New weapons in the long-standing fight against spinal cord injury
For those who’ve been suffering from spinal cord injury, a new hope recently arose in electric neuromodulation. When combined with intense physical rehabilitation, this experimental technique has already led to promising results in volunteers a few years after lesion, who saw their voluntary motor control greatly facilitated. But there is still work to be done before a larger range of people can benefit from this promising technique. So far, only a selected group of young paraplegic individuals obtained astonishing results from electric neuromodulation. This group had optimal abilities above the injury site, trained upper limb muscles and showed no side effects to continuous physical efforts. But those with more severe lesions haven’t been so lucky. Dr Giuliano Taccola aimed to extend the benefits of neurorehabilitation to a greater number of people thanks to funding under the EPI_NanoSTIM project – undertaken with the support of the Marie Curie programme. He successfully modified the patterns of electrical stimulation in preclinical experiments, while investigating novel technologies able to potentiate the effects of neuromodulation in the spinal cord. “Our new multielectrode epidural array can independently stimulate multiple sites adjacent to the spinal cord. In collaboration with the team of Prof. Wentai Liu and Prof. Reggie Edgerton at UCLA, we explored different options for the fabrication and choice of materials. One of these was the use of highly conductive metals and possible nanostructured coatings,” Dr Taccola explains. “As for the stimulating protocol, its principle arises from my previous research on in vitro biological preparations. It has been further refined and is now named Dynamic Stimulation, to distinguish it from the protocols of stereotyped impulses used by standard stimulation.” The protocol consists of the simultaneous delivery of two waveforms, highly variable in both frequency and amplitude, which are sampled from the recordings of a hindlimb muscle during locomotion. The two waves are applied to both sides of the dorsal cord, along the lumbosacral segment and with opposed cathode/anode polarity. Unlike standard alternatives, the new stimulation protocol potentiates the synaptic response within spinal circuits. According to data collected by Dr Taccola, the combination of dynamic stimulation and the multielectrode array could also facilitate cortico-spinal input in scenarios where the connection with supraspinal centers is compromised – which is the case in spinal lesions. “I do not see many barriers to the introduction of this new protocol in experimental clinics. Even though it has a higher frequency of stimuli compared to the protocols approved for clinical use, the efficacy of Dynamic Stimulation is observed at much lower intensities. Our pilot testing on animals, with or without lesions, suggests that the repetitive delivery of the protocol does not cause pain or other kinds of discomfort. Nevertheless, Dynamic Stimulation cannot be introduced in clinics without the creation of a similar, stimulating interface suitable for use in humans. In other words, the limit to the potential translation is essentially industrial,” says Dr Taccola. Should industry come forward, the array technology could soon be applied to the human spinal cord and make dynamic stimulation a viable solution for experimental clinics. The potential for the recovery of motor functions is huge, and applies to a wide range of people with spinal lesions.
Keywords
EPI_NanoSTIM, spinal cord injury, neurorehabilitation, electric neuromodulation, electrical stimulation, dynamic stimulation, spinal lesion
