Daily Archives: 19/12/2021

Facial Clefts

(See the details in the section “Specific abnormalities”.)

Fig 1, Fig 2

Premaxillary protrusion is an important clue to the presence of cleft lip and cleft palate and may be more conspicuous than the cleft itself.

Differential diagnosis for facial clefts

• Artifact: normal philtrum with midline groove of the upper lip misinterpreted as cleft
• Lateral cleft: Fig 3, Fig 4
  • most common facial abnormalities, more common on the left side
  • paramedial location
  • bilateral in 20% of cases
• Midline cleft: Fig 5
  • rare
  • holoprosencephaly
  • median cleft face syndrome
• Atypical cleft:
  • associated with amniotic band syndrome in most cases
  • asymmetric and bizarre
  • other anomalies are commonly seen.

Cleft lip:  Coronal scan of the face: small paramedial cleft (arrow)

Cleft lip:  Coronal scan of the face: paramedial cleft (arrow)

Bilateral cleft lips :  Coronal scan of the face: bilateral paramedial cleft (arrow)

Cleft lip and palate :  Transverse scan of the face: incomplete alveolar ridge (*) of the maxilla

Midline cleft lip:  Coronal scan of the face: midline cleft (arrow) (arrowhead = lens in the orbit)

Hypotelorism

Hypotelorism, abnormally close spacing of the orbits, is an uncommon disorder, which is usually associated with many other conditions including chromosome defects. Holoprosencephaly is the most common associated malformation. It should be diagnosed when both the interocular and outer or binocular distances are below the 5th percentile, usually first diagnosable in the second trimester, but possibly in the first trimester. The extreme case, median ocular fusion or cyclopia, is almost always related to holoprosencephaly. Binocular biometric parameters may be useful sonographic markers for trisomy 13 or holoprosencephaly.

Fig 1

The differential diagnoses of hypotelorism include:

• Holoprosencephaly (most common)
• Median facial clefts
• Chromosome abnormalities, especially trisomy 13
• Meckel syndrome
• Microcephaly.

Hypotelorism & Proboscis:  Coronal scan of the face: arrowhead = forehead, arrow = proboscis)

Hypotelorism & Proboscis:   Coronal scan of the face showing a proboscis above the cyclopia

Holoprosencephaly:  Transverse scan of the head: fusion of the lateral ventricle (*), no falx cerebri, marked hypotelorism (solid circle)

Neck Masses

          Fig 1, Fig 2

Differential diagnosis of common neck masses:

• Cystic hygroma (most common; multiseptate, no solid part; posterolateral; bilateral, hydrops)
• Cervical meningomyelocele (cystic, complex or solid; posterior midline, separation of cervical spine)
• Occipital cephalocele (cystic, complex or solid; posterior midline, skull defect)
• Goiter (generalized hypoechoic solid; anterior, bilateral)
• Cervical teratoma (solid-cystic; anterolateral, unilateral)
• Hemangioma (echogenic, variable in location, positive Doppler signals).

Cervical teratoma:  Sagittal scan of the thorax and neck: solid-cystic mass (*) lateral to the neck (arrowhead = spine)

Facial Masses

Most abnormal masses of the face are located in the periorbital areas.

Fig 1, Fig 2

The major differential diagnoses for periorbital masses are as follows:

• Proboscis: solid mass of abnormal nose formation, almost always associated with hypotelorism and holoprosencephaly.
• Daccryocystoceles: lacrimal duct cyst, hypoechoic mass inferomedial to the fetal orbit without displacement of the globe but with synchronous eye movements.
• Hemangioma: cystic or solid, placenta-like echogenicity, well-defined vascular space with characteristic Doppler signal.
• Anterior cephalocele: usually midline mass, displacing orbit inferiorly and laterally, anterior cranial defect.
• Teratoma or dermoid cyst: solid or cystic or complex, occasional calcifications.
• Anterior cystic hygroma: (rare) cystic or multicystic with loculations and septations varying in size.

Proboscis (holoprosencephaly) :  Midline solid mass at the forehead (proboscis) and fused ventricle

Normal Examination

Practically, most practitioners evaluate the face qualitatively, using three views: the coronal view, looking at bone and soft tissue from the surface well into the palate and orbits; the transverse view, looking at the mandible, maxilla, tooth buds, and orbits; and finally the sagittal view, evaluating the nasal bridge, the frontal bone, and the mandible. The measurements of various aspects of the fetal face have been studied in an attempt to quantify facial anomalies. Normative data of the fetal eye length, nose width and nostril distance, fetal upper lip and chin, binocular distance, and biparietal distance (BPD)/mandibular body length (MBL) ratio for diagnosis of micrognathia have been established. These data are expected to serve as a basis for the objective assessment of the fetal face in high-risk conditions.

