ultrasound diagnosis of fatal anomalies

THE CENTRAL NERVOUS SYSTEM AND THE EYE
formities of the thumb. Additional malformations
are present in 16% of cases. However, in
cases of obstructive hydrocephalus, associated
malformations are seen in 80%.
Ultrasound findings: The third ventricle and
lateral ventricles are widened, but not the fourth
ventricle. The cerebellum and cisterna magna are
normal, except in severely affected cases.
Measurement of the remaining cortex does not
allow accurate prediction of the prognosis, the
rim of cortex being thinnest in the occipital region.
Obstructive hydrocephalus may also develop
in the third trimester of pregnancy. Obstructive
hydrocephalus does not always cause enlargement
of the head, so that intrauterine head circumference
measurements are not predictive.
Clinical management: Karyotyping procedure,
possibly molecular-genetic diagnosis, and
screening for intrauterine infections (TORCH).
Intrauterine interventions such as placement of
ventriculoamniotic shunt were attempted in the
1980 s, without adequate benefits. Regular sonographic
assessments every 2–3 weeks as hydrocephalus
may increase considerably. After 30
weeks of gestation, the benefit of early delivery
and placement of a shunt has to be weighed up
against the possible risks of a premature birth. In
case of cephalic presentation and normal head
circumference, cesarean section does not offer
any advantage over vaginal delivery.
Procedure after birth: The postnatal management
depends on the presence of associated
anomalies. The placement of ventriculoperitoneal
or ventriculoatrial shunts will depend on
the enlarging head circumference and the protein
content of the cerebrospinal fluid. Shunts
have to be replaced frequently in repeated operations,
due to obstruction or as the child grows.
Fenestration of the third ventricle into the basal
cisterns is an alternative to shunt therapy.
Prognosis: The neonatal mortality is in the range
of 10–30%, depending on the accompanying
malformations. Only 10% of survivors have an intelligence
quotient (IQ) of over 70.
References
See section 2.9 (hydrocephalus).
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Arachnoid Cysts
Definition: Echo-free structures arising from the
arachnoid and located intracranially or in the
spinal cord.
Incidence: Rare.
Clinical history/genetics: Mostly sporadic. Isolated
cysts have been described, with autosomal-recessive
inheritance.
Teratogens: Congenital infections.
Embryology: The etiology of congenital
arachnoid cysts is uncertain. Maldevelopment of
the leptomeninges may be responsible. After
birth, these cysts may be acquired through infection
or trauma.
Associated malformations: Obstructive hydrocephalus
due to displacement of cerebrospinal
fluid circulation.
Ultrasound findings: These cysts appear as echofree
single structures connected in places to the
meninges and causing damage due to compression
of brain tissue or cerebrospinal fluid circulation.
This may cause obstructive hydrocephalus.
Clinical management: Repeated observations at
short intervals. In cases of severe hydrocephalus
and fetal maturity, premature delivery should be
considered. Bleeding within the cysts may occur
during labor.
Procedure after birth: Small cysts can be monitored
at regular intervals. Surgical intervention
such as placement of a shunt or fenestration of
the cyst may be necessary for large cysts causing
symptoms (seizures, hydrocephalus).
Prognosis: Generally good, depending on the location
of the cyst and possible complications of
surgical treatment.
Recommendation for the mother: The prognosis
is very good, as this is one of the few cases in
which the cause of hydrocephalus can be treated
successfully.
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