Prenatal diagnosis in pregnancies at risk for Joubert syndrome by ultrasound and MRI

Objectives To describe the prenatal imaging findings in fetuses at risk for Joubert syndrome (JS), review the literature and propose a protocol for prenatal diagnosis of JS using ultrasound and MRI. Methods We reviewed prenatal ultrasound and fetal MRI studies in two pregnancies at 25% recurrence risk for JS and correlated these findings with gross neuropathology in one affected fetus. Results While abnormalities such as occipital encephalocele or enlarged cisterna magna have been identified before mid‐trimester, the definitive diagnosis of JS, based on core cerebellar findings, has only been possible after 17 weeks' gestation. Conclusions With longitudinal monitoring, it is possible to diagnose JS in at‐risk pregnancies before 24 weeks' gestation. On the basis of our data and review of the literature, we propose a protocol for monitoring pregnancies at risk for JS, utilizing serial ultrasounds combined with fetal MRI at 20–22 weeks' gestation to maximize the accuracy of prenatal diagnosis. Copyright © 2005 John Wiley & Sons, Ltd.