Technique:

Fig 1, Fig 2, Fig 3, Fig 4, Fig 5, Fig 6, Fig 7

 Axial view

• From the BPD plane, move the transducer down to the face slowly to obtain the biorbital view (axial orbit view). Orbital sizes and distances could be assessed. The biorbital distance can be used in estimating the gestational age and allows detection of hypo-/hypertelorism.
• Move the transducer down directly to the lower level of the face. Maxilla (smooth C-shaped curve of the alveolar ridge). This is important for exclusion of cleft lip/palate. Furthermore, tooth sockets can also be assessed and the exact number after 19 weeks can be determined.
• Normal scan: symmetry of the orbits, normal inter and intra-orbital diameter.
• Abnormalities identified with the axial orbit view included hypotelorism, hypertelorism, microphthalmia, intra-ocular abnormalities, and periorbital mass, and with the axial maxilla view they included anterior cleft palate associated with cleft lip.

 Coronal view

• At the biorbital view, slide and rock the transducer so that the biorbital diameter becomes parallel to the vertical line, and move the biorbital diameter line to the middle of the image.
• Rotate the transducer 90 degrees with fine adjustment to get the coronal view; the variations of movement will reveal various images of the coronal view of upper lip, lower lip, nose, nostrils, chin, or cheeks.
• Normal scan: normal lips, nose (nostrils), chin, eyelids, or lens should be seen. Fetal blinking is very common and is increased in frequency with vibroacoustic stimulation.
• Abnormalities identified with this view included cleft lip and oropharyngeal mass.
• The coronal and sagittal planes obtained from the submandibular triangle can be used well for displaying the soft and hard palates in particular.

Facial profile view (sagittal midline view)

• At the biorbital view, slide and rock the transducer so that the biorbital diameter becomes perpendicular to the ultrasound beam, and move the biorbital diameter line to the middle of the image.
• Rotate the transducer 90 degrees with fine adjustment to get the sagittal view; the variations of movement will reveal various images of the facial profile view, especially the relationship of the forehead, nose, lip, and chin.
• Normal scan: normal forehead, nose, lips and chin and no abnormal masses.
• Evaluation of the jaw is usually subjective, however mandibular measurement may be necessary in some cases.
• Abnormalities identified with this view included micrognathia, premaxillary protrusion, proboscis, frontal bossing, flattened nasal bridge, and mass (neck, oral).

Ear

• From the facial area, move the transducer laterally to identify the ear and make fine adjustments to reveal various views of the ear. It is easily identified as a complex soft tissue protrusion externally to the skull.
• The location in relation to the skull and the shape of the ear should be demonstrated.
• Abnormalities identified with this examination included ear malformation, low set ear.

Neck

• Move the transducer downward from the axial plane of the face to the neck or just below the occipital region from the transcerebellar view; fine manipulation of the transducer is needed to visualize the axial plane of the neck.
• Nuchal skin thickness should be routinely evaluated in the transcerebellar plane; the critical landmarks include the cavum septum pellucidi, cerebral peduncles and cerebellar hemispheres. If the transducer is not angled in the correct plane but is too steep this will produce incorrect measurements for nuchal skin thickness.
• The cross-section of the neck appears round, containing hyperechoic spine and soft tissue structures anteriorly including esophagus, trachea, larynx and great vessels.
• Examination of the posterior neck and the base of the skull is important to detect abnormalities such as cystic hygroma, occipital cephalocele, and cervical meningomyelocele.
• Examination of the anterior and anterolateral neck is important to detect such abnormalities as goiter, hemangioma and teratoma. In the anterior neck, thyroid and the fluid-filled trachea and hypopharynx can normally be seen.

4D-US may be superior over 2D and 3D-US in the evaluation of complex facial activity and expression. Facial surface analysis and expressions such as eyelid and mouthing movements, smiling and scowling can be precisely observed using 4D-US.

