ULTRASOUND EVALUATION OF THE FETAL FACE AND NECK

11 ULTRASOUND EVALUATION OF THE FETAL FACE AND NECK





CRANIOFACIAL ANOMALIES


Craniofacial anomalies include a wide spectrum of malformations. Accurate sonographic diagnosis is possible from early gestation onward and has been described in many publications.15 However, a meticulous scanning technique is required that may be difficult to apply in all examinations. Part of the problem is the reconstruction from tomographic planes of the complex tridimensional anatomy of the face. Furthermore, the face is frequently difficult or impossible to access owing to the position of the fetus. Most national guidelines for the standard examination of fetal anatomy include only a few views of the fetal face, mostly demonstration of orbits and eyes, but do not consider feasible an examination of nose, lips, and chin. The accuracy of referral centers in the investigation of high-risk patients is universally reported to be very high.26 Conversely, the sensitivity of standard examinations in a low-risk group of patients is extremely variable, but tends to be low, in the range of 20% to 40%, with a general tendency to recognize facial malformations associated with other anomalies and to miss the isolated ones.710


Craniofacial malformations may be clinically relevant when seen in isolation, and they may also be associated with other congenital anomalies or be a part of a syndrome. Evaluation of the face is indeed an important part of the clinical genetic examination that is performed postnatally. Therefore, any time a fetal anomaly is identified, the diagnostic workup should include a detailed examination of the fetal face. Apart from obvious malformations, such examinations may also identify subtle dysmorphism that may be crucial for a definitive diagnosis.



Normal Sonographic Anatomy of the Fetal Face


With two-dimensional (2D) ultrasound, a combination of planes must be used to assess facial anomalies (Fig. 11-1).1,3,4,6 The following discussion applies mostly to the midtrimester fetus. However, many details of facial anatomy can be identified as early as 11 weeks, particularly by using transvaginal sonography. In the third trimester of gestation, the examination frequently fails because of intrauterine crowding and unfavorable fetal position. Necessary prerequisites of sonography of the fetal face are that it is accessible and there is a pocket of amniotic fluid in front of it, particularly for three-dimensional scanning.



The midsagittal plane is one of the most useful images in that it allows visualization of the profile, which is also one of the most easily recognizable sonographic images of the fetus for the parents. The forehead, nose, and jaw are readily appreciated in this view, which is important to assess the integrity of these structures as well (Table 11-1).


Table 11-1 Normal Appearance of Fetal Facial Features on Ultrasound in the Midsagittal Section Plane






























Structure Normal Appearance
Forehead Almost linear immediately above the articulation between the nasal bones and the frontal bone, followed by a smooth backwards bend. This view allows measurement of the thickness of the frontal skin (at the level of the middle of the frontal bend).
Nasal bones Oblique along a frontocaudal direction. This view allows measurement of the length of the nasal bones and of the superior facial angle (angle between the vertical section of the frontal bone and the nasal bones).
Nasal soft tissues The columella is oblique or horizontal but should not be vertical.
Upper lip The philtrum is linear, and should present no bulging. This view allows measurement of the length of the philtrum.
Secondary palate Thick echoic line, beginning at the alveolar level, and extending horizontally backward. Its middle is marked by a notch, present on both the superior and inferior edges, and corresponds to the tranverse palatal suture.32 The notch is mostly visible on the superior edge.
Oral cavity The tongue is slightly oblique upward (10–15°). Its tip lies immediately behind the alveolar ridge.
Inferior lip Rests edge to edge with the upper lip. Both lips are arranged along the same axis; there should be no anteroposterior shift between them.
Chin At the level of the vertical line traced on the prefrontal skin (esthetic vertical line of the face).

From Rotten D, Levaillant JM: Two- and three-dimensional sonographic assessment of the fetal face. 1. A systematic analysis of the normal face. Ultrasound Obstet Gynecol 23:224, 2004.


