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US Assessment of the Fetal Head and Neck: A State-of-the-Art Pictorial Review¹

¹ From the Departments of Radiology (J.R.M., R.L., J.F.) and Obstetrics and Gynecology (P.M.), McMaster University Medical Centre, 1200 Main St W, Hamilton, Ontario, Canada L8N 3Z5. Presented as a scientific exhibit at the 1998 RSNA scientific assembly. Received February 11, 1999; revisions requested March 4 and received March 31; accepted April 5. Address reprint requests to J.R.M.

	Abstract

Top Abstract INTRODUCTION NORMAL EXAMINATION ABNORMALITIES OF THE FETAL... ABNORMALITIES OF THE NECK CONCLUSIONS References

 
When attention is paid to the details of normal and abnormal fetal head and neck anatomy, abnormalities that normally would be missed at prenatal ultrasonography can routinely be diagnosed. Five basic views are used to assess the fetal head and neck: a transverse view of the head in the plane of the cavum septum pellucidum and cerebellum, a sagittal and a coronal view of the face to visualize the nose and lips, a sagittal view of the cervical spine, and a transverse view of the orbits to measure the biorbital and interorbital distances. Thickened nuchal fold, a common sign of Down syndrome, can be assessed with transverse images of the head. Transverse views are also useful to demonstrate cystic hygroma, occipital meningocele, and encephalocele, all of which can be associated with other severe anomalies. Micrognathia, cleft lip and palate, and macroglossia, which are best depicted with sagittal and coronal views of the face, are also associated with other fetal abnormalities. Visualization of these entities should prompt further search and amniocentesis. Lymphangioma of the tongue appears similar to macroglossia but is an isolated anomaly. Transverse views through the orbits are helpful for demonstrating orbital teratoma, orbital encephalocele, and hypo- and hypertelorism (the latter two being associated with other abnormalities). Sagittal views of the neck can demonstrate cystic hygroma, teratoma, and an enlarged thyroid.

Index Terms: Fetus, abnormalities, 856.8724, 856.874 • Fetus, central nervous system, 856.8724, 856.874 • Fetus, US, 856.12981 • Pregnancy, US, 856.12981

	INTRODUCTION

Top Abstract INTRODUCTION NORMAL EXAMINATION ABNORMALITIES OF THE FETAL... ABNORMALITIES OF THE NECK CONCLUSIONS References

 
In the routine obstetric ultrasonography (US) examination, attention is given to the fetal head (primarily the cerebral ventricles and cerebellum); heart; abdomen including the stomach, kidneys, bladder, and cord insertion; spine; and limbs. Guidelines have been established by various organizations (eg, the American Institute of Ultrasound in Medicine), which have defined the level of detail that should be achieved in a routine obstetric examination. Less attention is usually given to the fetal face and neck.

In this article, we describe the details of normal and abnormal fetal head and neck anatomy that can be demonstrated with modern high-resolution US equipment. When attention is paid to these anatomic details, abnormalities that normally would be missed before birth can routinely be diagnosed. Herein, we present an approach to the US assessment of the fetal head and neck, with emphasis on the views required for a complete examination. The spectrum of fetal head and neck abnormalities illustrated (listed here cephalic to caudal) include abnormalities of the orbits (hypotelorism, optic teratoma, optic encephalocele, and lacrimal duct cysts), mouth (cleft lip and palate), tongue (macroglossia and lymphangioma of the tongue), mandible (micrognathia), and neck (thickened nuchal fold, cystic hygroma, posterior encephalocele, teratoma, and enlarged fetal thyroid). In addition, we discuss specific US findings and their relationship to other fetal abnormalities.

	NORMAL EXAMINATION

Top Abstract INTRODUCTION NORMAL EXAMINATION ABNORMALITIES OF THE FETAL... ABNORMALITIES OF THE NECK CONCLUSIONS References

 
In the detailed US examination of the fetal head and neck, five basic views are obtained. A transverse view of the head in the plane of the cavum septum pellucidum and the cerebellum is used to assess the ventricles and the nuchal thickness (Fig 1a). We also obtain a sagittal view of the head to evaluate the facial profile (Fig 1b), a coronal view of the face to visualize the nose and lips (Fig 1c, 1d), and a sagittal view of the cervical spine (Fig 1e). In addition, a transverse view of the orbits is used to measure the biorbital and interorbital distances (Fig 1f).

