Histological differences between rootlets sectioned during selective posterior rhizotomy by two surgical techniques.

During selective posterior rhizotomy, for the treatment of spasticity in infantile cerebral palsy, the rootlets to be divided are chosen by the type of electromyographic response elicited by intraoperative electrical stimulation. Two different surgical techniques were used for exposing the lumbar roots. The first approach was to expose the conus medullaris through a T 12-L 1 laminectomy, while the other approach to the dorsal roots was distally in the cauda equina through a L 2-L 3 to S1 laminectomy. Although the clinical results obtained with either of them are not very different, there is anatomical evidence that suggests that the histological structure of the divided rootlets may be different in the two techniques. We designed our study to determine of a significant difference in the number of large myelinated fibers was found between rootlets divided close to the conus medullaris and those divided distally in the cauda equina. Two groups of five children with spasticity secondary to cerebral palsy where randomly designed to be operated upon by one of the techniques. The divided rootlets were processed with standard histological techniques and the large myelinated fibers were counted on enlarged (40 x) photomicrograph of the rootlet. A significantly (p less than 0.001) larger number of large myelinated axons was found in the rootlets dissected and divided close to the conus medullaris.