Modern approach to electrical conductivity mapping of spinal cord tissues

Over 30,000 patients per year receive electrical stimulation of the spinal cord (neuromodulation) as a means of pain management. However, optimizing the delivery parameters is difficult, partly because of an extremely valuable but incomplete dataset on the electrical conductivity of spinal cord tissues. We traced the lineage of the spinal tissue electrical conductivity sources of the majority of modern electrostimulation models to a single source, Ranck 1965. The experiments within Ranck 1965 only provided two types of data: (1) bulk spinal tissue conductivity at 5, 50, 500, and 5k Hz; and (2) small volume (8 mm3) of dorsal column tissue conductivity at 5-10 Hz. Since the distribution of spinal cord cells throughout the cord is not uniform, the bulk spinal tissue conductivity sweep does not provide enough spatial information for a detailed electrical model between different sections, layers, and tissue types of the spinal cord. Our project seeks to significantly improve on Ranck 1965 by obtaining 10-1M Hz, large-volume (40 cm3), and multi-directional conductivity data for electromagnetic modeling of neuromodulation using an electronically-controlled conductivity probe array. With our findings, neuroscientists and neuromodulation researchers and designers will be able to provide more targeted therapies as a result of a more-detailed and rigorous electromagnetic spinal cord model.