Cleft lip (cheiloschisis): Failure of fusion of maxillary and medial nasal processes.
Cleft palate (palatoschisis): Failure of fusion of lateral palatine/median palatine processes and nasal septum.
A cleft is a fissure or split in either the upper lip or palate of the mouth. It can also present as both. During the 6th and 12th week of fetal gestation, the left and right sides of the facial skeleton fuse together towards the midline. When these structures fail to do so, the result is a craniofacial cleft. Clefts can occur as an isolated occurrence or as apart of a specific syndrome. Most clefts can be picked up by ultrasound during the routine 20-week scan or soon after birth. Since clefts involve the anatomy of the cranium and vocal tract, effects on speech, feeding, hearing, jaw development and dental issues are common.
Cleft lip and palate is the most common facial birth defect.
In the UK, 1 in every 700 baby is born with a cleft, however, the type and severity of the cleft varies. In those babies affected, approximately half are born with both cleft lip and palate. One-third is affected with cleft palate only and 1/10 has cleft lip only. Boys are commonly affected with a cleft lip or combined cleft lip and palate, whereas cleft palate is more common in girls.
During the fourth and seventh weeks of gestation, the upper lip forms from the medial and maxillary processes. Lack of fusion between the medial nasal and maxillary processes at the fifth week of gestation results in an opening or gap. Severity of the cleft varies widely from a small slit to a large gap that may extend to the nose. It can occur unilaterally, bilaterally or at the center of the lip. Left sided unilateral clefts are the most common. In cases where fusion of the palatal shelves is impaired, cleft lip is accompanied by cleft palate.
Fusion of the palatal shelves, which eventually fuse to form the roof of the mouth, begin to unite between eight and twelve weeks of gestation. Failure of fusion of the palatal shelves results in cleft palate. Severity ranges from an opening at the back of the soft palate towards the throat, to a complete separation of the palate.
In addition to the previous orofacial malformations discussed, a cleft of the soft palate known as submucous cleft palate is worth mentioning. In this condition, the palate appears to be structurally intact, however there are bony and/or muscular malformations underlying the skin’s surface. It has a classical presentation of bifid, or split uvula as demonstrated in the figure. It can occur as an isolated condition (the majority) or with cleft lip. This type of cleft can go undiagnosed for several months or years until symptoms start appearing. Symptoms that may suggest a hidden cleft palate are:
Generally, orofacial clefts are diagnosed by physical examination at the time of birth, however until recent advances, facial clefts have been diagnosed in utero. During the routine 20-week ultrasound examination, diagnosis of clefts has been made when the fetal face is positioned correctly.
Although the exact cause of the condition is unknown, cleft lip and palate is considered a multifactorial disease, where genetics and environment play a significant role.
Several genes have been identified that may be responsible for the cause of cleft lip and palate.
The environment may also play a role in causing or interact with genetics to produce orofacial clefting. A list of factors is outlined below:
Cleft lip and palate are treatable conditions via surgery. Once diagnosed, children are referred to a cleft palate team that initiates the first steps of treatment. Treatment can be life long, and vary depending on the type and severity of the cleft. Generally, surgery to repair to an orofacial clefting is recommended within the first twelve months after birth.
Repair of cleft lip often follows the “rule of 10s” established by surgeons Wilhelmmesen and Musgrave which states that surgery be preformed on the child at 10 weeks of age, weighs at least 10 lbs, and has at least 10g hemoglobin. The most common procedure preformed is the Millard procedure founded by surgeon Ralph Millard. The figure below outlines how the procedure is carried out.
There are several techniques indicated for repair of a cleft palate, however, the trend is towards less scaring and tension on the palate. Scarring of the palate may cause impaired mid-facial growth. One method of repair, known as the Bardach method, uses a two-flap technique as indicated by the figure below.
Centers for Disease Control and Prevention. (2012, July). Facts about cleft lip and cleft palate. Retrieved from http://www.cdc.gov/ncbddd/birthdefects/cleftlip.html
NHS Choices. (2012, May). Cleft lip and palate . Retrieved from http://www.nhs.uk/Conditions/Cleft-lip-and-palate/Pages/Introduction.aspx
Tolarova, M. (2009, March ). Pediatric cleft lip and palate . Retrieved from http://emedicine.medscape.com/article/995535-overview
National Human Genome Research Institute. Retrieved from http://elementsofmorphology.nih.gov/index.cgi?tid=30b9e9da9758d9d7
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