In the transerse scan the normal neural arch appears as a closed circle with an intact skin coering , whereas in spina bifida the arch is " u " shaped and there is an associated bulging meningocele ( thin - walled cyst ) or myelomeningocoele 在横切面上,正常神经弓表现为闭合的环,有完整的皮肤覆盖,然而在脊柱裂,弓变成“ u ”型,有相应的脑膜膨出(薄壁的囊型结构)或脊髓脊膜膨出。