Although the fetal profile is an extremely important view, axial or coronal planes must be obtained to assess the integrity of eyes and lips. A transverse axial scan slightly caudal to the one commonly used for the determination of the biparietal diameter easily reveals orbits and eyes (Table 11-2). The lens and extraocular structures such as muscles, retro-orbital fat, and optic nerve may be visualized. Movements of the eyes are frequently seen during fetal life. It should be remembered that they are usually not synchronous and conjugated. Nomograms for binocular distance, interocular distance, and ocular diameter are available (Table 11-3). By moving the transducer caudally, the superior lip and palate can be visualized. Further caudal movements display the tongue inside the oral cavity and the mandible.


Table 11-2 Normal Appearance of Fetal Facial Features on Ultrasound in the Axial Section Planes





















Structure Normal Appearance
Orbits The interorbital axis is perpendicular to the strict sagittal axis. This view allows measurement of the inner and outer interorbital lengths.
Nasal septum, molar The nasal septum is perpendicular to the axial plane. The two malar arches are symmetric with regard arches to the nasal septum
Upper lip, maxilla There is no lack of continuity of the upper lip. The maxilla appears as a regular, U-shaped echoic alveolus, secondary plate bend. The alveolus and tooth buds appear as hypoechoic spots regularly layered along the alveolar ridge. There is no shift between adjacent alveoli. The hard palate appears as an echoic structure, with a complex shape. The anterior part is semicircular and lies immediately posterior to the alveolar ridge. The posterior part presents as a rectangle-shaped figure, with a notch on its distal side. This view allows measurement of the size of the maxilla.
Oral cavity The tongue occupies the totality of the oral cavity, and is glued to the alveolar ridge. Posteriorly, the tongue ends at the oropharynx level. This view allows measurement of the width and length of the tongue.
Mandible Appears as a regular V-shaped echoic image. Both hemimandibles are almost rectilinear. The symphysis menti is clearly visible. The alveoli appear as regularly layered phypoechoic spots. This view allows measurement of the size of the mandible (for example, mandible width and computation of mandible width/maxilla width ratio).

From Rotten D, Levaillant JM: Two- and three-dimensional sonographic assessment of the fetal face. 1. A systematic analysis of the normal face. Ultrasound Obstet Gynecol 23:224, 2004.



Coronal planes provide similar information to the axial ones (Table 11-4). However, a section tangential to the anterior face and demonstrating the tip of the nose, nostrils, and upper lip is probably the most useful one in assessing the integrity of the upper lip. The nostrils typically appear as two small anechoic areas. In this scanning plane, demonstrating that the hyperechogenic upper lip separates the anechoic nostrils from the oral rim virtually excludes the presence of cleft lip (CL).


Table 11-4 Normal Appearance of the Fetal Facial Features on Ultrasound in the Coronal Section Planes


















Structure Normal Appearance
Nose-mouth view The nostrils are symmetric. The columella is visualized as an intact line.
Alveolus, nasal septum The alveolar ridge is regular and appears as an echoic band where tooth buds appear as hypoechoic holes. The nasal septum is perpendicular to the alveolar ridge lining.
Hard palate Bow-shaped, with a symmetric bend. On each side, it is in continuity with the malar bone.
Retropalatal region The vomer bone appears as a medial echoic spot isolated in an empty space, with no visible supporting structure acquisition

From Rotten D, Levaillant JM: Two- and three-dimensional sonographic assessment of the fetal face. 1. A systematic analysis of the normal face. Ultrasound Obstet Gynecol 23:224, 2004.


