Key Points
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Craniofacial anomalies occur in as many as 1 in 500 to 1000 live births for cleft lip and palate, 1 in 2000 for isolated craniosynostosis, and 1 in 20,000 to 50,000 live births for some syndromic types of craniosynostosis. Many of these deformities may be treated by the otolaryngologist–head and neck surgeon with pediatric and/or facial plastic training.
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Craniofacial defects are often part of a broader syndrome affecting many functional systems.
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Appropriate care is best rendered by a multidisciplinary team with diverse expertise.
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Craniofacial disorders are etiologically diverse and genetically heterogeneous.
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Craniofacial skeletal anomalies are treated surgically with techniques that are reliable and reproducible.
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The application of craniofacial surgical principles, developed to treat congenital problems, also serves well for tumor extirpation and trauma repair.
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Several materials are currently available to reconstruct the craniofacial skeleton, but there is wide effort to develop more biomimetic bone substitutes.
Craniofacial surgery is an ever-evolving surgical subspecialty dedicated to restoring form and function to the soft tissues and craniofacial skeleton. Much of the field addresses congenital deformities in the pediatric population, although craniofacial techniques and principles cross over into the management of traumatic and neoplastic deformities in both adult and pediatric patients. Although attempts to alter craniofacial anatomy by surgery or intentional deformation date back thousands of years, much of the growth in this field has occurred in the past few decades. Craniomaxillofacial plastic and reconstructive surgery is a medical and surgical subspecialty that encompasses approaches and techniques developed in the past 50 years that allow for safe, reliable manipulation of the craniofacial skeleton, stable fixation, and decreased likelihood of relapse. Craniofacial anomaly refers to any malformation that involves the face, cranium, or cranial base.
Congenital craniofacial deformities commonly occur as isolated defects and less often as part of a syndrome. The Committee on Nomenclature and Classification of Craniofacial Anomalies of the American Cleft Palate Association has defined craniofacial malformations according to five categories: 1) facial clefts/encephaloceles and dysostoses; 2) atrophy/hypoplasia; 3) neoplasia/hyperplasia; 4) craniosynostosis; and 5) unclassified. Clinical entities such as orbital hypertelorism often exist within a syndrome that clearly fits into one of the aforementioned classifications. Hypoplasia of the midface and micrognathia is one example of atrophy/hypoplasia. Hematologic disorders, neural growth disorders, and overly aggressive cerebrospinal fluid (CSF) shunting may result in secondary craniofacial disorders in children, which may be classified as hyperplasia. Acquired deformities of the craniofacial complex also include those inflicted by means of a traumatic event. Neoplasm (third category) and its treatment are classified as acquired deformities.
The field of craniofacial surgery is large, with many and varied subfields including neurosurgery, general or facial plastic surgery, oral-maxillofacial surgery, otolaryngology, head and neck surgery, and pediatric subspecialties of all these. Because the care of such patients is complex, a multidisciplinary team including not only surgeons but also geneticists, pediatricians, anesthesiologists, ophthalmologists, speech and swallowing experts, audiologists, dentists, and orthodontists is often involved. The objective of this chapter is to provide an overview of craniofacial surgery, providing a framework based on the pathophysiology of major craniofacial anomalies and focusing on cranial vault and craniofacial bony defects. Disorders of first and second branchial arch derivatives that give rise to known craniofacial anomalies are briefly described. Trauma and neoplasm are important contributors to craniofacial disease and are examined briefly in this chapter but discussed in greater detail elsewhere in the text. Facial and palatal clefting is a very important subject in craniofacial surgery and is briefly discussed from a basic perspective.
Epidemiology
Craniofacial anomalies have been reported to constitute approximately one third of all congenital defects. The incidence of assorted individual deformities and syndromes varies. However, the overall incidence is considered to be 0.2 to 0.5 per 1000 births. Interestingly, some craniofacial deformities occur at a uniform rate across racial and ethnic populations, whereas others vary in frequency by race and ethnicity.
Craniofacial anomalies have been reported to occur as part of a genetic condition in about 20% of cases. However, with the discovery of new syndromes and the recognition that “isolated defects” often have a genetic etiology, the proportion of genetic cases is likely to be higher. Transmission can occur via autosomal dominant or recessive inheritance, and most anomalies have similar incidences in males and females. In general, the pathogenesis of craniofacial anomalies is complex, and their etiology is best described as multifactorial.
