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

OBJECTIVE: 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. METHODS: 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. RESULTS: Safe caudal extension of untethering is possible using this method. Illustrative operative photographs are shown. CONCLUSIONS: By using this method, safe untethering can be achieved avoiding root injuries in complicated lipomas such as chaotic or retethering cases.