Spinal dysraphism in children

Abstract

Spina bifida occulta is one form of spinal dysraphism, a term used to refer to imcomplete formation of the midline structure of the dorsum. It is therefore related to all the other forms of spina bifida which have been described under different names, spina bifida aperta or cystica. The basic differences between spina bifida cystica and spinal bifida occulta result from the nature of their origino The spina bifida cystica is a failure of development of the spinal cord tissues intrinsically, with added destructive processes in utero, and cellular hyperplasia, as well as brain anormalies. By contrast, in spina bifida occulta there may be some dysplasia of the spinal cord but none of the other destructive processes associated with cystica; Arnold-Chiari malformation is very unusual in spina bifida occulta. In cystica, clinical abnormaIities are present at birth because of the absence of nervous tissue. However, in occulta the anomalies are extrinsic tho the spinal cord. Clinical abnormalities usualy develop later. Normally, the nerve tissues change position with movements of the spine, particularly flexion and extension. During a long time it was thought that clinical symptoms developped later because the conus was fixed in low position by extrinsic factors as lipomas, adherences and so on. This theory was based in part on the fact that in most cases of spina bifida occulta the conus medullaris is found under the L 2 leve!. In our statistic the conus medullaris is situated lower than normal in the vertebral canal in 81 % of the 88 cases. We know now that absence of «ascension» of the spinal cord as cause of neurologic deficit is incorrecto Barson, in 1970, exarnined the normal spinal cord of 252 foetuses and children aged between 13 weeks gestation and puberty. He concluded that the normal spinal cord ends L 3 at 30 weeks, L 2 at 40 weeks, reaching the normallevel at L 1 L 2 about 9 weeks afier fullterm gestation. We think that the main faetors of secondary neurologieal deficit are repeated traumatism on a rigid, a fixed spinal cord and-possibly vascular deficit. The abnormalities grouped under the term «spinal dysraphism» include: 1. Malformations of the meninges (excluding the posterior meningocele): anterior, lateral, intra sacral meningoceles. Arachnoidal cysts. 2 . Malforrnations ofspinal cord and roots: Fibrous bands between cord and dura, abnormal roots, tethered eord, diastematomyelia 3 . Lipomas (subeutaneous, extramedullary, mtramedullary, in the filum terminale). 4. Derrnal sinus, dermoid cysts. 5. Neurenteric cysts. It is interesting to note that in many pa~ents some of these lesions are found together. Spinal dysraphism must be separated from the most common myelomeningoeele or meningoeele whieh are grouped under the term spinal raehisehisis.