Embryogenesis of triple neural tube defects: sonic hedgehog—a key?

Neural tube closure is a complex spatio-temporal process. Multiple neural tube defects (NTDs) in a single patient are extremely rare. Only a few cases of multiple NTDs have been reported in the world literature, including less than 20 cases of double NTDs and 3 cases of triple NTDs. We report a fourth case of triple NTDs and review the literature regarding the embryogenesis. An effort is made to understand the theories of neural tube closure in light of recent advances in molecular biology and identification of the signaling pathways involved.