Feasibility of Intravascular Femoral Nerve Stimulation using a Stent Electrode Array

In recent years, electrical stimulation of peripheral nerves has gained attention as a potential therapeutic approach for restoring impaired nerve function. Traditional electrode arrays typically require invasive surgical implantation, which imposes a significant burden on patients. Therefore, intravascular stent electrode arrays, as a less invasive alternative, have shown tremendous potential. This study aims to investigate the feasibility of stimulating the femoral nerve using an intravascular stent electrode array and compare its performance with a commercial cardiac pacing lead.

Background and Objectives

Electrical stimulation of peripheral nerves has been used to treat nerve dysfunction that cannot be recovered by conventional drug therapies, such as refractory epilepsy and depression. Additionally, this technique has been explored for applications in treating inflammatory bowel disease, musculoskeletal disorders, chronic pain management, and providing sensory feedback for prostheses. However, the invasive implantation surgery required for traditional electrode arrays has limited their practical application as a long-term treatment option.

The research described in this paper aims to address the gap in the application of intravascular stent electrode arrays in the peripheral nervous system, offering a more convenient and safer treatment alternative through intravascular techniques.

Research Source and Author Information

This research was conducted by Dr. Jingyang Liu (student), David B. Grayden, Janet R. Keast, Lindsea C. Booth, Clive N. May, and Sam E. John. The ethical approval for this study was granted by the Florey Institute of Neuroscience and Mental Health in Melbourne, Australia (ethics approval number: 21-065-FINMH). The research was published in the Journal of Neural Engineering.

Research Procedure Details

Experimental Design and Operational Procedure

1. Experimental Subjects and Anesthesia

   • After obtaining approval, four female Australian sheep were selected for the experiment.
   • The animals were anesthetized with isoflurane and mechanically ventilated via an endotracheal tube during the surgery.
   • Analgesics and antibiotics were administered to ensure the animals’ stability during the procedure.

2. Electrode Implantation and Experimental Operation

   • The femoral artery was surgically exposed, and a guiding sheath was inserted into the artery to facilitate the delivery of the cardiac pacing lead and stent electrode array.
   • In the initial experiment, a quadripolar pacing lead was used to stimulate the femoral nerve, and electromyography (EMG) from the quadriceps femoris muscle and electroneurography (ENG) from the distal branch of the femoral nerve were recorded.
   • Subsequently, the pacing lead was removed, and a bipolar stent electrode array was implanted, repeating the recording process.
   • During the stimulation, the response thresholds and strength-duration curves were measured at different pulse widths and intensities.

3. Data Processing and Analysis

   • MATLAB was utilized for data processing, including filtering the EMG and ENG signals to remove artifacts and interference.
   • Statistically significant minimum stimulation intensities were identified, and activation thresholds, total injected charges, and charge densities were calculated.

4. Histological Examination

   • After the experiment, tissue samples were collected for histological examination to analyze the spatial relationship between the electrode and the nerve, as well as the impact on surrounding tissues.

Experimental Results and Discussion

1. Feasibility of Electrical Stimulation

   • The study confirmed the feasibility of using a stent electrode array for femoral nerve electrical stimulation, eliciting strong muscle and nerve responses comparable to those achieved with a commercial pacing lead.

2. Threshold Currents and Charge Densities

   • The threshold currents for evoking responses with the stent electrode array were generally higher than those of the pacing lead, but by shortening the pulse width to 100µs, the charge densities were significantly reduced to a safe range.
   • Strength-duration curve analysis showed that the three key parameters (Rheobase, Chronaxie, and total injected charge) for the stent electrode array were similar to those of the pacing lead.

3. Long-term Tissue and Device Impacts

   • Although this study focused on acute experiments, future research should address the long-term stability and safety of the implanted stent electrode array.
   • Regarding electrode material selection and surface structure, more numerous and larger surface area electrodes, as well as increased porosity on the electrode surface, could be considered to improve charge injection densities and reduce the potential for irreversible electrochemical reactions during long-term implantation.

Conclusions and Research Significance

Through in vivo experiments, the feasibility and effectiveness of using an intravascular stent electrode array for peripheral nerve electrical stimulation have been demonstrated, providing new insights into exploring minimally invasive peripheral nerve interfaces. Future research will further evaluate the long-term stability of the stent electrode, the impact of implantation on local tissues, and the feasibility of recording peripheral nerve signals.

Research Highlights

1. First Application of Intravascular Stent Electrode Array for Peripheral Nerve Stimulation

   • Demonstrated the technical feasibility and safety of peripheral nerve stimulation through an intravascular stent electrode array.

2. Performance Comparison with Commercial Cardiac Pacing Lead

   • Within the clinically relevant parameter range, the stent electrode array exhibited similar stimulation effects, suggesting its potential as a less invasive alternative.

3. Optimization of Stimulation Parameters

   • Strength-duration curves indicated that shortening the pulse width can effectively reduce the threshold charge and charge density, further mitigating the risk of tissue damage.

4. Outlook for Future Research

   • Emphasized the importance of future research exploring the long-term impact on local tissues and hemodynamics, as well as advances in wireless stimulator technology.