Cystic retained medullary cord in an intraspinal J-shaped cul-de-sac: a lesion in the spectrum of regression failure during secondary neurulation.

We regard this case as an intermediate form between the typical RMC in which is regarded as regression arrest occurred after the terminal balloon collapsed and the medullary cord detached from the skin to the normal cul-de-sac, and the terminal myelocystocele which is considered the result of arrest at the phase of the persisted terminal balloon attached to the skin.