Ultrasound-driven piezoelectric current activates spinal cord neurocircuits and restores locomotion in rats with spinal cord injury

Bioelectronic Medicine, 2020 · DOI: https://doi.org/10.1186/s42234-020-00048-2 · Published: April 16, 2020

Simple Explanation

This study explores a new way to stimulate the spinal cord using piezoelectric materials and ultrasound. Instead of using traditional electrical stimulation that requires implanted batteries, this method uses an external ultrasound beam to power a small implanted device that generates electrical current. The researchers tested this method on rats with spinal cord injuries and compared it to traditional electrical stimulation. They found that the piezoelectric stimulation was just as effective in activating spinal cord circuits and helping the rats regain some movement. This new approach could offer a safer and more convenient way to treat spinal cord injuries and other neurological conditions because it eliminates the need for batteries and secondary surgeries.

Study Duration

4 weeks locomotion training

Participants

Seven Sprague Dawley rats (245–262 g body-weight)

Evidence Level

Not specified

Key Findings

1
Ultrasound intensity as low as 0.1 mW/cm2 could induce MEPs in the hindlimbs of rats.
2
Piezoelectric stimulation (pES) induced by 22.5 mW/cm2 ultrasound restored locomotion in paralyzed rats with complete thoracic cord injury, similar to conventional electrical stimulation (ES).
3
Locomotion EMG signals indicated that pES works the same as ES in restoring movement.

Research Summary

The study investigates the efficacy of piezoelectric stimulation (pES) to activate spinal cord neurocircuits compared to conventional epidural electrical stimulation (ES) in rats with spinal cord injury. The results demonstrate that pES, driven by ultrasound, can induce motor evoked potentials (MEPs) and restore locomotion in paralyzed rats, similar to ES. The authors propose pES as a novel neuromodulation technique that could potentially replace conventional ES due to its advantages, such as not requiring an implanted power source.

Practical Implications

Novel neuromodulation

Piezoelectric stimulation presents a new avenue for neuromodulation, potentially overtaking conventional electrical stimulation in future bioelectronic medicine.

Battery-free stimulation

The piezoelectric stimulator does not require any implanted power source, reducing the size of the implant and eliminating the need for secondary surgeries to replace batteries.

Restoration of locomotion

Piezoelectric stimulation can restore locomotion in paralyzed rats with complete spinal cord injury, offering a potential therapeutic approach for movement restoration.

Study Limitations

1
Slight drop of harvested voltage over time, possibly due to increase of acoustic impedance inside the body due to tissue growth and scar formation after implantation.
2
Difficulty in keeping the ultrasound probe well-placed on the skin during locomotion.
3
The threshold rising trends were probably due to the increase of epidural electrode impendence resulting from tissue and scar growth.

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