ultrasound diagnosis of fatal anomalies

SELECTED SYNDROMES AND ASSOCIATIONS
Fig. 11.26 Meckel–Gruber syndrome. Same fetus.
Demonstration of postaxial hexadactyly.
Miller–Dieker Syndrome (Lissencephaly Type I)
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Definition: This is a structural chromosomal
anomaly characterized by an almost complete
absence of the cerebral gyri. It is combined with
microcephaly, dysplasia of the ear, facial dysmorphisms
such as flared nostrils, and mental
impairment.
Incidence: Extremely rare; only 20 cases have
been described.
Origin/genetics: Usually, a defect in chromosome
17 (17 p13.3) is found; there is partial loss
of the short arm; translocation or a ring chromosome
may also be present. The risk of recurrence
is 25%, but in case of new mutation the recurrence
risk is not increased. In familial translocation
forms, diagnosis is possible during prenatal
screening by chromosomal analysis (high-resolution
banding).
Clinical features: Head and face: microcephaly,
high forehead, prominent occipital region,
bitemporal pitting, long upper lip median ridge,
thin upper lip, lissencephaly or pachygyria,
thickened skull, widening of cerebral ventricles,
microgenia, dysplasia of the auricles, broad nasal
bridge, flared nostrils. In addition, cardiac defects,
cryptorchism, clouding of the cornea,
neonatal fits, reduced muscle tone, severe mental
impairment.
Ultrasound findings: The diagnosis can be made
at 26 weeks at the earliest. Microcephaly and
agyria are first evident at this stage. Widening of
the cerebral ventricles and abnormal shape of the
head are suspicious for lissencephaly. Additional
findings are: hydramnios, growth restriction,
microgenia, dysplasia of the auricles, broad nasal
bridge, and flared nostrils. There is a reduction in
fetal movement. Cardiac anomalies, renal malformations,
cryptorchism, and duodenal atresia
may not always be present.
Differential diagnosis: Walker–Warburg syndrome,
Norman–Roberts syndrome, agenesis of
the corpus callosum, Cornelia de Lange syndrome,
Wolf–Hirschhorn syndrome, cri-du-chat
syndrome, Jacobsen syndrome, Fanconi anemia,
Freeman–Sheldon syndrome, Meckel–Gruber
syndrome, multiple pterygium syndrome, Neu–
Laxova syndrome, neural tube defects, Roberts
syndrome, Seckel syndrome, Shprintzen syndrome,
Smith–Lemli–Opitz syndrome, triploidy,
trisomy 9, trisomy 13.
Clinical management: Magnetic resonance imaging
at the prenatal stage is a useful method of
examining the cerebrum and other intracranial
structures. If the fetus is lying with a cephalic
presentation, then a vaginal scan can also be
used to examine intracranial structures.
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