Normal Anatomy of the Lips and Palates
Cleft lip and cleft palate are the most common types of orofacial clefting although there are approximately fifteen types. They are the most common head and neck congenital malformations. It is estimated that 1 in 700 live births has one of the malformations, with the incidence being 1 in 1000 in the United States. In the United States alone, it is estimated that 7,500 babies are born per year with an orofacial cleft. The average lifetime medical costs of these malformations are estimated at an average of $750 million per year. Cleft palate and cleft lip have other associated medical conditions that include speech problems, psychosocial issues, ontological diseases, and dental deformities. Understanding the etiology, embryology, and complications of these deformities are crucial to the effective management of the affected children.
There are gender and ethnic differences in the birth preference of cleft palate and cleft lip. Asian and Native American populations show the highest preference with a preference of approximately 2 per 1,000 live births. The European descendants have an intermediate rate of 1 per 100 live births. African populations have the lowest incidence of these deformities approximated at 1 per 2,500 live births (Mossey et al., 2012). There is a gender bias when it comes to the occurrence of these deformities in children. For every one female child affected, there are two male children with the same condition (cleft lip and cleft palate). However, females are more affected in deformities involving the palate alone. The difference in ratios has been hypothesized as occurring because the palatine shelves close one week earlier in boys than in girls.
The puzzle as to the cause of cleft palate and cleft lip has faced humanity for a long time, with many folklores composed in an attempt to answer the question. According to the Aztecs, the cause of eclipse was a bite of the moon (Marazita, 2012). Thus, expose to an eclipse in pregnancy resulted in a child’s mouth being bitten off, resulting in a cleft lip and palate. To prevent this occurrence, pregnant women placed an obsidian knife over their abdomens every time they wanted to go out in the night. Today, the belief is seen in Mexico, where during an eclipse, a metal safety pin or key is placed over a pregnant woman’s abdomen to protect a baby. On the other hand, in ancient China, they believed that if a woman ate a rabbit during pregnancy, a child will develop a “hare lip,” while others held the belief that wrongdoings and bad karma were the causes. The Filipinos believe that cleft lip and cleft palate are caused by force to the fetal face while the fingers are in the fetus’ mouth (Abad et al., 2014). Most of these ancient beliefs about the causes of cleft lip and cleft palate have been disapproved though science, except the belief that these anomalies had a familial component that has been supported by many scientific inquiries into their causes.
Familial inheritance might cause the occurrence of cleft lip and cleft palate in the children (Dixon et al., 2011). In tow unaffected parents with a child who has an orofacial cleft, there is a 4.4% chance for a future child to develop a cleft lip or palate, while there is a 2.5% chance of getting a child with cleft palate only. The likelihood of getting a child with cleft palate only increases to 6.8% if one of the parents is affected. However, if one child and one parent are affected, the risk for cleft palate only rises to 14.9% while that of getting a child with cleft lip with or without cleft palate increases to 15.8% (Dixon et al., 2011). Generally, as the number of family members with these deformities increases, the risk of getting children with these deformities in the future also increases.
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A large number of the cleft lip and cleft palate cases are non-syndromic. In fact, 50% of the isolated cleft palates and 70% of cleft lips with or without cleft palates occur as isolated anomalies (Dixon et al., 2011). The mechanism for their development has not been explained to date, but it is believed that they result from the interplay of many factors. Although it has been demonstrated that they tend to cluster in families, there is no demonstration that they have a Mendelian type of inheritance. It is thus held that these defects arise from interference with the normal developmental process of the palate and lips. However, there are syndromic clefts although they form a minority of the cases. Such clefts are associated with many other malformations in other organs. Van der Woude syndrome is the syndrome associated with a cleft palate and cleft lip (Guner et al. 2002). It is an autosomal dominant syndrome with orofacial clefts and lower lip pits characteristics.
A larger portion of the lips is formed by the orbicularis oris muscle that serves as the mouth sphincter. The red portion of the lip is called the Vermilion. The gutter like depression on the midline of the upper lip running up to the nose is the philtral dimple on either side of which are the philtral columns. On the other hand, the palate is divided into the hard and soft palate. The hard palate is formed by the horizontal processes of the palatine bone and the palatine process of the maxilla. Anteriorly and laterally, it is bound by alveolar arches. Posteriorly, it is continuous with the muscular soft palate. The incisive foramen marks the boundary between the primary and secondary palates developmentally and is the inlet for the nasopalatine nerve. The lesser and greater palatine foramina are the openings through which the lesser bad greater palatine artery and nerve enter the palate. This is to be kept in mind during repair of cleft palates because the flaps for palatoplasty are supplied with blood by the greater palatine artery. The soft palate also has two parts; an anterior formed by the palatine aponeurosis, an expanded portion of the tensor veli palatini tendon. The posterior part is composed of six muscles, levator veli palatini, palatopharyngeus, tensor veli palatini, palatoglossus, the uvular muscles, and superior pharyngeal constrictor (Moore et al., 2015).
