Low torcular Herophili position and large brain stem-tentorium angle in fetuses with open spinal dysraphism at 11-13 weeks of gestation.

In all fetuses with OSB the BST angle is significantly larger than in normal controls with the tentorium being almost perpendicular to the BS. This sign confirms the inferior displacement of the tentorium cerebelli in respect of its normal insertion on the occipital clivus already in the first trimester of pregnancy and is useful in the diagnosis of Chiari II at this early stage. In all these fetuses the low position of the tentorium and TH is also easily visible, even subjectively. This article is protected by copyright. All rights reserved.