Open access peer-reviewed chapter - ONLINE FIRST
Abstract
Cleft lip is an opening in the upper lip and cleft palate is a gap in the palate. Cleft lip and palate may be unilateral or bilateral occurring either in isolation or in various combinations. These orofacial congenital anomalies are birth defects caused by environmental and genetic factors though exact cause is still debatable. Whatever may be the cause, these anomalies cause difficulties in feeding, speech, hearing and ear infections affecting the health of a child. In addition to this, when child grows, the anomalies may give rise to psychosocial issues like self-esteem and social behavior along with anxiety and depression in children and in their parents. The aim of this chapter is to highlight the various types of cleft lip and palate, incidences, possible causes and development. The knowledge of cleft lip and palate is essential for surgeons for timely management of these orofacial congenital anomalies.
Keywords
- cleft lip
- cleft palate
- congenital orofacial abnormalities
- feeding disorder
- speech
1. Introduction
Cleft lip is a fissure in upper or lower lip extending to the nose [1]. Most commonly it involves upper lip and rarely lower lip. Earlier, the condition was known as “hare-lip” due to its resemblance to lip of hare or rabbit. But nowadays, this term is no longer used. Cleft palate is an opening in the palate forming the roof of the mouth [1]. Cleft lip may occur in isolation or in combination with cleft palate. The cleft lip may be unilateral or bilateral. Further, these congenital defects related to cleft lip and palate may be incomplete or complete. Cleft palate may involve only soft palate or both soft and hard palates. In addition to this, cleft palate may also occur in combination with the cleft lip which may be unilateral or bilateral [1]. The congenital cleft lip and palate may cause difficulties in feeding, speech, hearing and ear infections and 50% of cases are associated with other disorders [1]. Clefts are also observed in other parts of the face like eye, ears, nose, cheek and forehead. Paul Tessier elaborated on fifteen lines of cleft. Majority of these clefts are very rare and designated as Tessier clefts [2].
Besides, major forms of cleft lip, mild form of cleft lip, known as microform cleft [3] are also observed. A microform cleft usually looks like a small dent in the red part of the lip or appears like a scar extending from the lip up to the nostril [4]. Sometimes, muscle fibers in the lip beneath the cleft is affected and might require reconstructive surgery [5]. In such cases, it is advised to consult craniofacial clinicians to determine the severity of the cleft [6]. Thus, detailed knowledge of cleft lip and palate is very essential. The aim of this chapter is to highlight the various types of cleft lip and palate, incidences, possible causes and development.
2. Classification of cleft lip and palate
Cleft lip and palate may occur in isolation or in combinations involving lip, maxillary alveolus, hard and soft palate and can be classified in following types [7]
cleft lip
cleft lip and alveolus
cleft lip, alveolus and palate
cleft lip and palate (with an intact alveolus)
cleft palate
3. Etiology of cleft lip and palate
Cleft lip and palate are birth defects or congenital in nature occurring during development. The cause is unknown but risk factors attributing to this facial anomaly are smoking, diabetes, obesity, increased age of mother and certain drugs used during pregnancy [1, 8]. Cleft lip and palate are considered to be polygenic and multifactorial in origin with involvement of many genetic and environmental factors. Literature reports that the cleft lip and palate are due to involvement of genetic factors in 20 to 50% of cases and in rest of the cases, these facial anomalies are reported to be caused by environmental factors or a combination of gene and environmental factors [9]. Few authors are of the view that people with polygenic/multifactorial inheritance are born without cleft lip and cleft palate but umpteen number of genetic and environmental factors are said attributed to cleft lip and palate [9].
4. Genetic factors contributing to cleft lip and cleft palate
Certain syndromes are found to be associated with the cleft lip and palate. Although many types of cleft lip and palate are observed to be familial, in many cases, no identifiable syndrome is found [10]. Genes found to be associated with cleft lip and palate include cleft lip and palate transmembrane protein 1. In one study, cleft lip and palate were observed due to a mutation in hyaluronidase 2 gene [11].
