Abstract
(1) Background: Respiratory dysfunction is a debilitating consequence of cervical and thoracic spinal cord injury (SCI), resulting from the loss of cortico-spinal drive to respiratory motor networks. This impairment affects both central and peripheral nervous systems, disrupting motor control and muscle innervation, which is essential for effective breathing. These deficits significantly impact the health and quality of life of individuals with SCI. Noninvasive stimulation techniques targeting these networks have emerged as a promising strategy to restore respiratory function. This study systematically reviewed the evidence on noninvasive electrical stimulation modalities targeting respiratory motor networks, complemented by previously unpublished data from our research. (2) Methods: A systematic search of five databases (PubMed, Ovid, Embase, Science Direct, and Web of Science) identified studies published through 31 August 2024. A total of 19 studies involving 194 participants with SCI were included. Unpublished data from our research were also analyzed to provide supplementary insights. (3) Results: Among the stimulation modalities reviewed, spinal cord transcutaneous stimulation (scTS) emerged as a particularly promising therapeutic approach for respiratory rehabilitation in individuals with SCI. An exploratory clinical trial conducted by the authors confirmed the effectiveness of scTS in enhancing respiratory motor performance using a bipolar, 5 kHz-modulated, and 1 ms pulse width modality. However, the heterogeneity in SCI populations and stimulation protocols across studies underscores the need for further standardization and individualized optimization to enhance clinical outcomes. (4) Conclusions: Developing standardized and individualized neuromodulatory protocols, addressing both central and peripheral nervous system impairments, is critical to optimizing respiratory recovery and advancing clinical implementation.