The principles of three-dimensional (3D) ultrasound are described in detail elsewhere in this text (see Chapter 24). Diagnosis of craniofacial anomalies is one of the most important areas of application of this technique in obstetric sonography. The advantages over standard 2D ultrasound include the visualization of scanning planes that are physically impossible or very difficult to obtain; the demonstration of the surface of the face; and the possibility to have panoramic views of the entire face (Fig. 11-2). The limitations of the technique are the same as that for 2D sonograms. If the fetal face is not accessible or there is not a pocket of amniotic fluid separating the face from the surrounding structures, a 3D view will be of little help. However, in expert hands, a satisfying examination is possible in the majority of cases in the second to early third trimester. The relative value of 2D over 3D ultrasound has been debated.6,11 In expert hands, 2D ultrasound is extremely precise in the identification and categorization of craniofacial malformations and we have not found any significant diagnostic advantage from the use of 3D.6 It has been suggested that 3D ultrasound of fetal craniofacial anomalies has other potential benefits, such as offering the parents a realistic and understandable image of the fetal anomaly, and allowing better communication with the specialists involved in the management of the infant. Most of the experience with 3D ultrasound has been derived from referral centers. The impact of this technique in standard examinations has yet to be assessed. In general, 3D ultrasound is complex and probably beyond the scope of a basic evaluation of fetal anatomy in low-risk pregnancies. However, it is possible that four-dimensional ultrasound, which allows a rapid and accurate visualization of the external surface of the fetus, could prove useful for assessment of facial anatomy in such settings.



Once an ultrasound volume has been acquired, it can be studied with a variety of approaches. Thus far, three modes have been reported to be useful in the diagnosis of craniofacial anomalies. The multiplanar mode consists in the simultaneous demonstration of three orthogonal planes whose direction is chosen by the operator. Typically, the volume is obtained from the profile view of the fetus, which is displayed on the upper left corner of the screen, while the two perpendicular planes are demonstrated in the upper right and lower quadrants (see Fig. 11-2). The advantage is that it may be difficult at times to obtain the exact plane in a moving fetus. The surface mode allows one to visualize the external surface of the fetal face when it is surrounded by fluid (Fig. 11-3). Eventually, the maximum or transparent mode allows one to demonstrate the brightest echoes within the volume and it can be used to visualize the skull (Fig. 11-4).




One limitation of 2D ultrasound is the difficulty in visualizing clearly the posterior portion of the palate, owing to shadowing artifacts arising from the anterior palate. 3D sonography often overcomes this difficulty. One approach is the so-called reverse view of the face, that is, once the volume has been acquired, the face is viewed in surface mode from the back instead from the front (Fig. 11-5).11,12 Another approach consists in insonating the face at an angle that demonstrates the palate (Figs. 11-6 and 11-7).13





Magnetic resonance imaging has also been used in the diagnostic workup of craniofacial anomalies and may be helpful particularly in the assessment of facial clefts.14,15



Typical Facial Clefts


Facial clefts are the most frequent craniofacial anomalies and the second most common congenital malformation, accounting for 13% of all anomalies. The incidence is approximately 1.4 cases per 1000 births.7,16 Clefts can occur in any part of the face but typically involve the line running between each nostril and the central part of the posterior palate. Atypical types of facial clefts differ in the etiology, clinical implications, and in the diagnostic approach used to manage them, and therefore, they are discussed separately.


Typical facial clefts are commonly referred to as cleft lip (CL) and cleft palate (CP). CL may be associated with CP (CL-CP). CP refers to a defect of the posterior portion of the palate in the presence of a normal upper lip and anterior palate. The anatomy and pathogenesis of these defects can be better understood in light of the embryologic development. The fetal splanchnocranium derives from outgrowths of mesenchyme that surround the primitive oral cavity or stomodeum (Fig. 11-8). These outgrowths (frontonasal prominence, maxillary prominence, and mandibular prominence) are separated by grooves that eventually undergo fusion and obliteration. The palate originates from the fusion of three palatine processes. The median palatal process originates from the medial nasal prominences, and the two lateral ones originate from the maxillary processes. The palatine processes fuse also with the nasal septum, which divides the nasal cavities. The palate is commonly divided in three parts: the anterior or primary palate, the posterior or secondary palate, and the soft palate (Fig. 11-9). Typical facial clefts derive presumably from failure of fusion of the different bony structures and overlying soft tissues, with persistence of the embryologic grooves (Fig. 11-10).





