Anomalies_of_face_development.pdf

Anomalies of Face Development Fevziye Figen Kaymaz M.D., Ph.D. Prof. of Histology & Embryology [email protected] 1 OBJECTIVES • To learn the developmental anomalies of face • To identify the types of cleft lip and palate 2 ATRESIA OF THE NASOLACRIMAL DUCT • Part of the nasolacrimal duct...

Anomalies of Face Development Fevziye Figen Kaymaz M.D., Ph.D. Prof. of Histology & Embryology [email protected] 1 OBJECTIVES • To learn the developmental anomalies of face • To identify the types of cleft lip and palate 2 ATRESIA OF THE NASOLACRIMAL DUCT • Part of the nasolacrimal duct occasionally fails to canalize, resulting in congenital atresia (lack of an opening) of the nasolacrimal duct. Obstruction of this duct with clinical symptoms occurs in approximately 6% of neonates. CONGENITAL AURICULAR SINUSES AND CYSTS • Small auricular sinuses and cysts are usually located in a triangular area of skin anterior to the auricle of the external ear however, they may occur in other sites around the auricle or in the lobule (earlobe). Although some sinuses and cysts are remnants of the first pharyngeal groove, others represent ectodermal folds sequestered during formation of the auricle from six auricular hillocks (nodular masses of mesenchyme from the first and second arches that coalesce to form the auricle). The sinuses and cysts are classified as minor defects that have no serious medical consequences. 4 Auricular Sinus & Cysts • Remnants of 1st branchial cleft • Located at triangular skin region anterior to auricle • Little anomalies that not causes clinical importance CLEFT LIP AND CLEFT PALATE • Clefts of the upper lip and palate are common craniofacial birth defects. • they result in an abnormal facial appearance and defective speech. • There are two major groups of cleft lip and cleft palate: -Anterior cleft defects -Posterior cleft defects • Anterior cleft defects include cleft lip with the alveolar part of the maxilla. or without a cleft of • In a complete anterior cleft defect, the cleft extends through the upper lip and alveolar part of the maxilla to the incisive fossa, separating the anterior and posterior parts of the palate • Anterior cleft defects result from a deficiency of mesenchyme in the maxillary prominences and the median palatine process. • Posterior cleft defects include clefts of the secondary palate that extend through the soft and hard regions of the palate to the incisive fossa, separating the anterior and posterior parts of the palate • Posterior cleft defects result from defective development of the secondary palate and growth distortions of the lateral palatine processes that prevent their fusion. Other factors such as the width of the stomodeum, mobility of the lateral palatine processes (palatal shelves), and altered focal degeneration sites of the palatal epithelium may contribute to these birth defects. • A cleft lip with or without a cleft palate occurs approximately once in 1000 births, • Between 60% and 80% of affected neonates are male. • The clefts vary from incomplete cleft lip to those that extend into the nose and through the alveolar part of the maxilla • Cleft lip may be unilateral or bilateral. • A unilateral cleft lip results from failure of the maxillary prominence on the affected side to unite with the merged medial nasal prominences. Failure of the mesenchymal masses to merge and mesenchyme to proliferate and smooth the overlying epithelium results in a persistent labia Groove. The epithelium in the labial groove becomes stretched, and the tissue in the floor of the groove breaks down, resulting in a lip that is divided into medial and lateral parts. A bridge of tissue, called the Simonart band, sometimes joins the parts of the incomplete unilateral cleft lip. • A bilateral cleft lip results from failure of the mesenchymal masses in both maxillary prominences to meet and unite with the merged medial nasal prominences. The epithelium in both labial grooves becomes stretched and breaks. In bilateral cases, the defects may be dissimilar, with various degrees of defect on each side. • When there is a complete bilateral cleft of lip and alveolar part of the maxilla, the median palatal process hangs free and projects anteriorly. These defects are especially deforming because of the loss of continuity of the orbicularis oris muscle, which closes the mouth and purses the lips. • A median cleft lip is a rare defect that results from a mesenchymal deficiency. This defect causes partial or complete failure of the medial nasal prominences to merge and form the median palatal process. • A median cleft of the lower lip is also rare and results from failure of the mesenchymal masses in the mandibular prominences to merge completely and smooth the embryonic cleft between them. • A cleft palate with or without a cleft lip occurs approximately once in 2500 births, and it is more common