Model-driven stimulation for targeted functional restoration in chronic spinal cord injury

Injury to the spinal cord can lead to loss of motor and sensory function below the level of the lesion due to interruption of neural pathways. This has a devastating impact on quality of life, with little prospect of recovery beyond the acute phase. Recent advances using electrical neuromodulation have shown promise in restoring motor function, though these approaches are limited by the risks associated with the implantation of invasive stimulation systems.

The development of a non-invasive system for targeted spinal cord stimulation would represent a significant advance by allowing stimulation-facilitated rehabilitation while avoiding the risks associated with chronic implantation. Currently, non-invasive stimulation technologies are limited by a poor understanding of the distribution of transcutaneous electrical charge in the underlying tissues and how this distribution of charge influences the underlying neural tissue.

We intend to develop a system for accurately predicting the distribution of a non-invasively delivered electrical charge in the underlying tissue and the effect that this stimulation will have on the neural tissue of the spinal cord. We hypothesise that this work will allow us to generate focal stimulation of the spinal cord using non-invasive techniques. This would open the possibility of specifically targeted stimulation for functional recovery while completely eliminating the risks posed by implantation procedures and the presence of chronically implanted electronic devices.

Our proposed methodology involves computational modelling of neural anatomy and physiology to establish the theoretical basis for targeted stimulation for facilitated rehabilitation of specific functional networks. This project falls within the EPSRC Healthcare Technologies research area.

We intend to develop a system for predicting local current flow through the underlying spinal cord when stimulation currents are applied at the body surface, and for deriving the ideal electrode locations and stimulation parameters to specifically target areas of spinal cord, allowing precision stimulation.

This will allow us to assess the effect that a given stimulation field, and therefore a given stimulation paradigm, will have on cord-level neural networks. Using this model, we intend to develop a system for targeting specific physiological networks within the spinal cord using non-invasive stimulation.

We will assess the ability of our approach to generate focal stimulation of desired neural networks non-invasively by examining the ability of our model-derived stimulation protocols to produce focal paraesthesia in defined areas by targeting the dorsal column networks of human volunteers.

This work will allow us to further our understanding of the effects of stimulation on the spinal cord. It will improve our understanding of the effects of non-invasive stimulation and will establish a mechanistic basis for targeted stimulation using non-invasive techniques. From an applied perspective, we anticipate this work generating a targeted non-invasive stimulation system for functional restoration, which will be suitable for formal assessment in clinical trials of functional recovery in spinal cord injured patients.

In the long term, this work may allow improved functional restoration for patients following chronic spinal cord injury, with an associated improvement in functional status and quality of life. Through the use of non-invasive technology, the barriers to access and risks associated with implanted stimulators are removed, allowing far greater access to improved functional recovery among spinal cord injured patients.