Experimental spinal cord trauma, II: Blood flow, tissue oxygen, evoked potentials in both paretic and plegic monkeys.

Graded clinical motor deficits were produced in a series of Rhesus monkeys subjected to experimental spinal cord trauma from a variety of impact loads. An argon washout technique was used to measure spinal cord blood flow; tissue oxygen carbon dioxide, and somatosensory evoked potentials (SEPs) were also monitored. Each animal received a clinical grade and, after a week of study, the spinal cords were removed for histopathological grading. Blood flow in paraplegic animals was significantly decreased at two hours and seven days following injury (5 ml/min/100 gms tissue); paraparetic animals showed no significant difference from preinjury levels (14 ml/min/100 gms tissue). Animals which completely recovered demonstrated increased flow (27 ml/min/100 gms tissue). Composite tissue oxygen was generally depressed in paraplegic animals (28 mm Hg/kg) but showed no clear pattern in other groups. Only 8% of monkeys rendered paraplegic preserved a somatosensory evoked potential (SEP) at five minutes after injury. Paraparetic animals were more likely (40%) to show initial preservation of the SEP and in normal animals, the SEP always returned by three hours. Histopathological grading tended to parallel clinical grading in 92% of the cases. Although the extremes of possible postinjury deficits (complete paraplegia or recovery) can be predicted from a combination of these measurements, incomplete lesions (whether judged clinically or pathologically) present a more variable picture.