Impact of Intermittent Functional Internal Iliac Artery Occlusion on Spinal Cord Blood Supply during TEVAR

Background Measuring transcranial motor evoked potentials (EPs) and somatosensory EPs is a well-established method to assess spinal cord function during thoracic endovascular aortic repair (TEVAR). Functional occlusion of one or both internal iliac arteries by large bore sheaths during TEVAR can cause unilateral intermittently EP loss. Methods Between 2006 and 2016, 194 patients underwent TEVAR entailing EP monitoring. The ISIS IOM System (Inomed Medizintechnik GmbH, Emmendingen, Germany) was employed in all patients. EPs were recorded after inducing anesthesia, during the procedure, and before discontinuing anesthesia. Results We observed a unilateral intermittently EP decrease or loss in 12 (6.2%) patients. Most events were ipsilateral (9 of 12). The underlying pathologies were descending aortic aneurysm in six patients and type B dissection in six patients. An evoked-potential decrease or loss was always associated with the insertion of large bore stent-graft-introducing sheaths. The median duration of the unilaterally EP decrease or loss was 16 (10; 31) minutes (range, 2-77 minutes) with baseline values re-established at the end of the procedure after sheath removal in all cases. No patient developed irreversible symptomatic spinal cord ischemia. Conclusion A functional occlusion of internal iliac arteries via large bore TEVAR-introducing sheaths is associated with a unilateral intermittent decrease in or loss of EPs returning to baseline after sheath removal. This observation highlights the importance of the internal iliac arteries as one of the major spinal cord's blood supply territories, and may serve as a stimulus to reduce the duration of sheath indwelling to a minimum.