CL-CP and isolated CP are two different anomalies. With exceedingly rare exceptions, recurrences are type specific. If the index case has CL-CP, there is no increased risk for isolated CP, and vice versa. Roughly, of all cases with typical facial clefts, 25% have CL, 50% have CL-CP, and 25% have CP.


In the vast majority of cases, typical facial clefts have a multifactorial etiology. The empiric risks of recurrence for these cases are reported in Table 11-5. In some cases, however, facial clefts are a part of well-established genetic and nongenetic syndromes. The claimed risk associated with intake of diazepam and steroidal agents has not been confirmed in carefully controlled studies. Chromosomal abnormalities are rare in postnatal series but rather frequent in the prenatal ones.2,6,17,18 The discrepancy may be due to a high rate of intrauterine selection of aneuploid fetuses, as well as to the inclusion of an excess of atypical clefts.


Table 11-5 Risk of Recurrent Cleft Lip/Cleft Palate in Subsequent Offspring


































Variable Cleft Lip/Palate (%)
Unaffacted parent
No affected offspring 0.1
No affected offspring plus 1 affected first cousin 0.4
One affected offspring 4.0
Two affected offspring 9.0
One affected offspring plus one affected relative 4.0
Affected parents
One parent plus no affected offspring 4.0
One parent plus one affected offspring 10–17
Two parents plus one affected offspring 60.0

Facial clefts encompass a broad spectrum of severity. The typical CL appears as a linear defect extending from one side of the lip into the nostril (Table 11-6). CL-CP may extend through the alveolar ridge and hard palate, reaching the floor of the nasal cavity or even the floor of the orbit (Table 11-7). CP may include defects of the hard palate, the soft palate, or both or the submucosal tissue (see Table 11-8 and Fig. 11-10)


Table 11-6 Sonographic Characteristics of Unilateral or Bilateral Cleft Lip



















Section Plane Unilateral Cleft Bilateral Cleft
Sagittal and parasagittal




Axial

On each side, the protruding premaxillary prolabium is separated from the remaining upper lip extremites by the clefts. Both nostrils are flattened but complete.
Coronal The loss of lip continuity is clearly apparent. The defects in lip continuity are clearly apparent.

From Rotten D, Levaillant JM: Two- and three-dimensional sonographic assessment of the fetal face. 2. Analysis of cleft lip, alveolus and palate. Ultrasound Obstet Gynecol 24:402, 2004


Table 11-7 Sonographic Characteristics of Unilateral or Bilateral Cleft Alveolus















Section Plane Unilateral Cleft Bilateral Cleft
Axial The alveolar defect ranges from a simple slant to a cleft involving the alveolus and pre-maxilla. Clefts involving the alveolus present as a defect in alveolar continuity:




Coronal There is a defect in alveolar continuity, with missing buds. There is a median defect in alveolar continuity. This contrasts with an intact hard palate.

From Rotten D, Levaillant JM: Two- and three-dimensional sonographic assessment of the fetal face. 2. Analysis of cleft lip, alveolus and palate. Ultrasound Obstet Gynecol 24:402, 2004.


Table 11-8 Sonographic Characteristics of Unilateral or Bilateral Secondary Palate Cleft


















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Mar 10, 2016 | Posted by in ULTRASONOGRAPHY | Comments Off on ULTRASOUND EVALUATION OF THE FETAL FACE AND NECK
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Section Plane Secondary Palate Cleft With a Unilateral CLA Secondary Palate Cleft With a Bilateral CLA
Midsagittal and parasagittal The successive views show a defect in hard palate continuity. This defect is asymmetric. It is not strictly median, but lateralized, usually towards the same side as the CLA cleft.

Axial When looking for the palate caudally to the alveolus (remember that the alveoli are separated by a defect and a shift), one does not find it. The only apparent image is that of an oblique vomer bone (10–5°)


Coronal