Epidural spinal cord stimulation: anatomical and electrical properties of the intraspinal structures relevant to spinal cord stimulation and clinical correlations

Epidural spinal cord stimulation (SCS) has gained a secure place in the armamentarium of the surgeon treating chronic pain conditions (1, 2). The complexity of the intraspinal structures and their different susceptibility to electrical signals, however, has made it difficult to characterize the effects of the stimulation, Some important recent work has helped shed light on the electrical properties of the intraspinal structures and on the electrical field potentials generated with epidural spinal cord stimulation. This work, initially pioneered by Sin and Coburn, has successfully been expanded and perfected by Holsheimer and Strujik at the University of Twente, The Netherlands (3-8). The Dutch scientists developed a computerized volume conductor model of the spinal cord to represent in extreme detail the electrical properties of all the intraspinal structures, including the dorsal column and dorsal root fibers. The model can simulate the effects of epidural stimulation with different electrode geometries and configurations (8). The data generated from the model were then validated by comparing them to a large number of data collected by the author in implanted subjects (9-12). The author also conducted a detailed analysis of the clinical properties of the activation of the intraspinal structures at various electrode positions in the spine (13, 14).