Mechanisms of Postnatal Facial Growth
Craniofacial bony growth occurs in response to neural tissue growth and expansion. The developing brain highly influences the morphology of the basicranium, which in turn functions as a template for subsequent facial growth.
During development, the pattern of growth is influenced both by functional needs and by physical and biochemical relationships with nearby structures. Currently, craniofacial growth is understood to be a highly complex process, not solely regulated by the central nervous system.
Craniofacial physiology is affected by both displacement and remodeling. Displacement involves pushing away the bone from its articulation with other bones because of the combined effects of growth of the surrounding soft tissue and growth center/sutural activity. Remodeling occurs by resorption and deposition of new bone, resulting in a net vector of growth. The importance of soft tissues in determining growth is exemplified by “adenoid facies.” The entire craniofacial complex system is plastic and in flux throughout the growing period, and it retains some plasticity even after growth is complete, albeit to a far lesser extent. Thus, rigid nonbiologic implants such as titanium have the potential to interfere with normal growth if used during active development, because they lack the plasticity that is essential for dynamic growth.
Throughout the period of craniofacial growth, an overriding homeostasis exists among the different fields of growth. Small aberrations in one field may be counterbalanced by compensatory growth in another, resulting in constant equilibrium. This is very important for the physician to bear in mind when planning surgical or orthodontic intervention. Treatment failure or relapse is likely if that equilibrium is significantly disrupted. Generally, interventions are more likely to succeed if the cause of the abnormality is addressed during periods of rapid growth. In contrast, the effect of the abnormality is more successfully treated during periods of slow growth.
Craniofacial synostosis , or craniosynostosis, in which one or more than one suture closes prematurely, illustrates the morphologic consequence of defective skeletal growth and the importance of homeostasis in craniofacial development ( Fig. 7-1 ). The causes of craniosynostosis are likely multifactorial and the source of some controversy. Craniosynostosis has been associated with abnormalities in sutural biology, various biomechanical forces, and defects in the primary growth centers of the involved bones. Sutural growth is also affected by surrounding tissue interactions. The contacting dura, for instance, influences the continued patency of sutures and helps regulate their closure. Regardless of the underlying etiology of premature closure of cranial sutures, it is clear that a disruption in normal growth near the affected cranial suture(s) leads to compensatory growth in the cranium, at times the basicranium and even the facial skeleton, depending on both type of synostosis and duration of disease. If the synostotic suture is treated early in life while craniofacial growth is still quite active, normal homeostasis may be restored by releasing the synostotic suture. If treated later when active growth is largely complete, the morphologic sequelae of the synostotic suture, including structures affected by compensatory growth, will have to be addressed, because the sutural growth is no longer relevant.
Fusion of the facial processes during embryogenesis is another fundamental aspect of facial growth that is critical to normal development. Orofacial clefting results from a defect in this process. For opposing facial processes to fuse in the midline, the intervening epithelia must be eliminated so that the underlying mesenchymal tissue may coalesce. In the palate, epithelial elimination has been shown to occur through apoptosis, transdifferentiation of epithelial to mesenchymal cells, or cell migration. Lack of fusion may occur as a result of excessive apoptosis, underdevelopment of the mesenchyme of the involved subunits, or inadequate migration or reduced proliferation of neural crest ectomesenchyme. Facial clefting may also result from constricting anatomic defects. For example, in the Pierre Robin sequence, mandibular hypoplasia contributes to glossoptosis (downward or back placement of the tongue), which prevents the palatal shelves from fusing in the midline.
Pathophysiology
A diverse and heterogeneous group of factors may contribute to abnormal craniofacial development, but etiology remains incompletely understood. Great advances have been made in the past few decades toward an understanding of various genetic defects implicated in the development of craniofacial anomalies. In addition, numerous metabolic diseases are known to interfere with bone growth and suture function. Environmental factors have also been shown to exert important influences on embryologic craniofacial development.
