RESUMO
Objective To explore the diagnostic value of prenatal MRI in fetal Joubcrt syndrome and related disorders (JSRD).Methods Prenatal MRI data of 5 JSRD fetuses were analyzed retrospectively.The ratio of AP diameters of crown to root of molar tooth sign,the ratio of AP diameters of isthmus to interpeduncular fossa,and the ratio of the transverse to AP diameters of the roof of the fourth ventricle on the axial images of the midbrain were measured.Results Molar tooth signs were observed in 5 fetuses on the axial images of midbrain.The cerebellar vermis disappeared,and cleft sign was observed.Enlarged cisterna magna was observed in 3 fetuses.The ratios of AP diameters of crown to root were 0.58-0.90,of AP diameters of isthmus to interpeduncular fossa were 0.84-1.00,and of transverse to AP diameters of the fourth ventricle roof were 0.42-0.60.Conclusion Molar tooth sign and cleft sign were characteristic findings for JSRD on MRI,therefore being helpful to prenatal diagnosis of JSRD.