Various syndrome associated with cleft lip and palate are elaborated below:
Van der Woude syndrome is caused by changes in Interferon Regulatory Factor 6
gene. Children with this syndrome have three times more chances of developing cleft lip and palate [12, 13]. Cleft lip and palate associated with neural tube defects are found due to mutations in interferon regulatory factor 6.Siderius X-linked intellectual disability consisting of cleft lip and palate along with facial dysmorphism and mild intellectual disability syndrome is caused due to mutations in
finger protein (PHF)8 gene [14].Stickler syndrome includes cleft lip and palate, joint pain and myopia [15, 16].
Loeys-Dietz syndrome involves cleft palate or bifid uvula, hypertelorism and aortic aneurysm [17].
Hardikar syndrome consists of cleft lip and palate, Hydronephrosis and intestinal obstruction.
Other syndromes which may be accompanied by cleft lip and palate are Patau syndrome, Malpuech facial clefting syndrome, Popliteal pterygium syndrome, Cornelia de Lange syndrome, Treacher Collins syndrome and Pierre Robin syndrome [17].
5. Environmental factors causing cleft lip and palate
Environmental factors in isolation or interacting with genetic factors produce cleft lip and cleft palate. Example of environmental factors along with genetic factors causing the cleft lip and cleft palate is mutation in the gene
Maternal hypoxia due to smoking by pregnant women may also lead to cleft lip [20]. In 6.1% of cases, children were found to born with cleft lip and palate with women smoking during pregnancy. One important point to note here is that cleft lip and palate occur in very early pregnancy, so, stopping smoking after diagnosis of pregnancy may not reduce the incidence of these clefts [21]. Alcohol intake during pregnancy has also been attributed to cleft lip and palate as alcohol influences the development of cranial neural crest cells. But degree of influence of alcohol on neural crest cells is unknown and requires further research [22]. There is evidence of causing cleft lip and palate in children of women who received anti-hypertensive treatment during pregnancy [23]. Various other factors causing cleft lip and palate include pesticide exposure, maternal diet, retinoid intake, anticonvulsant drugs like nitrate compounds, organic solvents, parental exposure to lead, alcohol, cigarette use and intake of psychoactive drugs such as cocaine, crack cocaine and heroin [22].
6. Incidence of cleft lip and palate
Cleft lip and palate are found to present in 1 to 2 per 1000 births in the developed countries [8]. Incidences of cleft lip and cleft palate, alone or in combinations, have been found to differ in ethnic groups. In United States, the prevalence of cleft is found to occur in 6.35 per 10,000 births and that of cleft lip with or without cleft palate in 10.63 per 10,000 births [1]. Prevalence rates of cleft lip with or without cleft palate are observed to be highest in Native Americans and Asians and lowest in Africans. The prevalence of cleft lip with or without cleft palate in major ethnic group is appended below [8]
Native Americans: 3.74/1000
Japanese: 0.82/1000 to 3.36/1000
Chinese: 1.45/1000 to 4.04/1000
Caucasians: 1.43/1000 to 1.86/1000
Latin Americans: 1.04/1000
Africans: 0.18/1000 to 1.67/1000
Cleft lip with or without cleft palate is the most common congenital birth defect with highest cases reported in Asians and Native Americans followed by Europeans, Hispanics and African-Americans. 3800 deaths occurred in the world in 2017, while 14, 600 deaths in 1990 due to cleft lip and palate. Sometimes uvula is also found to have cleft and its prevalence varies from 0.02 to 18.8% being highest in Chippewa and Navajo and lowest in Africans [24, 25].
Cleft lip is two times more frequent in males as compared to females. However, cleft palate is more common in females [8].
7. Development of lip and palate
Face develops from five processes which are formed around primitive mouth called stomodeum. Five processes are frontonasal process, a pair of maxillary process and a pair of mandibular process. The frontonasal process besides forming forehead and nose also forms central part of upper lip called philtrum, the maxillary process forms lateral part of upper lip and lower lip is formed by mandibular process [26].
