Diagnostic ultrasound ( PDFDrive )

CHAPTER 33 The Fetal Face and Neck 1139
Prenatal diagnosis can be diicult; fetuses can appear normal
in midtrimester but show changes in late pregnancy, when normal
physiologic molding can be a confounder. In at-risk cases, head
shape changes have been seen as early as 12 weeks. he fused
sutures can be detected as absence of the sonolucent space
normally seen between skull bones. he loss of hypoechoic suture
appearance lags shape changes by 4 to 16 weeks. hree-dimensional
multiplanar and surface rendering are helpful. Associated
anomalies can allow diferentiation among types. 25-27
Additional problems can arise from the cranial deformity,
including intracranial hypertension, obstructive apnea, proptosis,
visual loss, dental malocclusion, and intellectual impairment.
Learning disorders have been observed in 47% of school-age
children. 26
Fetuses prenatally suspected to have craniosynostosis should
undergo detailed neurologic and anatomic sonography. MRI may
be helpful. Postnatally, computed tomography (CT) surface
rendering helps conirm the diagnosis and is needed for surgical
treatment planning. Family history and molecular analysis for
FGFR and TWIST mutations can help. Multidisciplinary counseling
including craniofacial and neurosurgical specialists is
important because therapy can involve molding helmets and
surgery. 26,28,29
Wormian Bones
Wormian bones are ossicles located in the sutures or fontanelles
and may be associated with multiple conditions, such as pyknodysostosis,
osteogenesis imperfecta, cleidocranial dysplasia,
hypothyroidism, and trisomy 21. hree-dimensional views
are particularly useful in the assessment of wormian bones
(Fig. 33.6).
Differential Diagnosis of Wormian Bones
Cleidocranial dysplasia
Congenital hypothyroidism
Hypophosphatasia
Osteogenesis imperfecta
Trisomy 21
Menkes kinky-hair syndrome
Progeria
Pyknodysostosis
Forehead Abnormalities
he forehead is best evaluated in the sagittal proile view, where
the angle between the frontal and nasal bone can be assessed.
Frontal bossing is abnormal prominence of the frontal bones
and is a rare inding on fetal sonography. However, it has been
reported in a variety of bony dysplasias and syndromes, including
achondroplasia and thanatophoric dysplasia, and in syndromes
with associated craniosynostosis.
Wolf-Hirschhorn (4p − ) syndrome has an abnormally sloped
forehead, the “Greek warrior facies” (Fig. 33.7). he forehead
can also be sloped in the settings of microcephaly and
encephalocele, in which the forebrain is underdeveloped
(Fig. 33.8).
FIG. 33.6 Wormian Bone. An extra ossiication center (arrow) is
identiied between the frontal bones of a fetus with trisomy 18.
Differential Diagnosis of Frontal Bossing
Achondroplasia
Acromegaly
Basal cell nevus
Cleidocranial dysostosis
Congenital syphilis
Crouzon syndrome
Fetal trimethadione
Pfeiffer syndrome
Russell-Silver syndrome
Thanatophoric dysplasia
Encephaloceles
An encephalocele or cephalocele is an abnormal protrusion of
the brain and/or meninges through a defect in the skull and is
considered a form of spinal dysraphism. In the United States
and Western Europe, the occiput is the most common location
for encephaloceles. Frontoethmoidal encephaloceles are more
oten found in Southeast Asia. Many encephaloceles are diagnosed
during fetal sonography; they appear as abnormal defects in the
calvaria with herniation of brain tissue or meninges. Fetal MRI
is excellent for evaluating contents of the encephalocele and in
assessing the appearance of the intracranial brain parenchyma.