Study design: Segmental arteries were interrupted bilaterally for up to 7 levels to study the effects on spinal cord blood flow and neurologic function in dogs.
Objective: To examine how many ligations of bilateral segmental arteries cause ischemic spinal cord dysfunction.
Summary of background data: Interruption of bilateral segmental arteries for up to 3 levels has been reported not to damage spinal cord function. However, to our knowledge, the effects of ligating more than 3 levels have not yet been clearly determined.
Methods: There were 15 dogs divided into 5 groups: sham group, no ligation; group 1, ligation of bilateral segmental arteries at 3 levels (T11-T13); group 2, at 4 levels (T10-T13); group 3, at 5 levels (T10-L1); and group 4, at 7 levels (T9-L2). Spinal cord blood flow at T12 measured by laser Doppler flowmetry, and spinal cord-evoked and motor-evoked potentials were measured simultaneously until 10 hours after ligation. Neurologic function was assessed using a modified Tarlov grading system 1 week after operation in 20 other dogs divided into 4 groups (1, 2, 3, and 4).
Results: Spinal cord blood flow was 99.3%, 80.7%, 71.5%, 44.3%, and 25.0% in the sham group, and groups 1, 2, 3, and 4, respectively, 10 hours after ligation. Abnormal spinal cord-evoked potentials were observed in 2 of 3 dogs in group 3 and all 3 in group 4. Abnormal motor-evoked potentials were observed in 1 of 3 dogs in group 3 and all 3 in group 4. Postoperative neurologic evaluation identified all 5 dogs in groups 1 and 2, respectively, and 3 in group 3 as having grade 5. There were 2 dogs in group 3 and 3 in group 4 that had grade 4, and 2 in group 4 had grade 3.
Conclusion: Interruption of bilateral segmental arteries at > or =5 consecutive levels risks producing a spinal cord ischemia capable of injuring the spinal cord.