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Spinal cord perfusion is provided by segmental arteries that originate from the vertebral, intercostal, lumbar, and hypogastric arteries. This segmental origin of spinal perfusion is supplemented by an extensive intraspinal and paraspinal anastomotic network that provides longitudinal collateral circulation among the horizontally distributed segmental arteries. However, this longitudinal anastomotic network is usually insufficient to maintain spinal perfusion when acute or extensive interruption of the segmental system occurs. The dorsal branches of the intercostal and lumbar arteries provide the segmental blood supply to the spinal cord through the radiculo-medullary arteries and to the paravertebral muscles (Figure 1). Interruption of the blood supply to an intercostal or lumbar artery results in decreased blood flow not only to the spinal cord but also to the paravertebral muscles. Therefore, monitoring perfusion to the paravertebral muscles provides an indirect evaluation of the spinal cord perfusion. Because interruption of the blood supply to the lower intercostals and upper lumbar arteries is associated with the higher rate of spinal ischemia, evaluating the perfusion of the paravertebral muscles at those levels will likely be more clinically significant.
Figure 1Diagram demonstrating the segmental blood supply to the spinal cord and paravertebral muscles. Note the common origin of the radiculo-medullary artery and the branches for the paravertebral muscles. This common origin provides the anatomic foundation for NIRS monitoring of the paravertebral muscles as an indicator of spinal cord ischemia.
expand on their previous work using near-infrared spectroscopy (NIRS) to noninvasively, in real time, and continuously monitor blood flow/oxygenation to the lumbar paravertebral muscles as an indicator of blood flow to the spinal cord.
In a swine model, the authors simulated the spinal ischemia that would occur with an extent II thoracoabdominal aorta replacement with and without reimplantation of the lower intercostal-upper lumbar arteries. The authors found that NIRS measurements correlate with the degree of spinal ischemia and neurologic outcomes. NIRS signal decreased early after artery occlusion and started to recover within 1 hour after occlusion. Persistent paraplegia was associated with more severe initial decrease and delayed and less than complete recovery of the NIRS signal. In addition, NIRS levels were directly correlated with the severity of the neurologic impairment; the lower the NIRS reading, the worse the neurologic outcome. Finally, as expected, animals with more severe neurologic impairment had more significant histologic changes in the spinal cord.
on the use of NIRS for the noninvasive continuous monitoring of spinal ischemia contributes to increase the safety of aortic surgery and endovascular procedures by identifying spinal ischemia early, allowing for early intervention, and hopefully preventing its devastating consequences. The utility of this monitoring technique should be further studied in clinical trials and potentially used during not only the surgical/endovascular procedures but also the early postoperative period.
References
von Aspern K.
Haunschild
Ziemann M.
Misfeld M.
Mohr F.
Borger M.A.
et al.
Evaluation of collateral network near-infrared spectroscopy during and after segmental artery occlusion in a chronic large animal model.
Ischemic spinal cord injury remains the most devastating complication after open and endovascular aortic repair. Collateral network near-infrared spectroscopy has been introduced to noninvasively monitor real-time spinal cord oxygenation. In view of recent advancements in endovascular treatment and minimally invasive staged preconditioning before aortic repair, this study sought to evaluate collateral network near-infrared spectroscopy during and after segmental artery occlusion in a chronic porcine model.
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