Beyond the wheelchair: how exoskeleton training redefines mobility and somatic sensation for incomplete spinal cord injury patients

Introduction. The use of assistive tools in patients with somatic deafferentation and motor deefferentation as a part of rehabilitative experience has shown significant promise in supporting processes of adaptive neuroplasticity, ultimately improving the living conditions of its users. One of the most significant benefits of such trainings is the reduction of chronic pain, which is a particularly disabling aspect for patients with spinal cord injury (SCI). Despite being unclear, the underlying mechanisms of how these trainings alleviate chronic pain make them increasingly relevant as a nonpharmacological approach to cope with neuropathic pain. Objective: We investigated the potential benefits of a long-term powered exoskeleton training on tactile perception and neuropathic pain in patients with SCI. Patients and methods: The study recruited 19 patients with complete and incomplete spinal cord lesions (below T4) and assessed their tactile threshold and neuropathic pain using a computerized pressure algometer and Numerical Rating Scale (NRS) and Neuropathic Pain Questionnaire in Spinal Cord Injury (NPQSCI), respectively. The assessments were conducted at the beginning of each training session (T0) and after 9 (T1) and 18 (T2) training sessions with ReWalk exoskeleton. Results: Participants who lacked sensitivity to algometer pressure were excluded from the study. The results showed a significant improvement in tactile sensitivity at T1 (p<0.002) and T2 (p<.01), particularly for the lower limb. Similar results were observed for pain intensity, with a reduction exceeding 30% throughout all the training sessions (T1 = p<0.009; T2 = p<0.045). Moreover, a significant correlation was found between pain intensity and improvements in tactile sensitivity (r =-0.63; p = 0.04), indicating that the degree of improvement in tactile sensitivity varied as a function of pain intensity. Conclusion: In the realm of neuroprosthetic technologies, our study highlights the potential of prolonged exoskeleton use as a promising rehabilitation alternative. Beyond improving patients' independence and functional mobility, exoskeleton training facilitates the reconstruction of a new bodily identity. By promoting adaptive neuroplasticity processes, these trainings allow SCI patients to update their altered brain-body representations, especially for the upper legs, which play a more active functional role compared to the wheelchair condition. Our findings underline the essential role of these neural mechanisms in reducing some of the most relevant clinical manifestations of SCI, including neuropathic pain