Using a Brain-Spine Interface (BSI)
Although the majority of SCIs do not directly damage the neurons located in the lumbosacral spinal cord, which receive executive commands from the brain in order to walk, the disruption of descending pathways interrupts the brain-derived commands that are necessary for these neurons to produce walking (Arber & Costa 2018; Courtine & Sofroniew 2019). The consequence is permanent paralysis (Lorach et al. 2023).
A spinal cord stimulation system can restore standing and basic walking in people with paralysis due to a SCI (Lorach et al. 2023). However, this recovery requires wearable motion sensors to detect motor intentions from residual movements or compensatory strategies to initiate the preprogrammed stimulation sequences (Rowald et al. 2022). Consequently, the control of walking was not perceived as completely natural; moreover, the participants showed limited ability to adapt leg movements to changing terrain and volitional demands (Rowald et al. 2022).
Recently, Lorach et al. (2023) suggested that a digital bridge between the brain and spinal cord would enable volitional control over the timing and amplitude of muscle activity, restoring more natural and adaptive control of standing and walking in people with paralysis due to SCI.
Discussion
The case report of Lorach et al. (2023) was carried out as part of the ongoing clinical feasibility study STIMO-BSI (‘Brain-controlled Spinal Cord Stimulation in Patients with Spinal Cord Injury’), which investigates the safety and preliminary efficacy of brain-controlled spinal cord stimulation after SCI (clinicaltrials.gov, NCT04632290). Before enrolment in the STIMO-BSI study, the participant was implanted with a spinal cord stimulation system, and completed a five-month intensive neurorehabilitation program, followed by a two-year period of independent use at home (Lorach et al. 2023). The results showed that the reliability of the brain–spine interface (BSI) remained stable over one year (including during independent use at home), that the BSI enabled natural control over the movements of the legs of the participant to stand, walk, climb stairs, and traverse complex terrains. Objective improvements were observed in standing balance (BBS and TUG), walking ability (WISCI II), and walking distance (6MWT), and the participant regained the ability to walk with crutches overground even when the BSI was switched off (Lorach et al. 2023). Although these promising results need to be replicated in larger studies, and broader implementation of such a device will require time and resources, the authors suggest that “the concept of a digital bridge between the brain and spinal cord augurs a new era in the treatment of motor deficits due to neurological disorders” (Lorach et al. 2023).
Conclusions
There is level 5 evidence (from 1 case report study: Lorach et al. 2023) that a brain-spine interface device enables natural control over the movements of the legs to stand, walk, climb stairs and even traverse complex terrains.
