Cat‐Ear‐Line: A Sonographic Sign of Cortical Development?

Objectives Diagonal echogenic lines outside the lateral ventricle have often been observed in the anterior coronal planes of the normal fetal brain by neurosonography. We have observed abnormal shapes of these echogenic lines in cases of malformation of cortical development (MCD). We named the ultrasound finding “cat‐ear‐line” (CEL). This study aimed to examine how and when CEL develops in normal cases compared with MCD cases. Methods We retrospectively examined the fetal brain volume dataset acquired through transvaginal 3D neurosonography of 575 control cases and 39 MCD cases from 2014 to 2020. We defined CEL as the hyperechogenic continuous lines through subplate (SP) and intermediate zone (IZ), pre‐CEL as the lines that existed only within the SP, and abnormal CEL as a mass‐like or mosaic shadow‐like structure that existed across the SP and IZ. All fetuses in the MCD group had some neurosonographic abnormalities and were ultimately diagnosed with MCD. Results The CEL was detected in 97.9% (369/377) of the control group from 19 to 30 weeks. The CEL visualization rate of the MCD group in the same period was 40.0% (14/35) which was significantly lower than that of the control group ( P < .001). Conclusions From this study, it appears that the CEL is an ultrasound finding observed at and beyond 19 weeks in a normally developing fetus. In some MCD cases, pre‐CEL at and beyond 19 weeks or abnormal CEL was observed. Maldeveloped CEL at mid‐trimester may help identify cases at‐risk of subsequent MCD.