Molecular Genetics
Mutations in a variety of genes have been identified that are directly associated with various craniofacial defects ( Table 7-1 ). Major categories of proteins encoded by these genes include:
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Growth factor receptors: fibroblast growth factor receptors (FGFRs) 1, 2, and 3; tumor growth factor-β receptors (TGFβRs) 1 and 2; PTC and FGDY gene products
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Ephrins: membrane-anchored ligands for Eph receptor tyrosine kinases
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Transcription factors: MSX2, ALX4, GLI3, MITF, PAX3, RUNX2, TWIST
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Connective tissue structural proteins: type II and XI collagen, fibrillin-1 (FBN1)
| Condition | Craniofacial phenotype | Gene * |
|---|---|---|
| Loeys-Dietz syndrome (aortic aneurysm, arterial tortuosity, hypertelorism, cleft palate/bifid uvula, craniosynostosis) | Craniosynostosis, cleft palate, hypertelorism | TGF β R1 TGF β R2 |
| Apert syndrome | Craniosynostosis (brachycephaly); wide midline defect closes by coalescence of bony islands; midface malformations; dental crowding; cleft or narrow palate with swellings | FGFR2 |
| Beare-Stevenson cutis gyrata syndrome | Craniosynostosis (kleeblattschädel) or cloverleaf skull | FGFR2 |
| Boston-type craniosynostosis | Craniosynostosis (kleeblattschädel), forehead retrusion, frontal bossing | MSX2 |
| Cleidocranial dysplasia | Delayed suture closure, frontal parietal bossing, wormian bone(s), hyperdontia, tooth eruption defects | RUNX2 |
| Craniofrontonasal syndrome | Craniosynostosis (brachycephaly), central defect between frontal bones, hypertelorism, divergent orbits | EFNB1 |
| Crouzon syndrome | Craniosynostosis (brachycephaly), pronounced digital impressions of skull, midface hypoplasia, shallow orbits | FGFR2 |
| Crouzon syndrome with acanthosis nigricans | Craniosynostosis | FGFR3 |
| Greigcephalopolysyndactyly | Craniosynostosis in small percentage of cases, frontal bossing, sagittal ridging, hypertelorism | GLI3 |
| Muenke-type craniosynostosis (nonsyndromic) | Craniosynostosis (brachycephaly) | FGFR3 |
| Parietal foramina | Symmetric parietal bone defects, cleft lip/palate | MSX2, ALX4 |
| Parietal foramina with cleidocranial dysplasia | Symmetric parietal bone defects | MSX2 |
| Pfeiffer syndrome | Craniosynostosis (brachycephaly) | FGFR1, FGFR2, |
| Saethre-Chotzen syndrome | Craniosynostosis (especially brachycephaly), flat forehead, low hairline | FGFR2, TWIST1 |
| Shprintzen-Goldberg (marfanoid) syndrome | Craniosynostosis (especially lambdoid and sagittal sutures), maxillary and mandibular hypoplasia, palatal abnormalities | SKI |
| Thanatophoric dysplasia II | Craniosynostosis (cloverleaf skull/kleeblatschädel deformity) | FGFR3 |
* Gene abbreviations that have not been defined/spelled out are not acronyms or abbreviations.
FGFRs are transmembrane receptors for fibroblast growth factors (FGFs). FGFs are involved in regulating cell proliferation, differentiation, and migration through a number of pathways. The receptor comprises an extracellular domain (receptor-ligand binding), a transmembrane domain, and an intracellular tyrosine kinase enzymatic domain (see Table 7-1 ). There are several variations of the FGFR protein, all of which have important cell growth functions. Signaling via FGFR1, for instance, has been shown to facilitate neural crest migration, and a defective receptor has been linked to midline facial clefting in mice. Defects in FGFR1 have been found to cause Kallmann syndrome type 2, which can include cleft lip and palate. Defects in FGFR1 and FGFR2 have been linked to syndromes such as Pfeiffer syndrome (in which both receptors are defective) and to conditions of which craniosynostosis is a feature. Mutations in FGFR2 have been shown to be responsible for Apert syndrome, Jackson-Weiss syndrome, Crouzon syndrome, and Beare-Stevenson cutis gyrata syndrome.
