Diagnostic ultrasound ( PDFDrive )

CHAPTER 33 The Fetal Face and Neck 1159
A
B
FIG. 33.29 Agnathia Microstomia. (A) Sagittal sonogram, and (B) magnetic resonance image show the absent mandible.
have shown that thickened NT measurements in the irst trimester
are associated with fetal aneuploidy, cardiac defects, other major
malformations, and adverse pregnancy outcome. 114-118 Images
must be obtained in midsagittal plane 119 by trained sonographers,
and measurements are combined with patient age, gestational
age, and serum testing to give a risk for aneuploidy (see Chapter
31). In the second trimester, the nuchal fold thickness is measured
in the suboccipital bregmatic plane. A measurement of 6 mm
or greater from 15 to 22 weeks is associated with an increased
risk of trisomy 21. 120,121 he measurement is taken in the midline
from the outer edge of the occipital bone to the outer edge of
the skin.
Lymphatic Malformation (Cystic Hygroma)
Lymphatic malformation, known historically as “cystic hygroma,”
is a septated luid collection behind the fetal neck, thought to
result from early maldevelopment of the lymphatic system. his
abnormality is highly associated with Turner syndrome (XO),
other chromosomal anomalies, and cardiac structural abnormalities.
When associated with hydrops, fetal mortality is very high.
As with an increased NT, if a lymphatic malformation is diagnosed
and chromosomes are found to be normal, the fetus should still
be carefully evaluated for cardiac abnormalities.
Lymphatic malformations can occur elsewhere in the head
and neck and may be microcystic or macrocystic. hey are
presumed to result from obstructed lymphatic sacs that do not
communicate with main lymphatic channels. Although benign,
morbidity is associated with mass efect on the fetal airway when
such masses arise in the face and neck (Fig. 33.31). In this setting,
fetal MRI is oten useful for evaluation of the fetal airway and
for delivery planning. Fluid-illed lymphatic malformations, even
when large, are much more malleable than solid teratomas of
the head and neck and are less likely to compromise the airway.
When these malformations involve the tongue, cystic hygromas
may interfere with swallowing and feeding ater birth.
Cervical Teratoma
Teratoma is the most common tumor in neonates, with the
majority located at the sacrum and coccyx. Approximately 5%
of teratomas arise in the neck or oropharynx. Cervical teratomas
occur equally in males and females. 122 Sonographically, teratomas
are usually complex masses composed of both cystic and solid
elements and are oten associated with regions of calciication.
here is usually vascular low within the solid portions of the
mass. In the neck, they are usually anterolateral in location and
can become quite large, oten involving the thyroid gland. When
they arise in the neck, teratomas may impinge on the airway,
interfere with fetal swallowing, and result in polyhydramnios.
Evaluation of the fetal airway is particularly important to delivery
planning and is oten best accomplished with fetal MRI
(Fig. 33.32).
When teratomas arise in the neck, there can be hyperextension
of the fetal neck, best seen in sagittal views. Teratomas of the
oropharynx (epignathus) oten protrude from the mouth.
Although most teratomas are histologically benign, prognosis
depends on the degree of mass efect on the trachea and the
ability to secure the infant’s airway at delivery. If there is substantial
mass efect on the airway, the ex utero intrapartum treatment
(EXIT) procedure may be necessary. his complex procedure
requires a team of specialists for the mother and fetus and involves
cesarean delivery, with preservation of the maternal-fetal circulation
through the placenta until the neonatal airway can be
secured. 123-127
Thyromegaly and Goiter
Fetal goiter is rare (1 per 30,000 to 50,000 live births) 128 and
most oten related to maternal thyroid disease, such as Graves
disease 129 or Hashimoto thyroiditis, with antibodies that cross
the placenta and lead to fetal thyroid dysfunction. Maternal use
of thyroid blocking agents (e.g., propylthiouracil) may also result