Cleft palate (palatoschisis) is a developmental disorder that involves incomplete fusion of the hard palate, posterior to the incisive foramen and/or the soft palate. It is one of the commonest congenital deformities, with a worldwide frequency of 1 in 700 births , and twice as common in females than males.
Cleft palate and cleft lip (cheiloschisis) often occur together; in fact, half of all infants with cleft lip also have cleft palate .
The prevalence of cleft palate varies for different ethnic groups, being the highest in children of Native American and Oriental origin (1/500), and the lowest in those of African and Caucasian origin (1/2500).
In the majority of cases the presence of cleft palate is obvious, especially when accompanied by cleft lip. Although cleft lip can now be detected in utero using prenatal diagnostic ultrasonography, cleft palate alone cannot be detected before birth. Diagnosis, therefore, is usually made during mouth inspection on routine physical examination, or when the child presents with related complaints:
The aetiology of cleft palate in not very well understood, yet there are some genetic and environmental factors that have been shown to play an important role in cleft palate development.
There are a number of syndromes associated with cleft palate including:
Some important genes have been identified in cleft palate developemnt. The TBX22 gene is expressed in the palatal shelves just prior to their elevation above the tongue. Tgfb3, Tfap2a and Gabrb3 genes have also been identified. Their expression supports craniofacial development and knockouts result in cleft palate, .
It can also be due to chromosomal disorders, e.g Trisomy 13 (Patau Syndrome) and Trisomy 21 (Downs Syndrome).
If a family member is affected by cleft palate, there is an increased risk to relatives. The more closely related the family member and the greater the number affected, the higher the degree of risk (refer to table below).
High concordance in monozygotic twins (between 40-60%) suggests a strong genetic causal factor. However, as there is not 100% concordance in monozygotic twins, genetic factors alone are insufficient to account for the development of cleft palate, .
The role of environmental factors must also be taken into consideration.
Palate formation begins at 4 weeks gestation. The illustration below show the sequential development of the palate;it is divided into the primary and secondary palate:
Primary palate development initially involves fusion of the medial nasal process and maxillary process followed by fusion of the lateral nasal process with the medial nasal process.
Secondary palate formation occurs after completion of primary palate formation. It is formed by inferior and medial growth and migration of the palatine shelves. Fusion of secondary palatal shelves begins at 8 weeks' gestation and continues usually until 12 weeks' gestation.
It is problems with palatine development that leads to the formation of cleft palate - It results from partial or complete lack of fusion of the palatine self, . The degree of clefting is related to when the fusion process is interrupted; the earlier the interruption, the greater the degree of clefting.
A good understanding of the anatomy of the palate is necessary in order to gain a full understanding of how surgical repair is carried out.
The main function of the palate is to separate the nasal and oral cavities; the palate forms the roof of the mouth and floor of the nasal cavity. It is divided into the hard palate and the soft palate (see figure below).
The soft palate is attached to the posterior border of the hard palate. Posteriorly it forms the uvula. It is composed of mucous membrane, palatine aponeurosis and muscles. Five paired muscles make up the soft palate:
The normal structure and function of the soft palate is dependent on the levator sling. The levator sling is formed by parts of the tensor veli palatini, palatoglossal, palatopharyngeal and uvular muscles.
There are several different classification systems for cleft palate. It is important to classify cleft palate as it can help to plan treatment.
Veau's Classification (see figure below):
Striped Y classification (see figure below):
The classificification is a pictoral representation of the cleft lip and palate, where the affected area is represented by a numbered box.
The main treatment for cleft palate is surgical intervention. Main aims include:
The timing of surgical repair is a controversial topic and there is much debate as to the optimum time. It is generally agreed that surgery should be carried out before one year, when significant speech development occurs. Repair later than this is associated with poor speech outcome and an increase in the likelihood of developing a palatal fistula. However, delayed closure (after 4 years) is associated with reduced retardation of mid-facial growth, .
There are several different surgical techniques for surgical repair, the most common being:
Also known as the Double opposing Z-plasty, this technique lengthens the soft palate as well as re-establishing the levator sling. It is preferable when the there is a narrow cleft. If fistulas form with Furlow technique, they commonly occur at the junction between the hard and soft palate.
The long term results are better when compared to other techniques in terms of fistula formation and speech development.
Von Langenbeck technique
This is a popular procedure and involves moving tissue towards the mid-line via lateral releasing incisions.
Von Langenbeck technique reduces maxillary growth retardation, however, it forms a mid-line scar, which may contract and increase the probability of speech disorder. There is also a high rate of post-operative fistulas with this procedure because of increased wound tension.
This is a two stage repair technique, developed to overcome the problems of mid-facial growth retardation seen with the Von Langenbeck technique.
First stage: soft palate repair at 4-6 months (and cleft lip if present).
Second stage: hard Palate repair at 18-24 months;
If surgery is refused or cannot be accessed then a palatial obturator (refer to picture below) can be used. This is prosthesis that is placed on the roof of the mouth over the defect in the palate. It can also be used as a temporary measure during feeding during surgical intervention, e.g. after the first step of palatal closure with the Schweckendiek technique.
There are several important post-operative conditions to consider.
One of the most important post operative complications is airway obstruction. This commonly occurs when the tongue prolapses into the oropharynx while the patient is sedated. One solution is to use a tongue traction suture can prevent the tongue prolapse.
Haemorrhage is also a common problem due to the rich blood supply of the palate by the Greater palatine artery. It is therefore important to assess haemoglobin levels pre-operatively.
Palatal fistula is also a very common post operative complication. It is an abnormal oro-nasal communication resulting from dehiscence of the primary cleft palate repair, . If the patient is symptomatic one solution can be a dental prosthesis can be used to occlude the defect. However, if the patient experiences symptoms then surgical closure of the fistula is the favoured treatment option.
Although surgical repair of cleft palate is the favoured treatment, surgical intervention can affect the intrinsic growth potential of the bones in the face, resulting in facial growth abnormalities, for example maxillary growth restriction. This means that the child may have to undergo future surgical treatment for such abnormalities.
The mother can try to avoiding exposures to smoke and alcohol during pregnancy as these are known to increase the risk of having a child with a cleft palate. Folic acid supplements (0.4mg) before conception and during pregnancy may also help prevent clefting. For those with a family history of clefting genetic counselling is an important part of pre-natal care.
Cleft palate is a common developmental disorder that affects a significant proportion of children worldwide.
As seen from above, it can be easily treated via surgical intervention if carried out early. However, the longer it is left, the more difficult it becomes to treat and the greater the likelihood of complications.
In the future, tissue engineering is likely to play a greater role in treatment, for example bone morphogenetic proteins could be used to induce bone growth.
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