Recent evidence has implicated FGFR3 in regulation of skeletal growth. A defective FGFR3 protein is responsible for crouzonodermoskeletal syndrome (Crouzon syndrome with acanthosis nigricans), Muenke-type craniosynostosis, and also the disease process seen in achondroplasia. In achondroplasia, the epiphyseal growth plates in long bones prematurely fuse, leading to abnormalities in the long-bone growth plates that resemble the gross and histologic pathology seen in synchondroses of the calvaria. In Fgfr3 knockout mice (mice in which the gene that encodes this protein has been eliminated), there is severe retardation of skeletal maturation.
The link between known syndromes or anomalies and genetic defects, however, may be complex and difficult to characterize. Defects in each of the three domains (in different FGFRs) may be associated with similar craniofacial abnormalities, yet defects in the same domain of one FGFR type may cause different phenotypes. For instance, identical mutations have been discovered in patients with Crouzon, Pfeiffer, and Jackson-Weiss syndromes, suggesting the involvement of other factors in the ultimate phenotypic expression. Conversely, as is evident in Figure 7-2 , mutations in several distinct domains on one particular FGFR can result in the same phenotype.
As previously mentioned, defects in transcription factors and connective tissue proteins are also implicated in the pathogenesis of craniosynostosis. MSX2 is a homeobox gene that encodes a DNA binding transcription factor. It has been associated with nonsyndromic craniosynostosis (Boston type), and ALX4 , another homeobox gene, has been linked to parietal foramina. Most cases of Saethre-Chotzen syndrome are caused by haploinsufficiency of the TWIST gene, which appears to encode a transcription factor. Mutations in GLI3 , a transcription factor gene, are responsible for Grieg cephalopolysyndactyly (a rare syndrome that can include craniosynostosis).
Genetic defects encoding several different extracellular matrix constituents may lead to anomalies of the craniofacial complex. Defective collagen, such as that seen in osteogenesis imperfecta, is clearly associated with bony abnormalities, although this disease only occasionally affects the craniofacial skeleton. Defective fibrillin (encoded by FBN1 ) results in Shprintzen-Goldberg syndrome with craniosynostosis and maxillary/mandibular hypoplasia. Genes responsible for Stickler syndrome include COL2A1, COL9A1, COL11A1 and COL11A2 , which encode types II, IX, and XI collagen, respectively. There are additional forms of Stickler syndrome for which the genes are yet unknown.
Metabolic Disorders
Several metabolic derangements are known to interfere with craniofacial development, including mucolipidosis, hyperthyroidism, and rickets. The mucopolysaccharidoses are a group of disorders characterized by a deficiency of lysosomal enzymes that results in a buildup of mucopolysaccharides. Although there are several clinical entities, patients with some of the more severe variations of the disease have large and dolichocephalic (long and narrow) skulls with premature closure of the sagittal suture and poor pneumatization of the mastoids and paranasal sinuses.
Intrauterine Causes
Environmental factors that contribute in utero to craniofacial maldevelopment may be categorized as teratogenic, infectious, nutritional, and mechanical. Fetal alcohol syndrome may involve a wide range of defects, including holoprosencephaly. Tobacco use during critical periods of embryogenesis has also been shown to adversely affect craniofacial development. Medications such as hydantoin, phenytoin, valproic acid, and isotretinoin (a vitamin A derivative used in the treatment of acne) can exert deleterious effects on embryogenesis, as can toluene, the environmental contaminant dioxin, and ionizing radiation.
Viral infections during pregnancy may affect expression of cleft lip/palate in patients with mutations of PVRL1 and IRF6 . Nutritional intake is also clearly linked to craniofacial development. Diets and medications that profoundly influence cholesterol levels may cause craniofacial malformations, because cholesterol modulates sonic hedgehog signaling, which is important in mediating craniofacial development. The link between a diet deficient in folic acid and neural tube defects has been well documented and has led to the widespread supplemental addition of folic acid to many processed foods throughout the developed world.
Finally, intrauterine constraint may cause deformation of the craniofacial skeleton. Factors that have been associated with intrauterine constraint include breech presentation, persistent or malpositioned fetal lies, early pelvic engagement of the head, oligohydramnios, primagravidity, multiple gestations, uterine malformations, amniotic bands, and defects in fetal neuromuscular development.
