Anatomical pattern of feeding artery and mechanism of intraoperative spinal cord ischemia.

BACKGROUND

We evaluated correlation between anatomical pattern of the spinal cord feeding artery, detected by preoperative multidetector row computed tomography, and the mechanism of spinal cord ischemia during aortic surgery.

METHODS

One hundred sixteen patients underwent multidetector row computed tomography before descending or thoracoabdominal replacement. Segmental arteries feeding the spinal cord were detected in 92 patients (79%), and were classified into "critical" (isolated hairpin shaped) or "supplemental" (confluence-shaped or multiple). Spinal cord ischemia was monitored together with distal aortic perfusion in 53 of them by motor-evoked potentials, evoked spinal cord potentials, or both. The relationship between monitoring results and operative management to the detected feeding arteries was analyzed.

RESULTS

When no feeding segmental artery was involved in the extent of replacement (n = 18), spinal cord ischemia was detected in 1 (6%), which was due to cross-clamping the subclavian artery. When a supplemental feeding artery was involved (n = 15), ischemia was detected in 7 patients (47%), and was reversed by stopping back-bleeding. When a critical feeding artery was involved (n = 20), ischemia was detected in 6 (30%). In 3 of them, ischemia was reversed by stopping back-bleeding, whereas it was reversed only after reconstruction of the critical feeder in the remaining 3. Paraparesis occurred in 1 of the latter 3, and the incidence of spinal cord injury was 2% (1 of 53).

CONCLUSIONS

When the involved feeding artery is a supplemental one, the steal phenomenon is the predominant mechanism of ischemia. Conversely, blood flow interruption to the critical feeding artery may cause spinal cord ischemia without steal phenomenon.