Checklists

Axial view:

• normal for both orbits
• normal biorbital distance
• normal maxilla

Facial profile view:

• normal forehead (no bossing or flat)
• normal nose
• normal lips
• normal chin (no micrognathia)

Coronal view:

• normal upper lips
• normal nose and nostrils
• normal tongue (no persistent protrusion)

Ear:

• normal shape
• normal location

Neck:

• no abnormal mass
• no nuchal thickenings.

Pitfalls

• Fetal positioning, maternal abdominal wall thickness and oligohydramnios can interfere with obtaining the optimal images of the fetal face.
• Midline groove of the upper lip: be careful not to mistake this for cleft lip.
• Nuchal cord: the umbilical cord wraps around the neck, and the nuchal cord is sometimes mistaken for increased thickening of the skin fold. This could be simply overcome by performing either pulse Doppler or color Doppler.
• Non-fused amnion versus cystic neck mass: this can give the artificial appearance of a cystic mass around the occiput, therefore, one should check elsewhere within the uterus for incomplete fusion of the amnion or check the fetus when it has moved into a different anatomic position in which the neck is separate from the amnion.
• Pseudonuchal thickening: too steep angulation and more coronal plane will artificially give the appearance of increased thickness of the skin over the posterior occiput.

Arachnoid Cysts

An arachnoid cyst is the accumulation of cerebrospinal-like fluid between the meninges, arising from the arachnoid separating into two layers. The cells lining the cyst wall produce CSF, which is trapped to form a cyst. The slipstreams of CSF within arachnoid cysts may not be channeled properly leading to possible damage of the surrounding brain parenchyma.

Incidence: Rare, sporadic occurrence, accounting for 1% of the intracranial lesions. Most are located above the tentorium and 5-10% occur in the posterior fossa. It has a male preponderance and increased incidence on the left side.

Sonographic findings:

• A well circumscribed, often circular fluid-filled space with a thin wall, located anywhere within the subarachnoid space.
• Usually displaces adjacent brain structures.
• Hydrocephalus secondary to a mass effect may be seen in some cases, however, most do not disturb normal brain function.
• The differential diagnosis for asymmetric cyst is porencephaly and for the midline cyst includes an interhemispheric cyst in the case of agenesis of the corpus callosum, Dandy-walker malformation, and dorsal sac of holoprosencephaly.
• MRI is helpful if the diagnosis is uncertain.
• Pitfalls:
  • The cyst is sometime beneath the subcutaneous lesion mimicking meningocele.
  • They may be missed if located in the portion of the brain closest to the transducer.
• Usually diagnosed in the second half of pregnancy, though may be detected as early as 13 weeks.

Associations: Rare.

Management: In general, isolated arachnoid cyst does not alter standard obstetric management.

Prognosis: Good, unless it is associated with other anomalies; most are asymptomatic, but they can cause neurological signs and symptoms, but good outcomes with neurosurgical intervention. Prenatal resolution can also occur.

Recurrence risk: Rare.

Arachnoid cyst:  Transverse scan of the head: isolated cystic, circular, thin-walled brain lesion (*)

Vein of Galen Aneurysm

Vein of Galen aneurysm is dilatation of the vein ranging from a large single arteriovenous malformation to multiple smaller communications. It is a rare but pathognomonic midline intracranial cyst, located posterior and slightly superior to the thalami within the subarachnoid space.

Incidence: Unknown.

Sonographic findings:

• Well-defined midline tubular cyst just posterior and superior to thalami.
• Demonstration of the feeding vessels with arterial or venous flow by Doppler and color-flow study. Moreover, pulsation in the vein of Galen is also suggestive of fetal compromise and occurs earlier than those in umbilical vein.
• High-output congestive heart failure, polyhydramnios, hydrops fetalis, and sequele of the aneurysm may be seen in some cases.
• Three-dimensional color power angiography aids in visualization of the feeder vessels.
• Differential diagnoses
  • interhemispheric cyst associated with agenesis of the corpus callosum
  • arachnoid cyst
  • dorsal sac associated with holoprosencephaly
  • the diagnosis of vein of Galen aneurysms is rapidly established with color and pulsed Doppler.
• Pitfalls:
  • A quadrigeminal cistern, a normal cystic structure posterior to the third ventricle, may be mistaken for the aneurysm, however, Doppler ultrasound will show no flow.
  • Centrally placed arachnoid cyst can be confused with the aneurysm, however, Doppler ultrasound will show no flow.
• Usually first diagnosable in the third trimester, but possible as early as 14 weeks.