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Embryology of the Palate and Lips
Understanding the normal development of the lips and plate is crucial to understanding how the anomalies occur. Around the fourth week of embryological life, the lip and palate start developing. They are completely developed by the 12th week. The five facial prominences are formed by the end of the fourth week. They are the paired maxillary processes, the frontonasal process, and the paired mandibular prominences. The five processes surround the primordial oral cavity. The frontonasal process develops to form the nasal placodes by the end of the 5th week (Moore et al., 2015). Invagination of the nasal placodes results in nasal pits, and the medial and lateral nasal swellings. The paired maxillary prominences grow medially and push the nasal prominences together by the end of the 6th week. When the medial nasal prominences fuse, they form the middle-upper lip, the nasal tip, the philtrum, and columella. The maxillary prominences form the lateral lip while the paired medial nasal processes and the paired maxillary prominences fuse to for the complete upper lip. Formation of the palate starts at the end of the 5th week and is complete by the end of the 12th week. The fusion of the medial nasal prominences forms the primary palate. It structures prior to the formation of the secondary palate. The hard palate starts developing in the 6th week as shelf-like outgrowths of the maxillary processes. They grow vertically down on either side of the tongue. By the 7th week, the tongue migrates inferiorly to allow the palatal shelves to assume a horizontal position (Moore et al., 2015). The fusion of the palate occur in the anteroposterior direction and is complete when the uvular fuses. This process occurs one week later in female fetuses compared to male fetuses. Disruption in any of the above growth processes results in the formation of a cleft lip or palate depending on the timing and position of the interference.
Classification of Clefts
Cleft lips and cleft palates are classified based on the developmental criteria. The incisive fossa is used as the reference landmark in the classification. These defects are conspicuous because of the abnormal facial appearance that they result in and the defective speech exhibited such people. An anterior cleft anomaly includes a cleft lip with or without clefting of the alveolar part of the maxillary bone. In cases where the cleft extends to involve the lip, alveolar part of the maxilla and incisive fossa is referred to as a complete anterior cleft anomaly. The anterior and posterior parts of the palate are normally separated in such a scenario. This type of clefting results from mesenchyme deficiency in the median palatal processes and the maxillary prominence (Moore et al., 2015).
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Clefts of the secondary palate that involve the hard and soft regions of the palate all the way to the incisive fossa and separating the posterior and anterior parts of the palate are referred to as posterior cleft anomalies. They normally occur as a result of defects in the development of the shelves and the secondary palate. These anomalies can also result from defective focal degeneration sites of the epithelium of the palate. Both cleft lip and cleft palate can be either unilateral or bilateral. Failure of the maxillary prominence on one side to fuse with the merged nasal prominences results in a unilateral cleft of the upper lip. The cause of such a developmental anomaly is the failure of the masses of mesenchyme to merge so that the mesenchyme can proliferate and smoothen the overlying epithelium. This failure leads to a persistent labial groove. Sometimes the epithelium in the labial groove is stretched until it breaks down dividing the lip into a medial and a lateral portion.
On the other hand, the epithelium may persist as a Simonart band that keeps the two parts joined to result in an incomplete cleft lip. When the merged nasal prominences fail to merge with the maxillary prominences of either side, a bilateral cleft lip results. The epithelia in both labial grooves break down eventually because of too much stretching. In such cases, the defects can be different, with a varying degree of defective development on either side. The profound deformity caused by these defects is as a result of the loss of the continuity of the orbicularis oris muscle that is responsible for pursing the lips and closing the mouth (Moore et al., 2015).
An extremely rare defect is a median cleft of the upper lip whose etiology is a deficiency of mesenchyme. It results in complete or partial failure of fusion of the medial nasal prominences to form the median palatal process. This defect is the characteristics of Mohr syndrome, an autosomal recessive trait inheritable from parents to children. Sometimes, though very rare, the mandibular prominences fail to merge completely and bridge the embryonic left existing between them thus resulting in a median cleft of the lower lip.
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A cleft lip, with or without a cleft lip, is more common in girls than boys. This anomaly may involve the uvula only, in case the uvula looks like the tail of a fish. It may also the extent to involve the hard and soft regions of the palate. In severe cases that are associated with a cleft lip, the defect extends through the lips and alveolar part of the maxilla on both sides. If the cleft extends from the soft palate to the incisive fossa anteriorly, it is referred to as a complete cleft of the posterior surface. Clefts of the anterior palate result from the failure to lateral palatal processes mesenchyme to melt and fuse with the mesenchyme of the primary palate. When the mesenchymal masses of the lateral palatal processes fail to meet and merge with one another and with the nasal septum, the resulting defect is referred to as cleft of the posterior palate. Sometimes the clefts involve both the primary and secondary palates. Such a defect occurs when the mesenchyme in the lateral palatal processes fails to melt and fuse with primary palate mesenchyme and with the nasal septum. It is not yet clear how teratogenic factors induce the development of the cleft palate and cleft lip (Dixon et al., 2011). Some of the teratogenic agents that have been associated with the development of cleft anomalies include anticonvulsant drugs. These defects are also more common in babies suffering from trisomy 13.
