Perfusion-limited recovery of evoked potential function after spinal cord injury

Study Design. The current study was designed to determine whether progressi ve spinal cord damage during residual compression is caused by low blood fl ow and ischemia. Objectives. The purpose of this experiment was to determine the effects of sustained spinal cord compression on regional blood flow and evoked potenti al recovery after time-dependent decompression. Summary of Background Data. Spinal cord injury after trauma is commonly ass ociated with residual cord compression. Although decreased blood flow has b een reported after spinal cord contusion, the effect of residual spinal cor d displacement on reperfusion of blood flow or recovery of neurologic funct ion remains unclear. Methods. Eighteen beagles were anesthetized, and the spinal cord at T13 was loaded dorsally under precision loading conditions until evoked potential amplitudes were reduced by 50%. At this function endpoint, spinal cord disp lacement was maintained for 90 minutes. Somatosensory-evoked potentials wer e measured at regular intervals until 3 hours after decompression. Regional spinal cord blood flow was measured with a fluorescent microsphere techniq ue at regular lime points during and after spinal cord decompression. Results. Within 5 minutes after dynamic cord compression was discontinued, evoked potential signals were absent in all dogs. Evoked potential recovery was observed after decompression in 7 of 18 dogs. Regional spinal cord blo od flow at baseline, 21.8 +/- 1.9 mL/100 g . min (mean +/- SE), decreased t o 3.9 +/- 0.9 mL/100 g min after dynamic compression was discontinued. Alth ough spinal cord-piston interface pressure dissipated by 87% of maximum int erface pressure during sustained compression, mean blood flow recovered to only 34% of baseline flow. in the 7 dogs that recovered evoked potential fu nction, blood flow increased to 11.3 +/- 2.7 mL/100 g . min immediately bef ore decompression (P less than or equal to 0.05). In the 11 dogs that did n ot recover evoked potential function after decompression, regional blood fl ow did not improve during sustained compression. Conclusions.; Recovery of evoked potential function after decompression cor responded with a greater return of blood flow during sustained displacement and greater reperfusion of blood flow associated with decompression.