ultrasound diagnosis of fatal anomalies

HYDROCEPHALUS INTERNUS
Stevenson DA, Hart BL, Clericuzio CL. Hydranencephaly
in an infant with vascular malformations. Am J Med
Genet 2001; 104: 295–8.
Vaughan JE, Parkes JR, Larsen P. Hydranencephaly: antenatal
diagnosis using ultrasound [letter]. S Afr Med
J 1984; 66: 675–6.
Hydrocephalus Internus
Definition: Widening of the lateral ventricles, as
well as the third and the fourth ventricle. Alteration
in the relationship between the rim of the
cortex and the width of the ventricles. It is
characterized by an abnormal accumulation of
cerebrospinal fluid, due either to increased production
or disturbed circulation and resorption.
Prenatally, hydrocephalus is a consequence of
obstruction or stenosis of the cerebral aqueduct.
Hydrocephalus ex vacuo results from the destruction
of brain tissue. It does not necessarily
imply a large head, as this is a late and inconsistent
sign.
Incidence: One in 1700–2000 births (hydrocephalus
without neural tube defect).
Sex ratio: M : F = 0.7 : 1
Associated malformations: Associated malformations
are expected in 80% of the cases. A
neural tube defect may be the cause of hydrocephalus
in 45–65%. In these cases, the characteristic
“lemon sign” and “banana sign” are observed.
In isolated cases, it may be difficult to detect
the neural tube defect, especially if it is a
simple spina bifida without a meningomyelocele.
There is an increased occurrence of renal
malformations. Chromosomal aberrations are
evident in 20% of cases. Particularly in cases of
trisomy 13, 18, and 21, an accompanying hydrocephalus
is often present. Familial incidence
through X-linked recessive inheritance is known
to affect 50% of male infants, with hydrocephalus
with stenosis of the aqueduct; 50% of
females are asymptomatic carriers. Antenatal infections
such as toxoplasmosis, cytomegalovirus,
syphilis, and listeriosis are causative
factors. In addition, hydrocephalus appears in
association with other syndromes, for example,
Meckel–Gruber syndrome, hydrolethalus, Peters
anomaly, Miller–Diecker syndrome, osteogenesis
imperfecta, and Apert syndrome.
Ultrasound findings: Assessment of ventricles is
carried out routinely in the ultrasound screening
of fetal anomalies. Under normal conditions, the
width of the posterior horns of the lateral ventricles
remains relatively constant from the end
of the first trimester, with an upper limit of
8–10 mm. This means that the relationship of
the ventricular width to the surrounding brain
tissue changes in favor of the developing brain as
the head circumference increases. In case of ventriculomegaly,
it is most important to locate the
defect (lateral ventricle, third or fourth ventricles).
In addition, a very careful search for
other anomalies is mandatory (for example,
agenesis of corpus callosum, Dandy–Walker
cyst).
Clinical management: Search for infections
(TORCH), karyotyping, molecular-genetic diagnosis
if necessary. Magnetic resonance imaging
may be useful in the differential diagnosis. Repeated
ultrasound at short intervals. Delivery
should be planned in a center with a pediatric intensive-care
unit with neuropediatric and neurosurgical
experience. Intrauterine placement of
a feto-amniotic shunt—a method propagated in
the 1980s without the promised success—has
been abandoned. There are no studies showing
benefit of premature delivery for the sake of surgical
intervention. In individual cases, delivery
may be appropriate at 33 or 34 weeks. The benefit
of a primary cesarean section is questionable.
If the large fetal head poses a mechanical obstacle
cephalocentesis may be an option in rare
cases to enable a vaginal delivery. Even in severe
cases of hydrocephalus, with only a tiny rim of
cortex, decompression of the brain tissue may
allow surprisingly good development of the
brain.
Postnatally, intracranial pressure possibly
may be estimated using Doppler sonography of
the medial cerebral artery. Increased intracranial
pressure is diagnosed when the diastolic
flow velocity decreases, even showing
reverse flow, and the resistance index increases.
It is not yet clear whether these parameters are
accurate for prenatal assessment of intracranial
pressure.
Procedure after birth: Detailed diagnostic intervention,
including molecular genetics, in the
presence of aqueduct stenosis and “hitchhiker
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