Associations: Most cases occur as isolated anomalies but cardiac defects, cystic hygroma and hydrocephalus may be seen in some cases. Pulmonary hypertension, and high-output heart failure or hydrops fetalis can be a consequence of the aneurysms.

Management: Termination of pregnancy may be offered, especially in the case of hydrops. In continuing pregnancies, serial sonographic monitoring to identify early signs of hydrops is indicated. Elective cesarean section when fetal lung maturity is attained may improve prognosis.

Prognosis: Poor in cases of heart failure or hydrocephalus, with numerous feeder vessels, a wide draining vein, and steal retrograde aortic flow; better in selected cases without suprasystemic pulmonary hypertension with appropriate surgical correction such as a staged endovascular technique or embolization. The malformations can also spontaneously disappear in rare cases.

Recurrence risk: Rare.

Aneurysm of vein of Galen:  Midline tubular cystic space, predominantly located posteriorly (Ant: anterior; T: thalamus)

Intracranial Hemorrhage In Utero

Fetal intracranial hemorrhage has rarely been observed. Such hemorrhage usually originates from germinal matrix with rupture into the ventricles. This may be due to the extreme capillary permeability of the vascular germinal matrix, which makes it susceptible to hemorrhage and often related to maternal factors, such as preeclampsia, or bleeding disorders. Germinal matrix or intraventricular hemorrhage is commonly classified in four grades as follows: Grade I: limited to subependymal matrix, Grade II: intraventricular extension, but without ventriculomegaly, Grade III: intraventricular extension, with ventriculomegaly, Grade IV: intraparenchymal extension.

Incidence: About 1 in 1000 pregnancies, very common in premature infants following delivery, may be as high as 40% among infants of <32 weeks.

 Sonographic findings:

• The sonographic appearance varies with the location, size, and age of hemorrhage.
• An echogenic clot filling the ventricles followed by ventriculomegaly. Once the hemorrhage resolves, only ventriculomegaly may be evident.
• Hydrocephalus with mixed echogenic debris layering within the ventricles.
• Large hemorrhages may produce a marked mass effect.
• Subdural hematomas appear as echogenic or complex fluid collections just beneath the cranium, displacing and distorting the brain.
• Occasionally, mixed echogenic, enlarged choroid plexus results from hemorrhage into the choroid plexus.
• Porencephalic cyst following the hemorrhage may be seen.
• Mostly occurs in the beginning of the third trimester of pregnancy.
• The primary differential diagnosis includes intracranial neoplasm or infection.
• MRI is helpful for differentiating intracranial echogenicities suspected of hemorrhage.

Associations: No specific anomaly.

Prognosis: Depends on the extent of hemorrhage and intraparenchymal hemorrhage. The outcome is usually poor, especially for those fetuses affected by higher-grade intraventricular hemorrhages, whereas it is better in the subgroup with intraventricular hemorrhage.

Intracranial Neoplasms

Fetal intracranial neoplasms are rare and most occur in the perinatal period. Teratoma is the most common tumor detected antenatally, accounting for 62% of cases.

Incidence: Approximately 0.34 per 1 million live births.

Sonographic findings:

• Usually irregular in appearance.
• Mostly echogenic mass with occasional cystic portions with or without distortion of normal symmetrical intracranial structures, calcifications.
• Located anywhere within the brain.
• Craniomegaly, obstructive hydrocephaly seen in some cases.
• Associated polyhydramnios and hydrops fetalis occasionally seen.
• Infrequently abnormal cerebral Doppler flow velocimetry.
• Prenatal ultrasonography had high specificity in the diagnosis of brain neoplasms but the accuracy in predicting the histological type was limited.
• Most diagnosed in late second and third trimesters.

 Association: No.

Management: Termination of pregnancy can be offered when diagnosed before viability.

Prognosis: Usually poor, though postnatal successful resection has been reported.

Recurrence risk: Rare.

Cephalocele

Cephalocele is a protrusion of intracranial contents through a bony defect of the skull. Most cephaloceles are midline and occipital extracranial masses. If only meninges protrude, it is called meningocele. Cephaloceles may be a part of several syndromes, especially Meckel syndrome (cephalocele, polycystic kidneys, and polydactyly) or trisomy 13, and are often associated with other malformations.

Incidence: 1-5 in 10,000 births, which varies with ethnic group and geographic region. Occipital cephaloceles are most common in the West, whereas anterior cephaloceles are much more common in Southeast Asia (1:5000 in Thailand compared with 1:35,000-40,000 in Europe).

