Magnetic resonance imaging of fetuses with intracranial defects.

Thirteen women whose fetuses had intracranial defects on ultrasound examination were offered magnetic resonance imaging (MRI) without charge. All fetuses were paralyzed with pancuronium before the study, which lasted approximately 1 hour. With the mother in the left lateral decubitus position to minimize transmitted maternal aortic pulsation, T1-weighted images were obtained using a Picker 0.5-tesla superconductive unit. Magnetic resonance imaging provided excellent detail of intracranial anatomy in all cases. In four of the 13 fetuses, the MRI diagnosis differed from that of ultrasound and ultimately proved correct. In another three, MRI added greatly to the ultrasound diagnosis by delineating intracranial anatomy more precisely. In the remaining six cases, MRI confirmed the ultrasound impression. For circumstances in which the ultrasound diagnosis is unclear or antenatal intervention might require exact knowledge of anatomical detail, the additional information provided by MRI may justify its cost.