Closed Loop Neuromodulation in Neurological Rehabilitation: Movement-Paired Vagus Nerve and Spinal Cord Stimulation for Motor Recovery

Abstract

Neurological physiotherapy is increasingly incorporating neuromodulation technologies that aim to enhance activity-dependent neuroplasticity and functional recovery. A recent advancement is the transition from conventional open-loop stimulation toward closed-loop neuromodulation, in which stimulation is temporally linked to voluntary movement, muscle activity, gait events, or neural activity. Movement-paired vagus nerve stimulation (VNS) and transcutaneous spinal cord stimulation (tSCS) represent two emerging approaches with potential applications in neurological rehabilitation. Clinical trials have demonstrated that VNS paired with upper-limb rehabilitation can improve motor impairment after chronic stroke, while recent research has extended this concept toward non-invasive transcutaneous auricular VNS (taVNS), wearable movement-triggered systems, and brain-computer-interface-synchronized stimulation. Similarly, tSCS combined with gait training has shown promising effects on walking-related outcomes, although substantial heterogeneity exists in stimulation parameters and treatment protocols.More recently, electromyography (EMG)-triggered spinal stimulation has introduced a physiological feedback mechanism for timing stimulation during gait.This mini-review discusses the neurophysiological rationale, current evidence, clinical applications, limitations, and future directions of movement-paired VNS and spinal stimulation, with particular emphasis on their integration into neurological physiotherapy.