PRENATAL SONOGRAPHIC DIAGNOSIS OF VERMAL AGENESIS

Agenesis of the vermis as detected during gestation by ultrasonography may indicate the existence of various malformation arrays or syndrome s. We report on our observations of five cases of complete vermal agen esis that were detected at 22-31 weeks of gestation. All had a vertex presentation and transvaginal sonography established the diagnosis of vermal agenesis. Two of the vermal agenesis cases had no associated an omalies outside the central nervous system (CNS). In one, the cerebell ar cleft was the only abnormality present and the other also had lobar holoprosencephaly. The three remaining fetuses had trisomy 13 and fea tured various additional extra-CNS anomalies. The association of compl ete vermal agenesis and trisomy 13 has not been previously reported. O ur experience with this series suggests that supplementation with vagi nal fetal sonography is a valuable tool for obtaining a more accurate view of the posterior fossa whenever a cyst or a cyst-like abnormality is detected by transabdominal sonography. A finding of isolated verma l agenesis appears to mandate a careful search for additional anomalie s and the performance of karyotype analysis. (C) 1997 by John Wiley & Sons, Ltd.