'Meningoceles' and 'meningomyeloceles' (ectopic spinal cord). Clinicopathological basis of a new classification.

While the terms 'meningocele' and meningomyelocele', as defined in a dictionary, appear clearly separate, these words have been qualified and assigned nuances by a variety of workers, rendering them somewhat confusing today. Thus for instance, a dictionary (Dorland, 1965) defines a meningomyelocele as 'a hernial protrusion of a part of the meninges and substance of the spinal cord through a defect in the vertebral column'. This, however, appears to be an over-simplification, since in most cases the lesion of the spinal cord is more than a simple herniation into a sac. In fact, as shown by Cameron (1956) in his comprehensive investigation, the initial malformation in all cases of 'meningomyelocele' was an open myelocele which tended to be covered in time by an epithelialized scar. The classification of the congenital lesions of the spine and cord, associated with a spina bifida, proposed by Cameron and endorsed by Willis (1962) and others (for example, Greenfield, 1963), is as follows: