BRAIN–SPINE INTERFACES AFTER CERVICAL SPINAL CORD INJURY: BIDIRECTIONAL NEURAL BYPASSES, EPIDURAL STIMULATION, AND SENSORIMOTOR RESTORATION
AbstractBackground. Cervical spinal cord injury disrupts descending motor commands, sensory information, and autonomic regulation, producing tetraplegia incompletely reversible with rehabilitation. Brain–spine interfaces seek to re-establish communication across the lesion by decoding cortical intention and delivering patterned spinal stimulation, while bidirectional systems restore somatosensory feedback.Materials and methods. A structured narrative review integrated trials, prospective cohorts, first-in-human studies, neurophysiological investigations, regulatory documents, and reports published through July 2026. Evidence was organized by biological plausibility, neural-signal acquisition, decoding performance, spinal-target selectivity, sensorimotor integration, safety, durability, rehabilitation dependence, and translational readiness. A prospective multicenter comparative protocol was developed for adults with chronic cervical injury and neurological stability.Results. The synthesis addresses cortical decoding, epidural and transcutaneous spinal neuromodulation, upper-limb and locomotor restoration, artificial sensory feedback, autonomic effects, and activity-dependent neuroplasticity. Implanted brain–spine systems have enabled intention- driven standing and walking in an individual with chronic tetraplegia, whereas non-invasive cervical stimulation combined with task practice has improved hand strength and sensation in cohorts. A double neural bypass reported in 2026 integrated intracortical decoding, patterned spinal stimulation, and cortical sensory stimulation, producing immediate assistance together with persistent motor and sensory gains in one participant. The proposed primary endpoint is functional independence measured by SCIM III and task-specific upper-extremity performance without device-related morbidity. Secondary endpoints include GRASSP, CUE-T, gait capacity, decoding latency, sensory localization, autonomic stability, quality of life, caregiver burden, durability, and cost-effectiveness.Conclusion. Brain–spine interfaces are evolving from proof-of-concept bypasses toward restorative neuroprosthetic systems. Multicenter validation, standardized endpoints, transparent algorithms, and long-term surveillance remain essential.Keywords: cervical spinal cord injury, tetraplegia, brain–spine interface, brain–computer interface, epidural spinal cord stimulation, transcutaneous stimulation, neural bypass, sensory feedback, neuroplasticity.