ULTRASOUND IN LISSENCEPHALY

• Without a previous history of an affected child the diagnosis cannot be reliable made until 26-28 weeks (when sulci and gyri become well defined sonographically).
• Absent gyri and a smooth brain.
• A detailed knowledge of the gestational age at which the cerebral sulci become visible is essential.

• Mild dilatation of the lateral ventricles (with colpocephaly).

• Rarely marked hydrocephalus.
• Microcephaly.
• Hypoplasia or agenesis of the corpus callosum.
• Dandy-Walker malformation (50%).
• Posterior cephalocele (25-50%).
• Polyhydramnios (impaired fetal swallowing).
• IUGR (50%).
• Less common abnormalities that have been reported include:
  micromelia, polydactyly, club foot, omphalocele, duodenal atresia, hepatosplenomegaly, cardiac and renal anomalies.

Lissencephaly (CT and Pathological specimen):

• Scan at 18 weeks demonstrate increased medial separation of the choroid plexus from the medial wall of the lateral ventricle.
• Normal sized ventricular atrium.
• Scan at 32 weeks demonstrates complete lack of sulci and gyri on the surface of the brain.
• Postnatal CT scan and pathological specimen in another case confirms the diagnosis.

REFERENCES

1. Saltzman DH, Krauss CM, Goldman JM et.al. Prenatal diagnosis of lissencephaly. Prenat Diagn 1991;11:139-143.
2. Okamura K, Murotsuki J, Sakai T et.al. Prenatal diagnosis of lissencephaly by magnetic resonance imaging. Fetal Diagn Ther 1993;8:56-59.