Autonomic dysreflexia (AD) is a serious cardiovascular disorder in patients with spinal cord injury (SCI). The primary underlying cause of AD is loss of supraspinal control over sympathetic preganglionic neurons (SPNs) caudal to the injury, which renders the SPNs hyper-responsive to stimulation. Central maladaptive plasticity, including C-fiber sprouting and propriospinal fiber proliferation exaggerates noxious afferent transmission to the SPNs, causing them to release massive sympathetic discharges that result in severe hypertensive episodes. In parallel, upregulated peripheral vascular sensitivity following SCI exacerbates the hypertensive response by augmenting gastric and pelvic vasoconstriction. Currently, the majority of clinically employed treatments for AD involve anti-hypertensive medications and Botox injections to the bladder. Although these approaches mitigate the severity of AD, they only yield transient effects and target the effector organs, rather than addressing the primary issue of central sympathetic dysregulation. As such, strategies that aim to restore supraspinal reinnervation of SPNs to improve cardiovascular sympathetic regulation are likely more effective for AD. Recent pre-clinical investigations show that cell transplantation therapy is efficacious in reestablishing spinal sympathetic connections and improving hemodynamic performance, which holds promise as a potential therapeutic approach.

Background:The combination of body weight-supported gait training with functional electrical stimulation (FES) may provide the optimal stimulus for improving overground walking after spinal cord injury (SCI). This potential benefit is likely due to the combination of specificity with the maximization of muscle contractions. Objectives: To investigate the effects of 12 weeks of FES-ambulation on overground walking and health-related quality of life (HRQOL) in individuals with SCI. Methods: Six individuals (60.5 ± 13.2 years) with SCI (C4-L3; AIS D; 9.3 ± 12.0 years post injury), completed a thrice-weekly, 12-week FESambulation training program. Locomotor function was assessed via the Walking Index for Spinal Cord Injury II (WISCI II), the 6-minute walk test (6MWT), the 10-meter walk test (10MWT), and the body-weight support required during training. HRQOL was assessed via the Short Form-36, the Perceived Stress Scale, and the Center of Epidemiological Studies for Depression scale. Results: Participants showed significant improvements in the 6MWT (223.6 ± 141.5 m to 297.3 ± 164.5 m; P = .03), the required body weight support (55.3% ± 12.6% to 14.7% ± 23.2%; P = .03), and a nonsignificant trend toward an increase in walking speed during the 10MWT (0.69 ± 0.4 m/s to 0.9 ± 0.5 m/s; P = .08) following the training program. Four participants showed improvements on the WISCI II (1-4 points). Participants also showed a decrease in the Short Form-36 pain score (6.5 ± 1.2 to 5.0 ± 1.7; P = .04) and an increase in the overall mental health score (47.8 ± 12.6 to 54.2 ± 6.7; P = .04). Conclusion: FES-ambulation was associated with enhanced overground walking in individuals with AIS D SCI, reduced pain, and improved mental health.

Study design: Review. Objectives: The purpose of this review is to discuss the utility of linear and non-linear heart rate variability (HRV) as well as the QT-variability index (QTVI) as indices of cardiac autonomic control in individuals with spinal cord injury (SCI). Setting: Brock University, Department of Kinesiology, St Catharines, Ontario, Canada. Brock-Niagara Centre for Health and Well-being, St Catharines, Ontario, Canada. Methods: Literature review. Conclusion: Non-invasive markers determined from the electrocardiogram, such as linear and non-linear HRV, and, more recently, the QTVI have all shown some promise as indices of cardiac autonomic regulation in the SCI population. However, there are inconsistencies in the literature that call to question their true validity in this regard. Studies using pharmacological blockade, sympathetic manoeuvres and exercise suggest that both linear and non-linear HRV reflect cardiac parasympathetic activity, whereas their ability to quantify cardiac sympathetic outflow remains uncertain. The QTVI, although a novel method, correlates with both limbs of the autonomic nervous system and therefore may hold value as a measure of both cardiac sympathetic and parasympathetic activity in individuals with SCI; however, more research is required to confirm its utility.

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