View larger version (153K): [in this window] [in a new window] [Download PPT slide]   Figure 1a.   Normal fetal head and neck. (a) Transverse image through the fetal head shows a normal nuchal fold thickness (arrowheads). The cursors measure a normal nuchal fold thickness of 3.9 mm. (b) Sagittal image through the fetal head shows a normal facial profile. (c) Coronal image of the fetal face shows the eyes, nose, and mouth. (d) Coronal image of the fetal nose (single arrowhead) and lips (double arrowheads). (e) Sagittal image of the fetal cervical spine. (f) Transverse image through the fetal orbits, with measurements indicated for the biorbital and interorbital distances (cursors).

View larger version (147K): [in this window] [in a new window] [Download PPT slide]   Figure 1b.   Normal fetal head and neck. (a) Transverse image through the fetal head shows a normal nuchal fold thickness (arrowheads). The cursors measure a normal nuchal fold thickness of 3.9 mm. (b) Sagittal image through the fetal head shows a normal facial profile. (c) Coronal image of the fetal face shows the eyes, nose, and mouth. (d) Coronal image of the fetal nose (single arrowhead) and lips (double arrowheads). (e) Sagittal image of the fetal cervical spine. (f) Transverse image through the fetal orbits, with measurements indicated for the biorbital and interorbital distances (cursors).

View larger version (132K): [in this window] [in a new window] [Download PPT slide]   Figure 1c.   Normal fetal head and neck. (a) Transverse image through the fetal head shows a normal nuchal fold thickness (arrowheads). The cursors measure a normal nuchal fold thickness of 3.9 mm. (b) Sagittal image through the fetal head shows a normal facial profile. (c) Coronal image of the fetal face shows the eyes, nose, and mouth. (d) Coronal image of the fetal nose (single arrowhead) and lips (double arrowheads). (e) Sagittal image of the fetal cervical spine. (f) Transverse image through the fetal orbits, with measurements indicated for the biorbital and interorbital distances (cursors).

View larger version (123K): [in this window] [in a new window] [Download PPT slide]   Figure 1d.   Normal fetal head and neck. (a) Transverse image through the fetal head shows a normal nuchal fold thickness (arrowheads). The cursors measure a normal nuchal fold thickness of 3.9 mm. (b) Sagittal image through the fetal head shows a normal facial profile. (c) Coronal image of the fetal face shows the eyes, nose, and mouth. (d) Coronal image of the fetal nose (single arrowhead) and lips (double arrowheads). (e) Sagittal image of the fetal cervical spine. (f) Transverse image through the fetal orbits, with measurements indicated for the biorbital and interorbital distances (cursors).

View larger version (141K): [in this window] [in a new window] [Download PPT slide]   Figure 1e.   Normal fetal head and neck. (a) Transverse image through the fetal head shows a normal nuchal fold thickness (arrowheads). The cursors measure a normal nuchal fold thickness of 3.9 mm. (b) Sagittal image through the fetal head shows a normal facial profile. (c) Coronal image of the fetal face shows the eyes, nose, and mouth. (d) Coronal image of the fetal nose (single arrowhead) and lips (double arrowheads). (e) Sagittal image of the fetal cervical spine. (f) Transverse image through the fetal orbits, with measurements indicated for the biorbital and interorbital distances (cursors).

View larger version (137K): [in this window] [in a new window] [Download PPT slide]   Figure 1f.   Normal fetal head and neck. (a) Transverse image through the fetal head shows a normal nuchal fold thickness (arrowheads). The cursors measure a normal nuchal fold thickness of 3.9 mm. (b) Sagittal image through the fetal head shows a normal facial profile. (c) Coronal image of the fetal face shows the eyes, nose, and mouth. (d) Coronal image of the fetal nose (single arrowhead) and lips (double arrowheads). (e) Sagittal image of the fetal cervical spine. (f) Transverse image through the fetal orbits, with measurements indicated for the biorbital and interorbital distances (cursors).

