Canine Laryngeal Paralysis Study Guide

Overview and Clinical Importance

Laryngeal paralysis (LP) is a common and potentially life-threatening upper airway disorder in dogs characterized by failure of the arytenoid cartilages to abduct during inspiration. This condition results from dysfunction of the recurrent laryngeal nerve, leading to denervation of the cricoarytenoideus dorsalis (CAD) muscle, the only muscle responsible for opening the glottis. The resultant airway obstruction causes characteristic clinical signs including inspiratory stridor, exercise intolerance, dysphonia, and in severe cases, respiratory distress and cyanosis.

Understanding laryngeal paralysis is essential for the NAVLE as it represents a frequently tested topic that integrates knowledge of neuroanatomy, clinical recognition, diagnostic procedures, and surgical management. The condition is most commonly seen in geriatric large-breed dogs and is increasingly recognized as part of a broader systemic polyneuropathy called Geriatric Onset Laryngeal Paralysis Polyneuropathy (GOLPP).

Anatomy and Neuroanatomy

Laryngeal Structure

The larynx is a semi-rigid organ composed of hyaline cartilage and muscles that connects the pharynx to the trachea. The key cartilaginous structures include the epiglottic cartilage (rostral), thyroid cartilage (lateral walls), cricoid cartilage (complete ring caudally), and the paired arytenoid cartilages. Each arytenoid cartilage has four processes: the cuneiform process (rostral), corniculate process (dorsal), vocal process (attaches to vocal fold), and muscular process (attachment point for CAD muscle).

The glottis is formed by the paired vocal folds attached to the vocal processes of the arytenoid cartilages and the rima glottidis (glottic cleft). The larynx performs two critical functions: protecting the lower airway during swallowing by closing the glottis, and allowing airflow during respiration by opening the glottis.

Innervation

The recurrent laryngeal nerve (a branch of the vagus nerve, CN X) provides motor innervation to all intrinsic laryngeal muscles except the cricothyroideus muscle (innervated by the cranial laryngeal nerve). The terminal portion of the recurrent laryngeal nerve is called the caudal laryngeal nerve.

Key anatomical point: The left recurrent laryngeal nerve is significantly longer than the right, as it loops around the aortic arch before ascending to the larynx, while the right recurrent laryngeal nerve loops around the right subclavian artery. This asymmetry explains why the left side is often affected first in acquired forms.

Intrinsic Laryngeal Muscles

Etiology and Classification

Congenital Laryngeal Paralysis

Congenital forms are uncommon and typically present before 1 year of age. An inherited polyneuropathy with autosomal dominant inheritance has been documented in certain breeds. Clinical signs appear in puppies between 2-6 months of age.

Acquired Laryngeal Paralysis

Acquired LP is the most common form and typically affects middle-aged to geriatric large and giant breed dogs. The median age of onset is 10-12 years. Males may be slightly overrepresented.

Causes of Acquired Laryngeal Paralysis

Breed Predispositions for Acquired LP

Labrador Retriever (most common), Golden Retriever, St. Bernard, Newfoundland, Irish Setter, English Setter, Great Dane, and Afghan Hound. Any large or giant breed dog can be affected.

Geriatric Onset Laryngeal Paralysis Polyneuropathy (GOLPP)

Research has revealed that most dogs with acquired idiopathic laryngeal paralysis have a progressive, generalized polyneuropathy rather than isolated laryngeal nerve dysfunction. This condition is termed GOLPP and represents a slowly progressive degeneration of multiple peripheral nerves.

Three Components of GOLPP

• Laryngeal Paralysis: Usually the first and most obvious sign; affects the recurrent laryngeal nerves leading to CAD muscle dysfunction
• Esophageal Dysfunction: Approximately 70% of dogs with idiopathic LP have concurrent esophageal dysfunction; may progress to megaesophagus
• Hindlimb Weakness: Generalized polyneuropathy leads to pelvic limb weakness, muscle atrophy, proprioceptive deficits; develops within 1-2 years of LP diagnosis

"The 3 Ls of GOLPP": Larynx (paralysis), Lumen (esophageal dysfunction), and Legs (hindlimb weakness)

Clinical Signs

Clinical signs develop gradually and may be initially subtle. Owners often attribute early signs to "slowing down with age." Signs worsen with exercise, excitement, stress, and exposure to hot/humid environments.

Diagnosis

Physical Examination Findings

• Inspiratory stridor audible from a distance; "loud machinery" sound on laryngeal auscultation
• Increased respiratory effort; anxious facial expression; prominent eyes
• Lips pulled back ("smiling") when panting; tongue hanging out
• Complete neurological examination - assess for concurrent polyneuropathy (hindlimb weakness, proprioceptive deficits, muscle atrophy)

Diagnostic Workup

Laryngoscopic Examination (Gold Standard)

Direct visualization of the larynx under light sedation is required for definitive diagnosis. The key is to achieve a plane of sedation that allows examination while preserving laryngeal reflexes.

