When the whole is greater than the sum of its parts: a scoping review of activity-based therapy paired with spinal cord stimulation following spinal cord injury

Spinal cord injury (SCI) results in both motor and autonomic impairments, which can negatively affect independence and quality of life and increase morbidity and mortality. Despite emerging evidence supporting the benefits of activity-based training and spinal cord stimulation as two distinct interventions for sensorimotor and autonomic recovery, the combined effects of these modalities are currently uncertain. This scoping review evaluated the effectiveness of paired interventions (exercise + spinal neuromodulation) for improving sensorimotor and autonomic functions in individuals with SCI. Four electronic databases were searched for peer-reviewed manuscripts (Medline, Embase, CINAHL, and EI-compedex Engineering Village) and data were independently extracted by two reviewers using pre-established extraction tables. A total of 15 studies representing 79 participants were included in the review, of which 73% were conducted within the past 5 years. Only two of the studies were randomized controlled studies, while the other 13 studies were case or case-series designs. Compared with activity-based training alone, spinal cord stimulation combined with activity-based training improved walking and voluntary muscle activation, and augmented improvements in lower urinary tract, bowel, resting metabolic rate, peak oxygen consumption, and thermoregulatory function. Spinal neuromodulation in combination with use-dependent therapies may provide greater neurorecovery and induce long-term benefits for both motor and autonomic function beyond the capacity of traditional activity-based therapies. However, evidence for combinational approaches is limited and there is no consensus for outcome measures or optimal protocol parameters, including stimulation settings. Future large-scale randomized trials into paired interventions are warranted to further investigate these preliminary findings.