One element of non-invasive neurostimulation treatments that has delayed their translation to general use has been the understanding that specialised stimulators are required. Our Project Spark studies have been testing this assumption by analysing which type of neurostimulation therapy may be more effective. This could reveal vital clues to help establish it as a treatment option and, ultimately, advance a cure for spinal cord injury (SCI).
Our partners at the Spinal Cord Injury Research Centre (SCIRC) at NeuRA are one step closer to determining this thanks to the results of their study published recently in The Journal of Physiology comparing the two types of electrical stimulation used in Project Spark – carrier-frequency stimulation and conventional pulsed stimulation. Carrier-frequency stimulation requires specialised equipment (such as the Digitimer DS8R Stimulator used in our trials) whilst pulsed stimulation can be delivered by off the shelf TENS machines which are more widely available and at a much lower cost. The recently completed eWALK trial evaluated the high frequency carrier-wave stimulation whereas the eWALK 2 clinical trial uses a conventional stimulation approach. Our Get a Grip trial is testing both kinds.
The new study compared the two modalities on 12 participants to measure impacts on pain tolerance and the thresholds for activation of sensory and motor axons, two types of nerve fibres that play crucial roles in the functioning of the nervous system.
Whilst this is a new and emerging area of research that requires further exploration, the results pointed to conventional stimulation being equally as good as the carrier-frequency type. Particularly in terms of pain measurement because it required lower levels of stimulation to achieve the desired result.
According to Professor Jane Butler, the results turned around earlier research hypotheses showing that the waveforms used in carrier-frequency stimulation resulted in less pain than conventional stimulation. Another highlight finding revealed that carrier-frequency waveforms were less effective at triggering sensory and motor nerve responses when compared to conventional stimulation.
“Given the small sample size, the jury is still out in terms of which type of stimulation is less painful and more effective in activating the muscles we need to pinpoint and trigger, paving the way for further research in this area,” said Professor Butler. “However, knowing what we know now does create more opportunities for conventional stimulation devices to be used in the future. The results that we see from Get a Grip and eWALK 2 will help to further validate this.”
Stay tuned for further updates.