A Comparison of FES and SCS for Neuroplastic Recovery After SCI: Historical Perspectives and Future Directions

Abstract

There is increasing evidence that neuroplastic changes can occur even years after spinal cord injury, leading to reduced disability and better health which should reduce the cost of healthcare. In motor-incomplete spinal cord injury, recovery of leg function may occur if repetitive training causes afferent input to the lumbar spinal cord. The afferent input may be due to activity-based therapy without electrical stimulation but we present evidence that it is faster with electrical stimulation. This may be spinal cord stimulation or peripheral nerve stimulation. Recovery is faster if the stimulation is phasic and that the patient is trying to use their legs during the training. All the published studies are small, so all conclusions are provisional, but it appears that patients with more disability (AIS A and B) may need to continue using stimulation and for them, an implanted stimulator is likely to be convenient. Patients with less disability (AIS C and D) may make useful recovery and improve their quality of life from a course of therapy. This might be locomotion therapy but we argue that cycling with electrical stimulation, which uses biofeedback to encourage descending drive, causes rapid recovery and might be used with little supervision at home, making it much less expensive. Such an electrical therapy followed by conventional physiotherapy might be affordable for the many people living with chronic SCI. To put this in perspective, we present some information about what treatments are funded in the UK and the US.

Effects of Functional Electrical Stimulation Cycling of Different Duration on Viscoelastic and Electromyographic Properties of the Knee in Patients with Spinal Cord Injury

“…We believe that the muscle latency and amplitude adjustments observed in the current study may depend on a functional adaptation occurred in the spinal circuits during the training. An important prerequisite to implement this adaptation after SCI is to provide spinal cord with an appropriate quantity and quality of somato-sensory afferents [ 18 , 25 , 26 , 27 , 47 , 48 ]. Studies to date indicate that hybrid physical interventions, with natural movement assisted by mechanical or electrical muscle stimulation, are suitable paradigms to obtain consistent muscle and joint sensory receptors activations [ 18 , 25 , 49 ].…”

“…Finally, on the basis of the well-documented association between spinal neuroplasticy and the amount of sensory afferents to the spinal cord [ 26 , 47 , 48 ], most of the neuronal adaptations should occur during the initial hemicycles of the pendulum test, as the amplitudes of the following leg oscillations were progressively reduced, producing an ever weakening sensory signal [ 51 ]. Therefore, the presence of the muscle responses mostly during the first flexion is a further clue indicating that the RF muscle behaviour observed in this study may be associated with a remodulation of spinal circuits.…”

Epidural and transcutaneous spinal cord stimulation facilitates descending inputs to upper-limb motoneurons in monkeys

“…This suggests that many clinicallycomplete lesions may nevertheless be anatomically incomplete, and that SCS can raise the excitability of spinal circuits to unmask weakened but surviving descending pathways (Minassian et al 2016). In conjunction with extensive rehabilitation, these pathways may be strengthened to further support restoration of function (Van Den Brand et al 2012, McPherson et al 2015, Krucoff et al 2016, Duffell and Donaldson 2020.…”

Transcutaneous spinal cord stimulation and motor responses in individuals with spinal cord injury: A methodological review

“…The electrode configuration (size, polarity, location) plays an important role in the electrical field produced by tSCS, and consequently the structures targeted. One of the criticisms of tSCS, when compared to the epidural alternative, is failure to create a localised electrical field thereby limiting activation selectivity [ 16 , 73 ]. This review found a lack of consensus regarding electrode configuration, particularly in the cervical region, and limited rationale for selected parameters throughout.…”