Disorders of the Equine Head and Neck: Larynx and Pharynx.

Overview

• This article provides a detailed review of diseases affecting the larynx and pharynx in horses, focusing on their anatomy, diagnosis, causes, treatment, and expected outcomes.
• It aims to enhance understanding of these upper airway disorders to improve diagnosis and management, thereby optimizing equine health and performance.

Anatomy of the Equine Larynx and Pharynx

• The larynx and pharynx are vital components of the equine upper airway responsible for respiration, phonation, and protection of the lower airway.
• The larynx includes cartilages, muscles, and nerves that regulate the airway opening.
• The pharynx serves as a muscular tube connecting the nasal passages to the larynx and esophagus, facilitating breathing and swallowing.

Diagnostic Methods

• Endoscopy is a key diagnostic tool allowing visualization of the laryngeal and pharyngeal structures during rest and exercise, which helps identify abnormalities.
• Ultrasound imaging supplements endoscopy by assessing structural changes in soft tissue and cartilage not clearly visible endoscopically.
• Additional diagnostic approaches may include clinical examination, auscultation, and possibly radiographic imaging to exclude other conditions.

Common Equine Upper Airway Disorders

• Recurrent Laryngeal Neuropathy (RLN):
  • Etiology: Degeneration of the recurrent laryngeal nerve causing paralysis or dysfunction of the arytenoid cartilage.
  • Clinical Signs: Inspiratory noise, exercise intolerance, and airway obstruction.
  • Management: Surgical interventions such as laryngoplasty (“tie-back”) and conservative therapy depending on severity.
• Arytenoid Chondropathy:
  • Etiology: Infection or trauma leading to inflammation and degeneration of arytenoid cartilage.
  • Clinical Signs: Respiratory distress, abnormal airway sounds.
  • Management: Antibiotic therapy for infections, surgery in severe cases to restore airway patency.
• Epiglottic Entrapment:
  • Etiology: Flap of subepiglottic mucosa covers the epiglottis causing obstruction.
  • Clinical Signs: Exercise intolerance, respiratory noise.
  • Management: Surgical correction to release the entrapped epiglottis.
• Dorsal Displacement of the Soft Palate (DDSP):
  • Etiology: Abnormal positioning of the soft palate over the epiglottis causing partial airway obstruction.
  • Clinical Signs: Gurgling noise during exercise, poor performance.
  • Management: Conservative management, use of tongue ties, and various surgical options if persistent.
• Nasopharyngeal Collapse:
  • Etiology: Weakness or flaccidity of pharyngeal walls causing airway collapse.
  • Clinical Signs: Inspiratory noise, exercise intolerance.
  • Management: Surgical techniques to stiffen or support pharyngeal walls, as well as medical management.

Prognosis and Performance Outcomes

• The prognosis varies depending on the disorder, severity, and treatment efficacy.
• Early and accurate diagnosis combined with appropriate intervention is critical to restore airway function and optimize performance.
• Some conditions respond well to surgery and have favorable outcomes, while others may result in persistent impairment affecting athletic capacity.

Summary

• Understanding the anatomy and pathology of the equine larynx and pharynx enables better diagnostic accuracy and therapeutic planning.
• The article emphasizes the importance of combining clinical signs with advanced diagnostic tools like endoscopy and ultrasound.
• Managing common conditions such as RLN, epiglottic entrapment, and DDSP improves airway function, leading to enhanced health and athletic performance in horses.