Contact combinations in epidural spinal cord stimulation. A comparison by computer modeling

Area of Science:

• Neuroscience
• Biomedical Engineering
• Computational Modeling

Background:

• Epidural spinal cord stimulation (SCS) is used to manage pain.
• Understanding fiber recruitment in the dorsal columns (DC) is crucial for optimizing SCS therapy.
• Current knowledge on optimal contact configurations for selective DC recruitment is limited.

Purpose of the Study:

• To theoretically investigate the geometrical characteristics of DC fiber populations recruited by different SCS contact combinations.
• To model the relationship between stimulation parameters, fiber geometry, and recruitment patterns.
• To predict how variations in fiber properties influence SCS outcomes.

Main Methods:

• Development of a 3D computer model of the low-thoracic spinal cord, surrounding tissues, and myelinated nerve fibers.
• Simulation of epidural spinal cord stimulation using various dorsomedial contact combinations.
• Calculation of the mediolateral and dorsoventral extent of recruited areas in the DC.

Main Results:

• The study found minimal variation (2-5%) in the extent of recruited DC areas for typical dorsomedial contact combinations.
• Model predictions suggest optimal bipolar stimulation contact separation depends on the dorsal cerebrospinal fluid width.
• The model predicts that cutaneous afferent recruitment begins laterally and progresses medially with increasing stimulus intensity, aligning with clinical observations of paresthesia spread.

Conclusions:

• A single 'best contact combination' for SCS does not exist; optimal settings are distance-dependent.
• The model supports the recruitment of large fibers in the posterior spinocerebellar tract during SCS.
• Theoretical modeling provides insights into SCS mechanisms and can guide therapeutic parameter selection.