Finite element analysis of electric field distribution during direct current stimulation of the spinal cord: Implications for device design

APL Bioeng, 2023 · DOI: 10.1063/5.0163264 · Published: November 2, 2023

Spinal Cord Injury Biomedical Biomechanics

Simple Explanation

Spinal cord injuries (SCI) disrupt neuronal tissues, leading to sensorimotor dysfunction. Electric field stimulation shows promise for neuronal regeneration, but understanding electric field distribution in injured tissue is key. This study uses finite element modeling to optimize electrode geometry and placement for spinal cord treatment, revealing how electrode shape, spinal cord size, and current magnitude impact the electric field. The study investigates how electrode shape, spinal cord size, and applied current affect electric field distribution. It shows electrode shape has minimal impact, electrode placement influences field distribution, and field magnitude depends on current and spinal cord morphology. Injury modality also affects field distribution, informing treatment parameters. This research provides guidance for designing electrodes for direct current electric field stimulation, potentially improving axonal regeneration in clinical applications. By understanding how various factors influence the electric field, treatments can be optimized for better outcomes in spinal cord injury patients.

Study Duration

Not specified

Participants

Human spinal cord model

Evidence Level

Not specified

Key Findings

1
Electrode shape has little effect on the induced electric field distribution within the spinal cord.
2
Electrode placement significantly influences the electric field distribution in the spinal cord, highlighting the importance of strategic positioning.
3
The magnitude of the electric field is governed by both the applied current and the morphology of the spinal cord.

Research Summary

This study uses finite element modeling to investigate electric field distribution during direct current stimulation of the spinal cord, focusing on the impact of electrode geometry, spinal cord size, and applied current magnitude. The findings offer insights into optimizing electrode design for future clinical applications in axonal regeneration. The research reveals that electrode shape has a minimal impact on the induced electric field, while electrode placement and spinal cord morphology significantly influence field distribution and magnitude. The study also demonstrates that injury modality affects the induced field, highlighting the importance of understanding injury characteristics for treatment parameter selection. The study emphasizes the importance of electrode geometry and placement to safely achieve uniform electric field distribution. The findings suggest that smaller electrodes may generate dangerously high, localized electric fields and that maintaining a minimum spacing between the contact edge and spinal cord lesion allows for a more uniform electric field distribution across the lesion.

Practical Implications

Electrode Design

Electrode dimensions can be personalized without significantly impacting electric field distribution, but smaller electrodes may pose safety concerns due to high electric field strengths.

Electrode Placement

Maintaining a minimum spacing of 20 mm between electrodes and 10 mm between the electrode edge and lesion boundary is crucial for achieving uniform electric field distribution.

Treatment Personalization

Understanding the injury modality and spinal cord morphology is essential for tailoring treatment parameters and optimizing outcomes for spinal cord injury patients.

Study Limitations

1
Modeling electrodes as perfectly conformal to the dorsal surface, which is rarely the case in practice.
2
Ignoring electrochemical effects, such as Faradaic reactions, that may form cytotoxic byproducts.
3
Simplifying lesion types, which are never as well-defined as those modeled, leading to unrealistic discontinuities in the electric field.

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