Hemifacial microsomia is the second most common facial anomaly after cleft lip and palate. It is a predominantly unilateral malformation of craniofacial structures that originally develop fromthe first and second branchial arches. The characteristic findings of hemifacial microsomia include hypoplasia of the malar, maxillary, and/or mandibular regions of the face with associated abnormalities of the ears and vertebrae (Burck, 1983). The term hemifacial microsomia was first used by Gorlin and Pindborg (1964), who described a condition consisting of unilateral microtia, macrostomia, and failure of formation of the mandibular ramus and condyle. Since then, hemifacial microsomia has been considered one phenotypic manifestation of a group of disorders that affect the face, ears, eyes, vertebrae, heart, and kidneys. This spectrumof disorders has been called “oculoauriculovertebral dysplasia,” although this is technically incorrect because the term dysplasia refers to abnormalities of cellular differentiation. An association between hemifacial microsomia, auricular malformations, and specific malformations of the eye known as epibulbar dermoids was first recognized by Goldenhar in 1952 (Heffez and Doku, 1984). Although the name Goldenhar syndrome is widely used, the use of the word syndrome is also incorrect because there is no known unique cause for this phenotype. At present, hemifacial microsomia is considered to be part of a complex developmental field defect known as the oculoauriculovertebral (OAV) anomaly. There is no agreement on the minimal diagnostic criteria and the phenotypic spectrum for this condition (Rollnick, 1988). It is not known whether OAV anomaly represents one entity with variability in the phenotype or whether there are several different entities with similar phenotypes. Causal heterogeneity for this group of conditions has been described (Rollnick, 1988). However, any fetus identified with asymmetry of the facial structures or hemifacial microsomia should be considered to be at risk for associated eye, ear, vertebral, cardiac, and renal malformations.

The incidence of hemifacial microsomia varies considerably according to the minimal diagnostic criteria used to define the condition. When the most mildly affected individuals are included, the incidence is on the order of 1 in 3000 to 1 in 5000 livebirths (Benacerraf and Frigoletto, 1988). When only the most severely affected patients are included, the incidence was on the order of 1 in 45,000 livebirths in one study performed in Northern Ireland (Morrison et al., 1992). Approximately two-thirds of cases of hemifacial microsomia are unilateral (Singer et al., 1994). When unilateral, the right side is more commonly involved (Poon et al., 2003). When the condition is bilateral, one side is more severely affected than the other (Heffez and Doku, 1984). In one report of 294 patients affected with the oculoauriculovertebral anomaly, a male to female ratio of 2:1 was observed (Rollnick et al., 1987). In the same study, 78% of affected individuals were white. In this study, 154 patients (52%) had no other congenital anomaly in addition to the anomalies required for diagnosis, which consisted of microtia, mandibular hypoplasia, anomalies of the cervical spine, and/or anomalies of the eye, including epibulbar dermoids or lipodermoids. Of the remaining patients, 51 (18%) had one additional anomaly and 89 (30%) had two or more additional anomalies (Rollnick et al., 1987).

Relatively few reports of prenatal sonographic diagnosis of hemifacial microsomia have been described. In 1986, Tamas et al. described a fetus with polyhydramnios, unilateral anophthalmia, and a malformed, low-set ipsilateral ear. This was followed by a report in 1988 from Benacerraf and Frigoletto, who described a fetus at 29 weeks of gestationwith moderate polyhydramnios, an abnormal fetal facial profile with micrognathia, a right kidney hydronephrosis and hydroureter, an enlarged echogenic left lung, a ventriculoseptal cardiac defect, and a two-vessel umbilical cord. Prenatally, a cystic adenomatoid malformation of the lung was suspected, but this was refuted postnatally when it was found that the right lung was absent and the left lung was hyperexpanded. The infant died during the newborn period. Physical examination at birth revealed a right-sided mandibular hypoplasia, an abnormal right ear, and vertebral anomalies that were not appreciated antenatally. Goldenhar syndrome was diagnosed postnatally (Benacerraf and Frigoletto, 1988).

