Multimodal Spinal Cord Mapping during Spinal Cord Stimulator Placement: Technical Note

Allott G, Krishnamurthy S.

Neurodiagn J. 2021 Dec;61(4):203-213. doi: 10.1080/21646821.2021.2003114.

Abstract

Spinal cord stimulation is used to treat patients with severe neuropathic pain and other forms of debilitating back pain. Spinal cord stimulators (SCS) can either be placed under sedation or general anesthesia (GA). This study evaluated the utility of neurogenic evoked potentials in enabling multimodal spinal cord mapping (MSCM) for the placement of SCSs under GA. The goal of our MSCM paradigm, which integrated recordings from multiple antidromic and orthodromic generators, was to enable the use of precise neuromonitoring techniques, typically used for localizing the midline of the dorsal spinal cord in intramedullary tumor cases, for the safe placement of SCSs. Two distinct modalities were incorporated - orthodromic responses from the somatosensory cortex (Cp3-Cp4 cancellation) and antidromic stimulation via the SCS which resulted in compound nerve action potentials of the extremities. In addition, two incidental findings were made. First, our results suggest that previous investigations may have incorrectly identified compound muscle action potentials as compound nerve action potentials. Additionally, anti D-wave responses, that are theorized to be the equivalent of a D-wave, were observed. This manuscript describes the first use of MSCM, which will ultimately provide neurophysiologists more information during SCS implantation, enabling them to confirm midline placement more confidently. MSCM also allows the application of techniques typically used in spinal cord tumors, allowing the neurophysiologist to maintain proficiency with these techniques on more common procedures. The parallel collection of several sources of data will allow for future studies that better define which mapping methods are the most accurate.