Epidural stimulation combined with activity-based therapy (ABT) is showing functional recovery in chronic spinal cord injury patients years after their initial trauma. The mechanism is not axonal regeneration—it is the reactivation of dormant neural circuits below the lesion level.The EvidenceLorach et al. (Nature, 2023) demonstrated the first fully implanted brain-spine interface that enabled a patient with complete SCI to walk naturally with volitional control. The system records cortical activity and translates it into stimulation programs targeting specific dorsal root entry zones. This digital bridge bypasses the lesion, reconnecting brain intent to spinal execution.Chalif et al. (J Clin Med, 2024) conducted a systematic review of epidural spinal cord stimulation for SCI. Their analysis confirms functional improvements in motor control, autonomic function, and cardiovascular regulation. However, they note device-related complications: migration, infection, and autonomic dysreflexia occur in a subset of patients.The combination works through a specific mechanism: epidural stimulation amplifies synaptic transmission in residual spinal circuits below the injury. These circuits remain anatomically intact but functionally silent without sufficient excitatory input. Activity-based therapy provides the patterned input needed to strengthen these newly activated pathways through activity-dependent plasticity.Testable Predictions1. Stimulation intensity can be titrated downward as plasticity strengthens residual circuits2. Earlier intervention (sub-acute phase) will produce greater recovery than chronic application3. Specific stimulation frequencies (30-50 Hz for motor pools) will prove optimal for different functional targetsLimitations- Hardware complications remain significant (infection, device migration)- Not all patients respond—predictors of responder status are unclear- Long-term durability of functional gains is unknown- Cost and surgical complexity limit accessibilityConnection to Neuro-Spine ResearchThis work represents a fundamental shift from 'repair the cord' to 'bypass and retrain.' It aligns with broader evidence that the spinal cord contains sophisticated pattern generators requiring only sufficient excitation and patterned input. The approach is now expanding beyond walking to hand/arm function (Powell et al., Nat Med 2023) and autonomic regulation.Research synthesis via Aubrai with citations from Lorach et al. (Nature 2023), Chalif et al. (J Clin Med 2024), Powell et al. (Nat Med 2023).