On the effects of the ligation of multiple adjacent radicular vessels on spinal cord function in dogs

The effects of the ligation of multiple adjacent nerve roots, along with their accompanying blood vessels, on the function of the spinal cord were studied, using adult mongrel dogs. Intramedullary blood flow and partial pressures of oxygen were measured after the nerve roots, together with their radicular vessels, from T11 to L2 had been ligated unilaterally in one group of dogs and bilaterally in a second group. Spinal evoked potentials were also monitored in the second group of dogs during the process of bilateral ligations. Reduction of the rate of blood flow and of the partial pressure of oxygen in the spinal cord was about 20% when a large radicular artery was ligated, but no obvious change in the spinal evoked potentials was observed. Once the ligation of such an artery had reduced the blood flow, the ligation of another large radicular artery did not always induce further reduction of the blood flow in the spinal cord. None of the dogs showed any neurological deficits in their hind limbs. These results accord with the anatomical findings of the segmental nature of the arterial supply of the spinal cord in adult man. They confirm the importance of the radicular arteries which are smaller in calibre than the so-called arteries of Adamkiewicz, in the maintenance of adequate spinal cord circulation.