	ABNORMALITIES OF THE FETAL HEAD

Top Abstract INTRODUCTION NORMAL EXAMINATION ABNORMALITIES OF THE FETAL... ABNORMALITIES OF THE NECK CONCLUSIONS References

 
Thickened Nuchal Fold
There is an association of a thickened nuchal fold with Down syndrome (1–4). A thickened nuchal skin fold is seen in 80% of newborns with Down syndrome (1). The sensitivity and false-positive rates of US have been reported to be superior to both advanced maternal age and maternal serum screening for a-fetoprotein as a predictor for Down syndrome (3,4).

Assessment of the nuchal fold is typically made at 15–21 weeks gestational age (1,2). The fold is measured by using a transverse image of the head (Fig 2). Landmarks to determine the correct plane include the cavum septum pellucidum, cerebral peduncles, cerebellar hemispheres, and cisterna magna. A nuchal fold thickness of greater than 6 mm is considered abnormal (1,2).

View larger version (137K): [in this window] [in a new window] [Download PPT slide]   Figure 2a.   Thickened nuchal fold. (a) Transverse image through the fetal head shows a thickened nuchal fold. In this fetus, the nuchal fold measured 6.4 mm in maximum thickness, as indicated by the cursors. (b) Four chamber view of the fetal heart shows an associated endocardial cushion defect (arrow).

View larger version (123K): [in this window] [in a new window] [Download PPT slide]   Figure 2b.   Thickened nuchal fold. (a) Transverse image through the fetal head shows a thickened nuchal fold. In this fetus, the nuchal fold measured 6.4 mm in maximum thickness, as indicated by the cursors. (b) Four chamber view of the fetal heart shows an associated endocardial cushion defect (arrow).

The US appearance of cystic hygroma depends on gestational age. It can vary from mild edema in the posterior cervical region in the first trimester (Fig 3) to large multiloculated cysts and generalized hydrops at a later gestational age (1). Cystic hygromas do not invariably progress to diffuse lymphangiectasia and have been reported resolve (9).

View larger version (171K): [in this window] [in a new window] [Download PPT slide]   Figure 3a.   Cystic hygroma. (a) Transverse image through the fetal head shows a small cystic structure in the posterior aspect of the neck (arrows and cursors). (b) Sagittal image through the fetal head and neck again shows the small cystic structure in the posterior aspect of the neck (arrows and cursors). In this particular case, no other significant fetal abnormalities were noted.

View larger version (174K): [in this window] [in a new window] [Download PPT slide]   Figure 3b.   Cystic hygroma. (a) Transverse image through the fetal head shows a small cystic structure in the posterior aspect of the neck (arrows and cursors). (b) Sagittal image through the fetal head and neck again shows the small cystic structure in the posterior aspect of the neck (arrows and cursors). In this particular case, no other significant fetal abnormalities were noted.

Meningocele and Encephalocele
Meningoceles and encephaloceles result from failure of the surface ectoderm to separate from the neuroectoderm, which results in a bony calvarial defect that allows herniation of the meninges (meningocele) or the meninges and brain (encephalocele) (10–12). The most common site for these abnormalities is in the occipital midline (75%), followed by the frontal midline (13%) (1). Associated anomalies include Arnold-Chiari malformation (with associated hydrocephalus), agenesis of the corpus callosum, Dandy-Walker syndrome, and Meckel-Gruber syndrome (encephalocele, microcephaly, polydactyly, and cystic dysplastic kidneys) (1).

At US, meningoceles are seen as fluid-filled cystic structures (Fig 4) and encephaloceles as brain-filled cystic structures (Fig 5) that extend through a bony calvarial defect, usually in the occipital or frontal region (11,12). The entity most commonly mistaken for a small meningocele is a cystic hygroma (1). Careful scanning, however, will reveal no calvarial defect with a cystic hygroma. Absence of brain tissue within the sac is the single most favorable prognostic feature (1,13).

View larger version (121K): [in this window] [in a new window] [Download PPT slide]   Figures 4, 5.   (4) Occipital meningocele with an associated Dandy-Walker cyst. (a) Transverse image through the fetal head shows a large cystic structure outside the calvaria in the occipital region (arrows). A large cystic structure is also seen in the posterior fossa, consistent with a Dandy-Walker cyst (arrowheads). (b) Sagittal image through the fetal head and neck shows the large cystic structure in the occipital region. A small defect is seen in the cranium at the base of the cyst (arrowhead). (5) Severe encephalocele. Transverse image through the fetal head shows a large posterior herniation of brain tissue, consistent with a large encephalocele (arrows).

