BRAIN–SPINE INTERFACES AFTER CERVICAL SPINAL CORD INJURY: BIDIRECTIONAL NEURAL BYPASSES, EPIDURAL STIMULATION, AND SENSORIMOTOR RESTORATION

Abstract

Abstract
Background. 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.