The Collateral Network Concept and Its Implications:
It should be noted that our thinking about spinal cord perfusion—and consequently about the causes of paraplegia following TAA/A repair—is somewhat unorthodox. On the basis of our clinical experience, the experiments we have done thus far in the pig model, and evidence from published literature, we believe that the entire network of collateral vessels surrounding the spinal cord and the paraspinous muscles are vitally important for cord perfusion, rather than any single large artery. We have called this hypothesis the Collateral Network Concept.
On the basis of this hypothesis, we have used a surgical technique clinically in which we serially sacrifice, whilst monitoring MEPs, all of the SAs coming from an aneurysm of the thoracoabdominal aorta prior to its excision. Thus far, this approach has resulted in a very low incidence of spinal cord injury at 2%. If the collateral network perfusion hypothesis is correct, routine and safe sacrifice of all intercostal and lumbar arteries should be an achievable goal.
Furthermore, if paraplegia can be prevented, the hope that hybrid open and endovascular strategies for repair of extensive TAA/A will be able to prevent rupture in many more patients becomes quite realistic. But, the sacrifice of large numbers of SAs is only likely to prove possible if one takes every precaution to safeguard the perfusion of the cord both during operation, and in the hours and days after, until the collateral circulation of the cord is fully stabilized. Our predictions about the safety of extensive SA sacrifice in the porcine model directly translate into furthering progress in hybrid open/endovascular repair of extensive TAA/A, and, more importantly, significantly reducing both mortality and morbidity of our patients.
Gabriele Di Luozzo, MD