The upper airway of the horse is an intricate and complex structure composed of the nostrils, nasal passageway, nasal sinuses, pharynx, larynx, guttural pouches and the trachea. The upper airway has important functions including deglutition (the proccess of swallowing), thermoregulation, filtering and conditioning the inspired air, and protecting the lower airway from aspiration. There are many diagnostic tools that can be used to evaluate and examine the function of the upper airway including endoscopy, dynamic endoscopy, sound analysis, ultrasound and radiographs.  

Endoscopy can be a great tool for investigating upper airway and guttural pouch diseases in horses. It is relatively noninvasive and allows us to observe the function and anatomy of the larynx (including the arytenoids, epiglottis, and vocal folds), the pharynx (including the soft palate position and pharyngeal wall), the ethmoid turbinates, nasal passages and guttural pouches. Un-sedated endoscopy is the first step to assess the airway function.  

When a patient comes into the hospital, an endoscope is passed up their right nostril without sedation. As the horse breathes, the arytenoids of the larynx are assessed for their ability to abduct (open) and close while the horse is breathing and swallowing. The position of the epiglottis is important to note as some diseases will displace the epiglottis. After an initial assessment has been made, the horse’s nostrils will be occluded so the airway can be observed under stress and to assess the amount of abduction the arytenoids can achieve when the nostrils are released and the horse takes a deep breath. These minimal tests can help pinpoint diseases the horse can get, with the most common disease we see being laryngeal hemiplegia.  

Normal Endoscopy: 

If a resting endoscopy is normal and no abnormalities are identified, the next step is a dynamic endoscopy. This is when the endoscope is placed and fixed within the nose, and a video records the upper airway while the horse is being exercised. This allows the upper airway to be evaluated while the horse is in active work replicating the noise or exercise intolerance that may be occurring. The following picture is an example of a horse undergoing dynamic endoscopy using the VetweareX Equine dynamic endoscopy system

 *Picture from VetweareX

Specific Diseases 

Laryngeal Hemiplegia 

Horses with laryngeal hemiplegia typically present with a complaint of “Roaring,” or exercise intolerance. The left arytenoid is most commonly affected. The function of the arytenoids are graded on a scale of I-IV. When horses are grades III or IV, typically surgical intervention is recommended, especially if exercise intolerance is a concern. The most common surgery performed is called a prosthetic laryngoplasty or more commonly known as a “Tie Back”. The following endoscopic picture is an example of a horse with Grade IV laryngeal hemiplegia of the left arytenoid. This means that the left arytenoid was completely paralyzed and not able to move. This horse did not have a history of exercise intolerance and presented for “Roaring” when being worked. His workload at the time was light and the owner wanted to investigate the cause of the noise.  

It was elected to perform a “Tie Back” procedure on this patient.   This surgical procedure uses implants to fix the arytenoid in an open position. This procedure can be performed in a standing sedated horse, or under general anesthesia. The success rate of this surgical procedure is about 70%. The most common complication of this surgery is chronic coughing, as the arytenoid is fixed, and cannot move when the patient swallows food. This surgery requires about 2 months of rest and rehab before returning the horse back to its normal level of performance.  The following picture is the patient’s post operative endoscopy showing the left arytenoid opened and fixed in position. 

Dorsal Displacement of the Soft Palate 

Another disease that is prevalent in horses is called dorsal displacement of the soft palate. This is when the soft palate moves on top of the epiglottis and the epiglottis cannot be identified. Horses are noted to have a “gurgling” noise or will persistently cough when they are being exercised. Most horses displace their soft palate intermittently, but some horses have permanent displacement. When an upper airway endoscopy is performed and this disease is recognized, we assess to see if the horse can replace the soft palate into the correct position. This disease is more commonly diagnosed on dynamic endoscopy, so the soft palate can be assessed while the patient is exercising. 

* Picture from Arizona Equine

Horses that present with coughing or exercise intolerance and a displaced soft palate is diagnosed during endoscopy, it is important to first rule out asthma as the cause. Lower airway inflammation has been associated with causing changes to the upper airway, and more specifically it has been shown that horses with asthma can have an intermittently displaced soft palate. The most important diagnostic tool that can be performed in a horse with asthma is a bronchial alveolar lavage. This procedure involves washing the lungs with fluid and collecting cells that are examined under a microscope. If the cells are indicative of inflammatory airway disease, the horses are first treated for asthma and then a recheck scope exam would occur in 6-8 weeks.  

*Picture from Texas A&M

If asthma has been ruled out and the patient is still displacing the soft palate while exercising, a laryngeal tie forward procedure can be performed under general anesthesia. Surgical success with this procedure ranges from about 70-80%

If you've noticed changes in your horse's respiratory patterns, coughing, and/or exercise intolerance be sure to let your primary care veterinarian know so that they can perform a physical exam and begin the diagnosis process.  Our surgeons, Dr. Alyson Booth and Dr. Charlene Noll, are available to consult on these cases to help you and your veterinarian get answers and a path forward!  Give us a call (804-798-3281) or send us an email (info@woodsideequineclinic.com) if you have questions related to upper airway disease or are interested in scheduling a consultation for your horse.