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

Abstract

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

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

Study design: 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.

Results: 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.

Conclusion: 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.

Keywords: central nervous system; cortex development; fetal brain; prenatal ultrasound.