Cleft Palate in Horses

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My filly, which is only a few days old, dribbles milk from her nose when she nurses her dam. The veterinarian who delivered her has been back out to check this, and he tells me that she has a cleft palate. Does this mean the same as it does in humans? What kind of problems am I going to have with this filly?

A cleft palate is an uncommon congenital defect in the foal that usually is the result of a developmental defect of the soft palate, and in rare occasions, the hard palate. This defect most often is detected at birth through the use of an endoscope.

A cleft palate refers to the tissue that separates the oral cavity from the nasal cavity. Toward the front of the skull, the palate is bony and termed the hard palate (the roof of the mouth). The back part of the palate is composed of only soft tissue, hence the term ‘soft palate.’ The palate forms from two sides that fuse together on the midline. When this fusion does not occur normally during embryological development, it is termed a cleft palate. The important point is that any part of the palate can be ‘cleft.’ In the horse, cleft palate most commonly involves only the soft palate and sometimes a bit of the hard palate. It is (fortunately) uncommon to have a completely cleft palate. A cleft lip also is possible in severe cases.

Symptoms of a cleft palate include bilateral nasal discharge during eating, difficulty swallowing, and signs of aspiration pneumonia, an infection in the lungs that is caused by the inhalation of food material. The most obvious symptom of a cleft palate is milk or other feed coming out of one or both nostrils. The palate serves to separate the mouth from the nose, and when there is a defect, food taken by mouth spills into the nasal passages and out the nose. This nasal regurgitation of milk is most obvious during nursing. Foals also will show secondary signs such as poor weight gain, pneumonia, and general unthriftiness.

The onset of symptoms depends on the severity of the cleft. In most cases, the milk coming from the nose is noted shortly after birth. Occasionally, horses exhibit signs that are subtle enough that the problem is missed for several weeks to months. There even have been unusual cases in which horses managed to be one or two years old before a cleft palate was diagnosed.

The only true treatment is surgical repair, which involves closure of the cleft defect. Several different approaches can be used. Correcting a cleft palate is a complex procedure that is considered major surgery since the healing process will be compromised. Surgical repair of cleft palates requires a longer healing period because of its site in the mouth. It is an area that is not exposed and therefore bandages can't be applied and removed on a daily basis. The site also is exposed to food or milk on a regular basis, which inhibits the healing process. In many cases, secondary complications that arise from the cleft palate need to be addressed in order to assure that the foal has the best chances of recovery.

The common surgical technique involves splitting the mandible (lower jaw) and spreading it apart to allow closure of the defect. Horses have very long skulls with mouths that do not open very wide, so the surgery is more complex than in other species such as humans or dogs. The surgery is much easier to do in a young foal.

The prognosis for a foal with a cleft palate varies, depending on the severity of the problem. If the cleft does not involve a significant amount of the hard palate, then chances for a successful recovery increase. However, the prognosis for normal upper respiratory tract function, including soft palate function, is quite guarded. There have been too few repaired and followed over time to have a firm idea of the consequences of surgery on the animal's athletic potential. Many horses will never achieve normal ‘athletic’ function, yet are serviceable for lesser activities, including breeding. Foals which are treated before six weeks of age show the most improvement since after that time, aspiration pneumonia complicates the outcome.