Potential sonographic findings in cases of hemifacial microsomia or OAV anomaly might include polyhydramnios due to impaired fetal swallowing. This is likely to be the result of either unilateral mandibular hypoplasia or micrognathia due to hypoplasia of the condyle and ramus, which has been documented in 60% of infants affected with these conditions (Heffez and Doku, 1984). Some infants with OAV anomaly have intrauterine growth restriction (Kobrynski et al., 1993). Inone fetuswith Goldenhar syndrome, a lipoma of the corpus callosum, which presented as a hyperechoic midline structure, was described (Jeanty et al., 1991). In another case, the prenatal sonographic diagnosis of OAV anomaly at 15 weeks’ gestation was suggested by the presence of a maxillary cleft in association with unilateral microophthamia (DeCatte et al., 1996). More recently, Goldenhar syndrome was diagnosed in a fetus at 24 weeks due to marked hemifacial microsomia and ipsilateral cerebellar hemisphere hypoplasia (Martinelli et al., 2004).

In any fetus in whom facial asymmetry is suspected, an attempt should be made to sonographically examine the fetal ears, because microtia or other ear abnormalities are frequently seen in association with the mandibular hypoplasia (Figure 24-1). The spine should be observed closely, as skeletal anomalies are the most common associated malformations (due to hemivertebrae and scoliosis) (Poon et al., 2003). The prevalence of associated congenital heart disease in infants with OAV anomaly is increased (Kumar et al., 1993; Poon et al., 2003). Two-thirds of these cases are either tetralogy of Fallot or a ventriculoseptal defect. In one study, 19% (6 of 32) of patients with OAV anomaly had congenital heart disease. The cardiac lesions in this study were varied and more complex than previously reported, including double outlet ventricle, pulmonary atresia with ventriculoseptal defect, and total anomalous pulmonary venous return. Five of the six cases were conotruncal malformations. Pulmonary and renal anomalies were noted to be more common in the patients with congenital heart disease. Morrison et al. (1992) also reported that 8 of their 25 patients with OAV anomaly had congenital heart disease. In fetuses with hemifacial microsomia, the presence of congenital heart disease is an important prognostic factor because of the very high neonatal mortality rate when congenital heart disease exists. In Morrison et al.’s study (1992), six of eight infants died before 2 years of age, and in Kumar et al.’s study (1993), four of six infants died during the newborn period.

A high incidence of urinary tract abnormalities has also been demonstrated in infants with OAV anomaly. Of 20 infants with OAV anomaly, 14 were demonstrated to have a variety of renal and urinary anomalies, including ectopic or fused kidneys, renal agenesis, vesicoureteral reflux, ureteropelvicobstruction, ureteral duplication, andmulticystic kidneys (Ritchey et al., 1994). Therefore, any fetus identified with hemifacial microsomia should undergo a detailed sonographic study with particular attention paid to the ears, heart, vertebrae, and kidneys.

Hemifacial microsomia, initially detected by prenatal sonography, has also been demonstrated by magnetic resonance imaging at 20 weeks of gestation (Hattori et al., 2005).

The differential diagnosis includes conditions that are considered to be part of the phenotypic spectrum of hemifacial microsomia and OAV anomaly, as well as other syndromes that include hemifacial microsomia as one component. The differential diagnosis of hemifacial microsomia variants includes microtia, hemifacial microsomia, Goldenhar syndrome, OAV dysplasia, and otomandibular dysostosis. The minimal criteria for these conditions are given in Table 24-1. Other conditions associated with the hemifacial microsomia phenotype include branchio-oto-renal syndrome, a dominantly inherited disorder that consists of hemifacial microsomia, preauricular and branchial sinuses and kidney anomalies; Townes–Brocks syndrome, another dominantly inherited disorder that consists of hemifacial microsomia and anal and digital anomalies; and hemifacial microsomia/radial limb defects, which include the additional finding of triphalangeal thumbs. There have been other case reports of hemifacial microsomia in association with other, more severe anomalies (Dodinval, 1979; Rollnick, 1988).