Practical approach to prenatal posterior fossa abnormalities using MRI.

This review focuses on the optimum use of fetal MRI as an additional imaging tool to sonographic data in posterior fossa (PF) abnormalities in the second and third trimesters of gestation. We have chosen three particular situations to demonstrate the value of MRI as a complementary investigation to US: (1) the pattern of increased fluid-filled space of the PF, (2) decreased cerebellar sonographic biometry and (3) the diagnosis of focal echogenic lesions of the cerebellum. For increased fluid-filled space of the PF and decreased cerebellar sonographic biometry, a practical approach is proposed, largely based on prenatal imaging, especially MRI.