Dorsal Displacement of the Soft Palate in Horses

The equine soft palate is a flap of tissue which, in its resting position, seals off the oral airway and opens up the nasal airway. In some horses, the soft palate can sometimes slide behind the epiglottis and move out of position, partially obstructing the passage of air. Intermittent dorsal displacement is most commonly seen in horses that work at high speeds, like racehorses, however, persistent dorsal displacement of the soft palate is consistent across horse populations. 

Dorsal displacement of the soft palate is a common respiratory disorder in horses who work at high speeds, such as racehorses, but uncommon otherwise.

Symptoms of dorsal displacement of the soft palate in horses will differ slightly depending on if it is an intermittent hindrance or a persistent condition. Both types of the disease will experience coughing and choking when they are experiencing trouble with their soft palates, but the onset and outcome are different. Intermittent DDSP is almost exclusively triggered by running, and the horse will abruptly reduce speed while coughing.

Once the animal has slowed itself down, it is able to swallow, which returns the epiglottis to its proper place and allows symptoms to cease. Animals with persistent DDSP will make loud gurgling noises with milder exercise, and will also present with the coughing and choking sounds, but swallowing will not clear the problem. They may also experience the coughing and choking when eating and drinking as food and liquid occasionally makes its way into the respiratory system. 

• Coughing
• Choking
• Trouble swallowing
• Gurgling noises

Types

Intermittent DDSP

This type of displacement occurs when a horse is breathing hard, often when running at full speed. When the horse is forced to slow down, they also tend to swallow, and the action of swallowing causes the epiglottis to slide back into the correct position. Intermittent displacement is much more widespread with horses like racehorses, that commonly work at high speeds.

Persistent DDSP

This type of displacement is less common than intermittent dorsal displacement, but it has consistent numbers across the horse populations. With persistent DDSP the epiglottis does not regain its rightful position when the horse swallows, leaving the airway partially blocked and the trachea partially open. This can lead to additional complications when eating and drinking as food particles and liquids are introduced into the lung area.

There are several theories regarding the reasons for both intermittent and persistent DDSP, although there is no consensus within the veterinary community as of yet. Some of the possible causes of intermittent DDSP include: 

• Damage to either the soft palate or epiglottis
• Excessive backward movement of the larynx
• Laryngeal inflammation
• Malformations of the soft palate or epiglottis
• Opening the mouth during racing

Persistent DDSP may also have several foundations, which can incorporate:

• Cysts or growths on the soft palate or epiglottis
• Damage to the soft palate or the epiglottis 
• Fungal or bacterial infections in the guttural pouch 
• Inflammation of the nerves that control both the larynx and the soft palate
• Malformation of the soft palate or epiglottis

Your veterinarian will start your consultation with a complete physical examination to rule out any other disorders such as epiglottic entrapment or vocal cord collapse that can cause many of the same respiratory symptoms. Persistent DDSP is relatively simple to diagnose using an endoscope. When an endoscope is introduced into the upper airway of a horse with a standard presentation, the epiglottis should be clearly visible, however, the epiglottis of a horse with persistent DDSP remains hidden behind the soft palate and is not generally visible using the endoscope.

Cultures may be taken to rule out or confirm any bacterial or fungal infections of the guttural pouch. Intermittent displacement can be slightly more challenging to diagnose as it only occurs when exercising. This means that an endoscopic examination, while the horse is at rest, will most likely look completely normal. In order to accurately diagnose intermittent DDSP, the patient will need to have the examination repeated while they are using a treadmill.

There are several treatment plans available for this disorder, and each situation is unique, any underlying causes, such as bacterial or fungal infections, will need to be addressed before the condition can be extinguished. Most treatment plans will start out conservative with anti-inflammatory medications and rest, and progress to surgical remedies only if the less invasive treatment options are unsuccessful. No one surgical treatment has been proven significantly more effective than the others. Some of the options your veterinarian may suggest can include:

• Medications (anti-bacterial, anti-fungal, anti-inflammatory)
• Rest
• Specialized tack
• Figure 8 noseband
• Tongue-tie

Surgical remedies may be required:

• Cauterization of the soft palate using thermal and laser procedures
• Epiglottic augmentation- Injection of collagen or Teflon into the epiglottis to stiffen it
• Laryngeal tie-forward
• Myectomy - A surgical transection of a muscle; for this condition, the muscles that are cut are the strap muscles of the neck
• Staphylectomy - This surgery is a procedure to remove a small portion of the back edge of the soft palate in order to stiffen the edge to make displacements less likely

Treatment of dorsal displacement of the soft palate will have variable results. Depending on the reason for the condition, recurrence may be a possibility, even after successful therapy. Horses who have had surgery for this condition will have a mandatory rest period of 2 to 4 weeks as well as prescribed medications that must be administered. The equine veterinarian will advise when your horse can return to activity.