral part of laryngitis, and if edema is severe, the rima glottidis may be obstructed. Edema may also result from allergy, inhalation of irritants, or surgery in the area. Intubation, especially when attempted with inadequate induction or poor technique, is likely to provoke laryngeal edema.
Brachycephalic and obese dogs and dogs with laryngeal paralysis develop laryngeal edema and laryngitis through severe panting or respiratory effort during excitement or hyperthermia. In cattle, laryngeal edema has been observed in blackleg, urticaria, serum sickness, and anaphylaxis. In pigs, it may develop as a part of edema disease.
Laryngeal chondropathy is a suppurative condition of the cartilage matrix that principally affects the arytenoid cartilages; it is believed to result from microbial infection, often as a sequela of inhalation of irritants or trauma to the area. In herbivores, trauma can occur when administering medications by bolus or drench or by ingestion of rough foodstuffs; in dogs, trauma can occur from sticks or foreign bodies.
Laryngeal chondropathy is characterized by necrosis and ulceration of the laryngeal mucosa (over or just caudal to the vocal cords) and abscessation within the arytenoid cartilage. Acute laryngeal inflammation is often present initially. Later, progressive enlargement of the cartilages commonly results in a fixed upper airway obstruction (present on inhalation and exhalation) with audible noise when breathing and decreased exercise tolerance.
Laryngeal chondropathy occurs in horses, sheep, and cattle, most often in young males. Texel sheep and Belgian Blue cattle are predisposed to the condition. Laryngeal contact ulcers are common in young feedlot cattle and often result in necrotic laryngitis and chondropathy.
Clinical Findings of Laryngeal Disorders in Animals
A cough is the principal clinical sign of laryngitis when edema is slight and the deeper laryngeal tissues are not involved. The cough is harsh, dry, and short at first but becomes soft and moist later and may be very painful. It can be induced by pressure on the larynx, exposure to cold or dusty air, swallowing coarse food or cold water, or attempts to administer medicines.
Vocal changes may be evident, especially in small animals. Stridor may result from swelling and decreased motion of the arytenoid cartilages in laryngeal chondropathy. Halitosis and difficult, noisy breathing may be evident, and the animal may stand with its head lowered and mouth open. Swallowing is difficult and painful.
Systemic clinical signs are usually attributable to the primary disease, as in infectious bovine rhinotracheitis, in which fevers of 40.5°C (105°F) may occur. Secondary systemic clinical signs due to inappetance and dehydration rapidly become apparent. Death due to asphyxiation may occur, especially if the animal has exerted itself.
Laryngeal edema, characterized by increased inspiratory effort and stridor, may develop within hours. Respiratory rate may slow as the effort of breathing becomes exaggerated. Visible mucous membranes are cyanotic, pulse rate increases, and body temperature rises. Horses may sweat profusely. Dogs with obstructions of the conducting airways (which warm and moisten air as it moves to the lungs) may show extreme disturbance of thermoregulation in hot weather; marked hyperthermia is not uncommon. Untreated animals with marked obstruction eventually collapse and often have clinical signs of pulmonary edema.
Diagnosis of Laryngeal Disorders in Animals
Clinical signs
Laryngoscopy
Tentative diagnosis of a laryngeal disorder is based on clinical signs, auscultation of the laryngeal region, and exacerbation of stridor by laryngeal palpation.
Definitive diagnosis requires laryngoscopy. In conscious horses and cattle, a flexible endoscope is passed per nasum, usually following sedation. In dogs and cats, anesthesia or analgesia is typically required. The patient's history and clinical signs usually permit rapid identification of the primary disease and associated laryngeal involvement.
Bilateral laryngeal paralysis, laryngeal abscess, pharyngeal trauma and cellulitis, and retropharyngeal abscesses or masses can cause similar clinical signs.
Treatment of Laryngeal Disorders in Animals
Steroids or NSAIDs
Avoidance of exertion and stress
+/- Antimicrobials
+/- Surgery
Identification and treatment of the primary disease are essential when treating a laryngeal disorder. In laryngeal obstruction, a tracheostomy tube should be placed immediately; if this is not possible, airway patency may be established by passing a pliable tube through the glottis.
Corticosteroids should be administered to decrease the obstructive effect of inflammatory swellings. Concurrent administration of systemic antimicrobials is also necessary. When corticosteroids cannot be used, NSAIDs can be given. Administration of diuretic drugs (eg, furosemide) may be indicated to resolve laryngeal edema and, if present, pulmonary edema.
Palliative procedures to speed recovery and give comfort include inhalation of humidified air; confinement in a warm, clean environment; feeding soft or liquid foods; and avoiding dust. Coughing may be suppressed with antitussive preparations and bacterial infections controlled with antimicrobials. Control of pain with judicious analgesic use, especially in cats, allows the animal to eat and thus speeds recovery.
Arytenoidectomy is an effective remedy for laryngeal chondropathy of horses.
Tracheolaryngostomies and permanent tracheostomies have been used successfully to salvage cattle and sheep with laryngeal chondropathy; however, these procedures carry substantial anesthetic risk. A medical alternative for ruminants is prolonged antimicrobial therapy with an antimicrobial able to penetrate cartilage, such as florfenicol (40 mg/kg, SC, in the neck, once; may need to repeat in 3–4 days) or tulathromycin (2.5 mg/kg, SC, once; may need to repeat in 4–5 days), plus initial, short-acting corticosteroids such as dexamethasone (0.2–0.5 mg/kg, IV or IM, every 24 hours for 3–5 days).
Key Points
Laryngeal disorders need rapid treatment, including recognition and treatment of the underlying problem.
Direct examination of the larynx is required for definitive diagnosis, using a laryngoscope or endoscope.
Anti-inflammatory medications are important aspects of treatment.
