FIGURE 10-17 Schizencephaly. This transverse image ofthe fetal head shows a large cleft that extends from the right lateral ventricle through the cortex. Because the borders of the cleft are sepa rate, the defect is termed open-lipped. (Used with permission from
Michael Davidson, ROMS.)
FIGURE 10-19 Midline face. This view demonstrates the integrity of the upper lip.
FIGURE 10-18 Sacrococcygeal teratoma. Sonographically, this tumor appears as a solid and/or cystic mass that arises from the anterior sacrum and tends to extend inferiorly and externally as it grows. In this image, a 7 x 6 cm inhomogeneous solid mass is visible below the normal-appearing sacrum. There is also an internal component to the tumor.
In contrast, porencephaly is a cystic space within the brain that is lined by white matter and mayior may not communicate with the ventricular system. It is generally considered to be a destructive lesion and may develop following intracranial hemorrhage in the setting of neonatal alloimmune thrombocytopenia or following death of a monochorionic co-twin (Fig. 45-20, p. 878). Fetal MR imaging should be considered when either of these CNS anomalies is identiied.
his germ cell tumor is one of the most common tumors in neonates, with a birth prevalence of approximately 1 in 28,000 (Derikx, 2006; Swamy, 2008). It is thought to arise from the totipotent cells along Hensen node, anterior to the coccyx. Classification of sacrococcygeal teratoma (SCT) includes four types (Altman, 1974). Type 1 is predominantly external with a minimal presacral component; type 2 is predominantly external but with a significant intrapelvic component; type 3 is predominantly internal but with abdominal extension; and type 4 is entirely internal with no external component. he tumor histological type may be mature, immature, or malignant.
Sonographiclly, SCT appears as a solid and/or cystic mass that arises rom the anterior sacrum and usually extends inferiorly and externally as it grows (Fig. 10-18). Solid components oten have varying echogenicity, appear disorganized, and may enlarge rapidly with advancing gestation. Internal pelvic components may be more challenging to visualize, and fetal MR imaging should be considered. Hydramnios is frequent, and hydrops may develop from high-output cardiac failure, either as a consequence of tumor vascularity or secondary to bleeding within the tumor and resultant anemia. Mentioned throughout this chapter, hydrops is more ully described in Chapter 15 (p. 309). Fetuses with tumors >5 cm oten require cesarean delivery, and classical hysterotomy may be needed (Gucciardo, 2011). s shown in Figure 16-3 (p. 320), fetal surgery is suitable for some SCT cases.
his rare anomaly is characterized by absence of the sacral spine and often portions of the lumbar spine. It is approximately 25 times more common in diabetic pregnancies (Garne, 2012). Sonographic indings include a spine that appears abnormally short, lacks normal lumbosacral curvature, and terminates abruptly above the level of the iliac wings. Because the sacrum does not lie between the iliac wings, they are abnormally close together and may appear "shield-like." here may also be abnormal positioning of the lower extremities and lack of normal local soft tissue development. Caudal regression should be diferentiated from sirenomelia, which is a rare anomaly characterized by a single fused lower extremity that occupies the midline.