Extramedullary impedance monitoring and stimulation of the spinal cord surface in percutaneous cordotomy. Technical note.

A needle with an insulated inner stylet has been developed for monitoring of impedance when the subarachnoid space is punctured in percutaneous cordotomy. Electric stimulation of the surface of the spinal cord with a flat-tipped electrode has been used in order to locate the optimal site for the subsequent penetration of the cord with a sharp lesion-making electrode.