Acquired Craniofacial Deformities
Several postnatal conditions predispose an infant to disrupted craniofacial growth and secondary craniosynostosis. Hematologic diseases such as thalassemias, sickle cell anemia, congenital hemolytic icterus, and polycythemia vera are associated with hyperplasia of the bone marrow, leading to bony overgrowth in the skull which may in turn cause the calvarial sutures to fuse prematurely. Iatrogenic craniofacial anomalies may occur in patients who require ventricular shunts. Excessive shunt volumes may result in a lack of tension across the sutures, which produces an environment that mechanistically resembles conditions predisposing to microcephaly. Trauma and neoplasms are rare causes of acquired craniofacial deformities.
Clinical Manifestations
Congenital Craniofacial Abnormalities
Craniofacial anomalies range from mild functionally asymptomatic defects (e.g., certain single-suture craniosynostoses) to severe anomalies that are not compatible with life such as some types of holoprosencephaly. The craniofacial surgeon may be consulted prenatally based on abnormalities identified on ultrasound or other types of antenatal testing, or sometime thereafter when a baby or child is noted to have an abnormal head shape or unusual craniofacial dysmorphism. A comprehensive history and examination may prompt further consultation with other experts if a syndrome is suspected or discovered. Evaluation by a skilled geneticist in conjunction with genetic testing may also yield important information, although genetic testing does not necessarily change the diagnosis or determine management.. The majority of cases of craniosynostosis are isolated with no other associated anomalies.
Craniosynostosis
Primary craniosynostosis refers to premature closure of one or more cranial sutures which leads to characteristic growth inhibition of calvarial bone perpendicular to the affected suture line (see Fig. 7-2 ). Isolated synostosis of a single suture rarely leads to functional consequences or neurodevelopmental delays. Because the brain is initially rapidly growing, compensatory growth occurs in other parts of the skull where skull growth is unimpeded. Both the growth restriction and the compensatory changes of calvarial shape occur in largely uniform and predictable ways that are characteristic of the underlying disease process, although there is variability in terms of severity and presentation of these deformities. Secondary synostosis may occur with any congenital, metabolic, infectious, or other disorder that leads to brain underdevelopment and subsequent microcephaly.
Scaphocephaly
Sagittal synostosis is the most common type of craniosynostosis, typically presenting with scaphocephaly or dolicocephaly (boat-shaped head/long head). Scaphocephaly may, however, be present as a result of postnatal positioning, which is not uncommon in extremely premature neonates in the NICU or as a normal variant without underlying sagittal synostosis. In sagittal synostosis, the sagittal suture, or part of it, prematurely fuses (see Fig. 7-2 ), which prevents calvarial growth in the transverse dimension. The compensatory growth occurs in the anteroposterior (AP) direction, leaving the patient with decreased biparietal and bitemporal dimensions. The resulting head shape is long and narrow with a cephalic index (transverse width/AP length × 100) of less than 70%, whereas normative cephalic indices are usually between 75% and 85%. There are several variations depending on the extent of premature sagittal fusion and whether or not the posterior portion of the sagittal suture is involved. Isolated occipital cupping may be referred to as “occipital bullet” deformity or bathrocephaly (podium head). Sagittal synostosis may involve primarily the anterior portion of the sagittal suture, in which case more pronounced anterior frontal bossing is present. Synostosis may vary from partial to complete synostosis.
Trigonocephaly
Trigonocephaly is associated with metopic suture synostosis and refers to the characteristic triangular shape of the head when viewed from the vertex or “birds-eye” view. There is a decrease in bifrontal diameter. There can be associated hypotelorism, but functional consequences or neurodevelopmental delays are rare. The suture area is thickened, resulting in an anterior midsagittal ridge, which has been described as resembling the keel of a ship. Metopic craniosynostosis may present along a spectrum; mild cases are manifested by a vertical ridge in the frontal bones termed a metopic ridge ( Fig. 7-3A ), whereas greater degrees of trigonocephaly are seen in more severe cases (see Fig. 7-3B ). The metopic suture is unusual in that it fuses much earlier than most of the other sutures, often by 9 months of age. When the metopic suture fuses, it completely disappears both radiographically and clinically, such that the diagnosis of trigonocephaly is clinical and not radiographic.