Cleft Lip and Cleft Palate Management
The management of a child with a cleft lip and or a cleft palate needs a multidisciplinary approach for a good outcome. The care team should include specialists in plastic surgery, audiology, otolaryngology, speech pathology, orthodontists, psychologists, pediatrician, oral maxillofacial surgery, and geneticist (Mossey et al., 2009). The management is meant to start at birth by addressing airway concerns and feeding difficulties. Other aims of the management are to address ontological diseases, surgical repair, as well as speech and language problems. Isolated cleft palates normally do not present with airway problems. However, a baby born with a cleft palate may develop airway compromise mostly caused by the Pierre Robin sequence. It refers to a U-shaped cleft palate, micrognathia, and glossoptosis. The initial management of an infant with this anomaly involves putting the baby in the prone position although severe cases may require tracheostomy.
The second concern in the management of a child with cleft lip and or cleft palate, other than the airway, is feeding and nutrition (Mossey et al., 2009). It is essential to establish feeding techniques before a patient can be allowed to leave the hospital. In a cleft palate, there is compromised the ability to such because the buccal and nasal cavities are continuous. However, a cleft lip alone causes little feeding problems. For patients with cleft palate, special feeding bottles have been developed to aid in their feeding. The examples are shown below.
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Most children born with cleft palate have a high risk of developing ear diseases. It is believed that the abnormal insertion of the muscle tensor veli palatini is the cause or a contributing factor to the development of ear diseases. Many children suffer from persistent otitis media commonly presenting as middle ear effusions. The effusions accumulate because of Eustachian tube dysfunction. All the patients with unrepaired cleft palate develop speech abnormalities later in life. The major goal of repairing the palate is to restore the functionality of the velopharyngeal valve. The repair restores normal speech in such patients. However, even after surgical repair of the palate, it has been reported that 10-20% of these patients still suffer velopharyngeal insufficiency. These patients display varying degrees of hypernasality. They also have articulation errors like pharyngeal fricatives and glottal stops. The insufficiency is initially managed with speech pathology immediately after surgery. In case the speech pathology is insufficient to restore the velopharyngeal functionality, palatoplasty or pharyngoplasty can be used as another measure. The use of dental prosthesis has also been advocated in the management of these patients.
Surgical repair is the most definitive way of managing a patient with cleft lip with or without cleft palate. The appropriate time for performing surgical repair varies depending on individual institutions. It is uncommon to have the surgical repair done in the first three months of life. Instead, pre-surgical techniques are preferred. Repair of a cleft lip is done at the age of three months. During the same procedure, myringotomy tubes are placed. The palate repair is done at the age of 9-12 months. The first orthodontic treatment is started at 1 year of age. At the age of 7-8 years, alveolar bone grafting is performed prior to the eruption of permanent teeth. Sometimes skeletal maturity mid-face advancement can be done at the age of 18 years if necessary (Mossey et al., 2009).
In the first three months of life, pre-surgical procedures are performed to ensure good surgical outcomes. If the cleft if wide, it is narrowed by tapping it. Taping can also help in molding pre-maxilla protrusion. Strips of hypoallergenic tape are preferred for this process. They are placed with tension over the cleft and secured to a child’s cheeks. Its only disadvantage is that it must be used.
Another option for narrowing the cleft before surgery is the use of orthopedic devices (Mossey et al., 2009). Nasoalveolar molding devices are used to mold the pre-maxilla, nasal cartilage, and alveolar ridge. They can also be used to elongate the columella as well as mold the nasal cartilage. The method takes advantage of nasal cartilage malleability and its ability to maintain form after correction. If taping and nasoalveolar molding are ineffective, lip adhesion is considered as the next pre-surgical step. The cleft is reduced from a complete cleft to an incomplete one surgically at the age of 2-4 weeks. However, it has a disadvantage of the formation of a scar that can interfere with the definitive repair. If lip adhesion is done, the definitive repair is delayed for 5-6 months to allow scar maturity and proper healing. After these pre-surgical procedures, definitive surgery is done to correct the anomaly and restore the normal appearance and functionality of the involved parts.
Cleft lip and cleft palate are the most common congenital malformations of the head and neck areas. There are many myths on why they occur, most of which have been refuted by science. However, the belief that inheritance contributes to their occurrence has been supported by scientific research. The main cause of the cleft lip and cleft palate is interference with normal migration and fusion of mesenchyme although some occur as part of a syndrome like in trisomy 13. Some medications like anticonvulsant used by the mother have also been implicating. The cleft lip and cleft palate can be complete or incomplete, anterior or posterior depending on the severity of the deformity and its location in relation to the incisive fossa. They cause cosmetic problems as well as psychological and nutritional problems. These patients also have a high frequency of middle ear diseases as well as speech problems. The definitive management of these defects is surgical repair which can be done when a child is three months of age. Pre-surgical steps are applied in the period between birth and three months to ensure good outcomes in the surgical repairs. Management is best done using a multidisciplinary approach involving both medical and surgical specialists.
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