Pharynx
The pharynx is a muscular funnel connecting the oral and nasal cavities to the esophagus and larynx. In the horse, the soft palate is unusually long, normally resting below the epiglottis, which means horses are obligate nasal breathers and cannot breathe through the mouth under normal circumstances. The pharyngeal muscles coordinate the complex swallowing reflex that directs food to the esophagus while protecting the airway.
The equine pharynx is a shared passage for both the respiratory and digestive tracts. During swallowing, the epiglottis flips to cover the laryngeal opening while the soft palate briefly drops to allow the food bolus to pass into the esophagus. Endoscopy (both resting and dynamic/overground) is the primary diagnostic tool for pharyngeal disorders.
The aryepiglottic fold envelops the epiglottis, impairing its function.
Chronic progressive thickening and distortion of the arytenoid cartilage.
Enlargement of pharyngeal lymphoid tissue, common in young horses.
Fungal infection of the guttural pouch, potentially eroding into the internal carotid artery.
The caudal free border of the soft palate displaces dorsally over the epiglottis during exercise, obstructing the airway.
Abscess formation in the retropharyngeal lymph nodes, frequently secondary to Streptococcus equi (strangles) infection.
A congenital defect where the thyroid cartilage is malformed and the sternothyroideus attachment is abnormal, contributing to upper airway obstruction in foals.
Recurrent laryngeal neuropathy (RLN), commonly known as roaring or whistling, is a progressive degeneration of the left recurrent laryngeal nerve leading to paralysis of the left arytenoid cartilage.
The aryepiglottic fold envelops the epiglottis, impairing its function. Signs include: Respiratory noise; exercise intolerance; abnormal swallowing; visible on endoscopy
Chronic progressive thickening and distortion of the arytenoid cartilage. Signs include: Inspiratory noise; exercise intolerance; may follow previous surgery
Enlargement of pharyngeal lymphoid tissue, common in young horses. Signs include: Cough; nasal discharge; mild exercise intolerance; usually self-limiting
Fungal infection of the guttural pouch, potentially eroding into the internal carotid artery. Signs include: Epistaxis (can be fatal); nasal discharge; difficulty swallowing; cranial nerve deficits
The caudal free border of the soft palate displaces dorsally over the epiglottis during exercise, obstructing the airway. Signs include: Gurgling respiratory noise during exercise; sudden exercise intolerance; characteristic 'choking down' at speed
Abscess formation in the retropharyngeal lymph nodes, frequently secondary to Streptococcus equi (strangles) infection. Signs include: Difficulty swallowing (dysphagia); nasal discharge; swelling between mandibles; extended head and neck posture; fever
A congenital defect where the thyroid cartilage is malformed and the sternothyroideus attachment is abnormal, contributing to upper airway obstruction in foals. Signs include: Dysphagia from birth; nasal return of milk in foals; aspiration pneumonia; failure to thrive; Respiratory noise from birth; stridor (high-pitched noise) at rest and exercise; exercise intolerance in foals; diagnosed on endoscopy and CT; may require surgical correction.
Recurrent laryngeal neuropathy (RLN), commonly known as roaring or whistling, is a progressive degeneration of the left recurrent laryngeal nerve leading to paralysis of the left arytenoid cartilage. This results in reduced airway diameter during inspiration and the characteristic inspiratory noise during exercise. It is one of the most important upper airway conditions affecting performance horses. ## What it is The left recurrent laryngeal nerve has a very long course (wrapping around the aortic arch), making it more susceptible to damage than the right nerve. Progressive axonopathy leads to denervation and atrophy of the cricoarytenoideus dorsalis (CAD) muscle, the only abductor of the arytenoid cartilage. As a result, the left arytenoid fails to open fully during exercise, causing turbulent airflow and the classic roaring sound. The condition is graded I to IV on endoscopic examination (Havemeyer system), with higher grades causing more significant airway obstruction. ## Signs and symptoms - Inspiratory noise ('roaring' or 'whistling') during exercise that worsens with speed and fatigue - Exercise intolerance or reduced performance - In severe cases, respiratory distress during intense work - Abnormal arytenoid movement on resting or exercising endoscopy - The noise is often absent or minimal at rest and becomes obvious only during exercise ## Causes and risk factors RLN is a distal axonopathy whose exact cause is not fully understood but has a genetic component. It is more common in larger horses (especially Thoroughbreds and drafts) and appears to have a hereditary predisposition. Risk increases with age and size. The left side is affected in over 95% of cases due to the longer nerve pathway. ## How it is diagnosed Diagnosis is confirmed by endoscopic examination of the larynx, ideally during exercise (dynamic endoscopy) to assess arytenoid function under stress. Resting endoscopy can grade the degree of paralysis but may underestimate the severity. The Havemeyer grading system (I to IV) is used to classify the severity based on arytenoid movement and position. ## Treatment and management Treatment depends on the grade and the horse's intended use. Mild cases (Grade I to II) may not require intervention. For performance horses with Grade III or IV, surgical options include laryngoplasty (tie-back procedure), in which the arytenoid is permanently fixed in an open position, often combined with ventriculocordectomy (removal of the vocal cord and ventricle). Other procedures such as arytenoidectomy are used in selected cases. Post-operative care and rehabilitation are important for success. ## When to call the vet Contact your veterinarian if your horse develops an abnormal respiratory noise during exercise or shows signs of reduced performance. Dynamic endoscopy is the best way to confirm the diagnosis and determine the appropriate treatment. ## Prevention There is no proven way to prevent RLN, but selective breeding away from affected lines may help reduce incidence over time. Early detection through routine endoscopic screening in young performance horses can allow for timely intervention. ## Frequently asked questions **Can a horse with roaring still compete?** Many horses return to successful competition after laryngoplasty (tie-back), though some degree of noise may remain and results vary. **Is roaring painful?** No. RLN itself is not painful, but the reduced airway can limit performance and, in severe cases, cause respiratory distress. **Does the tie-back surgery last forever?** The surgery provides long-term improvement in most horses, but complications such as implant failure or aspiration can occur in some cases. This information is for educational purposes only. Always consult with a licensed veterinarian for diagnosis and treatment of your horse. Signs include: Inspiratory noise ('roaring' or 'whistling') during exercise that worsens with speed and fatigue; exercise intolerance or reduced performance; in severe cases, respiratory distress during intense work; abnormal arytenoid movement on resting or exercising endoscopy; noise often absent at rest and becomes obvious only during exercise
The equine pharynx is a shared passage for both the respiratory and digestive tracts. During swallowing, the epiglottis flips to cover the laryngeal opening while the soft palate briefly drops to allow the food bolus to pass into the esophagus. Endoscopy (both resting and dynamic/overground) is the primary diagnostic tool for pharyngeal disorders.
See the Pharynx on our interactive 3D horse model. Open 3D Model