View larger version (111K): [in this window] [in a new window] [Download PPT slide]   Figures 4, 5.   (4) Occipital meningocele with an associated Dandy-Walker cyst. (a) Transverse image through the fetal head shows a large cystic structure outside the calvaria in the occipital region (arrows). A large cystic structure is also seen in the posterior fossa, consistent with a Dandy-Walker cyst (arrowheads). (b) Sagittal image through the fetal head and neck shows the large cystic structure in the occipital region. A small defect is seen in the cranium at the base of the cyst (arrowhead). (5) Severe encephalocele. Transverse image through the fetal head shows a large posterior herniation of brain tissue, consistent with a large encephalocele (arrows).

View larger version (146K): [in this window] [in a new window] [Download PPT slide]   Figures 4, 5.   (4) Occipital meningocele with an associated Dandy-Walker cyst. (a) Transverse image through the fetal head shows a large cystic structure outside the calvaria in the occipital region (arrows). A large cystic structure is also seen in the posterior fossa, consistent with a Dandy-Walker cyst (arrowheads). (b) Sagittal image through the fetal head and neck shows the large cystic structure in the occipital region. A small defect is seen in the cranium at the base of the cyst (arrowhead). (5) Severe encephalocele. Transverse image through the fetal head shows a large posterior herniation of brain tissue, consistent with a large encephalocele (arrows).

In the obstetric US examination, the facial profile view is the most useful for evaluating the size of the mandible (Figs 6, 7). The presence of micrognathia should prompt a careful search for other fetal abnormalities and performance of amniocentesis.

View larger version (102K): [in this window] [in a new window] [Download PPT slide]   Figures 6, 7.   (6) Micrognathia associated with a Dandy-Walker variant. (a) Sagittal view of the fetal facial profile shows a small mandible, consistent with micrognathia (arrow). (b) Transverse image through the fetal abdomen shows an associated single umbilical artery (arrows). (c) Transverse image through the fetal kidneys shows bilateral obstruction of the ureteropelvic junction (arrows). (d) Transverse image through the fetal head shows a cleft in the cerebellar vermis consistent with a Dandy-Walker variant (arrow). (7) Micrognathia. Sagittal image of the facial profile of a fetus shows a more obvious example of micrognathia (arrowhead).

View larger version (123K): [in this window] [in a new window] [Download PPT slide]   Figures 6, 7.   (6) Micrognathia associated with a Dandy-Walker variant. (a) Sagittal view of the fetal facial profile shows a small mandible, consistent with micrognathia (arrow). (b) Transverse image through the fetal abdomen shows an associated single umbilical artery (arrows). (c) Transverse image through the fetal kidneys shows bilateral obstruction of the ureteropelvic junction (arrows). (d) Transverse image through the fetal head shows a cleft in the cerebellar vermis consistent with a Dandy-Walker variant (arrow). (7) Micrognathia. Sagittal image of the facial profile of a fetus shows a more obvious example of micrognathia (arrowhead).

View larger version (118K): [in this window] [in a new window] [Download PPT slide]   Figures 6, 7.   (6) Micrognathia associated with a Dandy-Walker variant. (a) Sagittal view of the fetal facial profile shows a small mandible, consistent with micrognathia (arrow). (b) Transverse image through the fetal abdomen shows an associated single umbilical artery (arrows). (c) Transverse image through the fetal kidneys shows bilateral obstruction of the ureteropelvic junction (arrows). (d) Transverse image through the fetal head shows a cleft in the cerebellar vermis consistent with a Dandy-Walker variant (arrow). (7) Micrognathia. Sagittal image of the facial profile of a fetus shows a more obvious example of micrognathia (arrowhead).

View larger version (140K): [in this window] [in a new window] [Download PPT slide]   Figures 6, 7.   (6) Micrognathia associated with a Dandy-Walker variant. (a) Sagittal view of the fetal facial profile shows a small mandible, consistent with micrognathia (arrow). (b) Transverse image through the fetal abdomen shows an associated single umbilical artery (arrows). (c) Transverse image through the fetal kidneys shows bilateral obstruction of the ureteropelvic junction (arrows). (d) Transverse image through the fetal head shows a cleft in the cerebellar vermis consistent with a Dandy-Walker variant (arrow). (7) Micrognathia. Sagittal image of the facial profile of a fetus shows a more obvious example of micrognathia (arrowhead).