When cleft lip is in form of a small opening or an indentation in the lip, then it is known as partial or incomplete cleft lip. But, when the cleft continues into the nose then it is known as complete cleft lip. Cleft lip may be unilateral (Figure 1A) with gap present on one side of lip or it may be bilateral cleft lip (Figure 1B) when gap is present on both sides of lip. When the gap is in the middle part of lip, then it is known as central cleft lip (Figure 1C and D) [26, 27].
Figure 1.
Shows various types of cleft lip. A) unilateral cleft lip, B) Bilateral cleft lip, C) Central cleft lip.
Thus, unilateral cleft upper lip is formed when maxillary process fails to fuse with medial nasal process of that side. While bilateral cleft upper lip is formed due to failure of fusion of maxillary process with the frontonasal process. Central cleft upper lip also known as hair lip occurs when philtrum fails to develops [26, 27].
8. Development of cleft palate
Developmentally, palate consists of two parts; primary palate and secondary palate. Primary palate (Figure 2) is formed by fusion of two medial nasal processes. It ossifies to form pre-maxilla. Two shelf like outgrowths called palatine shelves (Figure 2) develop from the inner aspect of maxillary processes which grow medially and then fuse with each other forming secondary palate [28].
Figure 2.
Shows various components of developing palate.
Then ossification extends from the maxillae into the anterior three-fourth of secondary palate forming hard palate (Figure 3). While ossification does not occur in the posterior one-fourth of secondary palate. This part of secondary palate forms soft palate (Figure 3) [28].
Figure 3.
Shows various components of normal palate.
Cleft palate occurs due to failure of fusion of various components of secondary palate. Cleft palate may be complete involving both soft and hard palate or incomplete involving uvula, soft palate and small portion of hard palate [28].
Complete cleft palate: Complete cleft palate may be unilateral or bilateral. Unilateral complete cleft palate (Figure 4) occurs when maxillary processes do not fuse with each other as well as with the pre-maxilla of one side forming cleft between palate and pre-maxilla of one side (Figure 4). It is almost always associated with the cleft lip of same side [28].
Figure 4.
Shows complete unilateral cleft palate.
Bilateral complete cleft palate occurs when both the maxillary processes fail to unite with the pre-maxilla (Figure 5).
Figure 5.
Shows complete bilateral cleft palate.
Incomplete cleft palate [29]: it involves uvula and small portion of soft palate (Figure 6) or it may involve uvula, soft palate and small portion of hard palate (Figure 7).
Figure 6.
Shows incomplete cleft palate involving Uvula and soft palate.
Figure 7.
Shows incomplete cleft palate involving Uvula, soft palate and hard cleft.
9. Clinical implication of cleft lip and palate
Cleft lip may create difficulties during feeding, ear disease, speech, socialization and cognition. Cleft lip and palate may create problems during suckling causing difficulty in feeding [30]. Difficulty of feeding milk in infants with cleft lip and palate can be compensated to some extent by feeding milk in upright position as gravity prevents the milk entering into the nose. Nowadays, specialized gravity feeding instruments such as Haberman Feeder and customized bottles with a combination of nipples and bottle inserts are available for feeding infants with cleft lip and palate [30]. In addition to this, creating a large hole or slit in the nipple of bottle and regularly squeezing the bottle insert can regulate the flow of milk without creating difficulty in feeding. Moreover, maxillary plates can also be used to aid in feeding. Though these methods improve feeding milk to infants, breast feeding is the best option for feeding as it improves weight gain [30, 31]. But, these methods have disadvantage of nasal regurgitation due to communication between the oral cavity and nasal cavity caused by the cleft palate.
10. Dental problems
Appearance of teeth may be slowed up with increasing severity of cleft lip and palate. Most of the dental problems develop during eruption of permanent teeth though dental difficulties during primary teeth eruption cannot be ruled out [9]. Dental problems caused by cleft lip and palate include fused teeth, missing teeth and extra teeth. Moreover, the lateral incisors are found to be missing in some cases with cleft lip and palate. In children with cleft lip and palate, enamel is observed to be hypo-mineralized and so becomes hypoplastic making teeth susceptible for early decay and increased rate of cavities [32]. The cleft lip and palate may also be responsible for abnormal positioning of teeth affecting occlusion and thus creating open bite and cross bite [9, 33].
