Prenatal diagnosis of polymicrogyria by fetal magnetic resonance imaging in monochorionic cotwin death.

etal magnetic resonance imaging (MRI) is being used increasingly for confirmation and further characterization of brain abnormalities detected on routine prenatal sonography. It offers improved contrast resolution and direct visualization of both sides of the developing brain and is not susceptible to the limitations of sonography such as fetal position and amniotic fluid volume. With fetal MRI, more sensitive imaging of the cortical and sulcal development1–7 of the fetus can be obtained. Although most brain abnormalities occurring in cases of complicated monochorionic twin pregnancies are characterized by localized or diffuse areas of parenchymal destruction, cortical abnormalities have also been described postnatally or on fetal autopsy.8–21 We report a case in which fetal MRI showed not only encephalomalacia but also associated polymicrogyria in a survivor of a monochorionic intrauterine cotwin death.