Diagnostic ultrasound ( PDFDrive )

1180 PART IV Obstetric and Fetal Sonography
A
B
C
FIG. 34.12 Anencephaly. (A) Anencephaly at
14 weeks. Coronal view of fetus at 14 menstrual
weeks shows the spine ending in a clump of basal
skull bones without a formed cranial vault (arrow).
(B) Anencephaly at 12 weeks. Note that there is
an amorphous mass of tissue (angiomatous stroma,
arrows) above the face. (C) Amniotic band
sequence at 15 weeks mimics anencephaly, but
this fetal head and brain are stuck to the uterine
wall by obvious bands (arrow). Unlike anencephaly,
this condition is sporadic and unlikely to recur.
representing abnormal mesenchymal migration or, in the case
of frontonasal cephaloceles, a failure of closure of normal
diverticulation. Because many are skin covered, MS-AFP is
elevated in only 33% compared with spina biida (62%) and
anencephaly (92%). his makes ultrasound the primary diagnostic
tool. Cephaloceles are more likely to be associated with additional
cerebral and somatic abnormalities and syndromes. Common
associated cerebral abnormalities involve the midline structures
such as the corpus callosum, cerebellum, and brainstem and
include venous abnormalities, holoprosencephaly (HPE), HC,
and facial cleting (Table 34.2). Over 30 syndromes include
cephaloceles; many are related to gene dysfunctions that afect
both CNS and somatic development. hese additional abnormalities
strongly afect prognosis, so whenever a cephalocele is found,
there should be a detailed search for other anomalies, and MRI
and genetic evaluation should be considered. 102-105,107,108
Ultrasonographically, an encephalocele manifests as a cystic
mass at the surface of the skull, typically in the midline (see Fig.
34.13). Contained brain with a visible bony defect conirms the
diagnosis, but it may be diicult to see the contained, oten
abnormal, brain tissue, and the bony defect may also be small
and diicult to detect. Encephaloceles can be seen during
irst-trimester ultrasound and are oten preceded by an enlarged
rhombencephalic cavity. 99 MRI is helpful to conirm the diagnosis
and, more important, to search for additional features that can
afect prognosis and counseling. 18,101,102
Other lesions that should be considered in the diferential
diagnosis when a scalp lesion is seen include cystic hygroma,
hemangioma, scalp edema or cephalohematoma, epidermal scalp
cyst, branchial clet cyst, dermoid cyst, dacryocystocele, epignathus,
and cervical teratoma. 104,110,111
he atretic cephalocele is a variant that is infrequently
recognized prenatally, manifesting as a small, blisterlike subcutaneous
collection in the skin in the midline near the vertex
at the surface of a seemingly intact skull (see Fig. 34.13E).
Diagnostic clues are abnormalities of the superior sagittal
sinus, which may have multiple channels, and the persistence
of the prosencephalic vein of Markowski, which runs in the
falx (falcine sinus) from the region of the start of the vein of
Galen to the sagittal sinus underlying the encephalocele. As with
other cephaloceles, there may be other cerebral abnormalities,
especially involving the midline, which can afect outcomes.
However, if the cephalocele is isolated, the children in general
do well. 104,110,111