TY - CHAP M1 - Book, Section TI - ANOMALIES OF DORSAL INDUCTION A1 - Monteagudo, Ana A1 - Timor-Tritsch, Ilan E. A2 - Timor-Tritsch, Ilan E. A2 - Monteagudo, Ana A2 - Pilu, Gianluigi A2 - Malinger, Gustavo Y1 - 2017 N1 - T2 - Ultrasonography of the Prenatal Brain, 3e AB - KEY POINTSFailure of closure of the neural tube during neurulation results in neural tube defects. Neurulation, both primary and secondary, are completed by approximately 32 post-ovulatory days.Not all cases of neural tube defects are open lesions. Approximately 20% of spina bifida and 80% of cephaloceles are closed lesions. In this scenario the MSAFP is normal and the diagnosis is made at the time of the ultrasound examination.Approximately 80 to 90% of children with Chiari II will develop hydrocephaly.During the second and third trimesters the "classic" sonographic findings that aid in the diagnosis of spina bifida are the lemon and banana signs. Recently, three additional findings have been described: pointed lateral ventricles, beaked tectum, and interhemispheric cyst. In the first trimester, the newly proposed "intracranial translucency" may become an early sign of open spina bifida. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/03/28 UR - obgyn.mhmedical.com/content.aspx?aid=1138379082 ER -