A Method of Untethering by Skipping the Area of Positive Responses on Electrical Stimulation During Surgery of Lumbosacral Lipomatous Malformation: "Hopping on a Stepping Stone".

Abstract

In complex lumbosacral lipomatous malformation or retethering, "crotch" dissection, an incision on the dura or lipoma at the site lateral to the lipoma-cord fusion line saving underlying roots, is often not easy. Attempts of this dissection in complex and obscured conditions may cause damage to the spinal cord or nerve roots. A method for caudal extension of untethering while positive areas on electrical stimulation were encountered during the crotch dissection of lumbosacral lipomatous malformation is described. After thinning out the negative-response area just caudal to the positive-response area, a small perforation is made at the negative-response area skipping the positive-response area with probing the dissection direction through the subarachnoid space by an inside-out fashion. Subsequently, the procedure is continued caudally from the perforation site. Safe caudal extension of untethering is possible using this method. Illustrative operative photographs are shown. By using this method, safe untethering can be achieved avoiding root injuries in complicated lipomas such as chaotic or retethering cases.