Page 52 - Problem-Based Feline Medicine

44 PART 1 CAT WITH UPPER RESPIRATORY TRACT SIGNS

Neoplasia, affecting either the innervation of the larynx Dynamic causes of upper respiratory tract obstruction are:
(i.e., thyroid adenocarcinoma) or affecting the laryn- ● Brachycephalic airway syndrome (elongated soft
geal structures directly (i.e., squamous cell carcinoma) palate, lateral ventricle eversion).
can create laryngeal paralysis. ● Cervical tracheal collapse.
● Pyogranulomatous or lymphoplasmacytic laryngitis.
Parasitic involvement of the larynx and lead poisoning
are very rare associations. Other causes of fixed upper respiratory tract obstruc-
tion include:
Percutaneous ultrasound-guided radiofrequency heat
● Oropharyngeal neoplasia (SCC, oral melanoma,
ablation and ethanol injections for treatment of hyperthy-
nasopharyngeal polyp).
roidism in cats are both recent procedures, and laryngeal
● Tracheal neoplasia (intraluminal adenocarcinoma,
paralysis was a reported side effect of both.
extraluminal masses).
● Tracheal foreign bodies.
Clinical signs
Inspiratory dyspnea, tachypnea. Treatment
Stridor, worse with excitement or exercise. Correction of the underlying cause of the neuropathy is
rarely possible.
Occasional stertor.
Surgical intervention is generally required for bilat-
Voice changes (absent or whisper-like meow), harsh
eral disease.
purring sounds.
● Laryngeal tie-back surgery (arytenoid lateraliza-
Dysphagia and weight loss. tion) is recommended by most surgeons, although
other techniques are described. Success is directly
correlated with skill of the operator.
Diagnosis
In emergency respiratory distress, temporary tra-
Diagnosis is based on clinical signs of laryngeal stridor
cheostomy may be required.
and inspiratory dyspnea.
Laryngoscopic inspection under heavy sedation or Prognosis
light anesthesia with a rigid laryngoscope and blade
Generally good to excellent long-term prognosis with
reveals absent or paradoxical motion of the arytenoid
successful surgery.
cartilages. Normally they should abduct on inspiration.
If they close on inspiration, it is paradoxical motion.
Prevention
One retrospective study of 16 cases revealed 12 to be
None known.
bilateral, and four to be unilateral.
Erythema and swelling of the arytenoid mucosa (“kiss-
TRACHEOBRONCHIAL COLLAPSE
ing lesions”) may be evident from the repetitive trauma
at the contact surfaces.
Classical signs
Low-dose ketamine (4–6 mg/kg IV), ketamine/
● Harsh, honking cough.
diazepam (3–5 mg/kg/0.1–0.2 mg/kg IV) or propofol
● Stridor on inspiration if cervical segment
(4–6 mg/kg IV) allows visual inspection without dimin-
involved.
ishing laryngeal function.
● Very rare in cats.
Differential diagnosis
Clinical signs
Other causes of dynamic or fixed upper respiratory
tract obstruction are distinguished on laryngoscopic Tracheobronchial collapse is very rare in cats and
inspection. generally occurs secondary to trauma or to com-