TY - CHAP M1 - Book, Section TI - Anomalies of Neural Tube Development A1 - Monteagudo, Ana A1 - Timor-Tritsch, Ilan E. A2 - Malinger, Gustavo A2 - Monteagudo, Ana A2 - Pilu, Gianluigi A2 - Paladini, Dario A2 - Timor-Tritsch, Ilan E. PY - 2023 T2 - Timor's Ultrasonography of the Prenatal Brain, 4e 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.All cases of anencephaly, approximately 80% of spina bifida, and 18% of cephaloceles are open lesions. In cases of closed neural tube defects, the maternal serum alpha-fetoprotein (MSAFP) is normal and the diagnosis is made at the time of the ultrasound examination.In the first trimester, open spina bifida can be diagnosed by direct observation of the spinal defect or by using several posterior brain “clues” such as non-visualization of the intracranial translucency (IT) and cisterna magna (CM); increased brainstem (BS) diameter; decreased brainstem to occipital bone (BSOB) diameter as well as increased BS–BSOB ratio.During the second and third trimesters, diagnosis of spina bifida can be made by direct observation of the spinal defect or by the “classic” intracranial sonographic signs, namely the “lemon” and “banana” signs.Anencephaly is a lethal malformation. The outcome of cephalocele is dependent on the size and presence of associated anomalies or genetic syndromes. Open spina bifida and Chiari II malformation are not lethal anomalies, although they are associated with a significant amount of morbidity and mortality.Recurrence risk for neural tube defects (NTDs) ranges between 2% and 5%. SN - PB - McGraw Hill Education CY - New York, NY Y2 - 2024/03/29 UR - obgyn.mhmedical.com/content.aspx?aid=1194695773 ER -