Prenatal MRI evaluation of giant neck masses in preparation for the fetal exit procedure

Airway compromise at birth can be anticipated with giant neck masses, so that as much anatomic information as possible is necessary prior to delivery to establish a diagnosis and assess the airway. With this study, we evaluated the usefulness of prenatal magnetic resonance imaging (MRI) for evaluation of giant fetal neck masses prior to operating on placental support, the Ex Utero Intrapartum Treatment (EXIT) procedure, performed to secure the neonatal airway. Three pregnant women with an ultrasound (US) diagnosis of fetal giant neck mass were referred for prenatal MRI. As this was our initial experience performing prenatal MRI, a variety of imaging sequences were used including spin-echo, fast gradient-echo, half-fourier single shot turbo spin-echo (Haste), and echo-planar imaging (EPI). All sequences performed were able to demonstrate the fetal airway relative to the mass. In addition, the images were able to give a more global definition of the mass because of the larger field of view than could be obtained with MRI compared to US. The Haste sequence provided the best definition of a mass because of decreased motion artifacts. The prenatal diagnosis on MRI was teratoma in two and lymphangioma in one and was confirmed at birth. MRI provided essential information about the diagnosis and the anatomy of the giant neck masses and adjacent airway in three fetuses prior to selection for the EXIT surgical procedure.