Cranial venous system and the posterior fossa in spina bifida aperta.

A study of the cerebral venous system in children with S.B.A. was undertaken, and this report concerns the gross structure of this structure of this system in the posterior fossa. Noteworthy is the closeness of the torcular to the foramen magnum. The lateral sinuses ran near to the foramen magnum to the sigmoid sinuses. The dura of the posterior fossa consisted of a plexiform structure in which no clear distinction could be made between various sinus systems normally present in the dural layers of the posterior fossa, thus constituting an occipital plexus. The walls of the sinuses were weak and were vulnerable to mechanical pressure. The foramen magnum of the skulls of children with S.B.A. was larger than in normal children. The distance of the torcular to the ventral margin of the foramen magnum was smaller in S.B.A. This distance remained unchanged at least until nine months of age in normal children as well as in children with S.B.A., although there was an increase in size of the foramen magnum in both with advancing age.