Positional Plagiocephaly/Deformational Plagiocephaly
Plagiocephaly, meaning twisted or slanted head, is generally used to describe positional or deformational flattening that is nonsynostotic. It typically involves the occiput as the result of repeated postnatal supine sleep positioning, although intrauterine compressive forces likely play some role in deformation plagiocephaly (DP). It is estimated that 20% of all babies develop such flattening. DP has increased since the early 1990s. At that time, the American Academy of Pediatrics issued recommendations to place sleeping infants in the supine position in an effort to reduce sudden infant death syndrome.
Many babies favor one side when sleeping, which leads to characteristic unilateral occipital flattening with concomitant anterior shifting of the same-sided ear and ipsilateral frontal bossing. A “parallelogram” shape of the vertex skull results, although positional brachycephaly in which the entire occiput is flattened is also common. Congenital torticollis of the sternocleidomastoid muscle is the causative factor in about one third of DP, generally occurring contralateral to the side of head tilt. Congenital torticollis is manifested by ipsilateral head tilt and contralateral head twist and is itself likely related to fetal positioning and/or intrauterine constraint.
Mild positional flattening may self-correct as babies gain increased strength to turn their necks and roll over. When diagnosed in the first months of life, DP can be treated by encouraging “tummy time” or prone positioning while the child is awake. Repositioning the infant to minimize compressive forces on the flattened side and attempt to increase pressure on the more prominent occiput may also be effective. Congenital torticollis may be treated with neck stretching exercises and physical therapy; however, once a child reaches 5 to 6 months of age, repositioning maneuvers are less likely to be as successful in correcting head shape. For severe deformities, an orthotic molding helmet or band may be useful ( Fig. 7-4 ). Helmets are most effective when worn full time for 3 to 6 months and when used in the first year of life. Although there are reports of potential neurodevelopmental delays, visual problems, and displacement of the temporomandibular joint, most evidence suggests that the effects of deformational plagiocephaly on the calvarium are chiefly aesthetic.
Synostotic Plagiocephaly
Synostotic plagiocephaly may be either anterior or posterior , referring to unilateral coronal synostosis and lambdoid synostosis, respectively ( Fig. 7-5 ). In coronal synostosis, the forehead of the affected side is flat, whereas the supraorbital rim is elevated and displaced posteriorly at or posterior to the plane of the cornea. The supraorbital rim normally lies about 1 cm anterior to the cornea. The nasal root may be deviated to the side of the defect, and the contralateral forehead is bossed. If the supraorbital rim is pushed down. it may lead to vertical dystopia, which lends a quizzical or cockeyed squint to the eyes, manifested as the “Harlequin” appearance on plain X-ray imaging ( Fig. 7-6 ). The ipsilateral auricle is anteriorly displaced, but the occiput is minimally affected.
In unilateral lambdoid synostosis, there is an occipital flatness on the affected side, and the ipsilateral auricle is posteriorly displaced. The appearance when viewed from above has been termed a “trapezoid” shape, as the forehead is not typically affected. True lambdoid synostosis is a rare entity estimated to occur 1 of 100,000 live births. Lambdoid synostosis may be mistaken for the much more common entity of DP, as both involve a flat occiput. However, the diagnosis of DP can usually be established by a thorough history, as it is usually progressive and related to supine positioning on the affected side. Unlike DP, lambdoid synostosis does not characteristically present with ipsilateral frontal bossing, and the auricle is posteriorly rather than anteriorly displaced ( Fig. 7-7 ).
Brachycephaly
Brachycephaly or “short head,” occurs when the transverse dimension of the head is as long as the AP dimension. The cephalic index approximates 1. The head has an overall round appearance from the vertex view, as well as a round-appearing head and face from the frontal view. Brachycephaly is most commonly nonsynostotic and related to positioning ( Fig. 7-8 ).
