An algorithm for prenatal ultrasound diagnosis of congenital CNS abnormalities.

The variable expression of congenital CNS abnormalities makes their antenatal ultrasound diagnosis extremely difficult. Clinical decisions depend on ultrasound diagnosis; therefore, accurate antenatal diagnosis is imperative. A diagnostic algorithm based on ultrasonic demonstration of fetal cranial structures altered in congenital CNS abnormalities was constructed and applied retrospectively to 40 patients with clinicopathologic follow-up adequate to define the cranial abnormality. Using the algorithm our diagnosis was correct in 37/40 (92 per cent) compared with 30/40 (75 per cent) without its use. The algorithm was highly accurate in the diagnosis of hydrocephalus (13/14), anencephaly/amniotic band syndrome (13/13), and holoprosencephaly (8/8). A wide spectrum of CNS abnormalities can be accurately diagnosed by ultrasonography in the antenatal period by the application of our algorithm.