Fetal Sylvian Fissure Charts to Evaluate the Development of Fetal Brain using Prenatal MRI

Objective: To explore the normal developmental pattern of the sylvian fissure (SF) in fetuses by MRI for better identifying cortical abnormalities in the early stage by quantifying the morphological characteristics. Methods: This study retrospectively evaluated the prenatal MRI of 324 normal singleton pregnancies at 22-38⁺⁶ weeks of gestation (GA). Biparietal diameter (BPD), insula depth (ID), sylvian fissure width (SFW), uncovered insula length (UIL), uncovered insula rate (UIR), sylvian fissure depth (SFD), sylvian fissure anterior depth (SFAD), sylvian fissure posterior depth (SFPD), sylvian fissure superior depth (SFSD) and sylvian fissure inferior depth (SFID) were obtained in the axial and coronal position. Reproducibility for each parameter was assessed by 40 cases and verified via intraclass correlation coefficient (ICC). Analyze the correlation between above parameters and GA. Growth charts were drawn using an optimal fitting curve and correlation formula. A paired-sample t-test was used to compare the left-right disparities of the measured parameters, and an independent-sample t-test was used to compare the differences between SFAD and SFPD, and between SFID and SFSD. Results: The interobserver agreements were reproducible (ICC: 0.798-0.992). A range of reference for the correlative parameters of sylvian fissure at 22-38⁺⁶ weeks of normal gestation was established. The SF parameters showed a significant correlation with GA (|r| = 0.386 - 0.965, P< 0.05). In the axial plane, statistically significant differences were observed for SFW and UIR between the left and right sides. The length of SFPD was longer than that of SFAD on both sides with the differences reaching statistical significance (P < 0.05). while SFID was significantly longer than SFSD only on the left side (P < 0.05). Conclusion: The development of sylvian fissure is dynamic throughout gestation and is a reliable feature of fetal cortex gyration. We provide certain reference standards of prenatal MRI to assist in diagnosing abnormal fetal cerebral cortex development.