Brachycephaly when present at birth is usually associated with bilateral coronal synostosis. Synostotic brachycephaly is frequently associated with a syndrome (see Table 7-1 ; Fig. 7-9 ). It is often accompanied by turricephaly (tall head) or acrocephaly (pointed head). As a result of this sutural synostosis, the skull is unable to expand in the AP dimension. In order to accommodate the expanding intracranial content, the skull grows in the lateral and superior dimensions. The neonate’s cranium, therefore, has a smaller AP distance and greater lateral dimensions. The forehead comes right off the nose with a low hairline, and the glabellar depression is absent. Multisuture synostosis including synostotic brachycephaly carries a higher incidence of elevated intracranial pressure; thus, a good fundoscopic exam is important to rule out papilledema.
Acrocephaly
Acrocephaly (also known as oxycephaly and turricephaly ) consists of a skull that is high and conical ( Fig. 7-10 ). This abnormality can develop as a result of progressive postnatal involvement of both the sagittal and coronal sutures. Compensatory growth occurs through the anterior fontanelle.
Kleeblattschädel
Kleeblattschädel is also known as cloverleaf skull ( Fig. 7-11 ). It results from near pansynostosis in which premature fusion of all sutures occurs with the exception of the metopic suture. The bone overlying the sutures is very thick, but the intervening bone is thin. The expanding intracranial content tends to cause a ballooning of the thin bone between the sutures. This compensatory growth, in addition to expansion through the remaining open sutures, gives the characteristic lobular appearance of a cloverleaf. The skull growth falls drastically short of the needs of intracranial expansion, giving rise to neurologic impairment, increased intracranial pressure (ICP), and, often, secondary hydrocephalus. These patients exhibit exorbitism, in which the eyes bulge from hypoplastic orbits which may lead to corneal exposure, orbital keratitis and blindness. The optic nerves may also be at risk for damage. Kleeblattschädel requires prompt surgical attention to release the brain from multisuture synostotic compressive forces.
Facial Clefts
Facial clefts constitute a large category of facial anomalies that are distinct from more common orofacial clefts involving solely the lip and/or palate. In Tessier’s system ( Fig. 7-12 ), a facial cleft is classified on the basis of its position relative to the midsagittal plane. These anomalies may present unique challenges to the surgeon. Facial clefts are rare and may be associated with amniotic bands.
Encephalocele
An encephalocele is a protrusion of intracranial contents through a defect in the craniofacial skeleton ( Figs. 7-13 and 7-14 ). Encephaloceles may occur anywhere along the skull or skull base and are classified by location. These lesions may vary in their content and are named accordingly as meningoceles (containing meninges alone), meningoencephalocele (meninges and brain), or meningoencephalocystocele (ventricle, brain, and meninges).
Craniofacial Syndromes
The syndromes that cause craniofacial anomalies vary markedly in clinical presentation. Knowledge of the most common syndromes is important to focus the examination and understand which consultations are needed.
Crouzon Syndrome
Crouzon syndrome is an autosomal dominant condition that exhibits complete penetrance and variable expressivity. It often involves the coronal sutures, resulting in brachycephaly, but multiple sutures may be affected. Calvarial suture defects may occur prenatally or throughout the first 5 years of life. While the mandible is typically close to normal, hypoplasia of the midface (maxilla) leads to class III malocclusion. Exorbitism occurs as a result of decreased bony orbital volume (in contrast to exophthalmos, which results from greater intraorbital content). Intelligence is usually normal if patients are appropriately managed.
Apert Syndrome
Most cases of Apert syndrome arise sporadically through new mutations, although some familial cases with autosomal dominant transmission have been reported. Apert syndrome resembles Crouzon syndrome in several ways. The disorder is characterized by brachycephaly (with resultant turricephaly) and midfacial hypoplasia (with associated orbital and dental issues). Unlike Crouzon syndrome, Apert syndrome is associated with symmetric syndactyly of the hands and feet as well as other axial skeletal abnormalities. The palate frequently has a high arch and may be cleft. The defects in Apert syndrome are present at birth, and intelligence may be affected.
Pfeiffer Syndrome
Pfeiffer syndrome is an autosomal dominant disorder that features craniosynostosis. The coronal sutures are frequently involved, giving rise to brachycephaly, but the sagittal and lambdoid sutures may also be involved. Affected patients may have midface hypoplasia with associated orbital and dental issues, as well as enlarged thumbs and big toes.
