A New Parameter to Evaluate Fetal Sylvian Fissure by Transabdominal 2-D Ultrasound

Evaluation of the inclination direction and degree of the Sylvian fissure plateau has not been reported. We aimed to evaluate the Sylvian fissure plateau by Sylvian fissure plateau angle (SFPA) in axial views at 23-28 wk gestation.

A prospective ultrasound evaluation of 180 normal and 3 abnormal singleton pregnant women was conducted at 23-28 wk gestation. All cases were assessed in three axial planes of the fetal brain (the transthalamic, transventricular and transcerebellar plane) using transabdominal 2-D images. The SFPAs of all cases were measured between the brain midline and a line drawn along the Sylvian fissure plateau. Intraclass correlation coefficients (ICCs) were used to assess the intra- and inter-observer repeatability of SFPA measurements.

The SFPAs in normal cases in the transthalamic, transventricular and transcerebellar planes were all above y = 0, while in abnormal cases were below y = 0. However, there was no major difference between the angles measured on the transthalamic and transventricular planes (p = 0.365). There was a major difference between the SFPAs on the transcerebellar plane and transthalamic/transventricular plane (p < 0.05). The intra- and inter-observer ICCs were excellent at 0.971 (95% confidence interval [CI]: 0.945-0.984) and 0.936 (95% CI: 0.819-0.979), respectively.

The SFPAs of the normal cases in three axial views were stable at 23-28 wk gestation, suggesting that 0° may be a good cut-off value for evaluating abnormal SFPA. Findings offer a potential method by which the SFPA < 0°, as shown in three abnormal cases described herein, can be evaluated prenatally and thus serve as another tool for malformations of cortical development assessment, especially for frontoobitalopercula dysplasia. We recommend use of SFPA of the transthalamic plane to evaluate the Sylvian fissure in clinical work.