View larger version (109K): [in this window] [in a new window] [Download PPT slide]   Figures 6, 7.   (6) Micrognathia associated with a Dandy-Walker variant. (a) Sagittal view of the fetal facial profile shows a small mandible, consistent with micrognathia (arrow). (b) Transverse image through the fetal abdomen shows an associated single umbilical artery (arrows). (c) Transverse image through the fetal kidneys shows bilateral obstruction of the ureteropelvic junction (arrows). (d) Transverse image through the fetal head shows a cleft in the cerebellar vermis consistent with a Dandy-Walker variant (arrow). (7) Micrognathia. Sagittal image of the facial profile of a fetus shows a more obvious example of micrognathia (arrowhead).

At US, careful attention to the views of the nose and lips is required to make the diagnosis of cleft lip and palate or median cleft lip. The defect is recognized because of the gap in the upper lip seen on coronal views of the nose and lips (Figs 8, 9). On sagittal views of the face, one may miss the defect if the view is obtained in the midline (for a cleft lip and palate) or if it is focused on the normal side of a fetus with a unilateral cleft lip and palate (or median cleft lip). The palate can also be examined in the transverse plane.

View larger version (110K): [in this window] [in a new window] [Download PPT slide]   Figure 8a.   Cleft lip with associated abnormalities. (a) Coronal image of the fetal nose and lips shows a cleft in the upper lip (arrow). (b) Second coronal image of the fetal nose and lips again shows the cleft in the upper lip (arrow). (c) Transverse image of the fetal head shows associated bilateral choroid plexus cysts (arrowheads). (d) Coronal image of the fetal head shows low-set "elfin" ears (arrows).

View larger version (111K): [in this window] [in a new window] [Download PPT slide]   Figure 8b.   Cleft lip with associated abnormalities. (a) Coronal image of the fetal nose and lips shows a cleft in the upper lip (arrow). (b) Second coronal image of the fetal nose and lips again shows the cleft in the upper lip (arrow). (c) Transverse image of the fetal head shows associated bilateral choroid plexus cysts (arrowheads). (d) Coronal image of the fetal head shows low-set "elfin" ears (arrows).

View larger version (123K): [in this window] [in a new window] [Download PPT slide]   Figure 8c.   Cleft lip with associated abnormalities. (a) Coronal image of the fetal nose and lips shows a cleft in the upper lip (arrow). (b) Second coronal image of the fetal nose and lips again shows the cleft in the upper lip (arrow). (c) Transverse image of the fetal head shows associated bilateral choroid plexus cysts (arrowheads). (d) Coronal image of the fetal head shows low-set "elfin" ears (arrows).

View larger version (122K): [in this window] [in a new window] [Download PPT slide]   Figure 8d.   Cleft lip with associated abnormalities. (a) Coronal image of the fetal nose and lips shows a cleft in the upper lip (arrow). (b) Second coronal image of the fetal nose and lips again shows the cleft in the upper lip (arrow). (c) Transverse image of the fetal head shows associated bilateral choroid plexus cysts (arrowheads). (d) Coronal image of the fetal head shows low-set "elfin" ears (arrows).

View larger version (104K): [in this window] [in a new window] [Download PPT slide]   Figure 9a.   Cleft lip and palate. (a) Coronal image of the fetal nose and lips shows a cleft upper lip (arrow). (b) Transverse image through the palate shows a cleft in the palate (arrow).

View larger version (90K): [in this window] [in a new window] [Download PPT slide]   Figure 9b.   Cleft lip and palate. (a) Coronal image of the fetal nose and lips shows a cleft upper lip (arrow). (b) Transverse image through the palate shows a cleft in the palate (arrow).

Macroglossia
Macroglossia is an important finding at obstetric US examinations because of its association with Beckwith-Wiedemann syndrome (1,16,17). Other common anomalies associated with Beckwith-Wiedemann syndrome include omphalocele, hemihypertrophy, hepatosplenomegaly, nephromegaly, and cardiac abnormalities (1).

Macroglossia can be recognized in either the coronal view of the face through the nose and lips or in the facial profile. Intermittent protrusion of the tongue can be seen in normal fetuses, but a persistent protrusion of the tongue is abnormal (Fig 10). The tongue is considered normal sized if the tip remains behind an imaginary line drawn from the upper to the lower gum in the facial profile during most of the US scans. When it is enlarged, the tongue persistently protrudes from the open mouth (1,16,17).