in girls than in boys. The cleft may involve only the uvula or the cleft may extend through the soft and hard regions of the palate. In severe cases associated with a cleft lip, the cleft in the palate extends through the alveolar part of the maxilla and lips on both sides A complete cleft palate is the maximum degree of clefting of any particular type. For example, a complete cleft of the posterior palate is a defect in which the cleft extends through the soft palate and anteriorly to the incisive fossa The landmark for distinguishing anterior from posterior cleft defects is the incisive fossa. Unilateral and bilateral clefts of the palate are classified in three groups: • Clefts of the anterior palate (clefts anterior to the incisive fossa) result from failure of mesenchymal masses in the lateral palatal processes to meet and fuse with the mesenchyme in the primary palate. • Clefts of the posterior palate (clefts posterior to the incisive fossa) result from failure of mesenchymal masses in the lateral palatine processes to meet and fuse with each other and the nasal septum. • Clefts of the secondary parts of the palate (clefts of the anterior and posterior palates) result from failure of the mesenchymal masses in the lateral palatine processes to meet and fuse with mesenchyme in the primary palate, with each other, and the nasal septum. Cleft Lip and Cleft Palate Infant with unilateral cleft lip and cleft palate. Clefts of the lip, with or without a cleft palate, occur in approximately 1 in 1000 births; most affected individuals are boys. (Courtesy of A.E. Chudley, MD, Professor of Pediatrics and Child Health, Children's Hospital and University of Manitoba, Winnipeg, Manitoba, Canada.) • Most clefts of the upper lip and palate result from multiple genetic and nongenetic factors (multifactorial inheritance; with each causing a minor developmental disturbance. Several studies show that the interferon regulatory factor 6 gene (IRF6) is involved in the formation of isolated clefts. • Some clefts of the lip and/or palate appear as part of syndromes determined by single mutant genes. Other clefts are parts of chromosomal syndromes, especially trisomy 13. • A few cases of cleft lip and/or palate appear to have been caused by teratogenic agents (e.g., anticonvulsant drugs). • Studies of twins indicate that genetic factors are more important in cases of cleft lip with or without a cleft palate than in cleft palate alone. • A sibling of a child with a cleft palate has an elevated risk of cleft palate but has no increased risk of cleft lip. A cleft of the lip and alveolar process of the maxilla that continues through the palate is usually transmitted through a male sex-linked gene. When neither parent is affected, the recurrence risk in subsequent siblings is approximately 4%. OTHER FACIAL DEFECTS • Congenital microstomia (small mouth) results from excessive merging of the mesenchymal masses in the maxillary and mandibular prominences of the first pharyngeal arch. In severe cases, the defect may be associated with underdevelopment (hypoplasia) of the mandible. • A single nostril results when only one nasal placode forms. A bifid nose results when the medial nasal prominences do not merge completely; the nostrils are widely separated and the nasal bridge is bifid. • In mild forms, there is a groove in the tip of the nose. At the beginning of the second trimester, features of the fetal face can be identified sonographically. Using this imaging technique, facial defects such as a cleft lip are readily recognizable. FACIAL CLEFTS • Various types of facial clefts occur, but all are rare. Severe clefts are usually associated with gross defects of the head. Oblique facial clefts are often bilateral and extend from the upper lip to the medial margin of the orbita. When this occurs, the nasolacrimal ducts are open grooves (persistent nasolacrimal grooves). Oblique facial clefts associated with cleft lip result from failure of the mesenchymal masses in the maxillary prominences to merge with the lateral and medial nasal prominences. Lateral or transverse facial clefts run from the mouth toward the ear. • Bilateral clefts result in a very large mouth (macrostomia). In severe cases, the clefts in the cheeks extend almost to ears Tooth Abnormalities • Natal teeth have erupted by the time of birth. Usually, they involve the mandibular incisors, which may be abnormally formed and have little enamel. • Teeth may be abnormal in number, shape, and size. They may be discolored by foreign substances, such as tetracyclines, or be deficient in enamel, a condition often caused by vitamin D deficiency [rickets]. Many factors affect tooth development, including genetic and environmental influences. References 1. Sadler TW, Langman's Medical Embryology 13E 2. Moore KL, Persaud TVN, Torchia MG Developing Human 9e 3. Carlson BM Human Embryology & Developmental Biology, 5E 25