Sonographic findings:

Fig 1, Fig 2, Fig 3, Fig 4

• Skull defect, usually in the occipital area (90% of cases), best visualized on the standard transcerebellar and transthalamic view.
• Skull defect of anterior cephalocele is more difficult to visualize and may present as extracranial mass with hypertelorism and the cephalocele may best be seen on the facial profile view.
• Skull defect in an asymmetric area is often related to amniotic band syndrome and other associated anomalies may be seen.
• Extracranial mass protruding through the defect
  • meningocele, an entirely cystic mass
  • a solid mass, often showing gyri and sulci (encephalocele)
  • a solid cystic mass (meningoencephalocele).
• Microcephaly, commonly seen.
• Possibly ventriculomegaly.
• Polyhydramnios in some cases.
• The lemon-shaped appearance of the bony calvarium that occurs with open NTD and with the Arnold-Chiari type II malformation.
• Associated anomalies of specific syndrome, especially Meckel syndrome (cephalocele, polycystic kidneys, and polydactyly) , Waker-Warburg syndrome (cephalocele, ocular malformations, Dandy-Walker malformations), and Joubert syndrome.

Anterior meningocele:   Sagittal scan of the fetal face: frontal bone defect with midline cystic mass (meningocele)

• Pitfalls:
  • A scalp hemangioma, cephalhematoma, epidermal scalp cyst, caput succedaneum, or even the normal fetal ear can be mistaken for a cephalocele.
•  The primary differential diagnosis of occipital cephaloceles includes
  • cystic hygroma (most common); usually septate, cystic, no skull defect, often related to hydrops fetalis
  • cervical meningocele
  • cervical teratoma
  • cranial hemangioma
  •  iniencephaly (very rare).
• Usually diagnosable after 11-14 weeks (transvaginal ultrasound) .

Associations: Ventriculomegaly (most common), Meckel syndrome, amniotic band syndrome, and limb-body wall complex, chromosome abnormalities (14% of cases).

Management: Termination of pregnancy can be offered for a severe case diagnosed before viability. For the less severe form, a careful search for other anomalies and karyotyping is indicated. The fetus should be delivered and have surgical correction in a tertiary center. A cesarean section could improve the prognosis by avoiding birth trauma and contamination of brain tissue with vaginal bacteria.

Prognosis: Poor in most cases, but good for small, cystic isolated meningocele. Neurological outcome depended on the occurrence or not of hydrocephalus, while the intelligence level was mainly related to the absence of cerebral tissue within the sac.

Recurrence risk: About 2-4%. Periconceptional folic acid supplementation can significantly decrease the recurrent risk.

Exencephaly (Acrania)

Exencephaly is a developmental abnormality characterized by partial or complete absence of the cranial vault with relatively complete but heterogeneous and disorganized brain. It is an embryonic precursor of anencephaly. Some cases are an amniotic band sequence. The developing brain exposed to amniotic fluid is gradually destroyed and disappears or becomes residual tissue (angioma stroma).

Sonographic findings:

• Absence of the calvarial vault with brain tissue, relatively normal in amount, floating in amniotic fluid. Fig 1, Fig 2
• Frog-eye appearance face on the coronal view. Fig 3
• Abnormally-shaped brain with distorted specific structures such as the ventricles or choroid plexus and the visualization of surrounding membrane instead of skull.
• The first trimester exencephalic fetus may have a wide and bilobed head, a so-called Mickey Mouse head.
• Most diagnosed in the first trimester because of the rapid necrosis of brain tissue when exposed to amniotic fluid, subsequently leading to anencephaly.
• Echogenic amniotic fluid is found in nearly 90% of cases of acrania/anencephaly in the first trimester.
• The primary differential diagnosis includes sonolucent skulls such as osteogenesis imperfecta type II, hypophosphatasia.
• Pitfalls: An irregular fetal head outline in the first trimester can simply be overlooked.
• Diagnosable from 10 to 14 weeks of gestation, usually can be detected during NT scanning.

Exencephaly:  Coronal scan of the fetal face at 12 weeks: frog-face appearance with free-floating brain (*) above the orbits

Associations: Spina bifida, non-specific anomalies, chromosome abnormality is found in about 2% of fetuses with acrania.

Management: Termination of pregnancy should always be offered.

Prognosis: Uniformly lethal.

Recurrence risk: About 2-4%. Periconceptional folic acid supplementation can significantly decrease the recurrent risk