View larger version (114K): [in this window] [in a new window] [Download PPT slide]   Figure 10a.   Macroglossia. (a) Sagittal image through the fetal facial profile shows a protruding tongue (arrow). (b) Coronal image of the fetal face again shows a protruding tongue, consistent with macroglossia (arrow). The finding was subtle but was persistent throughout the US examination. It was also seen on more than one examination of the same fetus. The presence of macroglossia was confirmed at postnatal examination.

View larger version (132K): [in this window] [in a new window] [Download PPT slide]   Figure 10b.   Macroglossia. (a) Sagittal image through the fetal facial profile shows a protruding tongue (arrow). (b) Coronal image of the fetal face again shows a protruding tongue, consistent with macroglossia (arrow). The finding was subtle but was persistent throughout the US examination. It was also seen on more than one examination of the same fetus. The presence of macroglossia was confirmed at postnatal examination.

Lymphangioma of the Tongue
When lymphangiomas of the tongue develop, they occur predominantly on the dorsum of the tongue anteriorly. They vary from tiny cystic structures to diffuse lesions that infiltrate the entire tongue, resulting in macroglossia, or that extend into the surrounding structures. Lymphangiomas may be present at birth or may appear later in life (18).

A lymphangioma of the tongue is seen at obstetric US as a protruding tongue, an appearance similar to that of macroglossia (Fig 11). If the search for other significant fetal abnormalities reveals nothing, the diagnosis is most likely lymphangioma.

View larger version (103K): [in this window] [in a new window] [Download PPT slide]   Figure 11a.   Lymphangioma of the tongue. (a) Sagittal image through the fetal face shows a protruding tongue (arrow) (cf Fig 10). (b) Coronal image through the fetal face again shows the protruding tongue (arrow), but no other abnormalities were seen. At postnatal examination, a mass was found at the base of the protruding tongue. The mass was surgically removed and proved to be a lymphangioma.

View larger version (108K): [in this window] [in a new window] [Download PPT slide]   Figure 11b.   Lymphangioma of the tongue. (a) Sagittal image through the fetal face shows a protruding tongue (arrow) (cf Fig 10). (b) Coronal image through the fetal face again shows the protruding tongue (arrow), but no other abnormalities were seen. At postnatal examination, a mass was found at the base of the protruding tongue. The mass was surgically removed and proved to be a lymphangioma.

Lacrimal duct cyst, or dacryocystocele, is an isolated benign entity. Dacrocystoceles have a simple cystic appearance and are typically located anteromedial to the globe. They can be confused with an orbital encephalocele, but their typical appearance and location should allow correct diagnosis (Fig 12) (1).

View larger version (107K): [in this window] [in a new window] [Download PPT slide]   Figure 12a.   Lacrimal duct cysts. (a) Coronal image of the fetal face shows two small cysts adjacent and anteromedial to both the right and left orbits (cursors). (b) Sagittal image through the left orbit again shows the small cyst (cursors). Because of their location, the cysts were thought to be lacrimal duct cysts, a diagnosis that was confirmed at postnatal examination. No other significant abnormalities were noted.

View larger version (101K): [in this window] [in a new window] [Download PPT slide]   Figure 12b.   Lacrimal duct cysts. (a) Coronal image of the fetal face shows two small cysts adjacent and anteromedial to both the right and left orbits (cursors). (b) Sagittal image through the left orbit again shows the small cyst (cursors). Because of their location, the cysts were thought to be lacrimal duct cysts, a diagnosis that was confirmed at postnatal examination. No other significant abnormalities were noted.

Hemangiomas are typically highly echogenic and display blood flow on Doppler images. Teratomas may be benign or malignant and tend to be composed of both solid and cystic components (Fig 13), usually with a high degree of disorganization (1,20).

View larger version (116K): [in this window] [in a new window] [Download PPT slide]   Figure 13a.   Teratoma with neural elements. (a) Transverse image through both fetal orbits shows a complex cystic and solid mass involving the left orbit (arrowheads). The orbit was enlarged and deformed, and the left globe could not be identified. The right orbit appeared normal. The differential diagnosis includes an orbital teratoma and an orbital encephalocele. (b) Transverse image through the left orbit shows the complex cystic and solid mass (arrowheads and cursors). The findings were confirmed at postnatal examination. The mass was excised, and pathologic examination revealed a teratoma with neural elements.

