OP12.08: Assessment of the fetal sylvian fissure in the setting of cortical abnormalities detection: a comparison of published methods

Abnormal sylvian fissure (SF) can be an early indicator of malformation of cortical development (MCD). However, there is no accepted standard method for its assessment by prenatal ultrasound. The aim of this study is to compare the accuracy of the so far proposed techniques for SF evaluation on axial plane in normal cases and in fetuses with confirmed MCD. This was a retrospective study including prospectively enrolled fetuses between 22 and 34 weeks with no abnormal findings at expert neurosonography, and in a second group of cases with MCD confirmed at MRI and/or autopsy. The SF was assessed on 2D transabdominal axial plane by means of nine different techniques, including one subjective and eight objective methods derived from a literature search. The evaluation was performed twice by two Fetal Medicine fellows with a dedicated training in the expert assessment of the SF using different methods. The SF was defined as normal or abnormal in accordance with the definitions related to those techniques. The accuracy of the different techniques to predict the presence or the absence of MCD was compared. 100 cases were included at a median gestational age of 26 (22 – 34) weeks. Of these, 93 cases were normal. Subjective evaluation showed a 100% (95% CI: 59-100) sensitivity and a 100% (95% CI: 96-100) specificity for the prediction of absence or presence of MCD. Conversely, applying an objective method in the evaluation of the SF, the sensitivity ranged from 0% (95% CI: 0-41) to 86% (95% CI: 42-100) and the specificity from 23% (95% CI: 15-32) to 98% (95% CI: 92-100). The comparison of different methods for the expert assessment of the SF in axial plane has shown that the subjective evaluation of the SF is more accurate than other proposed methods in predicting the presence or absence of MCD.