Technique

• Position: ventral recumbency with head elevated
• Sedation: Propofol, thiopental, or ketamine-diazepam titrated to light plane; avoid deep sedation which can abolish normal laryngeal function
• Use laryngoscope or flexible endoscope to visualize larynx
• Assistant calls out "in" and "out" with respiratory phases to correlate arytenoid movement
• Doxapram (1-2 mg/kg IV) may be administered to stimulate respiratory effort and enhance arytenoid movement assessment

Laryngoscopic Findings

• Normal: Arytenoid cartilages ABDUCT (open) during inspiration; ADDUCT during expiration
• Laryngeal paralysis: Arytenoids remain in paramedian position; may show PARADOXICAL MOTION (adduct during inspiration due to negative airway pressure)
• Laryngeal edema and mucosal erythema are often present

Radiographic Findings

In one study, 70% of dogs with laryngeal paralysis had abnormal thoracic radiographs:

• Megaesophagus: 20%
• Bronchopneumonia/aspiration pneumonia: 15%
• Tracheal abnormalities: 20%

Aspiration pneumonia: Typically presents with alveolar pattern (air bronchograms) in cranioventral lung lobes; right middle and right cranial lobes most commonly affected.

Treatment

Emergency Stabilization

Dogs presenting in respiratory crisis require immediate stabilization before any diagnostic procedures:

• Minimize stress: Place in cool, quiet environment; avoid excessive handling
• Oxygen therapy: Flow-by, mask, oxygen cage
• Cooling: If hyperthermic (greater than 40 degrees Celsius), active cooling with cool water, fans, IV fluids
• Sedation: Acepromazine (0.01-0.05 mg/kg IV/IM) or butorphanol to reduce anxiety and decrease respiratory effort
• Anti-inflammatory: Dexamethasone (0.1-0.2 mg/kg IV) to reduce laryngeal edema
• Intubation: If not responding, may require induction and intubation
• Temporary tracheostomy: In severe cases for emergency airway access

Conservative (Medical) Management

Appropriate for mild cases or when surgery is not an option:

• Weight management (obesity worsens signs)
• Avoid hot/humid environments and strenuous exercise
• Use harness instead of collar
• Mild sedatives (acepromazine, trazodone) for anxiety-prone dogs
• Anti-inflammatory medications as needed

Surgical Treatment

Surgery is the definitive treatment for moderate to severe laryngeal paralysis. The goal is to permanently widen the glottis to reduce airway resistance while minimizing aspiration risk.

Unilateral Arytenoid Lateralization (Tieback) - Key Points

• Lateral approach through 3-4 inch neck incision
• Suture(s) placed from muscular process of arytenoid to caudodorsal cricoid cartilage
• Unilateral only - provides adequate glottic widening while minimizing aspiration risk
• Left side typically chosen (easier for right-handed surgeons; leaves right side as backup)
• Avoid overtightening - excessive lateralization increases aspiration risk

Complications

Aspiration Pneumonia

The most common and serious complication, occurring in 8-25% of dogs post-UAL. Can occur at any time after surgery (perioperatively or years later). Risk is lifelong.

Risk Factors for Aspiration Pneumonia

• Pre-existing megaesophagus or esophageal dysfunction
• Excessive lateralization of arytenoid
• Concurrent neurological disease
• Bilateral procedures

Clinical Signs of Aspiration Pneumonia

• Inappetence and lethargy (earliest signs)
• Productive cough
• Fever
• Increased respiratory rate and effort
• Abnormal lung sounds (crackles, harsh sounds)

Radiographic Signs

Alveolar pattern (air bronchograms) with cranioventral distribution; right middle lobe, right cranial lobe, and left cranial lobe most commonly affected.

Other Surgical Complications

Prognosis

• Post-UAL surgery: 88-90% of dogs show significant improvement in quality of life
• Client satisfaction: High; owners report dogs are "young again" after surgery
• GOLPP progression: Slow; many dogs maintain good quality of life for years after surgery despite underlying polyneuropathy
• Congenital forms: Guarded to poor; progressive neurodegeneration limits long-term survival

Postoperative Care and Client Education

Immediate Postoperative Period

• Keep calm and minimize excitement for 2-3 weeks
• Short leash walks only; use harness, not collar
• Sedatives (trazodone, acepromazine) may be needed to prevent barking

Feeding Modifications

• Small, frequent meals
• Consider elevated food/water bowls
• Some dogs do better with "meatball" feeding (hand-formed soft food)
• Avoid dry kibble if gagging is problematic

Lifelong Precautions

• Avoid swimming - water can easily enter the open airway
• Monitor for signs of aspiration pneumonia indefinitely
• Avoid overheating
• Maintain healthy body weight

"LAR PAR TIEBACK" L - Labrador (and large breeds most common) A - Arytenoid paralysis R - Recurrent laryngeal nerve dysfunction P - Polyneuropathy often underlying (GOLPP) A - Abduction failure R - Respiratory distress in crisis T - Tieback surgery is treatment of choice I - Inspiratory stridor is hallmark sign E - Emergency if cyanotic B - Beware aspiration pneumonia A - Avoid hot weather and excitement C - Cannot swim after surgery K - Keep calm postoperatively