Retrograde evoked compound action potentials as an alternative for close-loop spinal cord stimulation

Area of Science:

• Neuroscience
• Biomedical Engineering

Background:

• Evoked compound action potential (ECAP) is crucial for closed-loop spinal cord stimulation (SCS).
• Antegrade ECAP recording is common, but retrograde ECAP research is limited.

Purpose of the Study:

• To investigate retrograde ECAPs in rats.
• To assess the feasibility of retrograde ECAPs as feedback for closed-loop SCS.

Main Methods:

• Utilized custom-made epidural electrodes in 11 adult male Sprague-Dawley rats.
• Recorded ECAPs using a commercial electrophysiological recorder and a custom-made amplifier.
• Measured motor threshold (MT) and ECAP threshold (ECAPT) under anesthesia and in awake states.

Main Results:

• Average MT was 218.18 ± 69.54 μA and ECAPT was 107.27 ± 27.96 μA in anesthetized rats.
• ECAP amplitude increased with stimulation current and pulse width.
• ECAP amplitudes were larger in awake rats compared to anesthetized rats.
• The custom-made amplifier exhibited a lower signal-to-noise ratio than the commercial recorder.

Conclusions:

• Retrograde ECAP shows potential as a feedback signal for closed-loop SCS.
• Further development of sophisticated ECAP recording circuits is necessary for effective closed-loop systems.