FIGURE 10-55 Septo-optic dysplasia. Axial (A) and coronal (B) images at 30 weeks' ges sion syndrome (Hu, 2006). If hemorrhage tation confirm absence of the cavum septum pellucidum (arrowheads) in both. There is is seen, MR imaging characteristics may also associated mild ventriculomegaly (arrow).
FIGURE 10-56 Terminal myelocystocele, 36 weeks' gestation. A. In this sagittal T2-weighted image, the spinal cord is tethered, expanding into the terminal cyst (arrow).
B. Seen in this Tl-weighted image, the meningocele and terminal cyst are covered by subcutaneous fat (arrows) and skin.
indicate which structures are involved and approximately when bleeding occurred. In the setting of congenital fetal infections, ,1R imaging can delineate the variable degrees of neural parenchymal abnormality and subsequent maldevelopment (Soares de Oliveira-Szejnfeld, 2016).
Aside from cerebral structure, suspected spinal dysraphisms, including neural-tube defects, can also be further characterized for surgical planning. Figure 10-56 demonstrates a complex skin-covered dysraphism with associated tethering of the spinal cord. his terminal myelocystocele will benefit from early intervention following delivery.
Many thoracic abnormalities are readily seen with targeted sonography. MR imaging, however, may help delineate the location and size of space-occupying thoracic lesions and quantiy remaining lung tissue volumes. MR imaging can aid in characterizing the type of congenital cystic adenomatoid malformation and in visualizing the blood supply of pulmonary sequestration (p. 200). With congenital diaphragmatic hernia, MR imaging can help veriy and quantiy the abdominal organs within the thorax. his includes the volume of herniated liver and compressed lung tissue volumes (Fig. 10-57) (Debus, 2013; Lee, 2011; Mehollin-Ray, 2012). Also in fetuses with diaphragmatic hernia, MR imaging can assist in identiying other organ-system abnormalities, which may greatly afect fetal prognosis (Kul, 2012). MR imaging similarly is used for chest evaluation in skeletal dysplasia and to measure lung volumes in pregnancies with prolonged oligohydramnios secondary to renal disease or ruptured membranes (Messerschmidt, 2011; Zaretsky, 2005).
When sonographic viewing of fetal abdominal abnormalities is limited by oligohydramnios or maternal obesity, MR imaging may add value (Caire, 2003). Hawkins and coworkers (2008) found that lack of signal in a contracted fetal bladder on T2-weighted sequences was associated with lethal renal abnormalities (Fig. 10-58). Diferences in signal characteristics between meconium in the fetal colon and urine in the bladder may permit deinition of cystic abdominal abnormalities (Farhataziz, 2005). Given the predictable pattern of meconium accumulation within the gastrointestinal tract and high signal intensity on T1-weighted sequences, MR imaging is a complementary tool in diagnosing gastrointestinal abnormalities and complex cloacal malformations (Furey, 2016). Peritoneal calciications related to meconium peritonitis are more readily apparent