UBC Theses and Dissertations
Integrity of spinal autonomic pathways in sub-acute and chronic spinal cord injuries Wong, Shirley Candice
The outcome of spinal cord injury (SCI) is still commonly described in terms of motor and sensory function, despite increasing awareness that there is also damage to the autonomic nervous system (ANS). The purpose of this thesis was to examine the integrity of spinal autonomic pathways among individuals with sub-acute and chronic SCI. The selection of appropriate tests to assess autonomic function is challenging since the ANS is complex. Examining reliability and comparability among measures provides a comprehensive understanding of the validity of specific tools. This doctoral thesis is comprised of three separate investigations that focus on determining the integrity of spinal autonomic pathways following SCI. In the first study (Chapter 2), the focus was on the reliability of heart rate variability (HRV), sympathetic skin responses (SSRs) and an orthostatic challenge (sit-up test). Measures of HRV, SSRs and blood pressure changes during the sit-up test were found to be reliable. Additionally, the sit-up test was compared with the gold standard orthostatic challenge (tilt-table test), which revealed that the sit-up test provokes an orthostatic response comparable to the tilt-table test. In the last two studies (Chapters 3 and 4) HRV and changes in blood pressure (BP) during an orthostatic challenge, SSRs and the Valsalva manoeuvre (VM) were used to examine spinal autonomic integrity. The novel focus on integrity of spinal autonomic pathways revealed that it is affected by lesion level, neurologic severity of injury, and time post-injury. As expected based on extensive existing research on cardiovascular autonomic function following SCI, higher lesion levels produced greater cardiovascular impairments. That is, there is greater compromise to spinal autonomic integrity in high-level compared to low-level SCI. However, the association between neurologic and autonomic “completeness” of injury is unclear. Our findings suggest that time post-injury may affect the latter. During the sub-acute stage, autonomic tests revealed cardiovascular changes in patients in a one-month follow-up after admission to a rehabilitation hospital. The exact time course of alterations to integrity is unknown. Not acknowledging change to spinal autonomic integrity is inherently problematic since it is unclear what neurologic severity of injury infers about autonomic dysfunction.
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