Anatomical study of blood supply to the spinal cord

BACKGROUND: Low incidences of spinal cord ischemia after thoracoabdominal aortic aneurysm repair, despite sacrifice of all segmental arteries, have recently been reported. This, however, cannot be explained by previous anatomical findings, which prompted us to perform an anatomical study of blood supply to the spinal cord. METHODS: Fifty-five spinal cords from Japanese formol-fixed cadavers (mean age, 79 +/- 10 years) were studied. Diameters of the anterior spinal artery (ASA) above and below the junction with the arteria radicularis magna (ARM) and diameters of the ARM were measured using the NIH image program (National Institutes of Health Image 1.58). RESULTS: The degree of narrowing of the ASA, defined as the diameter above the ARM expressed as a percentage of the diameter below the ARM, ranged from 23% to 161% and averaged 66% +/- 30%. The degree of narrowing was plotted against the ARM diameter divided by the ASA diameter above the junction to examine the impact of the degree of narrowing on distal spinal blood flow from the ARM. The degree of narrowing was related to distal spinal blood flow from the ARM (r= 0.56, p < 0.0001). CONCLUSIONS: The degree of narrowing of the ASA varies considerably. Furthermore, distal spinal blood supply becomes progressively dependent on the ARM as the narrow point of the ASA becomes narrower. These anatomical findings of spinal blood supply should be useful for elucidating the mechanisms of spinal cord injury after repair of extensive thoracoabdominal aneurysms.