Defects (clefts) in the hard palate that forms the roof of the mouth, or the soft palate which lies caudally and separates the oropharynx from the nasopharynx may be congenital or acquired.The cleft can involve the soft palate alone, the hard palate alone or both. The defect can be bilateral (ie involve tissues lying both sides of the midline) or unilateral. The latter are usually seen in the soft palate.
A newborn puppy with severe cleft palate
Congenital cleft palate is an abnormality which is thought to occur during fusion of the maxillary process with the medial nasal process, when the mesodermal fusion develops across the fused epithelial surfaces. If the epithelial barrier does not degenerate or if the mesodermal connective tissue is deficient cleft palate results.
Acquired clefts are due to trauma - usually road traffic accidents or falls from a height.
A cat with acquired cleft hard palate and soft palate following trauma
There are several possible causes for congenital cleft palate:
a) Genetic cause
An hereditary basis for the disease is suspected for congenital clefts but the mechanism has not yet been determined. Any such genetic trait is thought to be multifactorial recessive, polygenic and dominant with partial penetration.
b) Excess vitamin A intake during pregnancy
In 1967 Wiersig and Swenson reported that 125,000 IU of Vitamin A per kilogram body weight given to Beagle bitches on days 17-22 of gestation resulted in cleft palate developing in their puppies.
Vitamin A is an essential nutrient for normal growth and defects in bone growth are seen with insufficient as well as excessive dietary intake. Vitamin A has a controlling influence over both the osteoblasts and osteoclasts in epithelial cartilage and so there is a rational explanation as to why excessive vitamin A intake might result in cleft palate.
In addition, commercially prepared complete pet foods contain more than sufficient available vitamin A yet breeders and owners frequently supplement their pet's ration with vitamin supplements. High vitamin A content is also a feature of many natural food sources including liver and fish oils. Cod liver oil is a very popular nutritional supplement with pet owners and it contains 18000mg per 100ml (4000 IU per gram). Some vitamin injections contain as much as 500,000 IU of vitamin A per ml.
Administration of cortisone during pregnancy can lead to the development of cleft palate in the fetus
Administration of the cytotoxic drug hydroxyurea (hydroxycarbamide) is reported to cause cleft palate.
Acquired cleft palate is common following falls from a height, and less commonly following road traffic accidents.
Brachycephalic breeds are reported to have about 30% risk, whereas German Shepherd Dogs have the lowest risk.
In cats cleft palates have been reported in mixed breeds, Siamese, Manx and Abyssinians - with Abyssinians having the highest risk.
Bronchopneumonia accounts for 30% of deaths due to cleft palate.
Cleft palate is sometimes associated with congenital deformities in other body systems.
Consider excess dietary vitamin A intake as a possible cause forcongenital cleft palate when it occurs and review the mothers nutritional history.
For the prevention of congenital cleft palate Provet makes the following recommendations :
Surgical repair of acquired lesions, and closure of congenital defects is recommended. In all cases surgery should be performed as soon as possible before secondary complications occur.
Most techniques involve the use of a flap taken by undermining the tissue on one or both sides of the defect and suturing them together. Techniques using artificial prostheses to close large defects have also been described in the literature, but these are not readily available and rejection is a common problem.
Long term problems