Spinal dysraphism.

Introduction Spinal dysraphism is a term which was revived by Lichtenstein (1940) under which he grouped disorders arising from cutaneous, mesodermal or neural derivatives of the dorsal median region of the developing embryo. Within this broad classification must be included the sub-groups of spina bifida aperta with myeloschisis, myelomeningocele or meningocele and spina bifida occulta with or without associated neuroectodermal and mesodermal abnormalities. Although grouping these disorders under the single heading of spinal dysraphism need not imply uniformity of aetiology or pathogenesis, this is of course considered by many to be the case (Brocklehurst, 1971). There is a group of disorders of development of the dorsal mid-line of the embryo including involvement of ectodermal, mesodermal, neural or endodermal elements which is in some respects separate from the various degrees of spina bifida cystica. It is this particular group, which includes such apparently diverse conditions as diastematomyelia, diplomyelia, dermoid cyst or sinus, lipoma of the conus medullaris, prolongation of the conus and a variety of fibrous bands between conus, nerve roots and dura, that I propose to consider. There may be slight theoretical justification for regarding this as an independent group, but, for practical purposes, it is useful to do so, because the conditions are so different from the commoner spina bifida cystica in their presentation, investigation, treatment and prognosis (Till, 1969).