Objective:To observe the morphological changes of the sylvian fissure on the transthalamic section of fetal brain at 20-32 weeks, and grade the fetal sylvian fissure development by means of a simple scoring system and explore its clinical feasibility.Methods:From September 2018 to June 2020, 487 normal single fetuses of 20-32 weeks were examined in Shenzhen Maternal and Child Health Hospital Affiliated to Southern Medical University. The sylvian fissure maturation was analyzed on the transthalamic section of fetal brain at 20-32 weeks and was graded from 0 to 5: un-visualized (grade 0), shallow arc (grade 1), obtuse-angled platform (grade 2), right-angled platform (grade 3), acute-angled platform (grade 4), and closed operculum (grade 5). The pregnancy outcomes and gestational age were recorded.Statistical analysis was performed by SPSS 20.0 software using box plot, Mann-Whitney U test, Weighted Kappa coefficient. Results:Left sylvian fissuer grades were obtained in 280 fetuses and right sylvian fissure grades were obtained in 247 fetuses. The fetal sylvian fissure maturation at 20-32 weeks was graded from 0 to 5, which increased with advancing gestation. Grade 0 only appeared in 3 fetuses at 20 weeks, and 99.4% fetuses at 20 weeks had grade ≥1. Grade 1 appeared in 20-22 weeks, grade 2 in 20-25 weeks, grade 3 in 22-26 weeks, grade 4 in 25-32 weeks, and grade 5 in 27-32 weeks. Box-plot and Mann-Whitney U test showed that gestational week distribution of sylvian fissure at all grades was symmetric on both sides ( P>0.05). The Weighted Kappa coefficients were 0.857(95% CI=0.750-0.957) and 0.939 (95% CI=0.859-1.000), respectively, with strong consistency regarding inter- and intra-observer agreements. Conclusions:Fetal sylvian fissure maturation at 20-32 weeks can be evaluated by means of a simple scoring system with symmetrical grading of both sides.

Objective:To assess the ultrasonographic features and potential diseases of fetal abnormal sylvian fissure(SF), and to explore the value of whole-genome sequencing (WGS) in prenatal detection.Methods:A total of 28 fetuses with a sonographic diagnosis of abnormal SF in Shenzhen Maternal and Child Health Hospital Affiliated to Southern Medical University between October 2018 and October 2020 were prospectively included. The fetal brain was evaluated by neuroultrasound and intrauterine MRI in detail. Amniotic fluid/cord blood obtained by amniocentesis or tissue samples from umbilical cord after birth were collected for WGS. Pregnancy outcomes and postnatal MRI were recorded, and neurodevelopment of live-born infants was followed up for more than 24 months after delivery.Results:During the study period, 28 fetuses with abnormal SF were identified, with a gestational age of 21.3-30.0 (24.8±2.0) weeks. Abnormal SF presented in MCD ( n=15, 53.6%), chromosomal anomalies ( n=3, 10.7%) or single-gene genetic syndromes ( n=3, 10.7%) with the affected fetuses showing developmental delay, hydrocephalus or leukomalacia ( n=4, 14.2%), corpus callosal agenesis with large interhemispheric cysts ( n=1, 3.6%), benign subarachnoid space enlargement with arachnoid cysts ( n=1, 3.6%), and multiple malformations ( n=1, 3.6%). Among the 15 cases with MCD, the most common pathology was lissencephaly/pachygyria, followed by schizencephaly, severe microcephaly, hemimegalencephaly with paraventricular heterotopia, and polymicrogyria. Abnormal SF presented bilaterally in 23 fetuses and unilaterally in 5. All cases were categorized into six types depending on SF morphology in the transthalamic section: no plateau-like or a small insula, linear type, irregular corrugated SF, Z-shaped, and cyst occupying type. In addition to abnormal SF, associated anomalies or mild variations were identified in all fetuses. There were 17 cases underwent intrauterine MRI, and 13 cases underwent postnatal MRI examination.And 25 pregnancies were terminated; 3 were born alive, and 2 had typical syndromic changes with poor neurodevelopmental prognosis. A related pathogenic genetic variant was detected in 57.1% (16/28) fetus, and the incidence of single nucleotide variants(SNVs) was 42.9% (12/28), among which de novo SNVs accounted for 91.7% (11/12). Conclusions:Fetal abnormal SF could be classified based on the ultrasonographic features of transthalamic section. Fetal abnormal SF may indicate MCD, some chromosomal abnormalities or single-gene genetic syndromes that may lead to poor neurodevelopmental outcomes, and may be affected by extra-cortical factors. It is suggested to carry out targeted prenatal genetic diagnosis for fetuses with abnormal SF.