Sylvian fossa sonographic measurements in 18 to 23 weeks fetuses with and without cerebral malformations

Abnormal sulcation of the brain is frequently associated with severe malformations, but the prenatal diagnosis is challenging, especially in early pregnancy.

Our study aimed to investigate the value of Sylvian fossa sonographic biometry in the diagnosis of cerebral malformation in the second trimester of gestation.

We prospectively established the normal values of the Sylvian fossa depth in a cohort of nonconsecutive patients, with singleton pregnancies and normal fetuses between 18+0 and 23+0 weeks' gestation. For each patient, a coronal view of the fetal brain, with a clear visualization of the anterior complex and the Sylvian fissure, was acquired by 1 sonologist, who also measured the depth of the fossa. Reproducibility for each parameter was assessed by a second sonologist using stored images. We also retrospectively acquired the same measurements in second trimester fetuses with central nervous system anomalies.

In 103 fetuses with a normal sonogram, the mean depth of the Sylvian fossa was 3.9±0.8 mm Interobserver reproducibility analysis demonstrated good results. Notably, 11 of 31 fetuses with cerebral malformations had a Sylvian fossa depth of <-2 z-scores, and these were found to have malformations of cortical development, lissencephaly in particular, or microcephaly.

Sonographic measurement of the Sylvian fossa during second trimester is feasible and reproducible. A shallow Sylvian fossa is associated with malformations of cortical development, microcephaly, or both.