View larger version (106K): [in this window] [in a new window] [Download PPT slide]   Figure 13b.   Teratoma with neural elements. (a) Transverse image through both fetal orbits shows a complex cystic and solid mass involving the left orbit (arrowheads). The orbit was enlarged and deformed, and the left globe could not be identified. The right orbit appeared normal. The differential diagnosis includes an orbital teratoma and an orbital encephalocele. (b) Transverse image through the left orbit shows the complex cystic and solid mass (arrowheads and cursors). The findings were confirmed at postnatal examination. The mass was excised, and pathologic examination revealed a teratoma with neural elements.

Hypotelorism and Hypertelorism
Hypotelorism refers to abnormal closeness of the eyes, whereas hypertelorism refers to the abnormal increased distance between the eyes. Causes of hypertelorism include the craniosynostoses syndromes, cleft lip and palate, frontal encephaloceles, and exposure to teratogens such as phenytoin (15). Hypotelorism is usually associated with severe brain malformation, with holoprosencephaly being the most commonly associated abnormality (1,21).

Measurements of the biorbital and interorbital distances can be made from the transverse view of the orbits and compared with normal values (1) (Fig 14). When hypotelorism or hypertelorism is diagnosed, the fetus should be evaluated for the other associated abnormalities.

View larger version (111K): [in this window] [in a new window] [Download PPT slide]   Figure 14a.   Hypotelorism with associated brain abnormalities. (a) Transverse image through the fetal orbits shows the interorbital and biorbital distances (cursors) . The chronologic age of the fetus was 19.9 weeks; however, the age based on the interorbital distance was 13 weeks. The age based on the biorbital distance was consistent with 20.0 weeks. (b) Transverse image through the fetal head shows significant associated brain abnormalities with severe atrophy of the cerebral cortex.

View larger version (100K): [in this window] [in a new window] [Download PPT slide]   Figure 14b.   Hypotelorism with associated brain abnormalities. (a) Transverse image through the fetal orbits shows the interorbital and biorbital distances (cursors) . The chronologic age of the fetus was 19.9 weeks; however, the age based on the interorbital distance was 13 weeks. The age based on the biorbital distance was consistent with 20.0 weeks. (b) Transverse image through the fetal head shows significant associated brain abnormalities with severe atrophy of the cerebral cortex.

	ABNORMALITIES OF THE NECK

Top Abstract INTRODUCTION NORMAL EXAMINATION ABNORMALITIES OF THE FETAL... ABNORMALITIES OF THE NECK CONCLUSIONS References

At obstetric US examination, views of the fetal neck demonstrate a dilated trachea filled with trapped fluid. Views of the fetal chest show enlarged, hyperechoic lungs, with dilated fluid-filled bronchi (Fig 15). Fetal ascites is usually present.

View larger version (119K): [in this window] [in a new window] [Download PPT slide]   Figure 15a.   Laryngeal atresia. (a) Coronal image through the fetal neck and chest shows the fluid-filled, dilated trachea and bronchi (arrows). The lungs are enlarged and hyperechoic. (b) Sagittal image of the fetal neck and chest again shows the hyperechoic lungs and the dilated, filled trachea (arrows). (c) Sagittal Doppler image of the fetal neck and chest shows the dilated trachea adjacent to the neck vessels. (d) Coronal image through the fetal chest and abdomen shows the enlarged hyperechoic lungs adjacent to the liver. Note the concave shape of the hemidiaphragms toward the liver, secondary to the enlarged lungs (straight arrows). Ascites is also seen adjacent to the liver (curved arrow).

View larger version (122K): [in this window] [in a new window] [Download PPT slide]   Figure 15b.   Laryngeal atresia. (a) Coronal image through the fetal neck and chest shows the fluid-filled, dilated trachea and bronchi (arrows). The lungs are enlarged and hyperechoic. (b) Sagittal image of the fetal neck and chest again shows the hyperechoic lungs and the dilated, filled trachea (arrows). (c) Sagittal Doppler image of the fetal neck and chest shows the dilated trachea adjacent to the neck vessels. (d) Coronal image through the fetal chest and abdomen shows the enlarged hyperechoic lungs adjacent to the liver. Note the concave shape of the hemidiaphragms toward the liver, secondary to the enlarged lungs (straight arrows). Ascites is also seen adjacent to the liver (curved arrow).