Jackson-Weiss Syndrome
Jackson-Weiss syndrome is an autosomal dominant disorder with high penetrance and variable expressivity with features similar to Pfeiffer syndrome. Brachycephaly is common, the big toes are abnormally wide, but the thumbs are typically normal. Midfacial hypoplasia is more common than in Pfeiffer syndrome. Jackson-Weiss syndrome was originally identified in the Amish population, but may occur in other populations as well.
Saethre-Chotzen Syndrome
Saethre-Chotzen syndrome is an autosomal dominant disorder with full penetrance. Affected patients have craniosynostosis, often with brachycephaly, with a low hairline, ptosis, brachydactyly, and a high arched palate with occasional palatal clefting. Midface hypoplasia is not common.
Carpenter Syndrome
Carpenter syndrome is a rare autosomal recessive syndrome. Craniosynostosis may involve the sagittal, lambdoid, and coronal sutures. Midfacial hypoplasia, if present, is usually mild. Other features include developmental delay, preaxial polysyndactyly of the feet, and other syndactyly.
Stickler Syndrome
Stickler syndrome is an autosomal dominant syndrome with variable expressivity, with an incidence of about 1 in 10,000. It is a connective tissue disorder with ocular, orofacial, skeletal, cardiac, and auditory manifestations, caused by mutations in genes that encode collagen. The orofacial phenotype is characterized by occasional midface underdevelopment, mandibular hypoplasia, and cleft palate. About 30% to 40% of patients with Pierre Robin sequence (micrognathia, glossoptosis, and cleft palate) also have Stickler syndrome. It is thus the most common syndrome associated with Pierre Robin sequence, but often goes unrecognized in its mild forms.
Velocardiofacial Syndrome
Velocardiofacial syndrome is an autosomal dominant syndrome with variable expressivity and penetrance, caused by deletions in chromosome 22q11. There are numerous associated anomalies aside from the well-documented craniofacial, cardiac, and vascular malformations. The craniofacial anomaly broadly consists of a more open angle of flexion in the basicranium, which affects the appearance of the midface and lower face (mandible). Clefting of the secondary palate may be overt, a submucous cleft, or an occult submucous cleft that is apparent only on nasopharyngoscopy. Velocardiofacial syndrome may be difficult to recognize, especially in patients with normal or mildly affected facial features.
Treacher Collins Syndrome (Mandibulofacial Dysostosis)
Treacher Collins syndrome is an autosomal dominant disorder with variable penetrance and expressivity. It involves numerous bilateral developmental abnormalities in structures that derive from the first and second branchial arches. Clinical features include zygomatic hypoplasia, micrognathia, dysplastic ears, antimongoloid slants to the eyes, colobomas of the lower eyelids, and deficient eyelashes in the medial two thirds of the lower eyelids. Mandibulofacial dysostosis is associated with Pierre Robin sequence and palatal clefting in 35% of cases. Severe obstructive apnea secondary to the micrognathia and glossoptosis often requires intervention.
Hemifacial Microsomia or Craniofacial Microsomia
Hemifacial microsomia (HFM) refers to a group of anomalies that originate from unilateral defects in the first and second branchial arches, with an incidence of 1 per 5600 births. Most cases are sporadic, although familial cases have been reported. No specific molecular etiology has been identified, although one theory proposes that this syndrome results from a unilateral hemorrhagic event involving the stapedial artery during early craniofacial development. HFM, also known as Goldenhar syndrome, is more aptly termed craniofacial microsomia because it is often bilateral. The manifestations of HFM are present at birth and may be quite diverse in terms of severity and scope, involving the soft and skeletal tissues of the face and external and middle ears. Patients with HFM may manifest temporal, zygomatic (malar), maxillary, and mandibular hypoplasia; hypoplastic facial musculature; and cleft lip and palate. HFM involves a wide variety of external and middle ear deformities, including atresia of the external auditory canals and preauricular skin tags HFM. Ocular involvement may present as colobomas, epibulbar choristomas, blepharophimosis, and/or strabismus. A variety of other, noncraniofacial abnormalities are associated with HFM, including fusion of vertebrae, spina bifida, and other vertebral anomalies.
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