Electrode array for reversing the recruitment order of peripheral nerve stimulation: a simulation study

Area of Science:

• Biomedical Engineering
• Neuroscience
• Computational Biology

Background:

• Electrical stimulation typically activates large nerve fibers first.
• Previous research indicated selective small fiber activation is possible with specific electrode configurations.
• Understanding nerve fiber recruitment is crucial for targeted neuromodulation.

Purpose of the Study:

• To investigate the efficacy of different multi-contact electrode array sizes for selective peripheral nerve stimulation.
• To determine the influence of electrode contact number and spacing on nerve fiber recruitment order.
• To assess the independence of selective activation from stimulation pulse width.

Main Methods:

• Finite element modeling of the ventral sacral root was employed.
• Simulations tested electrode arrays with 5, 7, 9, and 11 contacts.
• Axon activation thresholds were analyzed for varying internodal distances and pulse widths (50 µs and 200 µs).

Main Results:

• A 5-contact array selectively activated small axons (<7.5 µm) before larger ones.
• Arrays with 7, 9, and 11 contacts suppressed excitability in axons with internodal distances near the intercathodic distance (~15 µm).
• Selective activation was consistent across different pulse widths, and 5- and 7-contact arrays reduced recruitment curve slope.

Conclusions:

• Electrode arrays with 5 and 7 contacts show promise for selective activation of small nerve fibers.
• This selective activation is achievable irrespective of the stimulation pulse width.
• These findings support the development of advanced neuromodulation therapies with enhanced precision.