Congenital atresia of the foramen of Monro.

Two cases of congenital atresia of the foramen of Monro are described, one 8 days old and the other 2 months old. Both are associated with a parieto-occipital paraventricular diverticulum and spontaneous ventriculostomy with the passing of the cerebrospinal fluid to the posterior fossa and the formation of a cyst in the supracerebella region which compressed and displaced the structures of the posterior fossa.