12. Direct dorsal columns stimulation as a mapping technique in intramedullary spinal cord tumors

Abstract

Dorsal Columns Mapping is used intraoperatively in order to reduce postoperative sensory deficits. Actually the following techniques have been described: Recording somatosensory evoked potentials from a multicontact electrode over the exposed spinal cord. Recording from peripheral nerves following electrical stimulation of the exposed dorsal columns. Recording the phase reversal of cortical SEPs P37/N37 following electrical stimulation of dorsal columns through a multicontact electrode. Intraoperative data from 5 patients affected by IMSCT are shown. Intraoperatively the exposed dorsal columns have been stimulated through a bipolar microfork probe; responses were recorded from the ipsilateral and contralateral popliteal fossa. In one case, beyond responses from the popliteal fossa, cortical SEPs were recorded. In all subjects it has been possible to obtain clear reproducible responses from the ipsilateral popliteal fossa; the stimulation of the midline elicited bilateral responses with similar latencies. In one subject a phase reversal of cortical SEPs at C3′–C4′ was observed when the stimulation moved from a dorsal column to the opposite one. Direct stimulation of dorsal columns is a fast and easy-to-perform technique that can be used for identify the midline in IMSCT. The combined recording of peripheral and cortical responses may increase the accuracy of the method.