11. Hearing problems
Children with cleft palate are more susceptible to middle ear infection and otitis media causing hearing impairment. Otitis media results from blockage of Eustachian tube, negative middle ear pressure and collection of fluid in middle ear [34]. Breast milk feeding in children with cleft palate decreases the incidence of otitis media [33].
12. Speech problems
Due to cleft palate, communication is established between mouth and nose causing velopharyngeal insufficiency in which air leaks into the nasal cavity culminating into hypernasal resonance voice and nasal emissions during talking [35]. Other effects of velopharyngeal insufficiency due to cleft palate are speech articulation errors like distortions, substitutions, omissions, compensatory misarticulations and mispronunciations [36].
Hearing is associated with art of speaking. This is because the children with cleft palate have hearing problems so cannot mimic the sounds of speech and have difficulty in acquiring receptive language. In addition to this, lips and palate are used in pronunciation. The hard palate is essential to produce palatal consonants “J” and “T”. Therefore, children with cleft palate find it difficult to pronounce “J” and “T” [35, 36]. So, these children normally require the help of speech therapist in speaking with correct pronunciation.
Thus, children with cleft lip and palate face difficulties in suckling, mastication and speaking and have defective pronunciation.
13. Psychosocial issues
Cleft lip and palate may affect the psychosocial development like self-esteem, social skills and behavior of children. It is reported that children with cleft lip and palate have self-concept akin to their peers without a cleft lip and palate [37]. But as child with cleft lip and palate grows and his interaction with society increases, they do not mix with the peers in a normal way and tend to have increased level of social anxiety due to associated stigma of visible deformities and speech impediments [37]. Moreover, children with cleft lip and palate are reported to have more feelings of anger, sadness, fear and alienation from their peers. In addition to this, psychological issues are not only associated with children with cleft lip and palate but also involve their families specially mothers who experience varying degree of depression and anxiety [38, 39]. In early life, extent and severity of cleft lip and palate can be diagnosed using ultrasound [40]. In ultrasound, upper lip defect is best appreciated on angled coronal scanning. A vertical hypoechoic region through the fetal upper lip usually represents the defect in the cleft lip [40].
Thus, diagnosis and correction of cleft lip and palate are very essential for both children and parents and should be done early in life.
14. Management of cleft lip and palate
Incidence of cleft lip and palate is found to be higher in children with low socioeconomic status [41]. Cleft lip and palate are managed by two methods viz. single stage and multiple stages. As these clinical entities are taken care by coordination of clinicians, dentists along with speech therapist geneticists, nurses, etc., single-stage repair involves low financial burden compared to the multiple stage repair. Therefore, single-stage method should be advocated as the therapy of choice [42].
Nasoalveolar molding (NAM) is advocated by some for repairing the cleft lip and palate. Esenlik et al., in review on (NAM), analyzed the advantages and disadvantages of this method in children with cleft lip and palate and found that NAM method does not have much effect on skeletal facial growth but certainly benefits the affected children with cleft lip and palate, clinicians and society [43]. Reconstructive surgery is another method of managing cleft lip and palate. But, about 50% of children undergoing reconstructive surgery for speech therapy had defective speech and require speech therapy [44]. So, this method is of limited use for correcting cleft lip and palate.
15. Conclusion
Cleft lip and palate are congenital anomalies and may not be disabling but these anomalies definitely affect feeding and speech in children. But as child grows, he may not mix well with peers due to facial disfigurement and it is also responsible for development of anxiety, anger, sadness and fear. In addition to this, parents of children with cleft lip and palate also develop anxiety. So, cleft lip and palate should not be taken lightly and clinicians should be consulted for repairing the cleft lip and palate.
Acknowledgments
No funding has been received from any agency. There is no conflict of interest.
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