Abstract
Purpose: To compare neurovascular coupling in the posterior cerebral artery (PCA) between those with spinal cord injury (SCI) and able bodied (AB) individuals. Methods: A total of seven SCI and seven AB were matched for age and sex. Measures included PCA velocity (PCAv), beat-by-beat blood pressure and end-tidal carbon dioxide. Posterior cerebral cortex activation was achieved by 10 cycles of (1) 30 s eyes closed (pre-stimulation), (2) 30 s reading (stimulation). Results: Blood pressure was significantly reduced in those with SCI (SBP: 100 ± 13 mmHg; DBP: 58 ± 13 mmHg) vs. AB (SBP: 121 ± 12 mmHg; DBP: 74 ± 9 mmHg) during both pre-stimulation and stimulation, but the relative increase was similar during the stimulation period. Changes in PCAv during stimulation were mitigated in the SCI group (6% ± 6%) vs. AB (29% ± 12%, P < 0.001). Heart rate and end-tidal carbon dioxide responded similarly between groups. Conclusions: Clearly, NVC is impaired in those with SCI. This study may provide a link between poor perfusion of the posterior cerebral region (containing the medullary autonomic centres) and autonomic dysfunction after SCI.
Highlights
Spinal cord injury (SCI) leads to devastating paralysis, and serious cardiovascular complications [1,2,3,4]
The difference in blood pressure between the two groups remained throughout the stimulation period; the change occurring from pre-stimulation to stimulation was similar
The average pre-stimulation PCA velocity (PCAv) was similar between the able bodied (AB) (37 ± 6 cm/s) and SCI (37 ± 10 cm/s) participants (Table 1)
Summary
Spinal cord injury (SCI) leads to devastating paralysis, and serious cardiovascular complications [1,2,3,4]. Cardiovascular disease has been identified as a primary cause of death in those with SCI [5]. Cerebral vascular disease is of major concern, as those with SCI have a two to three-fold increase in the risk of stroke ( ischemic stroke) [6]. Cerebrovascular reserve is an important marker of the relationship between blood pressure and cognitive function. A reduction in cerebrovascular reserve has been associated with impaired neurovascular metabolic coupling (NVC) and reduced cognitive function [7]. Neurovascular coupling refers the coupling of brain metabolism and blood flow in the human cerebral circulation [8] involving the interactions between blood vessels, neurons, and other nervous system cells (e.g., astrocytes and other glial cells) [7]. The continuous assessment of cerebral blood flow velocity (CBFv, a surrogate of cerebral blood flow) via transcranial Doppler ultrasonography [9]
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