Split cord malformations of the lumbar region. A model for the neurosurgical management of all types of 'occult' spinal dysraphism?

From a group of 84 patients with split cord malformations presenting to our Department between 1976 and 1990, we have selected 47 cases in whom the split cord was confined to the lower dorsal-lumbar region and in whom there were no other dysraphic features such as meningocele, lipoma or dermoid cyst. We have studied these cases of 'pure split cord malformation' in an attempt to decipher its natural history and the effects of surgical procedures designed to untether the spinal cord. We conclude that the 'neuro-orthopaedic syndrome' (which includes lower limb asymmetry, talipes and modest sensory and motor problems) is, in most cases, an inevitable consequence of the abnormal functional anatomy of the split cord and is not due to any mechanical effects of tethering of the spinal cord. Its emergence as a child grows (assuming that it was not obvious at birth) is not influenced by surgery. True neurological deterioration (defined as the loss of a previously established neurological or urological function) is a rarer event. It may occur at any age--including well into adulthood--but in children the average age at presentation is 6.8 years (range 2 years 9 months to 11 years). It is due to the mechanical effects of tethering of the spinal cord and is more likely to be arrested than improved by surgery. 'True' deterioration did not occur in any of our cases who had undergone prophylactic untethering of the spinal cord and we have concluded, therefore, that surgery has a role in the prevention of late neurological problems affecting the lower limbs and bladder. Surgery to untether the spinal cord will not, however, have any affect upon the emergence of the neuro-orthopaedic syndrome.