Key result
Spinal cord injury is linked to selectively impaired sympathetic reflexes with preserved vagal control.
Why the study?
The study was conducted to assess whether autonomic nervous system control disturbances differently affect vagal and sympatho-vagal markers during sleep and orthostatic challenge according to spinal cord injury location.
Does the site of spinal cord injury alter cardiac autonomic regulation and sympatho-vagal balance during sleep and orthostatic challenges?
Observational (n=18)
No
Does the site of spinal cord injury alter cardiac autonomic regulation and sympatho-vagal balance during sleep and orthostatic challenges?
p-value: p=group p = 0.006, interaction p = 0.011
Spinal cord injury selectively impairs sympathetic positive feedback reflexes in a level-dependent manner while preserving vagal negative feedback, underscoring the potential for targeted neuroprosthetic autonomic interventions.
May inform lesion-level autonomic monitoring in SCI; hypothesis-generating for targeted sympathetic neuroprosthetics.
Purpose: The goal of this study on Spinal Cord Injury (SCI) patients with cervical or thoracic lesion was to assess whether disturbances of ANS control, according to location, might differently affect vagal and sympatho-vagal markers during sleep and orthostatic challenge. We analyzed with linear and nonlinear techniques beat-by-beat RR and arterial pressure (and respiration) variability signals, extracted from a polysomnographic study and a rest–tilt test. We considered spontaneous or induced sympathetic excitation, as obtained shifting from non-REM to REM sleep or from rest to passive tilt. We obtained evidence of ANS cardiac (dys)regulation, of greater importance for gradually proximal location (i.e., cervical) SCI, compatible with a progressive loss of modulatory role of sympathetic afferents to the spinal cord. Furthermore, in accordance with the dual, vagal and sympathetic bidirectional innervation, the results suggest that vagally mediated negative feedback baroreflexes were substantially maintained in all cases. Conversely, the LF and HF balance (expressed specifically by normalized units) appeared to be negatively affected by SCI, particularly in the case of cervical lesion (group p = 0.006, interaction p = 0.011). Multivariate analysis of cardiovascular variability may be a convenient technique to assess autonomic responsiveness and alteration of functionality in patients with SCI addressing selectively vagal or sympathetic alterations and injury location. This contention requires confirmatory studies with a larger population.
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Guaraldi et al. (2022) conducted an observational in Spinal Cord Injury (n=18). Spinal cord injury (cervical or thoracic) vs. Matched healthy controls without spinal cord injury was evaluated on Change in sympatho-vagal balance (LF and HF normalized units) during orthostatic challenge and REM sleep (p=group p = 0.006, interaction p = 0.011). Spinal cord injury, particularly with cervical lesions, selectively impaired sympathetic reflex responses to orthostatic challenge and REM sleep (group p=0.006 for LF/HF balance) while preserving vagally mediated negative feedback reflexes.
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