Characterizing preserved autonomic regulation following spinal cord injury: Methods of a novel concerted testing battery and illustrative examples of a new translationally focused data representation

Abstract

Autonomic dysfunction is common after spinal cord injury, though differing from motor and sensory function, there are currently no established batteries of tests to comprehensively characterize these deficits. Further, while individual established autonomic tests have a long history and sound scientific background, translating these autonomic testing results to inform clinical understanding is a major barrier. Herein, we outline a battery of six laboratory autonomic tests which were carefully curated to collectively describe the ability of individuals with spinal cord injury to inhibit and recruit sympathetic activity through the injured spinal cord. Presenting normative control data in 23 uninjured individuals completing this testing battery, we further demonstrate the utility of extracting three key testing metrics for each test, comparing these control results to 11 individuals with spinal cord injury. Results demonstrate strong normality of data with testing psychometrics suggesting reliable reproducibility on repeat testing. Further, even in this preliminary sample of individuals with spinal cord injuries, clear differences begin to emerge. This illustrates the ability of this collective testing battery to characterize autonomic regulation after spinal cord injury. To aid in clinical translation, we further present a graphical representation, anautonomic phenotype, which serves as a snapshot of how normal or abnormal sympathetic inhibition and recruitment of activation may be after spinal cord injury. Utilizing theseautonomic phenotypes, three example cases of individuals with spinal cord injury highlight evidence of varied degrees of autonomically complete spinal cord injury. Together, this represents a key advancement in our understanding of autonomic function after spinal cord injury.