View larger version (158K): [in this window] [in a new window] [Download PPT slide]   Figure 15c.   Laryngeal atresia. (a) Coronal image through the fetal neck and chest shows the fluid-filled, dilated trachea and bronchi (arrows). The lungs are enlarged and hyperechoic. (b) Sagittal image of the fetal neck and chest again shows the hyperechoic lungs and the dilated, filled trachea (arrows). (c) Sagittal Doppler image of the fetal neck and chest shows the dilated trachea adjacent to the neck vessels. (d) Coronal image through the fetal chest and abdomen shows the enlarged hyperechoic lungs adjacent to the liver. Note the concave shape of the hemidiaphragms toward the liver, secondary to the enlarged lungs (straight arrows). Ascites is also seen adjacent to the liver (curved arrow).

View larger version (128K): [in this window] [in a new window] [Download PPT slide]   Figure 15d.   Laryngeal atresia. (a) Coronal image through the fetal neck and chest shows the fluid-filled, dilated trachea and bronchi (arrows). The lungs are enlarged and hyperechoic. (b) Sagittal image of the fetal neck and chest again shows the hyperechoic lungs and the dilated, filled trachea (arrows). (c) Sagittal Doppler image of the fetal neck and chest shows the dilated trachea adjacent to the neck vessels. (d) Coronal image through the fetal chest and abdomen shows the enlarged hyperechoic lungs adjacent to the liver. Note the concave shape of the hemidiaphragms toward the liver, secondary to the enlarged lungs (straight arrows). Ascites is also seen adjacent to the liver (curved arrow).

In the fetus, the most common location for a teratoma is in the sacrococcygeal region (1); however, teratomas can be seen in other locations, including the neck (Fig 16). The vast majority of these lesions are benign. In the neck, a teratoma is typically seen as a large solid or cystic mass in an anterolateral location. Teratomas may be so large as to obstruct the airway. They usually occur as an isolated finding, although approximately 30% of cases have associated polyhydramnios (16).

View larger version (126K): [in this window] [in a new window] [Download PPT slide]   Figure 16.   Teratoma. Sagittal image of the fetal head and neck shows a large complex mass anterior in the neck (arrows and cursors). Postnatal diagnosis was a teratoma.

Enlarged Thyroid
Most anterior neck masses detected prenatally are either cervical teratomas or goiters (16). Congenital hypothyroidism occurs in approximately one in 3,700 births, and in most cases, the mother has a history of thyroid blocking therapy (16).

Typically, an enlarged thyroid or goiter is seen as a bilateral anterior neck mass, and it may appear either solid or cystic. Most such masses are seen as isolated findings, although they can accompany polyhydramnios and are associated with a family history of goiter (16).

An enlarged thyroid is best seen on sagittal views of the neck (Fig 17).

View larger version (150K): [in this window] [in a new window] [Download PPT slide]   Figure 17a.   Enlarged thyroid. (a) Sagittal split-screen image of the fetal neck shows a small hypoechoic mass (arrowhead) in the lower anterior portion of the neck. (b) Transverse image of the fetal neck again shows the small hypoechoic mass (arrowhead). At postnatal examination, the mass proved to be an enlarged thyroid.

View larger version (139K): [in this window] [in a new window] [Download PPT slide]   Figure 17b.   Enlarged thyroid. (a) Sagittal split-screen image of the fetal neck shows a small hypoechoic mass (arrowhead) in the lower anterior portion of the neck. (b) Transverse image of the fetal neck again shows the small hypoechoic mass (arrowhead). At postnatal examination, the mass proved to be an enlarged thyroid.

	CONCLUSIONS

Top Abstract INTRODUCTION NORMAL EXAMINATION ABNORMALITIES OF THE FETAL... ABNORMALITIES OF THE NECK CONCLUSIONS References

	References

Top Abstract INTRODUCTION NORMAL EXAMINATION ABNORMALITIES OF THE FETAL... ABNORMALITIES OF THE NECK CONCLUSIONS References

 

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