Memantine for prevention of spinal cord injury in a rabbit model

Background: This study was conducted to investigate the effect of memantine , a noncompetitive N-methyl-D-aspartate receptor antagonist, on the neurolo gic outcome of spinal cord ischemia after aortic occlusion, Materials and m ethods: New Zealand White rabbits were anesthetized and spinal cord ischemi a was induced for 40 minutes by infrarenal aortic occlusion, Animals were r andomly allocated to 3 groups. Group 1 (n = 8, control) received no pharmac ologic intervention, group 2 (n = 8) received intra-aortic memantine infusi on (20 mg/kg) after aortic crossclamping, and group 3 (n = 8) was treated w ith systemic memantine infusion (20 mg/kg) 45 minutes before aortic occlusi on. Neurologic status was scored by the Tarlov system tin which 4 is normal and 0 is paraplegia) at 12, 24, 36, and 48 hours after the operation. Lumb ar spinal root stimulation potentials and motor evoked potentials from lowe r limb muscles were monitored before, during, and after the operation. Afte r the animals were killed, the spinal cords were studied histopathologicall y, Results: All potentials disappeared shortly after aortic crossclamping. They returned earlier in both memantine-treated groups than in the placebo group. Histologic examination of spinal cords revealed a few abnormal motor neurons in memantine-treated rabbits but found extensive injury in the con trol group. At 12 hours the median Tarlov scores were 0 in the control grou p (group 1), 2 in the intra-aortic memantine group (group 2, P =.001 versus control), and 3 in the systemic group (group 3, P =.0002 versus control). At 24 hours median Tarlov scores were 0, 2.5 (P =.0002), and 4 (P =.0002), respectively. Finally, at both 36 and 48 hours median Tarlov scores were 0, 3 (P =.0006), and 4 (P =.0002), respectively. Conclusion: Memantine signif icantly reduced neurologic injury related to spinal cord ischemia and reper fusion after aortic occlusion.