Description

The soft palate in a horse is la flap of tissue at the back of the pharnyx. In it's natural position the soft palate is down which seals off the oral airway and opens up the nasal airway.

Dorsal displacement of the soft palate (DDSP) occurs when the epiglottis, which is normally positioned above the back edge of the soft palate and serves to separate the nasal and oral cavities in the horse's head, does not return to the normal position after the horse swallows.

Once the palate is displaced, the horse is unable to breathe sufficiently to sustain exercise, and the displacement leads to rapid slowing or stopping of breathing accompanied by a loud guttural noise on expiration. The exercise intolerance and gurgling noise are due to the soft palate creating an airway obstruction that doesn't allow air to be expelled properly.

When the horse cannot maintain the palate in the proper position during exercise, performance decreases. The soft palate also plays an important role in swallowing. In addition, when the opening of the trachea is not covered during eating, the horse may have bouts of coughing and become vulnerable to aspiration pneumonia.

Symptoms

• Difficulty in breathing
• Exercise intolerance
• Loud guttural noise
• Coughing

Causes

The cause of soft palate displacement in horses is not agreed upon by researchers. The soft palate is a complex, muscular organ. In the horse, it is extremely elongated and during normal breathing the posterior border lies under the epiglottis. In this position, maximal airflow is possible through the pharynx which is the long tube extending from the back of the nasal cavity  and the mouth to the esophagus.

According to veterinarians and researchers, the factors that are believed to contribute to this condition include: inflammation of the airway, abnormal size and shape of the epiglottis, an abnormally soft, flaccid palate, abnormal retraction of the larynx, excessive flexion at the poll, neuromuscular disease, mal positioning of the horse's tongue over the bit, and excitement on the part of the horse.

Prevention

To date, no absolute preventive methods have been determined. Good horse and stable management that contribute to the health of the horse are always important.

Treatment

Treatment of the disease ranges from conservative approaches to more serious surgical procedures. The first step is to alleviate any inflammation of the throat and airways by giving the horse a period of rest accompanied by administration of antibiotics, anti-inflammatory drugs, topical throat sprays or washes, and all scheduled vaccinations for influenza and rhinopneumonitis viruses.

Young horses may need a longer period of rest and may need to be turned out for several weeks to allow inflammation to subside and allow them time to mature.

Other options that may be suggested by the veterinarian include application of a tongue-tie and/or a figure-eight nose band. These methods may be effective because they help to counteract the caudal retractile forces that are believed to contribute to DDSP.

Switching bits is sometimes effective, especially with bits that hold the tongue down and in place and alter the horse's headset.

Numerous surgical procedures have been tried, including a myectomy that involves removing a section of muscle, epiglottic augmentation to change the size and shape of the epiglottis, and staphylectomy which involves trimming the palate so that scar tissue is formed that stiffens the back of the border of the palate and gives it more rigidity. In each case, approximately 60% of horses improve with these treatments.

Depending on the age of the horse, proceeding with a conservative approach initially is recommended. If this doesn't work, surgery or a combination of surgeries may be recommended.