Effect of Lead Position and Polarity on Paresthesia Coverage in Spinal Cord Stimulation Therapy: A Computational Study

Abstract

ObjectivesThe effect of lead placement and programming strategies on spinal cord stimulation (SCS) therapy has been widely studied; however, there is a need to optimize these parameters to favor dorsal column (DC) over dorsal root (DR) stimulation in complex pain treatment. This study aimed to determine the optimal lateral distance between two leads and the effect of transverse stimulation using a mathematical model. Materials and MethodsA three-dimensional computational SCS and a nerve fiber model were used to determine the effect of the lateral distance between two leads at the same vertebral level T8 and the effect of the addition of anodes with two parallel leads at T8 and three different lateral distances on the model-based results (perception thresholds, activated DC fiber area and depth, and position of the first stimulated fiber). ResultsWith two parallel leads programmed with symmetrical polarities, the maximal DC fiber area stimulated was found for a lateral distance of 5 mm. The results also show a higher preference for DR stimulation as the lateral distance increased. The addition of positive contacts at the same level of active contacts in the second lead produces a displacement of the first stimulated fiber laterally. ConclusionsA lateral distance of 5 mm shows a DC stimulated fiber area greater than when leads are placed contiguously. The addition of anodes creates an effect whereby the area of paresthesia is not displaced to the midline, but in the opposite direction. This may be useful when the leads are too close and stimulation of one of the sides is compromised.