Modeling dermatome selectivity of single-and multiple-current source spinal cord stimulation systems

A recently published computational modeling study of spinal cord stimulation (SCS) predicted that a multiple current source (MCS) system could generate a greater number of central points of stimulation in the dorsal column (DC) than a single current source (1CS) system. However, the clinical relevance of this finding has not been established. The objective of this work was to compare the dermatomal zone selectivity of MCS and 1CS systems. A finite element method (FEM) model was built with a representation of the spinal cord anatomy and a 2×8 paddle electrode array. Using a contact configuration with two aligned tripoles, the FEM model was used to solve for DC field potentials across incremental changes in current between the two cathodes, modeling the MCS and 1CS systems. The activation regions within the DC were determined by coupling the FEM output to a biophysical nerve fiber model, and coverage was mapped to dermatomal zones. Results showed marginal differences in activated dermatomal zones between 1CS and MCS systems. This indicates that a MCS system may not provide incremental therapeutic benefit as suggested in prior analysis.